**Consumption of Goat Cheese Naturally Rich in Omega-3 and Conjugated Linoleic Acid Improves the Cardiovascular and Inflammatory Biomarkers of Overweight and Obese Subjects: A Randomized Controlled Trial**

### **Cristina Santurino 1, Bricia López-Plaza 1,\*, Javier Fontecha 2, María V. Calvo 2, Laura M. Bermejo 1, David Gómez-Andrés 3,4 and Carmen Gómez-Candela 1,5**


Received: 17 March 2020; Accepted: 28 April 2020; Published: 5 May 2020

**Abstract:** This study examines the value of a goat cheese naturally enriched in polyunsaturated fatty acids (PUFA) (n-3 PUFA and conjugated linolenic acid (CLA)) as means of improving cardiovascular and inflammatory health. Sixty-eight overweight and obese subjects (BMI <sup>≥</sup> 27 and <sup>&</sup>lt;40 kg/m2), with at least two risk factors for cardiovascular disease (CVD) in a lipid panel blood tests, participated in a randomized, placebo-controlled, double-blind, parallel designed study. The subjects consumed for 12 weeks: (1) 60 g/d control goat cheese and (2) 60 g/d goat cheese naturally enriched in n-3 PUFA and CLA. Diet and physical activity were assessed. Anthropometric and dual-energy X-ray absorptiometry (DXA) tests were performed. Blood samples were collected at the beginning and at the end of the study period. Changes in health status, lifestyle and dietary habits, and daily compliance were recorded. The consumption of a PUFA-enriched goat cheese significantly increased plasma high-density lipoprotein (HDL)-cholesterol, as well as in apolipoprotein B, and it significantly decreased high-sensitivity C-reactive protein concentrations compared to the control goat cheese (*p* < 0.05). The significant improvement of the plasma lipid profile and inflammatory status of people with risk for CVD due to the consumption of PUFA-enriched cheese suggests a potential role of this dairy product as an alternative to develop high nutritional value food in a balanced diet comprising regular exercise.

**Keywords:** n-3 PUFA; CLA; cheese; blood lipids; dairy fat

#### **1. Introduction**

Cardiovascular disease (CVD) is the leading cause of death worldwide. The major risk factors are well-established and are mediated mainly by hypertension, dyslipidemia, and smoking, as well as others such as obesity, elevated cholesterol, poor diet, and physical activity. Due to the significant influence exerted by diet and lifestyle, the current nutritional recommendations like controlling the amount and quality and quality of the fats consumed in the diet and salt intake, as well as regular physical exercise, are key to the prevention and treatment of CVD [1].

Within this framework, the effect of polyunsaturated fatty acids (PUFA), such as α-linolenic acid (ALA) n-3, has been demonstrated through mechanisms involving anti-inflammatory, anti-arrhythmic, and anti-thrombotic properties, which reduce low-density lipoprotein cholesterol levels (LDL-C) and, to a lesser extent, high-density lipoprotein cholesterol levels (HDL-C) when they replace saturated fatty acids (SFA) [2]. Even though these beneficial effects are well known, in the last 100 years, the dietary ratio of n-6/n-3 PUFA in modern Western diets has dramatically increased to 15-17:1, which has been associated with an increase of many other illnesses including inflammatory diseases and cholesterolaemia [3]. In addition, some clinical trials in humans have indicated that conjugated linolenic acid (CLA) may have several beneficial effects for health, such as improving the blood lipid profile related to CVD and diabetes [4]. However, it is important to know the exact dose of CLA and the duration of the treatment to know the biological effects [4].

In recent decades, a wide variety of functional foods have been designed to reduce some of the factors that induce cardiovascular risks and to improve health [5]. Thus, one possible way to increase PUFA consumption is to enrich foods that are regularly consumed by the majority of the population such as dairy products. Even though full fat dairy products consumption has long been considered a risk factor for cardiovascular health, such products contribute to the mean daily intakes of energy (11%), protein (14%), fat (17%), calcium (48%), phosphorous (24%), and vitamin A (27%). Though further studies are needed, a recent meta-analysis has demonstrated that dairy product consumption is not associated with CVD [6]. Some studies have even proposed a distinction between dairy and other food sources of SFA based on their different effects on blood lipids [7] and the possible cardioprotective effect of eating fermented dairy products [8].

Modulating milk FA composition through the ruminant feeding, particularly with oilseeds rich in PUFA, has shown to be a valuable tool to improve milk nutritional value [9]. In particular, goat´s milk possesses some inherent properties and a great nutritional quality determined by its lipid composition, which makes it an attractive alternative to developing dairy products with a high added value, like cheese. In this respect, our group developed and characterized a goat cheese naturally enriched in CLA and omega-3 [9] to be further employed in a clinical trial on cardiovascular risk prevention in humans.

Thus, a randomized controlled trial was performed in order to assess the effect of the consumption of that PUFA-enriched cheese in modulating blood lipids (total cholesterol (TC), HDL-C, LDL-C, triglycerides (TAG), apolipoprotein A1 (ApoA1), apolipoprotein B (ApoB), and free fatty acids (FFA), as well as other cardiovascular risk factors, such as inflammatory markers, in overweight and obese subjects.

#### **2. Materials and Methods**

The present study was registered at http://clinicaltrials.gov under the number NCT02630602.

#### *2.1. Subjects*

For the present study, the Clinical Nutrition Department of La Paz University Hospital (HULP) in Madrid (Spain) recruited 68 overweight and obese subjects (52 women and 16 men) between January and March 2014. The inclusion criteria were: aged 18–65 years living in the region of Madrid, Spain; body mass index (BMI) <sup>≥</sup> <sup>27</sup> <sup>&</sup>lt; 40 Kg/m2; to have a CVD risk score <sup>&</sup>lt; 10% [10]; at least two atherogenic risk factors: TAG ≥ 150 mg/dL and <200 mg/dL, TC ≥ 200 mg/dL, HDL-C <40 mg/dL men or <50 mg/dL women, and/or LDL-C ≥130 mg/dL and <160 mg/dL, reflecting a risk for CVD [10]; having a suitable understanding of the clinical trial level; agreeing to voluntarily participate in the study; and signing the informed consent. Exclusion criteria were a diagnosis of diabetes mellitus, chronic degenerative diseases (e.g., liver or kidney), dyslipidemia, mental illness or diminished cognitive function, or the taking of antihypertension or lipid-lowering medication (e.g., statins, omega-3 supplements). Persons with lactose intolerance and dairy protein allergies were not enrolled. Pregnant or breastfeeding

women were also excluded. The participants were individually allocated to one of the two study groups by randomization (Figure 1).

In addition, all groups followed the same balanced hypocaloric diet. All subjects gave their informed consent to take part in the study, which was approved by The Scientific Research and Ethics Committee of the Hospital Universitario La Paz (HULP 4092) and conformed to the ethical standards of the Declaration of Helsinki [11]; authorization for the disclosure of protected health information was obtained from all subjects before protocol-specific procedures. The participants were individually allocated to one of the two study groups, generated by a randomization procedure provided by the Biostatistics Unit of La Paz University Hospital. The allocation ratio of the study groups was 1:1.

#### *2.2. Study Design*

The controlled, randomized, double blind, parallel dietary intervention trial consisted of a 12-week investigation period (84 days). The control group (CG) received 60 g/day of a commercial goat cheese, and the experimental group (EG) received 60 g/day of the goat cheese that was naturally enriched with n-3 PUFA and CLA. Both control and enriched cheeses were produced as described by Santurino et al. (2017) [12]. Immediately after manufacture, the control and enriched cheeses were vacuum packed, refrigerated, and marked to maintain the conditions of blinding. Thus, neither the participants nor the researchers knew to which group the members belonged until the end of the study.

