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Article

Chemical Characterization of Cider Produced in Hardanger—From Juice to Finished Cider

by
Ingunn Øvsthus
1,*,
Mitja Martelanc
2,
Alen Albreht
3,
Tatjana Radovanović Vukajlović
2,
Urban Česnik
2 and
Branka Mozetič Vodopivec
2
1
Norwegian Institute of Bioeconomy Research, P.O. Box 115, NO-1431 Aas, Norway
2
Wine Research Centre, University of Nova Gorica, Glavni Trg 8, SI-5271 Vipava, Slovenia
3
Laboratory for Food Chemistry, Department of Analytical Chemistry, National Institute of Chemistry, Hajdrihova 19, SI-1000 Ljubljana, Slovenia
*
Author to whom correspondence should be addressed.
Beverages 2024, 10(3), 73; https://doi.org/10.3390/beverages10030073
Submission received: 24 May 2024 / Revised: 5 July 2024 / Accepted: 23 July 2024 / Published: 13 August 2024
(This article belongs to the Topic Advances in Analysis of Flavors and Fragrances: Chemistry, Properties and Applications in Food Quality Improvement)
Browse Figure
Review Reports Versions Notes

Abstract

:
Our investigation delves into the previously uncharted territory of cider composition from Norway. This study aimed to obtain an overview of the qualitative and quantitative compositions of general chemical parameters, polyphenols (individual and total expressed as gallic acids equivalents), selected esters, and selected C6-alcohols in ciders with the PDO label Cider from Hardanger. In total, 45 juice and cider samples from the fermentation process were collected from 10 cider producers in Hardanger in 2019, 2020, and 2021. Individual sugars, acids, ethanol, and 13 individual phenols were quantified using HPLC-UV/RI. Seven ethyl esters of fatty acids, four ethyl esters of branched fatty acids, ten acetate esters, two ethyl esters of hydroxycinnamic acids, and four C6-alcohols were quantified using HS-SPME-GC-MS. For samples of single cultivars (‘Aroma’, ‘Discovery’, ‘Gravenstein’, and ‘Summerred’), the sum of the measured individual polyphenols in the samples ranges, on average, from 79 to 289 mg L−1 (the lowest for ‘Summerred’ and highest for ‘Discovery’ and ‘Gravenstein’). Chlorogenic acid was the most abundant polyphenol in all samples. Ethyl butyrate, ethyl hexanoate, ethyl octanoate, ethyl decanoate, ethyl isobutyrate, ethyl 2-methylbutyrate, isoamyl acetate, and hexanol were present at concentrations above the odour threshold and contributed to the fruity flavour of the Cider from Hardanger.

1. Introduction

Over the last decade, the consumption of ciders has increased worldwide. Norwegian ciders, especially ciders produced in the Hardanger region, have become popular and have received attention in international cider competitions. The Hardanger region is the leading fruit-growing area in Norway, contributing to approximately 50% of Norwegian fruit production. The typography, with orchards planted in steep hills and a mild coastal climate, makes the Hardanger fjord area suitable for growing fruit at a latitude of approximately 60° N. There are three milestones that are important for the increasing interest in cider from the Hardanger region: (1) in 2003, the Hardanger Cider Association was established; (2) in 2009, Cider from Hardanger became a geographically protected designation of origin; and (3) a change in Norwegian alcohol regulations in 2016, allowed cider producers to sell bottled ciders from the farm. In the period from 2012 to 2022, the sale of Norwegian cider in the state wine monopoly (Vinmonopolet) had a 20-fold increase. In 2023, the total sale of Norwegian cider (including sales at Vinmonopolet, the HORECA market, and farms) corresponded to 550,000 L. The total amount of cider produced in Hardanger sold corresponds to 80% of the total Norwegian sales. In 2023, the production of cider in the Hardanger region was approximately 700,000 L. The goal is to increase cider production to 1 million litres in the Hardanger region by 2025 (personal communication, Anna Gursli Langesæter, Hardanger Cider Association).
The main sensory drivers in cider are phenolics such as flavan-3-ols (catechin and procyanidins); hydroxycinnamic acids (5-caffeoylquinic acid or chlorogenic acid); 4-p-coumarylquinic acid; dihydrochalcones (phloretin); dihydroflavanols, and anthocyanins [1]; as well as organic acids and aroma compounds like esters, higher alcohols, fatty acids, aldehydes, and ketons [2]. In recent years, norisoprenoids have also been confirmed in cider [2]. The sensory profiles and chemical quality of ciders are influenced by various factors, including (1) the apple cultivar; (2) orchard-related agronomic factors; (3) processing technologies; (4) fermentation conditions (alcoholic and malolactic), such as nutrition and temperature; and (5) ageing [2,3,4]. To achieve the cider production target, differentiating the cider and ensuring uniform sensory quality is of importance to increase sales [2]. A comprehensive study [5] analysed sensory profiles of 14 traditional and commercial ciders from Sweden, Denmark, and the UK. The researchers identified unique characteristics in industrially produced and traditionally made ciders, grouping them based on their production technology, including wood ageing, spontaneous fermentations, controlled malolactic fermentation, and industrial production with commercial yeast and addition of other fruit and herb aromas.
Due to the numerous processing steps affecting cider quality, significant variation exists among products from different producers and years. Establishing product differentiation and consistent quality requires identifying the essential chemical composition contributing to the sensory quality in ciders from Hardanger. Unfortunately, limited information is available about the chemical compositions of ciders from both Hardanger and Norway [3,6,7]. To gain a better insight and distinguish Ciders from Hardanger, further research efforts and consistent monitoring are essential. In a groundbreaking 2024 study, researchers compared the general chemical composition of Norwegian ciders, including those from Hardanger, to selected French ciders for the first time. The samples were purchased from wine monopoly stores (Vinmonopolet) in Norway [3]. Notably, the Norwegian ciders were found to be fresher and lighter than their French counterparts, with observed differences in total phenol content and aroma profiles [3].
The Cider from Hardanger is mainly made of apple cultivars produced for fresh consumption in Norway, including ‘Aroma’, ‘Discovery’, ‘Gravenstein’, and ‘Summerred’. Some producers also cultivate specific cider apples and old cultivars. The resulting Norwegian consumer apples are typically low in phenols and high in acids, contributing to a fresh cider style [3,6,8]. A key question is how cultivars and season influence the chemical parameters and diversity of ciders among producers with varying production technologies and accessibility to equipment. In order to gain a deeper insight into the chemical properties of Cider from Hardanger, it is essential to obtain samples from real market producers.
Our goal was to enhance the understanding of the chemical properties of ciders from Hardanger by identifying and quantifying taste-specific compounds present in the juice and final cider samples collected from producers in Hardanger. Juice and cider samples were from various apple cultivars commonly used in Hardanger cider production. Moreover, the collected samples from different producers and seasons show variations of chemical composition in apple juice and ciders produced in Hardanger.

