1. Introduction
Meat is a typical source of protein, vitamins, minerals and essential fatty acids required by the human body. The growth in urbanisation and per capita income alters eating patterns, thus increasing the utilisation of animal-derived foods. According to the United Nations Food and Agriculture Organization projections, global meat consumption is expected to increase by up to 0.4 kg per capita by 2028, with developing countries undergoing the fastest growth. Recent years have seen a surge in interest in developing meat and meat products with physiological functions that promote health and reduce disease risk. Therefore, the enrichment of meat products with health-enhancing ingredients are widely studied.
In tropical and subtropical regions, one of the most cultivated and consumed fruit is banana. However, only 12% (w/w) of the plant is considered edible, and banana cultivation and commercialisation produce considerable waste. Furthermore, 38% of the total banana weight is constituted by the banana peel (BP). Often, BP is discarded without further utilization, thus causing environmental an issue and industrial concern.
BP contains various vitamins, minerals, phytonutrients, dietary fibre (DF) and antioxidants [
1]. In addition, several bioactive compounds, such as tannins, phlobatannins, alkaloids, glycosides and terpenoids, could be found in the BP, and they are beneficial in terms of specific pharmacological and biological aspects.
DF is naturally found in cereal, vegetables, nuts and fruits. DF has been demonstrated to deliver health benefit to the human digestive system, such as preventing constipation, absorbing harmful substances in the gut, providing satiety, controlling body weight, and reducing the concentration of glucose and triglycerides in blood. The DF’s recommended daily intake should be at least 30 g a day, regardless of gender [
2]. However, rapid urbanisation has changed the current food intake habit as people are more likely to consume more fast foods and an unbalanced diet, and have an excessive calorie intake [
3]. As a result, most people worldwide are unable to achieve the daily recommended DF intake.
Therefore, the DF supplementation in foods, especially meat products, has been widely studied to provide a solution to increase the DF intake without extensively changing current eating habits [
4]. Moreover, considering the nutritional benefit of a BP, it could be an excellent vehicle to improve the nutritional value of food, especially meat products. From a technological perspective, DF incorporation in meat products offer improved functional properties, such as water and oil binding, and gelling capacity in meat products [
5]. In turn, this incorporation can boost the emulsion stability, viscosity and rheological properties, and sensory aspects, of meat products. The present study aimed to apply BP from two varieties as fibre sources and filler in the production of chicken sausage.
2. Materials and Methods
2.1. BP Flour Preparation
The ripening stage of banana was assigned according to a seven-stage scale (
Table 1) reported in previous studies [
6].
Ripe (stage 7)
M. balbisiana and M. acuminata were selected for this study. The debris was removed by washing before the peel was separated from its pulp with a knife. Next, the peels were treated with a 0.5% (
w/
v) citric acid solution to minimize enzymatic browning. After the solution was drained, the sliced peels were dried for 48 h at 40 °C in a drying cabinet (Thermolite, Malaysia). Then, the peels were ground and screened using 60-mesh screens (250 m).
Table 2 show the proximate composition and total dietary fibre (TDF) of prepared BP flour.
2.2. Chicken Sausage Production
The boneless chicken breast was purchased from Desa Hatchery Sdn. Bhd. The constituents of the sausage (chicken breast, fat, ice water, potato starch, isolated soy protein, sugar, pepper, and salt) were thoroughly mixed with a cutter to obtain a homogeneous mixture, which was then mixed with each BP at three different compositions (2%, 4% and 6% dry matter). Next, the cellulose casing (2.5 cm in diameter) was filled with meat batter by using a sausage stuffer. Two chicken sausages were prepared from each treatment, where each sausage weighed 10 g. Then, the samples were labelled before being steamed for 30 min at 75 °C. Afterwards, the sausages were dipped in cold water at 15 °C for 20 min. Finally, the water was drained, and the sausages were stored in airtight bags at 4 °C.
2.3. Funtional Properties of BP Flour
2.3.1. Water-Holding Capacity (WHC) and Oil-Holding Capacity (OHC)
The methods in [
7] were employed to obtain the WHC and OHC of BP flour samples. The results were expressed follows:
2.3.2. Swelling Power
The swelling power of the BP flours was determined in accordance with [
8]. A 0.1 g sample was heated in 10 mL distilled water for 30 min in a water bath at 60, 75 and 90 °C separately with constant mixing. For 15 min, the samples were centrifuged at 365×
g. The precipitated portion was weighed and calculated using the following equation:
2.3.3. Water Solubility
The method in [
9] was used to determine the solubility of water. Samples (0.5 g) in a 10 mL distilled water were heated in a water bath at 60, 75 and 90 °C separately for 30 min. Then, they were centrifuged at 365×
g for 10 min. The supernatant (5 mL) was separated, dried and weighed using the following equation:
2.4. Functional Properties of Chicken Sausage Added with BP Flour
2.4.1. Texture Profile Analysis
The TA.XT Plus Texture Analyzer was used for texture analysis (Stable Micro System, Surrey, UK) [
10]. Each sample had six replicates in the present study. The samples were standardised in size, measuring 20 mm in height and 25 mm in diameter, and they were compressed to 50% of their original size. Cohesiveness, springiness, stiffness and chewiness were the attributes measured in this study.
2.4.2. Colour
A Konica Minolta chromameter (CR400, Tokyo, Japan) [
11] was used to determine the colour of the samples. Six measurements were taken perpendicularly, with images of the sausage’s various surfaces. CIE L* (lightness), a* (redness) and b* (brightness) were used to represent the values (yellowness).
2.4.3. WHC
WHC was determined using the centrifugation technique with modifications [
12]. A 10 g sample was mixed with 15 mL of 0.6 M NaCl solution and centrifuged for 15 min at 4 °C at 1280×
g inside a tube. The following formula was used to determine WHC:
2.4.4. Rheology
A rheometer (AR500 TA Co., Ltd., New Castle, DE, USA) was used to measure the rheological aspects, which included a measuring temperature of 10 °C in a stainless-steel cone plate with a diameter of 60 mm and a gap width of 2 mm, and a sweep stress test from 0.1 to 100 Pa at 1 Hz frequency. The samples were analysed in triplicate.
2.4.5. Microstructure
The sausage samples were grilled with an electric grill until they reached 71.5 °C and left to cool for 30 min before being refrigerated for 24 h. The samples were then freeze-dried (−50 °C) for 24 h prior to analysis. Scanning electron microscopy (SEM, Carl Zeiss MA10, Oberkochen, Germany) was used to determine the microstructure of the samples which were prepared following [
13]. The working distance ranged from 5 to 9 mm with a working voltage of 15 to 20 kV using a solid-state secondary electron detector and a backscattered electron detector. Observations were conducted under different magnifications (from 100
to 1000
) and the most representative image analysis and micrographs were selected.
2.5. Sensory Profiling
For sensory evaluation, a seven-point hedonic scale was used in this assessment (from 1 = extremely despise, 7 = extremely like). The sausages were sliced evenly and distributed in random order. The sensory panellists were selected among the faculty’s 40 untrained students. The parameters evaluated in the experiment were taste, aroma, appearance, hardness, colour, juiciness and overall acceptability.
2.6. Statistical Analysis
The t-test was used to evaluate the BP flour properties of the two varieties. One-way ANOVA was also used to evaluate the effects of BP on chicken sausage’s physicochemical and sensory properties. The trial was replicated twice (two independent batches), each replication corresponding to a different production day. Data were analysed using SPSS version 24.0 statistical processor software (IBM corp., Armonk, NY, USA). The Tukey test was used to evaluate the significant difference between the means for the various attributes (p < 0.05).