#### *2.3. Dietetic, Physical Activity and Comorbidities' Data*

Balanced hypocaloric and personalized diets were individually prescribed for all participants. An energy restriction of approximately 400 kcal/day was prescribed depending on gender, age, BMI, nutritional habits, physical activity, comorbidities and previous dietary treatments. Dietary intake was recorded using a food frequency questionnaire and a "3-day food and drink record" validated for the Spanish population [13] for computing energy, fat and protein intake. Two weekdays and one weekend day were included in the dietary record to take any differences in nutrient intake during weekdays and weekends into account. This was achieved by guidance from our dietitian. Subjects attended the department to collect the test food and for follow-up every three weeks throughout the intervention period. A questionnaire was fulfilled to collect the current use of medications and supplements, and the presence of relevant previous diseases and a physical activity metabolic equivalent of task (MET) score was determined based on self-reported energy-consuming activities during work, at home, while travelling, and at leisure time based on "Global Recommendations on Physical Activity for Health" by the WHO.

#### *2.4. Anthropometric Variables*

Blood pressure and heart rate were measured three times at 5-min intervals on the right arm using a Welch automatic monitor (Allyn Spot Vital Signs 420 series, Amsterdam, The Netherlands) (accuracy ±5 mmHg). The measurements were taken with subjects sitting, and the means were calculated. Dual-energy X-ray absorptiometry (DXA) was used to measure the total fat mass (TFM (%)), bone mineral density (BMD (g/cm2)), android fat (AF (%)), gynoid (GF), and the lean mass (LM (%)), employing a GE Lunar Prodigy apparatus (GE Healthcare, Madison, WI, USA). Finally, anthropometric measurements as subject composition (TANITA BC-420MA, Biológica Tecnología Médica S.L. Barcelona, Spain), BMI, and waist and hip circumference were measured and recorded while adhering to international norms set out by the WHO.

#### *2.5. Blood Collection*

Blood samples were taken at baseline and at the end of the study period after a 12 h overnight fast at the Extraction Unit of the Hospital Universitario La Paz (Madrid, Spain). Samples were collected early in a 5 ml vacutainer tube with EDTA, and they were centrifuged at 4 ◦C over 7 min at 3500 rpm. Finally, samples were kept at −40 ◦C until analysis. A biochemical serum lipid profile (TC, HDL and

LDL cholesterol, triglycerides, apolipoprotein A1, apolipoprotein B, and free fatty acids), and glucose determinations were performed by an enzymatic-spectrophotometric assay using an Olympus AU 5400 apparatus (Izasa, CA, USA). C-reactive protein (CRP) concentrations were determined using a BNII nephelometer (Siemens Healthcare Diagnostics GmbH, Eschborn, Germany). Tumor necrosis factor-α (TNF-α) and interleukin 6 (IL-6) were determined using a Luminex ®-100 (Luminex Corporation. Texas City, TX, USA) multianalyte profiling system with commercially available immunoassay panels. Total lipid peroxides in plasma were determined as an indicator of oxidative stress by using the thiobarbituric acid reactive substances (TBARS) method21. The results were expressed as μmol MDAeq/mL. Data were analyzed using the xPONENT v.3.1 software (Merck Millipore, Burlington, VT, USA) and were determined using specific protocols of La Paz University Hospital.

#### *2.6. Compliance and Adverse Events*

Compliance was measured at the end of each experimental period using a specific questionnaire, and a subject was considered compliant when he/she consumed the contents of ≥70% of the product. Adverse events were recorded during the experimental periods. An adverse event was defined as any unfavorable, unintended effect reported by a subject or observed by the investigator. All were recorded along with the symptoms involved (nausea, vomiting, diarrhea, halitosis, and/or constipation). No participants showed any signs of intolerance to the supplement of the study diets. Subjects were informed of their right to withdraw from the study at any time.

#### *2.7. Statistical Analysis*

The sample size of 30 subjects in each group was calculated to provide 90% power at a 5% level of significance by the power analysis (nQuery Advisor Release 2.0, Statistical Solutions, Boston, MA, USA) based on LDL-C as a target effect size. The primary outcomes of the study were the changes from baseline to week 12 in the TC, low density lipoprotein cholesterol, and high-density lipoprotein cholesterol. Changes in triglycerides, free fatty acids, lipoproteins apoA-1 and apoB, fasting glucose, fasting insulin, body mass index, waist circumference, and the percent of fat tissue and its distribution assessed by android-to-gynoid fat percent ratio, as well as the total visceral adipose tissue, inflammatory markers (CRP, IL-6, TNF-α, oxidized low-density lipoprotein (OxLDL), and fibrinogen), calcium, phosphate, vitamin D, ghrelin, and leptin were considered as secondary outcomes. Baseline features in the intervention and control group were compared by a t-test (continuous variables) or by a chi-squared test (categorical variables). Changes in the primary and secondary outcomes from baseline to week 12 were defined by the absolute difference of the value of a parameter in week 12 minus the value at baseline. The statistical analysis of not normally distributed parameters were assessed by a Mann–Whitney U non-parametric test. The 95% confidence intervals of the absolute difference of the mean changes between the intervention and control groups were calculated by adjusted bootstrap percentile method after a 1000-replication bootstrap. Statistical calculations were performed in R (R Core Team (2013), Vienna, Austria).

#### **3. Results**

#### *3.1. Recruitment and Study Population*

Eighty possible patients were screened for enrolment in this study, but only sixty-eight met the inclusion and exclusion criteria and were randomized. The participant flow diagram is shown in Figure 1. Nine participants did not finish the study due to personal reasons, refusal to participate further, or relocations. Thus, fifty-nine subjects finished the 12-wk intervention period (control group: 31 subjects; experimental group: 28 subjects); only their data were included in analysis.

*Nutrients* **2020**, *12*, 1315

**Figure 1.** Flow chart describing the present trial.

#### *3.2. Baseline Characteristics*

The baseline characteristics of the fifty-nine subjects who completed the study were found to be comparable between the two groups are described in Table 1. The treatment compliance was high, and no differences were observed between groups (>85% of the scheduled doses consumed in the CG; >87% in the EG; *p* < 0.374) (Table 1).

**Table 1.** Baseline characteristics and anthropometric parameters of the study participants before and after the intervention.


Data are expressed as the means ± SDs. Abbreviations: BMI: body mass index; Waist circ.: waist circumference; BMD: bone mineral density; BP: blood pressure; and HR: heart rate.

#### *3.3. Dietetic and Anthropometric Variables*

In general, the diets followed by the volunteers showed a similar intake of macro- and micro-nutrients. No significant baseline differences in the basal diet were noted among the groups, except for the weekly rations of legumes (*p* = 0.025) and water (*p* = 0.012), which were higher in the EG compared to the CG. Instead, weekly rations of meat (*p* = 0.021) were higher in the CG. Regarding the low number of adverse events reported, no conclusion towards a relationship with a specific intervention could be drawn. There was no significant change in body weight in either treatment group, nor in the BMIs after the 12 weeks of study (*p* > 0.05) (Table 1). Additionally, there were no significant differences between treatments in all the parameters of the DXA analysis, which allowed us to obtain accurate values of the variation of body composition (*p* > 0.05) (Table 1). Regarding the waist circumference, no significant differences were found in the baseline GC and EG values (*p* > 0.05).