2. Materials and Methods

2.1. Samples

Juice from pressed apple fruits and end-fermented cider were sampled from 10 cider producers in Hardanger (Norway) during the 2019, 2020, and 2021 seasons. The samples were mainly from single apple cultivars ‘Aroma’, ‘Gravenstein’, ‘Discovery’, and ‘Summerred’. However, some samples were from blends of the main cultivars or other cultivars (‘Gravenstein’/‘Elstar’, ‘Gravenstein’/Cider apple, ‘Gravenstein’/‘Signe Tillisch’, ‘Gul Gravenstein’, and ‘Rubinstep’). Samples were collected from cider-makers’ fermentation tanks during the fermentation process. A total of 45 samples were collected and subjected to different chemical analyses. Results in the current manuscript’s tables and figures present chemical properties of juices and end-fermentation ciders of the four main cultivars ‘Aroma’, ‘Discovery’, ‘Gravenstein’, and ‘Summerred’, which were represented by a higher number of samples among the producers, while in Supplementary Materials, we present the whole sampling and chemical database collected. The juice and fermented apple juice were produced according to cider-makers’ ‘in-house’ method. They used different pressing methods (from belt to basket press, with or without enzyme addition); the maturity stage of the apple fruits was different and was not assessed in this experiment (it was determined based on cider producer experience). Some used spontaneous fermentation, and some added commercial yeast. Fermentation temperatures were also different (in the range from 12 to 18 °C). Information about producers and samples is presented in Table 1. Samples (apple juice and cider) were analysed for general chemical compounds at Norwegian Institute of Bioeconomy Research (NIBIO), location Ullensvang (Norway) (total phenols, yeast-assimilable nitrogen (YAN), titratable acidity). Each sample was analysed twice. NIBIO Ullensvang prepared the samples for measuring ethanol, individual sugars, acids, polyphenols, and aroma compounds using high-performance liquid chromatography (HPLC) and gas chromatography (GC) coupled to different detectors (described in later subchapters). These samples (juice and cider) were stored in small dark glass containers at −18 °C at NIBIO Ullensvang before shipment under cold conditions to the University of Nova Gorica, Slovenia. All samples were analysed two months after being sampled from producers.

2.2. HPLC-UV/RI Analysis of Sugars, Acids, Ethanol, as Well as Titratable Acidity

Chemicals for high-performance liquid chromatography (HPLC) coupled to ultraviolet (UV)/refractive index (RI) analysis: glucose (99%) (Acros Organics, Fair Lawn, NJ, USA), fructose (99%) (Acros Organics, Fair Lawn, NJ, USA), sucrose (99.9%) (Acros Organics, NJ, USA), tartaric acid (Alfa Aesar, Karlsruhe, Germany), lactic acid (30%) (Sigma, Steinheim, Germany), D-L malic acid (99%) (Sigma-Aldrich, Steinheim, Germany), and citric acid (99.9%) (Sigma, Steinheim, Germany) as standards. Concentrated sulfuric acid (VI) was purchased from VWR Chemicals (Leuven, Belgium).
HPLC–UV/RI analysis was performed using an Agilent 1100 series HPLC system (Agilent Technologies©, Palo Alto, CA, USA) equipped with Agilent OpenLab CDS ChemStation 2.3.54 software, a UV detector (G1314A VWD) for the analysis of organic acids (detection at 210 nm) and a refractive index detector (model G7162A) for the analysis of sugars (fructose, glucose, and sucrose) and ethanol. Samples were filtered using polytetrafluoroethylene (PTFE) 0.45 µm syringe filters (VWR® International, Radnor, PA, USA). The organic acids were determined using a reversed-phase HPLC-UV method [4]. Glucose, fructose, and sucrose determination was performed using the HPLC method based on hydrophilic interaction liquid chromatography [4], while the assessment of ethanol was performed on a Phenomenex ROA Organic Acid H+ (8%) column with a size of 300 × 7.8 mm with detailed method description published elsewhere [9]. All HPLC quantifications were performed with external calibration in the range of the expected values for the juice and cider samples [4].
Titratable acidity was determined by mixing 1 mL of the samples with 49 mL of distilled water and titrating the sample to pH 8.2 using 0.1 M NaOH (T5 titrator, Mettler-Toledo, Zurich, Switzerland), and the result was calculated as malic acid equivalents (g L−1) [10].

2.3. Enzymatic Determination of YAN

Megazyme L-Arginine/Urea/Ammonia (Rapid) determined via the reaction of amino nitrogen in juice spectrophotometric assay kits (Megazyme, Bray, Ireland) and the Megazyme primary amino nitrogen (PAN) were used to measure yeast-assimilable nitrogen (YAN) in the juice and cider samples according to the manufacturer’s specifications and read on a VWR-UV 3100PC spectrophotometer at λ 340 nm (VWR, Leuven, Belgium).

2.4. GC-MS Analyses of Volatile Compounds

In juice and ciders, we determined selected esters and C6-alcohols using an automatic robotic system for head space (HS) solid-phase microextraction (SPME) combined with gas chromatography coupled to mass spectrometry (GC-MS). The compounds were quantified and identified using validated MS-SPME_GC-MS methods described elsewhere [11].
The samples were extracted using headspace solid-phase micro extraction (HS-SPME) using SPME Fiber Assembly (50/30 μm DVB/CAR/PDMS, Stableflex, 24 Ga, Autosampler, Gray (Supelco, St. Louis, MO, USA)). Into a 20 mL SPME vial, 1 mL of juice and cider samples was added to 2 g of NaCl and 9 mL of deionized water and spiked with 20 μL of internal standard solution. The vials were tightly sealed with a PTFE-lined cap. The solution was then homogenized using a vortex mixer, and the samples were loaded onto a Gerstel MPS Robotic autosampler (CTC Analytics AG, Zwingen, Switzerland). The fibre was inserted into the SPME Arrow Conditioning Module for 2 min at 270 °C. Thereafter, the fibre was inserted into the headspace of the sample vial for 30 min at 40 °C with simultaneous sample swirling at 250 rpm using the Agigator module. Afterwards, the fibre was transferred to the injector for desorption at 250 °C for 15 min. The sample injection time into the GC column was set to 30 s, followed by fibre cleaning in the SPME Arrow Conditioning Module for 10 min at 270 °C.
HS-SPME-GC-MS analyses were carried out on an HP 8890 GC System coupled to a 5977 B GC/MSD quadrupole mass spectrometer (Agilent, Santa Clara, CA, USA) equipped with a Gerstel MPS Robotic autosampler. For quantification, a Mass Hunter Workstation Software (Version 10.1) (Agilent Technologies) was used. Identification of all analysed compounds was performed by comparing the retention times and mass spectra with the pure analysed standards. Library from the NIST Mass Spectral Search Program (Version 2.4, 2020) was also used for additional confirmation of the analysed compounds. For the purpose of quantification of analysed compounds, internal standards were spiked accordingly. Each internal standard was dissolved in ethanol solution separately to obtain a stock solution.
Injections were performed in the splitless mode for 0.5 min, using ultra-inert inlet single taper liner. A DB-WAX UI capillary column (60 m × 0.25 mm × 0.25 μm film thickness, Agilent Technologies, USA) was used, and the carrier gas was helium (H 6.0) with a flow of 3 mL min−1. The oven temperature was programmed at 40 °C for 5 min, then raised to 200 °C at 3 °C min−1, further increased to 240 °C at a rate of 10 °C min−1, and held for 10 min. The mass spectrometer was operated in electron ionization mode at 70 eV with selected-ion-monitoring (SIM) mode.