#### *3.4. Blood Pressure and Biochemical Variables*

On the other hand, at the end of the intervention period, both systolic and diastolic blood pressure remained within normal values for the general population (120/80 mmHg). Though systolic blood pressure decreased by −5.21 ± 21.35 mm Hg in the EG there were no significant differences among groups, possibly due to intragroup differences, nor were there any significant differences at baseline or after the intervention for 12 weeks (*p* > 0.05) (Table 1).

The subjects' blood lipids and apolipoproteins concentrations before and after intervention are shown in Table 2. At the end of the study, the level of TC increased significantly in the EG in comparison to the CG (*p* > 0.05), despite no significant difference from baseline observed in either group. Even though randomization, there was an imbalance between both groups in baseline HDL-C concentration (*p* = 0.04), with lower baseline HDL-C levels in the EG. However, this result was corrected, and a significant increase of HDL-C in favor of the EG occurred at the end of the intervention. The plasma levels of ApoA1 and ApoB remained within the reference values for the study population throughout the intervention period (Table 2). At the end of the intervention, no changes in ApoA1 levels (related to HDL-C, the most abundant apolipoprotein in plasma, which contributed to a good cardiovascular health [14]) were detected in any group. On the contrary, the plasma concentration of ApoB increased in the EG by the end of the intervention period (Table 2).

Additionally, the increase of TC in the EG could have been related to the significant increase of the HDL content in this group. Conversely, the consumption of cheese in both intervention groups did not significantly affect LDL-C values, leading to a significant improvement in the LDL/HDL ratio, a good lipid indicator of atherogenic risk along with the TC/HDL-C ratio (Table 3).



Data are expressed as the means ± SDs. Statistical analysis was assessed by Mann–Whitney U test. \* Significant difference between groups at week 0 *p* < 0.05. # Significant difference between groups at the end of the intervention period (week 0–week 12) *p* < 0.05. Abbreviations: TC: total cholesterol; HDL-C high-density lipoprotein cholesterol; LDL-C low-density lipoprotein cholesterol; and TAG triglycerides.


**Table 3.** Values of total cholesterol/high-density lipoprotein (TC/HDL), low-density lipoprotein (LDL)/HDL and apolipoprotein B/apolipoprotein A1 (ApoB/ApoA1) ratios before and after the intervention.

Data are presented as mean ± s.d. \* Significant difference between groups before and after the intervention *p* < 0.05. Abbreviations: TC: total cholesterol; HDL-C high-density lipoprotein cholesterol; LDL-C low-density lipoprotein cholesterol; and TAG: triglycerides.

#### *3.5. Inflammation Variables*

Systemic inflammation (TNF-α, IL-6, CRP, and others) is described in Table 4. At baseline, there was no difference between groups in any of these characteristics. After intervention, there was a significant decrease in CRP in the EG by 36%, taking into account the intragroup variation.

Plasma calcium and phosphorous remained within the ranges of normality described throughout the intervention period (Table 5). At baseline, there was no difference between groups in the plasma levels of vitamin D, but there were lower than the reference range for the study population (20–40 ng/mL) in both the CG and the EG, maybe linked to overweight and obesity status [15]. In contrast, at the end of the intervention period, vitamin D plasma levels were found within values considered in the reference range for the study population [16]. There was also no significant change in ghrelin and leptin after the intervention in either group.



Databetween groups at the end of the intervention period (week 0–week 12) *p* < 0.05. Abbreviations: CRP: high-sensitivity C reactive protein; TNF-α: tumor necrosis alpha factor; interleukin 6; oxLDL: oxidized LDL; and FFA: free fatty acids.



Data are presented as mean ± SDs.

#### **4. Discussion**

This study was designed to evaluate the combined effect of a enriched cheese with a balanced hypocaloric diet and physical activity in overweight and obese subjects on cardiovascular risk factors. This diet enriched with n-3 PUFA and CLA did not significantly modify the body composition of either group. The lack of significant differences is in agreement with recent clinical trials in which the consumption of cheese naturally enriched with PUFA did not significantly modify the body composition of both healthy volunteers and subjects with altered lipid profiles [4,17]. Though the difference was not significant between both groups (*p* > 0.05), the reduction of the waist circumference in both intervention groups could be related to the good efficacy of the nutritional intervention and the guidelines for physical activity carried out in both intervention groups, thus decreasing the metabolic risk in relation to waist circumference specified by the WHO (>88 cm in women and >102 cm in men) (Table 1) [18]. These results are in accordance with those obtained in a recent clinical trial in which cheese consumption did not significantly modify anthropometric parameters related to metabolic risk among the different study groups [19]. Lastly, the slight non-significant decrease in heart rate observed at the end of the study in both groups may have been a consequence of weight loss, thus improving an important cardiovascular risk (CVR) factor [20] (Table 1). These results are in accordance with those obtained in a recent clinical trial in which a similar intervention period of 12 weeks has been previously shown to induce significant weight loss [21].

The DXA analysis revealed a baseline value of TFM that exceeded the typical values in overweight people (BMI 25–30 kg/m2) in both intervention groups. Though no significant differences were obtained between treatments, probably due to the low-calorie diet received by all volunteers (*p* > 0.05), at the end of the intervention, both groups had a slightly decreased TFM, AF and GF (Table 1). Recent studies have shown that weight loss and/or muscle mass could lead to a loss of BMD, thus highlighting the importance of a good dietary strategy in the management of overweight and obesity and avoiding the loss of muscle mass by performing regular physical exercise [22]. Consequently, the results showed the good follow-up of the recommendations for the daily performance of physical activity by all volunteers.

Regarding the increase in TC (the sum of HDL-C and LDL-C) in the EG, TC provides limited information about cardiovascular risk, and it is not useful for diagnosing metabolic syndrome [23] because it cannot be associated with a circulating increase in atherogenic lipoprotein concentration [24]. However, the significant increase in HDL-C in the EG after the intervention period was in line with another clinical trial in which hypercholesterolemic volunteers consumed PUFA-enriched yogurt for 10 weeks [25]. Furthermore, de Goede et al. (2015) in a recent review, concluded that the cheese intake as compared to butter might have beneficial effects on certain plasma lipids that are directly related to the antiatherogenic properties of CLA. Though the differences in the LDL-C/HDL-C ratio between the CG and the EG were not statistically significant (*p* > 0.05), the results showed a slight decrease in the atherogenic risk only in the EG at the end of the intervention. These results were in line with a recent study that evaluated the effect of the consumption of a LC n-3-PUFA-enriched cheese on the lipid profile in hypercholesterolemic adults [26]. In the study, no significant differences were found between both groups on plasma TAG (Table 2). This approach is in line with a recent review and meta-analysis where de Goede et al. (2015) concluded that cheese consumption has no effect on TAG levels in humans, and this effect could also be dependent on the intervention time [27]. Furthermore, a recent large review of nine RCT suggests that CLA did not significantly affect TC, TAG, or LDL-C contents [28]. On the contrary, Carrero et al. (2007) [29] supplemented hyperlipidemic volunteers with a milk product containing EPA plus DHA, and they observed a significant reduction in TAG and TC after eight weeks. In terms of increasing the plasma ApoB concentration in the EG, previous studies have reported significant changes in plasma ApoB concentration or even increases when prescribing therapies with LC n-3-PUFA, underscoring the importance of treatment duration to attain consistent results [30]. However, ApoB plasma levels in both groups were in the reference range of Apo B levels in adults, and there were no significant changes in plasma LDL-C levels, so this increase in ApoB levels cannot be considered an increase of cardiovascular risk [31]. The ApoB/ApoA1 ratio reflects

the balance between two processes: the transport of cholesterol to peripheral tissues and the reverse transport to the liver. Due to the results obtained for the ApoA1 and ApoB values in both intervention groups, significant differences between the CG and the EG in the ApoB/ApoA1 ratio between before and after the intervention were not observed, but this ratio slightly increased at the end of the clinical trial in both groups.