2.5. HPLC-UV and HPLC-MS Analysis of Phenolic Compounds and Total Phenol Using Folin–Ciocâlteu Method

Total phenols were measured spectrophotometrically using the Folin–Ciocâlteu method following the protocol of Singleton [6]. The juice and cider samples were filtered using syringe filters (MACHAREY-NAGEL GmbH & Co. KG, Düren, Germany), Folin–Ciocalteu reagent (Sigma-Aldrich, Steinheim, Germany) was used in accordance with Singleton et al. [12], and a gallic acid standard (Merck KGaA, Darmstadt, Germany) was used for calibration. All results are expressed as gallic acid equivalents (GAE mg L−1). Total phenol content was determined using a VWR-UV 3100PC spectrophotometer at 765 nm (VWR, Leuven, Belgium).
Quantitative and qualitative analyses of individual phenolic compounds in juice and cider samples were carried out using the HPLC-UV method, employing an Agilent 1100 series HPLC system (described in Section 2.2) at a wavelength of 285 nm for identification (comparisons to the standard compound) and quantification with external curves, prepared with HPLC grade standards from Extransynthese (Genay, France), as listed in Table S1.
Briefly, the studied compounds were separated on a Phenomenex Luna C18(2) HPLC column (150 mm × 2 mm i.d., 3 µm) protected by a guard column. The mobile phase consisted of solvent A, 0.5% acetic acid, and solvent B, HPLC-grade methanol, and the following solvent gradient was applied: 100% A, 0–6 min; 90% A, 6–7 min; 85% A, 7–35 min; 70% A, for 35–53 min; 55% A, 53–68 min; 100% B for, 68.1–77 min; 100% A, and 78–90 min. The flow rate was set to 0.3 mL min−1, the tray and column oven temperatures were maintained at 13 °C and 30 °C, respectively, and 10 µL injections were made for each analysis. Samples were thawed and filtered through a 0.45 µm polyvinylidene difluoride (PVDF) syringe membrane filter prior to analysis. The data from the UV detector were acquired at 285 nm.
Qualitative analysis of phenolic compounds in cider samples was performed using HPLC-UV-MS2. The analytical system consisted of an Accela 1250 UHPLC system (Thermo Scientific, Waltham, MA, USA) coupled with an LTQ Velos MS system (Thermo Scientific, Waltham, MA, USA). This method was adopted according to Ivanović et al. [13] with some modifications. The studied compounds were separated on the same column as for HPLC-UV analysis, the Luna C18(2) HPLC column from Phenomenex (150 × 2 mm i.d., 3 µm), which was protected by a guard column. The mobile phase consisted of solvent A, 0.5% acetic acid, and solvent B, methanol, and the following solvent gradient was applied: 0–6 min (0% B), 6–7 min (0–10% B), 7–35 min (10–35% B), 35–53 min (35–45% B), 53–68 min (45–70% B), 68–68.1 min (70–0% B), and 68.1–88 min (0% B). The flow rate was set to 0.3 mL/min, tray and column oven temperatures were maintained at 13 °C and 38 °C, respectively, and 5 µL injections were used for each analysis. Samples were thawed and filtered through a 0.45 µm PVDF syringe membrane filter prior to analysis. Data were acquired with the PDA detector at 280 nm, and UV-Vis spectra were recorded in the range of 230–600 nm. Ionization of the compounds was achieved with ESI operating in negative mode. The settings for the MS system were as follows: source voltage, 3 kV; source temperature, 325 °C; capillary temperature, 350 °C; sheath gas, 60 arbitrary units (a.u.); auxiliary gas, 10 a.u. The presence of the analytes in the samples was confirmed by comparison of the retention time, targeted MS2 spectra, and UV-Visible (Vis) spectra (where possible) with those of the reference standard materials (Table S2).

2.6. Statistical Analysis

For each cultivar and collection time (juice or finished cider), results are expressed as mean and minimum and maximum values (mean (min–max)) in the tables. The values were calculated using Minitab 20 (version 20, State College, PA, USA) and Microsoft Excel.
Principal component analysis (PCA) was performed using Minitab 20 to evaluate the overall impacts of varieties on the contents of selected volatile aromas.

3. Results and Discussion

3.1. Chemical Composition of Apple Juices and End Fermented Cider of Different Apple Fruit Cultivars

We present the multi-year composition of ciders produced from individual apple cultivars to understand the differences between them.

3.1.1. Acids, Sugars, Ethanol, and YAN

The concentration and composition of the organic acids in the cider affect the pH, taste, and microbial stability. The acids in the finished cider were present in the raw materials; however, their concentrations can change during fermentation by yeasts or malolactic bacteria [14,15,16]. Malic acid content decreased during fermentation for all cultivars (Table 2 and Table S3). Such a decrease is common because of yeast metabolism of malic acid and conversion of malic acid to lactic acid [16]. The latter is also supported by the data in Table 2, showing some extent of malolactic fermentation conversions. In juices, the average titratable acidity (expressed as malic acid equivalent) ranged on average per cultivar from 6 (‘Discovery’) to 8.9 (‘Aroma’) g L−1. The level of titratable acidity decreased during fermentation, likely because of possible chemical transformations and precipitation reactions [17]. After fermentation, the average titratable acidity ranged from 5.2 (‘Discovery’) to 7.2 (’Summerred’) g L−1.
Malic acid is the dominant acid in apples [18]. The malic acid contents in apple juices varied from 2.5 g L−1 (‘Discovery’) and up to 22.1 g L−1 (‘Aroma’). The average concentrations of malic acid in the juice of the four cultivars ranged from low to high in the following order: ‘Discovery’, ‘Summerred’, ‘Gravenstein’, and ‘Aroma’. During fermentation, the content of different acids generally decreases [18]. Malic acid contents were reduced by 53%, 32%, 70%, and 9% on average during the fermentation of ‘Aroma’, ‘Discovery’, ‘Gravenstein’, and ‘Summerred’, respectively. The reduction in malic acid in cider from Hardanger was higher than that found by Whiting et al. [14], who found a reduction of malic acid during fermentation of up to 40%, while Maslov Bandić [16] reported a slight decrease in malic acid in two ciders from Croatia during fermentation. This reduction, as previously mentioned, is the result of many biochemical reactions and yeast assimilation of malic acid. Malic acid can also be reduced by lactic acid bacteria, and the amount of lactic acid produced at the end of fermentation indicates malolactic fermentation, as mentioned previously. The highest measured level of lactic acid in all ciders in the study was over 4.8 g L−1 (‘Aroma’). The reduction in malic acid content reduces the sour taste of the cider [19]. Lactic acid, on average, increased during the fermentation of ‘Aroma’, ‘Discovery’ and ‘Gravenstein’, but not for ’Summerred’ ciders. The citric acid content was low in the monitored samples, which agrees with Maslov Bandić et al. [16]. We also detected small amounts of tartaric acid in all the samples, and no acetic acid.
The main sugars in the juices were fructose, glucose, and sucrose, as expected for apple juice and fruit [9]. In juices of four different apple cultivars (‘Aroma’, ‘Discovery’, ‘Gravenstein’, and ‘Summerred’), the content of glucose, fructose, and sucrose ranged on average, respectively, as follows: 9.8–26.3, 38.8–90.2, and 9.9–38.7 g L−1. Juice of ‘Gravenstein’ and ‘Aroma’ cultivars had the highest level of total sugar, and that of ‘Discovery’ was the lowest (Table 2). The sugar content decreases during fermentation, mainly due to yeast assimilation and translation into ethanol, but also to other metabolites [17]. The yeasts are mainly glucophilic [17], so it is no surprise that end products have more fructose than glucose, regardless of the cultivar or the amount of total residual sugar. Residual sugars (sum of glucose and fructose) ranged on average from 7.9 (‘Summerred’ ciders) to 25.8 g L−1 (‘Aroma’ ciders) in finished cider. Technologies and decisions regarding the target of residual sugars in end-fermented ciders differ among producers.
Chaptalization with sucrose is a traditional technique used in cider production in the Hardanger area to increase the alcohol content to reach 6–7% vol. [6]. Some producers add sucrose before the onset of fermentation, and some during fermentation. This explains the variation of sucrose in juices. In all the final products, the sucrose content was zero (or near zero).
Ethanol ranged in final ciders on average from 7 to 8.5% vol. Naturally present sugars in apple juices from Hardanger that undergo fermentation enable up to 5% natural ethanol, which is in agreement with the theoretical yield of alcoholic fermentation [17]. This is why most of the cider producers, as already mentioned, add sucrose to increase the start density of apple juice and final ethanol contents from 6 to 7% vol. [3,6]. Our study is a case study, focusing on the chemical composition of apple juices and ciders like they are produced in different seasons by real producers. We are, of course, aware that the level of chaptalization was not monitored particularly, and that could have influenced the chemical properties of ciders. However, the study’s findings on the natural compositional variations of Cider from Hardanger remain valid and significant part of the established database.

3.1.2. Total Phenols and Individual Polyphenols

Polyphenols are important for cider colour, stability, taste (bitterness and astringency), and aroma. Processing apple fruits to juice impacts the phenolic content due to the presence of enzymes. This is explained by differences in the extraction of phenolic compounds [20] and the degradation or transformation of phenols through oxidation [21,22,23,24]. Table apples have lower levels of phenols than cider apples [25,26]. The apple fruits produced in Hardanger are mostly table apples, and we already know that ciders from Hardanger have lower amounts of total phenols than French ciders [2]. As evident from Table 3, the single-cultivar juices had total phenol content ranges on average from 198 mg L−1 (‘Summerred’) to 789 mg L−1 (‘Discovery’), determined in gallic acid equivalents using the Folin–Circulate method. These results agree with earlier reports of other Norwegian groups of scientists [27], who found the concentration of total phenols in the juice of cv. ‘Summerred’ to be 272 mg L−1. Table apples have lower levels of phenols than cider apples [25,26]. In the juice from mixtures of Gravenstein and cider apples (Table S4), the total phenol reached 1772 mg of gallic acid L−1. The contents of phenolic compounds analysed using the Folin–Ciocâlteu method showed quantitative changes during fermentation but not the same pattern for all cultivars. The juice with the highest total phenols was from ‘Discovery’ and ‘Gravenstein’, where we observed a similar decrease during fermentation, reaching 496 and 306 mg of gallic acid L−1 in the final ciders, while in ‘Aroma’ and ‘Summerred’, the total phenols did not change. The literature presents various findings regarding changes in phenolic compounds during fermentation. Some studies indicate a decrease in these compounds during fermentation [1,28], while others indicate an increase [16,29]. Our data are in the range of previous findings about Norwegian ciders [6,27] and from the other ciders made from table apples, containing total phenols from 110 mg L−1 up to 706 mg L−1 (expressed as gallic acid equivalents [16,28,30].
In our study, we monitored the contents of 13 individual polyphenols in the collected samples using the HPLC-UV method. The sum of the measured individual polyphenols in the juice ranged from 77 to 269 mg L−1 (the lowest for ‘Summerred’ and highest for ‘Discovery’ and ‘Gravenstein’) (Table 3). The total polyphenols measured using the Folin–Ciocâlteu method are at a higher level than the total polyphenols measured by HPLC. An overestimation of the polyphenol concentration when using the Folin–Ciocâlteu method is well known, as reagents react with other reducing compounds, such as reducing sugars, sulfur dioxides, and proteins [31]. In our samples, there were sugars, which are even more abundant in the juice than in the finished cider.
The main individual polyphenols in the juices and ciders were chlorogenic acid (ranging from 22.3 to 214 mg L−1 in juices and from 10 to 231 mg L−1 in the ciders), followed by catechin, epicatechin, and dimeric procyanidins B1 and B2 (Table 3). This is in accordance with the findings of Maslov Bandic et al., Nogueira et al., and Tsao et al. [1,16,32] who found flavanols (catechin, epicatechin, and procyanidins), hydroxycinnamic acids (chlorogenic acids, 5-caffeoylquinic acid and 4-p-coumaroylquinic acid), dihydrochalcones (phloridzin, phloretin glucoside, and xyloglucoside), flavonols (quercetin glucosides), and anthocyanin (cyanidin galactoside) to be the main polyphenols in apples. The concentrations of chlorogenic acid in our ciders were in similar concentration ranges as those in a Croatian study for Idared and Cripps Pink apple ciders [16]. The average level of chlorogenic acid in ‘Aroma’ and ‘Discovery’ shows a tendency to decrease from juice to cider, most likely due to oxidation or because of hydrolysis into caffeic acid and quinic acid. An increasing trend (on average) was observed for the other two cultivars, ‘Gravenstein’ and ‘Summerred’. This variation appears to be cultivar- and yeast-dependent [1,16]. Changes in caffeic acid have been observed in all ciders (compared to juices) and are in agreement with the literature reporting on increasing trends of caffeic acids during the fermentation of apple juice [1,27], assumably due to the hydrolysis process of chlorogenic acid, as already mentioned before. With respect to juices from the same cultivar, the most obvious increase was observed in the ‘Discovery’ ciders whereas for the other samples, it was not as obvious.
Catechin and epicatechin and their dimeric (B and A types) and trimeric derivatives (C type) contribute to the bitter taste of alcoholic beverages like wine [17,23]. In wines, procyanidins with longer chains of epicatechin, catechin, and their derivatives (up to four subunits) are known to be responsible for a bitter taste, while high molecular tannins (procyanidins with >7 subunits of flavan-3-ols) are responsible for astringency. The main proanthocyanidin was B2, ranging in average from 2.2 mg L−1 in ‘Summerred’ ciders up to 24.9 mg L−1 in ‘Gravenstein’ ciders; similar concentrations ranges (slightly lower) were observed for B1 proanthocyanin (2.8 mg L−1 in ‘Summerred’ and 21.7 mg L−1 in ‘Discovery’ ciders.). The level of catechin seems to be quite stable in all cultivars during fermentation, except for ‘Gravenstein’, where an average increase was observed from the initial 7.9 to the final 15.0 mg L−1. A slightly higher concentration of epicatechin in comparison to catechin was observed in all ciders, but only for ‘Aroma’ can we see the trends of increase during fermentation from the initial 25.7 to 34.2 mg L−1 [1,4].