Weight loss is associated with reduced levels of pro-inflammatory cytokines responsible for inflammation, such as TNF-α and IL-6 [32]. Though recent studies have shown an increase in TNF-α and IL-6 levels due to the state of inflammation related to overweight and obesity [15], the consumption of 60 g/day of cheese, following a balanced and hypocaloric diet, kept these levels stable at the end of the intervention period (Table 4). These results were in line with those reported by Dawczynski et al. (2013) [7], where the consumption of PUFA-enriched yogurt did not significantly modify the values of inflammation markers studied in overweight and obese volunteers. Similarly, in our study at the end of 12 weeks of supplementation, there was no significant effect in plasma OxLDL, fibrinogen, and FFA compared with the control group, probably due to the wide variability among the volunteers in each group. These results were in line with those obtained by Joseph et al. (2011) [5] in an eight-week crossover clinical trial in which dietary supplementation with CLA-enriched oil did not modify plasma OxLDL values in overweight and hyperlipidemic subjects. Additionally, the plasma CRP concentration increases its levels in response to generalized inflammation, as in the case of overweight and obese individuals [33]. At the end of the intervention, the plasma CRP concentration increased by 37% in the CG, whereas this value, taking into account the intragroup variation, significantly decreased in the EG by 36%. This significant decrease in the plasma CRP concentration only in the EG did not coincide with previous studies in which the consumption of enriched dairy products in FA n-3 did not significantly modify the plasma levels of pro-inflammatory cytokines [33]. The lack of significant changes in levels of CRP has been also attributed to the duration of the intervention. Additionally, the reduction in CRP levels could be directly related to weight loss, decreasing 0.13 mg/dL CRP per kg of weight lost [33]. The consumption of FA n-3 increases their concentration in blood, cells, and tissues, and it alters the physical properties of cell membranes and the function of membrane proteins. FA n-3 is incorporated into cell membranes in competition with n-6 FA and AA. Considering that the replacement of n-6 FA with n-3 FA in membranes of the immune active cells may induces leucocytes to produce pro-inflammatory processes and lead to the reduced formation of pro-inflammatory compounds, the significant changes of plasma CRP levels in overweight and obese subjects only in the EG could have been due to the synergistic effect among the anti-inflammatory effect of the consumption of dietary FA n-3 and CLA, weight loss, and the consumption of a balanced diet, together with regular physical activity.

Calcium and phosphorus interact in numerous processes of the organism. Blood calcium values considered normal for a studied population are usually between 8 and 10.5 mg/dL, as well as between 2.4 and 4.5 mg/dL for phosphorus. For the population under study, the normal blood calcium and phosphorus values ranged between 8 and 10.5 mg/dL and between 2.4 and 4.5 mg/dL, respectively. In regards to vitamin D (which regulates mineral homeostasis, protects the integrity of the skeleton, and modulates cell growth and differentiation in a wide variety of tissues [34]), although there were no significant differences between both groups, the baseline levels of vitamin D in both the GC and the EG were lower than those considered normal for the study population (20–40 ng/mL), and this may be linked to overweight and obesity status [35]. On the other hand, hormonal regulators of satiety, such as ghrelin and leptin, are also related to body weight. Though no significant changes were seen in terms of intervention time and treatment group at the end of the clinical trial, an intragroup analysis revealed a slight decrease in leptin levels in both the GC and the EG. These results were expected after the hypocaloric diet and the consequent weight loss in both groups, as well as changes in the blood lipid profile [36].

#### **5. Conclusions**

Overall, the consumption of 60 g/day of cheese (both control and enriched), within the context of a balanced hypocaloric diet and recommendations for physical activity, was effective for the reduction of body weight, BMI and waist circumference in both the CG and the EG. Additionally, the healthy habits carried out by all subjects resulted in a slight decrease in heart rate, as well as maintenance of the BMD, resulting in a decrease in CVR.

On the other hand, the significant increase of HDL and the significant decrease in blood levels of CRP in the EG improved the plasma lipid profile and the inflammatory status, thus producing a decrease in the atherogenic risk. Therefore, the consumption of this PUFA n-3 and CLA naturally enriched goat cheese could have a potential role as a high nutritional value food to improve the state of health.

**Author Contributions:** Conceptualization, B.L.-P. and C.G.-C.; Methodology, L.M.B.; Formal analysis D.G.-A. and B.L.P.; Investigation, B.L.-P., L.M.B., C.G.-C., and C.S.; Resources, M.V.C.; Data curation, C.S.; Writing—Original draft preparation, C.S. and J.F.; Writing—Review and editing, J.F., B.L.-P., C.G.-C., and C.S.; Visualization, J.F.; Supervision, C.G.-C. and M.V.C.; Project administration, B.L.-P., J.F., and C.G.-C. All authors have read and agreed to the published version of the manuscript.

**Funding:** This study was supported by the LODYN S.L. group through the Centre for the Development of Industrial Technology CDTI of Economy and Competitiveness Ministry of Spain (MINECO).

**Acknowledgments:** We thank LODYN S.L. for the manufacture and supply of the experimental and control cheeses.

**Conflicts of Interest:** The authors declare no conflicts of interest.

#### **References**


© 2020 by the authors. Licensee MDPI, Basel, Switzerland. This article is an open access article distributed under the terms and conditions of the Creative Commons Attribution (CC BY) license (http://creativecommons.org/licenses/by/4.0/).

## *Article* **Dairy Products Quality from a Consumer Point of View: Study among Polish Adults**

#### **Marta Sajdakowska \*, Jerzy G ˛ebski, Dominika Guzek, Krystyna Gutkowska and Sylwia Zakowska-Biemans ˙**

Department of Food Market and Consumer Research, Institute of Human Nutrition Sciences, Warsaw University of Life Sciences (SGGW-WULS), 159C Nowoursynowska Street, 02-787 Warsaw, Poland; jerzy\_gebski@sggw.edu.pl (J.G.); dominika\_guzek@sggw.edu.pl (D.G.); krystyna\_gutkowska@sggw.edu.pl (K.G.); sylwia\_zakowska\_biemans@sggw.edu.pl (S.Z.-B.) ˙ **\*** Correspondence: marta\_sajdakowska@sggw.edu.pl; Tel.: +48-225-937-145

Received: 10 April 2020; Accepted: 19 May 2020; Published: 21 May 2020

**Abstract:** The aims of the current study were (a) to deepen the understanding of food quality from animal origin with particular emphasis on dairy products, including yoghurt; (b) to determine the level of acceptance of methods and ingredients used to enhance the quality of food from animal origin; (c) to identify how the perception of animal products quality affects the acceptance of changes in production methods and (d) to identify the projective image of consumers purchasing high-quality yoghurt. The data were collected using a CAPI (Computer Assisted Personal Interview) survey on a sample of 983 consumers. The k-means clustering method (k-means clustering algorithm is an unsupervised algorithm that is used to segment the interest area from the background) was used to identify five clusters of consumers. Moreover, the logistic regression models were used in order to examine the impact of opinions related to the quality of product on acceptance of food production methods. The results showed that food quality is generally perceived by consumers using the following attributes: its freshness, naturalness, production method, as well as appearance, taste and smell, but when it comes to the quality of food from animal origin, convenience, connected with the availability, nutritional value and health benefits is of primary importance. The most accepted production method of high-quality food is animal production that takes into consideration the welfare of farm animals. Results also show that the increase in the level of education among the surveyed people contributed to the acceptance of ensuring welfare of farm animals as a method of increasing food quality while consumers openness to new products favored the acceptance of adding health-promoting ingredients to livestock feed. As regards the assessment of the level of acceptance of enhancing food with beneficial ingredients, people for whom health aspects were important declared their willingness to accept such a method of increasing food quality. The research findings can be used to develop educational campaigns as well as marketing communication of enterprises operating on the food market. Furthermore, the results could be used to strengthen the competitive position of food enterprises searching for innovative solutions.