3.2. Volatile Compounds in Apple Juice and in Cider

In this study, seven ethyl esters of fatty acids, four ethyl esters of branched fatty acids, ten acetate esters, four C6-Alcohols, and two ethyl esters of hydroxycinnamic acids were analysed in juice and finished ciders. The aromatic compounds analysed are listed in Table S5, which include descriptions of odour and odour thresholds from the literature, and the results are presented in Table 4 and Table S6.
To evaluate the overall correlation between the measured volatile aroma compounds and apple cultivars, principal component analysis (PCA) was conducted for juice (Supplementary Materials Figure S1) and finished ciders (Figure 1). The PCA plot shows variation between different samples, indicating that production practice impacts the contents of volatile aromas. However, there is a grouping in the PCA plot. The score plot in Figure 1 shows that ‘Summerred’ has a wide grouping at the top of the score plot, with higher levels of acetate esters (hexyl acetate and isoamyl acetate) and ethyl esters of aliphatic acid (ethyl hexanoate, ethyl octanoate, ethyl decanoate, and ethyl butyrate). Also, some ‘Aroma’ samples have high levels of these esters. In contrast, ‘Gravenstein’ and ‘Discovery’ showed sample clusters in the middle/lower part of the PCA plot with higher levels of hexanol and ethyl isovalerate. One explanation for these wide groupings could be the nitrogen availability from amino acids for the yeasts. Only a few of the cider producers added nitrogen supplements to support fermentation. Nitrogen content and the amino acid profile, which is mainly composed of asparagine, aspartic acid, glutamic acid, proline, and serine in apples [33], are important for ester formations during fermentation [34]. Esters and nitrogen will be a topic for future cider research.
The quantitative headspace results for the esters and C6-alcohols are presented in Table 4. In the juice and ciders of the cultivar ‘Aroma’, ‘Discovery’, ‘Gravenstein’, and ‘Summerred’, the ethyl esters of aliphatic acids ethyl butyrate, ethyl hexanoate, and ethyl octanoate, and the ethyl esters of branched fatty acids isovalerate and ethyl 2-methylbutyrate, were in concentrations over the odour threshold limit (Table 4 and Table S5). ‘Aroma’ and ‘Discovery’ juice and ciders had butyl acetate concentrations above the threshold limit. In addition, isoamyl acetate, ethyl decanoate, ethyl isobutyrate, and hexyl acetate were present at concentrations above the threshold limit in ciders but not in juice for all cultivars. The volatile aroma in the juices is in accordance with other research findings that contribute to the flavour of apples, which is mainly ethyl butyrate, ethyl hexanoate, butyl acetate, hexyl acetate, 2-methylbutyl acetate, and ethyl 2-methylbutyrate [35]. In general, the total ester content increased (e.g., ethyl isobutyrate, ethyl isovalerate, and ethyl cinnamate) or decreased (e.g., E-2-hexenyl acetate and octyl acetate) during the fermentation process. However, some first increased and then decreased (e.g., ethyl butyrate, ethyl hexanoate, ethyl octanoate, ethyl decanoate, and ethyl dodecanoate).
Fatty acid ethyl esters are esters found in the highest concentrations (ethyl butyrate, ethyl octanoate, ethyl hexanoate, and ethyl decanoate). They give a fruity, apple, and sweet flavour (Table 4 and Table S5), and are the result of the esterification process of sugar alcohols with fatty acids during fermentation [36,37]. Among the ethyl esters, ethyl acetate is important for the pleasant and fruity cider flavour at appropriate concentrations [36]; however, this ester was not included in the study.
In this case study, statistical differences in individual esters between the cultivars were not produced because of too many varietal factors in the dataset. However, the trend is that ethyl hexanoate, ethyl octanoate, and ethyl decanoate are highest in ‘Summerred’ cider compared to the other cultivars (as illustrated in the PCA plot, Figure 1). Similar trends between apple cultivars for ciders have also been identified by Hinkley et al. [38]. The increases in ethyl esters during fermentation are many-folded compared to juice and are affected by the apple variety, pH, sugar, nitrogen, and amino acid composition [38]. Different apple cultivars have different chemical compositions and thus different ester precursors. The precursors for different aromatic compounds are amino acids, carbohydrates, and fatty acids [39]. The YAN concentration in ‘Summerred’ was, on average, higher in the juices (70 mg L−1) than that of the other cultivars (23–38 mg L−1) (Table 2). However, further investigation of the amino acid composition is needed to determine the relationship between the YAN/amino acid profile and ester production. The same is true for yeast strains and other technological factors.
The aroma profile of apples is dependent on the degree of maturation. Aldehydes are the most abundant aromatic compounds before maturation, and esters are the main group of aromatic compounds in ripe apples. In our study, the ripeness of apple fruit was not identified as the juice samples were delivered by producers. According to Rosend [40], unripe apple fruits contain isoamyl acetate, hexyl acetate, butyl acetate, and ethyl hexanoate.
C6-alcohols result in a green flavour of cider, and at high concentrations, this can be negative. C6-alcohols are produced during the processing of the fruit via the bioremediation of unsaturated fatty acids, while during fermentation, the C6-alcohol content normally decreases [41]. The hexanol concentrations identified in this study varied a lot between the producers, years, and cultivars. Some increase, some decrease, and some decrease and increase. In apple juice, hexanol is an indicator of ripeness [42].

4. Conclusions

The primary objective of this case study was to investigate the chemical makeup of ciders with the PDO designation Cider from Hardanger by analysing selected chemical parameters in juice and cider samples collected from 10 producers in Hardanger, Norway. We measured high acidity in all ciders, with malic acid being the major one. Cultivars responded differently to fermentation changes in malic acid. Thus, on average, a 70% and 9% decrease in the initial malic acid was observed in ‘Gravenstein’ and ‘Summered’, respectively. The concentration of individual polyphenols varied among single cultivar samples, with chlorogenic acid being the most prevalent. Our data about total phenols in juices and ciders agree with previous findings on differences in the total phenol contents among apple juices and ciders from Hardanger. However, our study showed different changes (an increase or decrease) in total phenols during fermentation among cultivars monitored.
The field sampling involved many sources of variation on selected secondary metabolites, enabling conclusions only as trends. However, to understand the big set of data, we performed a PCA on aroma compounds that are behind the aromatic profile of ciders.
The score plot for apple cultivars showed that the cultivars have a wide range of results, indicating that technological factors (e.g., the chosen yeast strain and temperature) and the seasonal variation of the fruit (e.g., maturity degree, climate, and agronomical factors) impact the composition of esters in ciders. However, ‘Summerred’ showed tight clusters at the top of the PCA plot, indicating that the aroma profiles of ciders from ‘Summerred’ apple have more of the esters hexyl acetate, isoamyl acetate, ethyl hexanoate, ethyl octanoate, ethyl decanoate, and ethyl butyrate than in other ciders. The reason for this difference could be the naturally present sources of nitrogen in the cultivars; however, more research efforts employing controlled experiments are needed to understand and confirm the observed differences. This study found the presence of several ethyl esters and acetate esters at concentrations above the odour threshold, which contribute to the fruity flavour of the ciders.
This research emphasizes the significance of identifying key chemical components that influence the sensory quality of Cider from Hardanger in order to establish product differentiation and consistent quality. Variations in ciders are expected to arise due to factors such as cultivars, production methods, fermentation conditions, and ageing.

Supplementary Materials

The following supporting information can be downloaded at: https://www.mdpi.com/article/10.3390/beverages10030073/s1. Table S1: HPLC-UV calibration curves and concentration ranges of individual polyphenols; Table S2: Targeted MS2 spectra and UV-Vis spectra of standard phenolic compounds; Table S3: Measured values for titratable acidity, acids (malic acid, lactic acid, citric acid, tartaric acid), and sugars (fructose, glucose, and sucrose), ethanol content, and yeast assimilable nitrogen (YAN) for Gul Gravenstein, Rubinstep, and blends of Gravenstein/cider apples, Gravenstein/Elstar, Gravenstein/Signe Tillisch; Table S4: Total phenol content in gallic acid equivalent (GAE mg L−1) and polyphenol profile from HPLC (mg L−1) in apple juice, and finished cider of Gul Gravenstein, Rubinstep, and blends of Gravenstein/cider apples, Gravenstein/Elstar, Gravenstein/Signe Tillisch; Table S5. Odour description and odour threshold from the literature; Table S6: Contents of esters and C6 alcohols in juice and cider of Gul Gravenstein, Rubinstep, and blends of Gravenstein/cider apples, Gravenstein/Elstar, Gravenstein/Signe Tillisch collected i Hardanger in 2019, 2020 and 2021. Figure S1: Principal component analysis loading plot (A) and score plot for cultivars (B) for measured esters and C6-alcohols in the collected samples in 2019, 2020, and 2021.