**Keywords:** consumer; quality; animal-derived food; yoghurt

#### **1. Introduction**

Consumers take various factors into consideration when choosing food; they include taste and freshness as well as naturalness [1,2]. In addition to taste, smell, freshness and naturalness of the product, the following factors also affect consumer choices: the method of food production and processing, ensuring welfare of farm animals and maintaining the health values of food, especially for consumers for whom it is most crucial [3,4]. Moreover, results of studies also indicated that relative advantage, naturalness, novelty and discomfort are the most important factors of the perception of some innovative food products [5]. The literature showed that from a consumer perspective, among other factors, food selection factors are seen as food quality [6–8]. This also applies to dairy products [6,7]. The results of studies confirm that consumers take into account a number of attributes associated with quality, so they expect the product to be safe, natural, healthy and generally of high quality [9]. Furthermore, some consumers underlined the role of quality signs, particularly in the field of positioning origin and organic products in the segment of premium prices, emphasizing the authenticity of these products [10].

Moreover, when it comes to functional food, consumer acceptance was also analyzed from the perspective of consumer quality perception of food products. Functional foods provide, from the consumers perspective, synergies between healthiness and convenience but may, in the consumers opinion, lead to trade-offs between healthiness on the one hand and taste and naturalness on the other hand [11].

The results of studies showed that acceptance of functional dairy products increases among consumers with higher diet/health-related knowledge, as well as with ageing. General interest in health, food-neophobia and perceived self-efficacy seem also to contribute to shaping the acceptance of functional dairy products [12]. Furthermore, products with "natural" matches between carriers and ingredients have the highest level of acceptance among consumers [12,13]. A review by Kaur and Singh indicated that a high level of education and high income greatly influence consumer uptake of functional food, as well as an increased personal health consciousness [14]. Furthermore, results of the research indicate that health benefits and ingredient naturalness are positively valued, but such preferences and valuations depend on an individual s education, income and food purchase behaviors; thus, naturally occurring nutrients are preferred over fortification [15].

As earlier mentioned, taking into account food safety and food naturalness, the method of food production is also a crucial point. When it comes to the method of food production, including animal welfare-friendly methods, the results of studies among European consumers indicate that public perceptions of farm-animal welfare represent a potentially important driver of consumption behaviors by European consumers [16]. However, some Europeans currently do not think there is sufficient choice of welfare-friendly animal food products in shops and supermarkets [17]. In addition, there is an increasing need to develop policies pertaining to animal production diseases, sustainable intensification and animal welfare, which incorporate consumer priorities as well as technical assessments of farm animal welfare. Consumers may have concerns about intensive production systems and whether animal production disease pose a barrier to consumer acceptance of their increased use [18].

With reference to yoghurt, its nutritional content varies depending on the processing method and the ingredients used. Similar to milk, it is a good source of protein and calcium and may be a source of iodine, potassium and B vitamins [19]. Moreover, some dairy products are fortified with vitamin D [20]. Furthermore, during the past years, interest in yoghurt manufacture has increased for scientific and commercial reasons [21]. Additionally, the functional food market has experienced a tremendous level of growth particularly in yoghurt in the last couple of decades, due to the ease of incorporating pre- and probiotics [22].

Yoghurt still plays an important role in the human diet today due to its pleasant taste and health benefits [22,23]. Moreover, yoghurt is the most-frequently consumed healthy and nutritious food around the world. Therefore, it offers an appropriate potential to provide nutritious ingredients to human diet [24]. Furthermore, the results of research indicate that with respect to the safety and health effects of food products, the probiotic yoghurt is recommended for consumption [25]. Considering the fast evolution of functional yoghurts either at research stage or marketplace, further development would require an accurate measure of quality, safety and efficacy to meet consumers' expectations on quality and claimable health benefits [26].

Therefore, the aims of the current study were (a) to deepen the understanding of the quality of food from animal origin with particular emphasis on dairy products, including yoghurt; (b) to

determine the level of acceptance of methods and ingredients used to enhance the quality of food from animal origin; (c) to identify how the perception of animal products quality affects the acceptance of changes in production methods and (d) to identify the projective image of consumers purchasing high-quality yoghurt.

#### **2. Material and Methods**

#### *2.1. Data Collection Process*

The sample in our study (*N* = 983) was drawn from the Social Security addresses database and was representative of the national population in terms of age, gender and the region that consumers lived in. The survey was conducted in each of the 16 voivodships in Poland. After drawing the starting addresses, the random route method was used in the selection of the sample [27,28]. A good number of sampling points were drawn with a probability proportional to population size, for total coverage of the country and for population density. In order to achieve this, the sampling points were drawn systematically from each of the "administrative regional units", after stratification by individual unit and type of area. They thus represent the whole of Poland as well as the distribution of the resident population. In each of the selected sampling points, a starting address was drawn at random. Further addresses were selected by standard "random route" procedures from the initial address. In each household, a respondent was drawn at random (following the "closest birthday rule").

The interviews were conducted face-to-face at respondents' homes by a professional market research agency in accordance with the ESOMAR (European Society for Opinion and Marketing Research) code of conduct using the CAPI (Computer Assisted Personal Interview) technique. All respondents were aged 21+. Only those respondents who met the recruitment criteria, i.e., made their own or cooperative food purchases and declared dairy product consumption, participated in the study.

#### *2.2. Description of Questionnaire*

The questionnaire used in the study was structured in a few main blocks and covered aspects such as consumer opinion towards: (1) the quality of food, including quality of animal origin food and (2) production methods of animal origin food, formulated into various types of questions:

	- (I) *Below are statements describing food of animal origin. For each statement, how much you agree are indicated on a 1–7 scale, where 1 is the lowest level of compliance and 7 is the highest level of compliance; High-quality animal food is food (1) with the right taste and traditional recipe; (2) preservative free and with a short shelf life, (3) having nutritional value and health benefits, (4) produced in an environmentally friendly area, including taking into account production ensuring welfare of farm animals, (5) of low processing level*/*derived from an organic production method, (6) which is easy to prepare and easily available in a wide range;*
	- (II) *Please indicate how much you agree with the following statements. Please provide answers on a scale of 1–7, where 1 means "strongly disagree" and 7 means "strongly agree"; (1) I buy dairy products because they have a positive e*ff*ect on my figure, (2) I buy dairy products because they have a good e*ff*ect on my children's health, (3) Quality is important to me when choosing dairy products, (4) I buy dairy products for those members of my family who have health issues;*

#### *2.3. Data Analysis*

Referring to analysis of the results collected using the open question, the χ<sup>2</sup> test was applied in order to determine statistically significant differences between the variables (part A of the questionnaire). Moreover, the k-means clustering method was used to identify segments of consumers. In the k-means method (k-means clustering algorithm is an unsupervised algorithm that is used to segment the interest area from the background), in order to increase its efficiency, the average values for individual clusters obtained using the hierarchical method were used as seeds. The statements about the characteristic of food of animal origin were used as segmentation variables (part B I of the questionnaire; Table 1).