Author Contributions

Conceptualization. I.Ø. and B.M.V.; methodology. M.M., A.A., T.R.V., I.Ø. and B.M.V.; software. I.Ø.; formal analysis. T.R.V., M.M., U.Č. and A.A.; investigation. I.Ø. and B.M.V.; resources. I.Ø.; data curation. I.Ø.; writing—original draft preparation U.Č., M.M., A.A., I.Ø. and B.M.V.; writing—review and editing. I.Ø. and B.M.V.; visualization. I.Ø.; supervision. B.M.V.; project administration. I.Ø.; funding acquisition. I.Ø. All authors have read and agreed to the published version of the manuscript.

Funding

This research was funded by Vestland Regional Research Fund (RFF Vestland) grant number 299284 and Slovenian Research and Innovation Agency—research programme P1-0005 (Functional food and food supplements).

Data Availability Statement

The data presented in this study are available on request from the corresponding author.

Acknowledgments

The authors would like to thank Marianne Hotle for taking care of the samples at NIBIO Ullensvang.

Conflicts of Interest

The authors declare no conflicts of interest. The funders had no role in the design of the study; in the collection. analyses. or interpretation of data; in the writing of the manuscript; or in the decision to publish the results.

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Beverages 10 00073 g001
Figure 1. Principal component analysis loading plot (A) and score plot for cultivars (B) for measured esters and C6-alcohols in the collected samples in 2019, 2020, and 2021 for ciders. Aroma compounds in bold letters are in concentrations over the threshold limit.
Figure 1. Principal component analysis loading plot (A) and score plot for cultivars (B) for measured esters and C6-alcohols in the collected samples in 2019, 2020, and 2021 for ciders. Aroma compounds in bold letters are in concentrations over the threshold limit.
Beverages 10 00073 g001
Table 1. Overview of the 10 producers from Hardanger (Norway) and samples.
Table 1. Overview of the 10 producers from Hardanger (Norway) and samples.
ProducerVarietyYearSample Type
(Juice-J, Cider-C)		Production System and Production Volume (Litre of Cider)
Producer 1Summerred2019J and CHydropress, steel tank, production volume per year 10,000 L
Producer 2Discovery2019J and CSteel tank, added yeast, production volume per year 5000 L
Gravenstein2019J and C
Aroma2021C
Producer 3Summerred2019J and CBelt press, steel tank, added yeast, production volume per year 7000 L
Gravenstein2019J
Aroma2019J and C
Aroma2021C
Producer 4Discovery2019J and CBelt press, steel tank, spontaneous fermentation, production volume per year 12,000 L
Aroma2021J and C
Gravenstein/ciderapple2019J and C
Gravenstein/Signe Tillisch2019J and C
Gul Gravenstein2021J and C
Producer 5Gravenstein/Elstar2021J and CBelt press, steel tank, spontaneous fermentation, centrifugation, production volume per year 150,000 L
Producer 6Aroma2020J and CBelt press, steel tank, added yeast and yeast nutrition, production volume per year 150,000 L
Summerred2021J and C
Discovery2021J and C
Gravenstein2021J and C
Rubinstep2021J and C
Producer 7Aroma2020J and CPack cider press, steel tank with floating lid, spontaneous fermentation, production volume per year 4000 L
Gravenstein2020J and C
Producer 8Summerred2020J and CBelt press, steel tank, added yeast and nutrition, production volume per year 100,000 L
Producer 9Aroma2020J and CBelt press, steel tank, added yeast and nutrition, production volume per year 130,000 L
Rubinstep2021J
Producer 10Gravenstein2020JBelt press, steel tank, added yeast, production volume per year 60,000 L
Table 2. Mean values for titratable acidity, acids (malic acid, lactic acid, citric acid, and tartaric acid), sugars (fructose, glucose, and sucrose), ethanol content, and yeast-assimilable nitrogen (YAN). The results are presented as mean and minimal to maximal values in brackets.
Table 2. Mean values for titratable acidity, acids (malic acid, lactic acid, citric acid, and tartaric acid), sugars (fructose, glucose, and sucrose), ethanol content, and yeast-assimilable nitrogen (YAN). The results are presented as mean and minimal to maximal values in brackets.
JuiceCider
ParameterVarietyNMean (Min–Max)NMean (Min–Max)
Titratable acidity (g L−1 g of malic acid) Aroma58.92 (6.54–12.8)77.07 (5.19–9.33)
Discovery35.95 (5.20–6.54)35.22 (3.89–6.73)
Gravenstein57.43 (6.14–9.25)35.73 (5.47–5.90)
Summerred47.99 (5.98–9.91)47.20 (7.79–9.05)
Malic acid (g L−1)Aroma513.0 (5.90–22.1)75.61 (0.60–10.7)
Discovery34.38 (2.50–7.15)32.96 (0.70–6.70)
Gravenstein512.5 (6.46–21.6)33.52 (0.10–6.30)
Summerred47.23 (3.72–14.6)46.57 (2.80–11.2)
Lactic acid (g L−1)Aroma50.16 (0.02–0.32)71.11 (0.10–4.81)
Discovery30.17 (0.06–0.36)31.06 (0.06–3.05)
Gravenstein50.16 (0.09–0.32)30.49 (0.04–1.19)
Summerred40.84 (0.04–3.03)40.77 (0.02–2.80)
Citric acid (g L−1)Aroma50.09 (ND–0.14)70.17 (0.05–0.60)
Discovery30.02 (ND–0.07)30.05 (ND–0.10)
Gravenstein50.14 (0.09–0.20)30.20 (ND–0.50)
Summerred40.04 (ND–0.10)40.07 (ND–0.10)
Tartaric acid (g L−1)Aroma50.17 (0.05–0.40)70.12 (0.07–0.21)
Discovery30.05 (0.03–0.09)30.10 (0.08–0.14)
Gravenstein50.20 (0.10–0.38)30.16 (0.13–0.21)
Summerred40.13 (0.05–0.27)40.13 (0.03–0.22)
Acetic acid (g L−1)Aroma50.02 (ND–0.10)70.01 (ND–0.10)
Discovery30.07 (ND–0.20)3ND
Gravenstein50.08 (ND–0.30)3ND
Summerred40.05 (ND–0.10)40.05 (ND–0.20)
Fructose (g L−1)Aroma579.0 (31.9–141)716.6 (1.30–38.9)
Discovery338.8 (22.1–67.9)37.90 (ND–18.2)
Gravenstein590.2 (55.1–142)313.0 (ND–37.5)
Summerred441.0 (22.8–63.4)46.38 (ND–18.1)
Glucose (g L−1) Aroma520.3 (8.20–31.3)79.24 (0.30–21.0)
Discovery312.6 (7.80–21.0)31.67 (0.70–3.10)
Gravenstein526.3 (18.1–38.3)34.47 (1.4–9.1)
Summerred49.82 (4.60–16.8)41.55 (0.40–2.80)
Sucrose (g L−1) Aroma538.7 (0.60–94.1)72.46 (ND–14.6)
Discovery39.90 (4.80–17.9)3ND
Gravenstein527.6 (10.2–67)3ND
Summerred433.5 (19.8–57.3)40.28 (ND–1.10)
Fructose + Glucose (g L−1)Aroma599.2 (40.0–172)725.8 (3.70–53.8)
Discovery351.5 (30.0–88.9)39.60 (1.20–21.4)
Gravenstein5117 (75.2–180)317.5 (2.90–46.5)
Summerred450.8 (27.4–80.2)47.92 (1.10–20.9)
Ethanol (vol %) Aroma5ND 78.45 (6.33–11.3)
Discovery3ND 37.11 (5.33–8.12)
Gravenstein5ND 38.34 (6.33–10.3)
Summerred4ND 47.07 (2.77–11.4)
YAN Total (mg L−1)Aroma538.1 (17.7–62.3)79.37 (ND–22.5)
Discovery323.1 (0.80–35.5)312.9 (9.74–18.6)
Gravenstein528.4 (3.81–51.7)317.0 (6.88–36.6)
Summerred469.7 (49.9–101)412.5 (108–14.6)
Table 3. Total phenol content in gallic acid equivalent (GAE mg L−1) and polyphenol profile from HPLC (mg L−1) in apple juice and finished cider. Values are the mean concentrations, with the minimal and maximal values shown in parentheses.
Table 3. Total phenol content in gallic acid equivalent (GAE mg L−1) and polyphenol profile from HPLC (mg L−1) in apple juice and finished cider. Values are the mean concentrations, with the minimal and maximal values shown in parentheses.
Juice (mg L−1)Cider (mg L−1)
ParameterVarietyNMean (Min–Max) NMean (Min–Max)
Total PhenolAroma5483 (306–680)7473 (334–685)
Discovery3789 (746–836)3496 (146–761)
Gravenstein5737 (572–933)3306 (153–418)
Summerred4198 (160–217)4215 (159–279)
Gallic acidAroma50.25 (ND–1.00)71.00 (ND–3.00)
Discovery30.67 (ND–2.00)30.67 (ND–2.00)
Gravenstein5ND3ND
Summerred40.67 (ND–2.00)41.25 (ND–5.00)
Protocatechuic acidAroma5ND7ND
Discovery3ND3ND
Gravenstein5ND3ND
Summerred4ND4ND
Procyanidin B1Aroma58.48 (ND–15.5)712.3 (ND–31.0)
Discovery312.0 (ND–18.0)321.7 (12.0–39.0)
Gravenstein510.3 (ND–21.0)318.7 (15.2–22.0)