Five well-separated clusters were obtained, which was confirmed by both statistics assessing the selection of clusters such as CCC (Cubic Clustering Criteria), pseudo T2 or ANOVA (Analysis of Variance) statistics comparing the average values of variables for individual clusters. Socio-demographic variables such as gender, age, education, subjective assessment of the financial situation and size of the place of residence were used to profile the clusters. The independence χ<sup>2</sup> test was used to assess the diversity of profile features between clusters.

In all statements analyzed, statistically significant (*p* < 0.05) differences between mean scores particularly clusters have been observed. Additionally, post-hoc test (Waller–Duncan K-ratio *t* Test) was used to compare mean values of opinions between pairs of clusters.

As mentioned, the segmentation analysis made it possible to identify five consumer segments. Clusters have been named according to consumers opinions towards statements referring to high quality food of animal origin (Table 1):



**Table 1.** Statements used as segmentation variables regarding the characteristics of high-quality products of animal origin.

One-Way ANOVA (Analysis of Variance), *p* < 0.05; a, b, c, d, e—Means with the same letter are not significantly different in Waller-Duncan test.

In the second step of data analysis, logistic regression was performed to determine how the perception of animal products quality impacts on:


Due to the dichotomous nature of dependent variables (accept/not accept), logistic regression models were used [29,30], where dependent variables (regressants) were declarations regarding the acceptance of the above-mentioned 3 methods, and explanatory variables (regressors) were opinions about yoghurts and dairy products expressed in questions, i.e.,: *How much do you agree with the statements describing the quality of dairy products, Who do you think is the most willing to buy high-quality yoghurt? Do you think the content of the ingredients listed below should be increased in dairy products?* The models were built with a stepwise selection of explanatory variables. Only statistically significant variables at the significance level α = 0.05 were included in the models. The statistical analysis was carried out using IBM SPSS Statistics, version 25.0 (IBM Corp., Armonk, NY, USA) and SAS 9.4 statistical package (SAS Institute, Cary, NC, USA).

#### **3. Results**

#### *3.1. Profile of the Total Sample and Perception of Food Quality*

The detailed socio-demographic characteristic of the sample and segments identified is included in Table 2.




**Table 2.** *Cont.*

**\*** Differences between groups not significant (χ<sup>2</sup> test, *p*-value > 0.05).

Results of the study show that the quality of food of animal origin is connected with the ease of preparation, availability, as well as nutritional value and health benefits (Table 1), but when it comes to the food quality in general, it is perceived by consumers mainly through the following attributes: its freshness, naturalness, production method, as well as appearance, taste and smell (Table 3).


**Table 3.** Attributes describing food quality in consumer reviews (%).

Test of independence χ<sup>2</sup> *p* < 0.05.

Results also show (Tables 2 and 3) that in segment No. 1 ("Convenience-oriented"; *N* = 208; 21%) the largest share of opinions indicate that the quality of food of animal origin is evidenced by its naturalness, production method, but also its freshness. This segment was characterized by the largest share of middle-aged people (45–54 years).

In segment No. 2 ("Uninvolved"; *N* = 172; 18%), the largest share of the food quality is reflected in its freshness, naturalness and the production method. This segment had a relatively high share of people with low levels of education.

In segment No. 3 ("Health-oriented"; *N* = 218; 22%), the highest share of answers indicating that the quality of food is reflected in its freshness was recorded. There was also a relatively large share of opinions indicating that the quality of food of animal origin is reflected in its naturalness and production method. The additional attribute of food quality that was mentioned by people was lack of preservatives in the product.

In segment No. 4 ("Particularly demanding in terms of quality"; *N* = 159; 16%), there was a relatively large share of opinions indicating that the quality of food of animal origin is reflected in its composition and nutritional values as well as appearance, taste and smell. The segment had the largest share of indications that the determinant of food quality is its price. This segment had the relatively high share of people with low levels of education.

In segment No. 5 ("Neutral but valuing food quality"; *N* = 226; 23%), among the indications characterizing the quality of food of animal origin, mainly its freshness, naturalness, method of production as well as the aspects referring to composition and nutritional value of food were mentioned.

#### *3.2. Methods of Improving Quality of Animal Origin among The Clusters of Consumers*

The results show that among the methods of increasing the quality of food of animal origin, consumers scored the highest for the production method ensuring welfare of farm animals compared to the other two methods. Comparison of the segments show that respondents from segment No. 3 ("Health-oriented") displayed significantly lower acceptance, compared to other segments regarding the method of adding health-promoting ingredients to livestock feed (Table 4).

**Selected Methods of Increasing Food Quality Mean Convenience-Oriented***N* = **208; 21%1 Uninvolved** *N* = **172; 18% 2 Health-Oriented** *N* = **218; 22% 3 Particularly Demanding in Terms of Quality** *N* = **159; 16% 4 Neutral But Valuing Food Quality** *N* = **226; 23% 5** *p***-Value** Animal production ensuring welfare of farm animals 5.90 6.21 a 6.32 a 6.18 a 5.13 c 5.60 b <0.0001 Adding health-promoting ingredients to livestock feed 4.14 4.32 a 4.35 a 3.39 b 4.43 a 4.35 a <0.0001 Enhancing food products with health-promoting ingredients at the processing stage 3.85 3.89 b 4.21 b 2.84 c 4.61 a 4.00 b <0.0001

**Table 4.** The level of acceptance of methods to increase food quality of animal origin in the opinion of respondents.

One-Way ANOVA, *p* < 0.05; a, b, c—Means with the same letter are not significantly different in Waller–Duncan test.

In addition, scores on production ensuring welfare of farm animals by respondents in segment No. 5 ("Neutral but valuing food quality") was significantly lower compared to consumers in segments 1, 2 and 3, while respondents from segment No. 4 significantly displayed lower acceptance of this type of production compared to other segments. Scores on enhancing food products with health-promoting ingredients at the processing stage by respondents from segment No. 4 ("Particularly demanding in terms of quality") was significantly higher compared to other segments, and respondents from segment No. 3 ("Health-oriented") had significantly lower acceptance of this type of enrichment compared to other segments (Table 4).

Regarding the increase of some ingredients in dairy products, live bacterial cultures and cholesterol lowering ingredients were the most important types of ingredients that should be increased in the consumers opinion in dairy products (Table 5). Consumers in segment 2 ("Uninvolved"), which was also significantly higher compared to segments 3, 4 and 5, agreed that the content of cholesterol-lowering ingredients should be increased in dairy products. "Uninvolved" also declared a significantly higher level of acceptance compared to other segments, in terms of increasing the content of live bacterial cultures and coenzyme Q10 in dairy products. In the case of increasing the content of minerals and increasing the fiber content in dairy products, the "Uninvolved" significantly agreed with this opinion in comparison to "Health-oriented" and "Particularly Demanding in Terms of Quality". On the other hand, "Health-oriented" segment displayed the lowest degree of acceptance with regards to increasing the level of Omega-3 acid, proteins and Coenzyme Q10 in dairy products compared to other segments (Table 5).


**Table 5.** Consumers opinion on increasing in dairy products the level of ingredients that have a positive impact on health.

One-Way ANOVA, *p* < 0.05; a, b, c—Means with the same letter are not significantly different in Waller–Duncan test.

The next part of the study was aimed at determining the image of consumers of high-quality yoghurt (Table 6). Respondents perceived consumers of high quality yoghurts referring to two main aspects: (1) health and (2) physical activity.


**Table 6.** Projective image of high-quality yoghurt consumers.

One-Way ANOVA, *p* < 0.05; a, b, c—Means with the same letter are not significantly different in Waller–Duncan test.