Summerred45.47 (ND–16.4)42.8.0 (ND–10.0)
CatechinAroma58.87 (ND–18.3)78.20 (ND–12.7)
Discovery312.7 (8.00–15.0)312.0 (10.0–14.0)
Gravenstein57.90 (ND–14.0)315.0 (12.0–16.9)
Summerred41.17 (ND–3.5)40.18 (ND–0.70)
Caffeic acidAroma53.30 (0.50–6.70)77.63 (0.90–16.0)
Discovery33.67 (ND–7.00)322.3 (4.00–32.0)
Gravenstein54.55 (2.00–10.0)36.40 (3.00–12.0)
Summerred41.93 (ND–5.00)43.15 (0.60–10.0)
Chlorogenic acidAroma585.6 (56.0–135)752.6 (25.0–101)
Discovery3177 (151–214)3146 (75.0–231)
Gravenstein5100 (46.6–142)3139 (122–171)
Summerred447.4 (22.3–97.0)462.5 (10.0–150)
Procyanidin B2Aroma517.9 (ND–32.0)715.0 (ND–38.0)
Discovery331.3 (9.00–43.0)320.7 (12.0–31.0)
Gravenstein515.5 (ND–33.0)324.9 (21.0–30.6)
Summerred44.53 (ND–9.00)42.20 (ND–7.00)
EpicatechinAroma526.9 (ND–42.1)734.2 (ND–47.8)
Discovery323.3 (ND–36.0)317.7 (ND–30.0)
Gravenstein511.9 (ND–26.6)323.4 (23.0–24.2)
Summerred44.50 (ND–13.5)40.58 (ND–2.30)
Procyanidin C1Aroma50.75 (ND–3.00)72.00 (ND–5.00)
Discovery3ND31.00 (ND–3.00)
Gravenstein51.25 (ND–4.00)31.67 (ND–5.00)
Summerred4ND4ND
p-Coumaric acidAroma50.50 (ND–1.60)71.07 (ND–3.00)
Discovery32.67 (ND–4.00)32.00 (ND–4.00)
Gravenstein51.13 (ND–3.00)30.83 (ND–2.50)
Summerred4ND40.08 (ND–0.30)
Procyanidin A2Aroma50.33 (ND–1.30)70.64 (ND–2.30)
Discovery3ND3ND
Gravenstein5ND30.97 (ND–2.90)
Summerred4ND4ND
Ferulic acidAroma50.75 (ND–3.00)70.43 (ND–3.00)
Discovery3ND3ND
Gravenstein5ND3ND
Summerred4ND40.23 (ND–0.90)
PhloridzinAroma54.25 (ND–11.0)74.91 (ND–7.00)
Discovery33.67 (ND–11.0)34.00 (ND–12.0)
Gravenstein54.10 (ND–12.0)38.03 (ND–14.0)
Summerred43.33 (ND–10.0)44.00 (ND–11.0)
Total PolyphenolsAroma5236 (68.0–401)7186 (49.8–414)
Discovery3269 (238–287)3248 (179–360)
Gravenstein5174 (106–238)3289 (209–382)
Summerred477.0 (23.0–124)479.2 (11.0–193)
Table 4. Contents of esters and C6-alcohol (mg L−1). Values are mean, and minimal and maximal values are shown in brackets. Bold values indicate contents over the threshold limit according to Table S5.
Table 4. Contents of esters and C6-alcohol (mg L−1). Values are mean, and minimal and maximal values are shown in brackets. Bold values indicate contents over the threshold limit according to Table S5.
Juice (mg L−1)Cider (mg L−1)
ParameterVarietyNMean (Min–Max) NMean (Min–Max)
Ethyl esters of aliphatic acids
Ethyl propanoate Aroma5105 (39.6–253)7270 (84.8–589)
Discovery3141 (38.5–316)3543 (338–763)
Gravenstein565.7 (38.7–122.7)3543 (291–897)
Summerred445.1 (36.0–63.7)4219 (121–357)
Ethyl butyrateAroma5709 (163–1346)7648 (240–1149)
Discovery3712 (42.0–1887)3860 (304–1926)
Gravenstein5474 (63.0–859)3796 (610–1149)
Summerred4195 (56.1–336)4882 (409–1805)
Ethyl hexanoate Aroma547.4 (11.8–59.0)7839 (311–2697)
Discovery353.5 (4.90–94.8)3964 (798–1114)
Gravenstein549.8 (9.90–66.4)31109 (687–1626)
Summerred445.7 (12.1–68.5)42533 (630–6055)
Ethyl octanoateAroma51.70 (ND–8.50)7816 (179–2202)
Discovery36.17 (ND–18.5)3841 (344–1639)
Gravenstein52.32 (ND–11.6)31258 (514–1885)
Summerred45.50 (ND–22.0)42171 (535–4523)
Ethyl decanoateAroma530.7 (10.0–40.2)7198 (8.60–608)
Discovery348.3 (40.8–62.2)3400 (64.0–1005)
Gravenstein540.6 (17.4–75.8)3440 (175–910)
Summerred438.4 (29.2–53.1)4550 (148–866)
Ethyl valerateAroma50.72 (0.40–1.5)75.69 (2.10–12.5)
Discovery31.7 (0.40–3.70)35.80 (5.20–6.50)
Gravenstein51.36 (0.30–2.90)316.0 (7.20–23.3)
Summerred41.00 (ND–2.5)46.62 (4.80–10.1)
Ethyl dodecanoateAroma510.2 (4.10–16.7)761.0 (6.20–239)
Discovery316.9 (12.0–22.9)3190 (23.1–302)
Gravenstein519.1 (5.80–49.2)396.1 (13.6–248)
Summerred49.63 (7.90–13.0)4105 (23.3–264)
Ethyl esters of branched acids
Ethyl isobutyrateAroma51.88 (0.50–3.40)729.4 (5.30–58.4)
Discovery34.37 (ND–12.6)338.7 (34.3–42.0)
Gravenstein52.24 (0.80–4.00)357.3 (41.5–68.0)
Summerred40.63 (0.30–1.00)451.3 (31.1–64.1)
Ethyl isovalerateAroma53.06 (1.50–8.60)79.34 (4.10–16.6)
Discovery33.87 (1.30–8.60)37.43 (4.90–9.30)
Gravenstein53.66 (1.50–11.4)312.9 (9.80–16.0)
Summerred43.45 (1.50–8.70)47.08 (4.80–9.50)
Ethyl 2-methylbutyrateAroma575.9 (17.4–165)768.5 (24.9–125)
Discovery3347 (20.0–986)3153 (65.5–312)
Gravenstein554.0 (17.4–164)356.1 (47.3–61.5)
Summerred440.3 (16.8–101)452.9 (29.5–108)
Ethyl leucateAroma54.70 (0.40–17.6)797.0 (25.6–340)
Discovery3482 (2.00–1442)321.1 (11.4–26.4)
Gravenstein52.56 (1.60–4.10)3141 (28.1–320)
Summerred41.58 (0.70–2.30)430.0 (16.9–40.1)
Acetate esters
propyl acetateAroma598.5 (23.3–170)786.5 (16.3–114)
Discovery3635 (167–1150)3152 (54.9–279)
Gravenstein510.1 (6.90–18.2)349.0 (19.1–85.7)
Summerred48.95 (5.10–16.3)474.0 (20.7–130)
Isobutyl acetateAroma547.0 (16.6–98.4)7124 (30.8–352)
Discovery364.0 (14.0–131)376.7 (55.3–88.1)
Gravenstein55.80 (3.50–12.0)370.7 (30.8–107)
Summerred47.18 (4.10–16.1)4173 (47.3–297)
Phenylethyl acetateAroma529.8 (9.2–69.2)7401 (100–1402)
Discovery345 (18.2–97.7)3282 (228–330)
Gravenstein518.56 (9.1–32.6)3419 (246–570)
Summerred413.25 (8.1–26.1)4532 (221–1120)
Butyl acetateAroma52249 (261–6480)71573 (144–2821)
Discovery33286 (1366–4996)3924 (308–1948)
Gravenstein582.3 (28.9–128.7)3231 (108–342)
Summerred446.02 (26.5–55.1)4315 (121–623)
Isoamyl acetateAroma5150 (47.6–386)71250 (314–2980)
Discovery3537 (324–938)31128 (769–1525)
Gravenstein56.56 (2.90–12.9)31962 (347–3381)
Summerred45.2 (1.70–14.3)44138 (2590–6243)
Hexyl acetateAroma5796 (ND–2772)7517 (ND–1171)
Discovery31147 (ND–2650)3290 (164–382)
Gravenstein553.7 (ND–89.2)3307 (78.0–615)
Summerred427.5 (ND–40.3)41241 (715–1817)
z-3-hexenyl acetateAroma53.40 (1.20–8.80)73.73 (0.90–8.30)
Discovery32.97 (0.90–5.40)31.67 (0.90–2.20)
Gravenstein50.92 (0.40–1.30)31.80 (1.00–3.00)
Summerred40.65 (0.30–0.80)42.63 (1.60–4.30)
E-2-hexenyl acetateAroma53.96 (1.10–9.30)70.97 (0.50–1.70)
Discovery36.50 (3.00–11.5)30.83 (0.60–1.10)
Gravenstein51.36 (0.50–2.30)30.87 (0.60–1.00)
Summerred40.68 (0.50–1.00)41.05 (0.60–1.70)
Ethyl phenyl acetateAroma50.44 (0.30–0.60)72.56 (1.00–4.60)
Discovery30.40 (0.20–0.70)34.30 (2.80–6.20)
Gravenstein50.42 (0.20–0.90)36.53 (2.20–13.5)
Summerred40.30 (0.20–0.40)42.15 (1.70–2.60)
Octyl acetateAroma55.06 (0.30–12.2)71.04 (0.30–2.20)
Discovery36.80 (2.60–15.2)31.40 (0.80–2.30)
Gravenstein50.64 (0.10–1.10)31.27 (0.90–1.90)
Summerred40.48 (0.20–0.60)41.25 (1.00–1.70)
Ethyl Esters of hydroxycinnamic acid
Ethyl cinnamateAroma50.76 (0.40–1.50)70.84 (0.40–1.60)
Discovery30.73 (0.40–1.30)30.63 (0.40–0.80)
Gravenstein50.60 (0.10–1.10)31.03 (0.30–2.10)
Summerred40.50 (0.40–0.60)44.47 (0.30–11.6)
Ethyl dihydrocinnamateAroma50.22 (0.20–0.30)70.37 (ND–1.10)
Discovery30.20 (ND–0.40)30.10 (0.10–0.10)
Gravenstein50.16 (ND–0.40)30.43 (0.10–0.90)
Summerred40.08 (ND–0.30)40.60 (0.10–1.80)
C6-Alcohols
HexanolAroma515,778 (2895–33,297)77799 (4602–12,850)
Discovery313,441 (2556–27,675)310,022 (6958–11,849)
Gravenstein515,380 (6166–28,187)311,655 (6824–20,464)
Summerred49101 (1752–24,950)48183 (6963–9490)
Z-3-hexenolAroma5142 (7.60–272)780.8 (10.2–187)
Discovery329.5 (11.6–42.2)331.9 (17.8–48.3)
Gravenstein578.4 (11.7–164)358.6 (15.4–106)
Summerred432.9 (5.60–97.1)434.9 (26.9–39.1)
E-2 hexenolAroma5648 (84.0–1839)76.57 (ND–14.5)
Discovery31267 (67.0–2059)313.4 (5.60–21.6)
Gravenstein5634 (75.0–1717)313.4 (8.70–17.8)
Summerred4552 (188–1207)410.4 (7.70–14.7)
E-3 hexenolAroma519.8 (ND–37.6)723.1 (6.80–56.8)
Discovery325.8 (4.80–62.5)335.6 (21.8–51.8)
Gravenstein518.1 (4.80–32.1)336.0 (11.5–50.4)
Summerred411.5 (1.90–26.6)437.4 (28.4–57.8)
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MDPI and ACS Style