Respondents from segment No. 4 ("Particularly demanding in terms of quality") in the least degree compared to the other segments agreed with the opinion that such consumers are people who can be characterized as: doing sports, young people, as well as people with abnormal intestinal motility and people who are particularly health-conscious.

#### *3.3. Impact of Selected Attributes on Methods of Improving Quality of Animal Origin Food*

In the next stage of the study, the extent in which consumers would accept 3 methods aimed at increasing the level of food quality was assessed.

The rise in the acceptance of opinion that the content of live bacterial cultures in dairy products should be increased resulted in a 47% increase in the willingness of accepting production ensuring welfare of farm animals (OR: 1.47; 95% CI: 1.14–1.90), while maintaining other model parameters at a constant level. The level of education had an impact on the acceptance of production, ensuring the welfare of farm animals. The higher the level of education, the greater the willingness of this acceptance. This willingness in the case of people with secondary education increased four times compared to people with primary education (OR: 4.06; 95% CI: 1.82–12.93). In the case of higher education, the willingness of acceptance increased more than 10-fold (OR: 10.25; 95% CI: 1.95–22.49) in relation to people with primary education (Table 7).


**Table 7.** Prediction of the acceptance of production ensuring welfare of farm animals.

e<sup>β</sup> (OR)—point estimate; β—estimate; 95% Wald CI—95% Wald confidence interval.

The rise (by 1 point) in acceptance of the opinion that the content of minerals in dairy products should be increased resulted in a 21% increase in the willingness of acceptance of adding health-promoting ingredients to livestock feed (OR: 1.21; 95% CI: 1.06–1.37). The rise in importance of the opinion that high-quality yoghurts are bought by people involved in sports resulted in a 27% decrease in willingness of acceptance of adding health-promoting ingredients to livestock feed (OR: 0.73; 95% CI: 0.58–0.91). The increase in the rank that high-quality yoghurts are bought by those looking for novelty foods increased by 19% compared to the willingness of acceptance of adding health-promoting ingredients to livestock feed (OR: 1.19; 95% CI: 1.02–1.40). People declaring that quality is important to them when choosing dairy products showed a 19% lower willingness of accepting the addition of health-promoting ingredients to livestock feed (OR: 0.81; 95% CI: 0.65–0.99) along with increasing the rank of this opinion by 1 level (Table 8).


**Table 8.** Prediction of acceptance of adding health-promoting ingredients to livestock feed.

e<sup>β</sup> (OR)—point estimate; β—estimate; 95% Wald CI—95% Wald confidence interval.

The rise in importance of the opinion that the content of cholesterol-lowering ingredients should be increased in dairy products resulted in a 29% increase in the willingness to accept enhancing food products with pro-health ingredients at the processing stage (OR: 1.29; 95% CI: 1.13–1.47). Obviously, while maintaining the remaining model parameters at a constant level. The increase in the rank referring to opinion that high-quality yoghurts are bought by the professionally active individuals resulted in a 30% decrease in the level of acceptance of enhancing food products with pro-health ingredients at the processing stage (OR: 0.70; 95% CI: 0.56–0.86). The increase in the rank of the opinion that high-quality yoghurts are bought by people with abnormal intestinal motility gave a 31% greater willingness of accepting enhancing food products with health-promoting ingredients at the processing stage (OR: 1.31; 95% CI: 1.06–1.60). Similar results were seen in the responses that high-quality yoghurt is bought by those looking for price bargains. In this case, the willingness of accepting enhancing food products with health-promoting ingredients at the processing stage increased by 24% (OR: 1.24; 95% CI: 1.08–1.41). The willingness to accept enhancing food products with health-promoting ingredients at the processing stage decreased by 26% in the case of persons agreeing with the opinion that quality is important for them when choosing dairy products (OR: 0.74; 95% CI: 0.60–0.90). The rise in the rank of the opinion that *I buy high-quality dairy products for those family members who have health issues* resulted in a 17% increase in enhancing food products with health-promoting ingredients at the processing stage (OR: 1.17; 95% CI: 1.04–1.33) (Table 9).

**Table 9.** Prediction of acceptance of enhancing food products with health-promoting ingredients at the processing stage.


e<sup>β</sup> (OR)—point estimate; β—estimate; 95% Wald CI—95% Wald confidence interval.

#### **4. Discussion**

The study presents the results of a survey on a representative sample of consumers. The analysis of the obtained results indicated that the quality of animal origin food with particular emphasis on dairy products is of great importance to consumers, and they are willing to accept new methods of production and ingredients in dairy products.

#### *4.1. The Food Quality from a Consumer Point of View*

Our study revealed that the consumer's perception of food quality differ among segments. Furthermore, the high-quality products of animal origin were perceived by consumers in various ways depending on the segment, so the results are consistent with previous studies stating that understanding the personal and context specific influences on consumer quality perceptions is important in developing products that meet consumer needs [31].

In general, referring to the aspect of food quality, the results showed that taking into account the consumer segments, consumers in segment No. 4 ("Particularly demanding in terms of quality") slightly agreed with the opinion that the group of people buying yoghurts perceived as high-quality yoghurts includes people involved in sports, young people, people with abnormal intestinal motility and those concerned about their health. Analysis of the research findings showed that consumers in segment 2 ("Uninvolved") showed high levels of indications in terms of increasing the level of health-promoting ingredients, which may suggest that despite a relatively indifferent position on food quality compared to other consumer segments, these people were interested in increasing the amount of selected ingredients, and at the same time, it may prove that consumers expect producers and processors to take appropriate action on their behalf to improve their health. This is reflected in the studies by other authors, which emphasized the importance of health as a value influencing the acceptance of specific type of food [32]. Moreover, referring to milk products, the totality of available scientific evidence supports the fact that intake of milk and dairy products contributes to meet the nutrient recommendations and may protect against the most prevalent chronic diseases, whereas, very few adverse effects have been reported [33]. Furthermore, lactose malabsorption is widespread in

most parts of the world, with wide variation between different regions and an overall frequency of around two-thirds of the world's population [34].

#### *4.2. The Acceptance of Production Ensuring Welfare of Farm Animals*

Our study assessed the level of acceptance of methods used to increase the food quality and selected factors that may affect the level of this acceptance among consumers. In general, animal welfare is the credence quality attribute [7] that is of great interest to consumer. The results showed that the increase in education contributed to the acceptance of production ensuring welfare of farm animals as a way of increasing the level of healthy ingredients in food. The results of other studies indicate that individuals involved in health and/or sustainable eating are more likely to be better educated than those who are not involved [35]. This may be due to a greater awareness of ensuring adequate welfare of farm animals (and/or probably due to the sensitivity of this group of people to animal suffering) [36]. Results also show that the use of appropriate production ensuring welfare of farm animals as a method of increasing food quality is also accepted by consumers who willingly accept increasing the content of live bacterial cultures in dairy products. This can be associated with the positive consumer perception of yoghurt through the aspect referring to health issue, which is confirmed by the studies of other authors [26,37].