Øvsthus, I.; Martelanc, M.; Albreht, A.; Radovanović Vukajlović, T.; Česnik, U.; Mozetič Vodopivec, B. Chemical Characterization of Cider Produced in Hardanger—From Juice to Finished Cider. Beverages 2024, 10, 73. https://doi.org/10.3390/beverages10030073

AMA Style

Øvsthus I, Martelanc M, Albreht A, Radovanović Vukajlović T, Česnik U, Mozetič Vodopivec B. Chemical Characterization of Cider Produced in Hardanger—From Juice to Finished Cider. Beverages. 2024; 10(3):73. https://doi.org/10.3390/beverages10030073

Chicago/Turabian Style

Øvsthus, Ingunn, Mitja Martelanc, Alen Albreht, Tatjana Radovanović Vukajlović, Urban Česnik, and Branka Mozetič Vodopivec. 2024. "Chemical Characterization of Cider Produced in Hardanger—From Juice to Finished Cider" Beverages 10, no. 3: 73. https://doi.org/10.3390/beverages10030073

APA Style

Øvsthus, I., Martelanc, M., Albreht, A., Radovanović Vukajlović, T., Česnik, U., & Mozetič Vodopivec, B. (2024). Chemical Characterization of Cider Produced in Hardanger—From Juice to Finished Cider. Beverages, 10(3), 73. https://doi.org/10.3390/beverages10030073

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