The results of other studies indicate that consumers with a higher income and higher education were willing to pay more for farm animal welfare [38]. The results of studies revealed also that referring to animal welfare, the provision of additional information significantly increased the intention to purchase higher than the conventional welfare products. The empathy measures revealed that younger participants, females and those with lower household incomes all had significantly higher AES (Animal Empathy Score). Moreover, this score was associated with the intent to purchase higher welfare products [39]. However, some studies showed that consumers are, in general, unaware about welfare issues at the farming level [40,41]. In addition, an analysis of the results of surveys performed under Euro barometer 2019 [42] indicated that the most important factors for Europeans when buying food are where the food comes from (53%), cost (51%), food safety (50%) and taste (49%). Nutrient content is considered slightly less important (44%), while ethics and beliefs (e.g., considerations of animal welfare, environmental concerns) rank lowest in importance (19%) [42]. However, Vanhonacker and Verbeke [43] noticed that the role of information on animal welfare as well as the type of consumer to whom this information is presented is important when making purchasing decisions. Moreover, in their opinion, the issue involves acknowledging that not everyone has the same level of interest in animal welfare or in purchasing higher welfare products. Furthermore, not all individuals with an interest in higher welfare products share the same motivation. Information sharing should thus be adjusted to specific target segments [43]. On the other hand, the results of more recent research [39] suggest that concern for the welfare of animals farmed for food remains high and continues to grow. Moreover, this research indicates that providing consumers with descriptive signals referring to the welfare condition at the point-of-purchase can boost welfare purchase intentions [39].

#### *4.3. The Acceptance of Adding Health-Promoting Ingredients to Livestock Feed*

The second method of increasing the food quality that was accessed in the survey, was adding health-promoting ingredients to livestock feed. It was observed that consumer acceptance of opinions on increasing mineral components at the same time inclines them to accept adding health-promoting ingredients to livestock feed. The results of other studies showed that in the area of animal nutrition, the opportunity for improving quality is by adding health-promoting ingredients to livestock feed containing additives such as vitamins, vitamin-like compounds, minerals including trace elements, fatty acids, probiotics and other bioactive compounds [44,45].

The results also showed that with the increase in acceptance of novelty on the food market, the level of acceptance of the production method which entails adding health-promoting ingredients to livestock feed increases. This may be associated with generally greater openness to changes in the

food market and a higher level of acceptance of changes in this market in relation to some consumer groups [46]. When it comes to Polish consumers, in general, the new generation of Poles is relatively more open to new food products due to the wide range of food products available on the free market. Furthermore, the group of well-educated consumers with a higher level of income has increased in size, and this includes people interested in knowledge of a product's nutritional value and its impact on health [47]. Results showed that people for whom quality was important when choosing dairy products and people doing sports did not accept this method of improving quality, which confirms their special interest in health aspects and possible consequences and/or concerns related to the consumption of this category of food.

#### *4.4. The Acceptance of Enhancing Food Products with Health-Promoting Ingredients at The Processing Stage*

Among various food choice motives, health is thought to be the highly important factor in consumer opinion [3]. Our results showed that with regard to the third method of increasing the food quality, people seeking the possibility of lowering blood cholesterol levels, people who believe that "high-quality yoghurt is bought by people with abnormal intestinal motility" and those who bought yoghurt for members of their families with health issues expressed their willingness to accept increasing the level of ingredients at the food processing stage.

The results of other studies indicated that respondents with a history of familial diseases were more likely than others to have consumed margarine with plant sterol, fruit juices fortified with vitamin C, and breakfast cereals fortified with vitamins and minerals [48]. It was also found in other studies that consumers who considered health, sensory appeal, natural content, and ethicality to be important factors in their food choices and were concerned about their health, considered yoghurts which were reasonably sour, thick, and genuine in flavor to be more pleasant [3]. Results of similar studies among consumers regarding functional food showed that food benefits were more positively evaluated when attached to a more attractive carrier (e.g., yoghurt). Moreover, benefits of improving the body's natural defense system were most favored by all groups of surveyed consumers while benefits about specific diseases were suitable to tailor for certain groups [13]. Generally, our results are consistent with other studies showing that claims referring to prevention of the diseases are accepted by the consumers [49,50].

It should be emphasized, however, that the results of our study showed that consumers paying special attention to quality were afraid of the above-mentioned methods, declaring their low level of acceptance, which may indicate that they believe there are some concerns related to increasing the level of some ingredients or the fear of using selected methods are not well known to them, which may be associated with so-called food technology neophobia [51]. Research shows that the majority of consumers have relatively little knowledge about the technologies used in food production [52]. However, when it comes to advertising and marketing to consumers about new technologies, campaigns that incorporate convenience, naturalness, taste and benefit for the consumer could have a positive impact on consumer food choices, particularly when the message is concise and from trusted sources [53].

#### **5. Conclusions**

The significant role of food quality in decisions taken on the food market, as well as the availability of products with special health benefits, encourages the assessment of consumer behavior in relation to food perceived as the high-quality food and learning about consumer opinions on products that have a positive impact on health.

The results show that in general, food quality is perceived by consumers mainly through the following attributes: freshness, naturalness, production method, as well as appearance, taste and smell, while when it comes to the quality of food of animal origin, convenience connected with availability, nutritional value and health benefits are of primary importance.

The most accepted production method of high-quality food is animal production with respect to the welfare of farm animals. It is a particularly important aspect, because animal welfare is an important element of sustainable development, including food consumption and human diet and can positively contribute to food quality. Results also show that the increase in the level of education of the surveyed people contributed to the acceptance of production, ensuring welfare of farm animals as a method of increasing food quality.

With regard to the acceptance of other methods aimed at increasing the content of health-promoting ingredients, it should be emphasized that consumer openness to new products favored the acceptance of adding health-promoting ingredients to livestock feed. Regarding the assessment of the level of acceptance by consumers of enhancing food with beneficial ingredients at the processing stage, people for whom health aspects were important declared their willingness to accept such a method of increasing food quality.

Moreover, the research findings can be used to develop educational campaigns as well as in marketing communication of enterprises operating on the food market. When it comes to the educational campaigns, there are opportunities to increase the level of consumer awareness referring to animal welfare that is still not considered an issue for many of the Central and Eastern European citizens. Moreover, to strengthen the competitive position of food enterprises, an important point could be the development of the food products labelled with information on animal production, ensuring welfare of farm animals.

In addition, in terms of information on the methods of improving quality communicated to consumers, for some people, the manner in which this information is presented will play an important role, as well as the level of awareness of the recipients to whom it was addressed, and the possible health consequences they perceive. Therefore, the observed impact of the level of education as well as the health benefits of accepting some methods of increasing food quality should be used on the food market. This aspect could be particularly important according to the development of health and nutrition claims.

The present study fills the relevant research gaps regarding enhancing the quality of food from animal origin and explores methods referring to increasing the level of food quality, providing a new perspective to food industry and the scholars. On the one hand, there are some differences regarding the consumer acceptance referring to methods of enhancing food quality. On the other hand, the determinants that impact the level of acceptance are also various. Future research studies should concentrate on investigating and developing the level of consumers' acceptance of new production methods. Nevertheless, it should be noted that our results indicated the main directions regarding the acceptance of the used productions methods as well as designated the possible changes that may be accepted by consumers.

**Author Contributions:** M.S. developed the concept of the study, supervised the survey, interpreted the data and wrote the manuscript. J.G. analyzed the data and contributed to its interpretation. M.S., J.G., D.G., S.Z.-B. and K.G. ˙ were involved in critically revising the manuscript, and have given their approval to the manuscript submitted. K.G. was responsible for funding acquisition and supervision. All authors have read and agreed to the published version of the manuscript.

**Funding:** This research was funded by "BIOFOOD—Innovative, Functional Products of Animal Origin" grant number [POIG.01.01.02-014-090/09] that was co-financed by the European Union from the European Regional Development Fund within the Innovative Economy Operational Programme 2007–2013 And The APC was funded by Polish Ministry of Science and Higher Education within funds of Institute of Human Nutrition Sciences and Faculty of Human Nutrition, Warsaw University of Life Sciences (WULS), for scientific research.

**Conflicts of Interest:** The authors declare no conflict of interest.

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*Article*
