The effects of apple variety, ripening stage, and yeast strain on the volatile composition of apple cider

The potential of red-fleshed apples for cider production

Cider quality is influenced by numerous factors relating to the apples used during production. While extensive research has been done to explore the phenolic content, sensory quality, and storage stability of various apple products, the domain of fermented apple products, such as ciders, remains underrepresented. Red-fleshed apples (RFAs) have naturally high concentrations of phenolic compounds, which indicate their potential in the production of novel cider products. However, a knowledge gap remains regarding the application of RFAs in cider production and how their physicochemical and sensory properties are changed during processing. This review is the first to comprehensively investigate whether and to what extent apple categories (dessert, cider, and RFAs) differ regarding their physicochemical and sensory properties from harvest throughout cider processing. Furthermore, it highlights the importance of a holistic understanding of apple characteristics, encompassing both traditional and RFA varieties in the context of cider production. The findings offer valuable insights for stakeholders aiming to enhance product quality, providing a foundation for future studies on optimizing processing methods for a diverse and appealing range of ciders.

Diversity and dynamics of microbial communities during spontaneous fermentation of different cultivars of apples from China and their relationship with the volatile components in the cider

Microorganisms involved in spontaneous fermentation are critical in cider productivity, quality, and aroma. This study examined the composition and dynamic changes of indigenous microbial communities during spontaneous fermentation of three apple cultivars (Qin Guan, Fuji, and Qin Yue) from Shaanxi, China, and their influence on cider's volatile components. Samples were collected at three time points and analyzed using high-throughput sequencing and HS-SPME-GC-MS. A total of 2961 bacterial and 618 fungal operational taxonomic units (OTUs) were identified, distributed among 20 bacterial and 5 fungal phyla. Alpha diversity analysis and Permutation multivariate analysis of variance (PERMANOVA) demonstrated that the cultivar significantly influenced fungal diversity and microbial composition at the start of the fermentation (p < 0.05). Moreover, the particular microbial communities inherent to the cultivar were maintained at the end of the fermentation. The characteristic fungal genera were Hanseniaspora in Qin Guan, Rhodosporidiobolus and Pichia in Fuji, and Debaryomyces in Qin Yue. A total of 43 volatile compounds were identified, among which 40 exhibited significant differences across different cultivars (p < 0.05). The characteristic volatile flavor components of Qin Guan included Isobutyl acetate, Ethyl 3-methylbutanoate, Hexyl acetate, Ethyl 2-hydroxypropanoate, 1-Hexanol, 1-Heptanol, and 2-Methylpropanoic acid. Fuji's characteristic component was Diethyl butanedioate, while Qin Yue's was (E)-3-Hexen-1-ol. Using partial least squares regression (PLSR) and Spearman analyze the correlation between microbiota and volatile compound production, the abundances of Hanseniaspora uvarum, Pichia kudriavzevii, Vishniacozyma victoriae, and Meyerozyma guilliermondii were positively correlated with the production of esters and higher alcohols. This research demonstrated that different apple cultivars influence the microbial community composition and, in turn, impact the cider aromas during spontaneous fermentation.

Profiles of Killer Systems and Volatile Organic Compounds of Rowanberry and Rosehip-Inhabiting Yeasts Substantiate Implications for Biocontrol

Yeasts produce numerous antimicrobial agents such as killer toxins, volatile organic compounds (VOCs), and other secondary metabolites, establishing themselves in developing natural and sustainable biocontrol strategies for agriculture and food preservation. This study addressed the biocontrol potential of yeasts, isolated from spontaneous fermentations of rosehips (Rosa canina L.) and rowanberries (Sorbus aucuparia L.), focusing on their killer phenotypes and VOCs production. Yeasts were isolated using spontaneous fermentations with Hanseniaspora uvarum and Metschnikowia pulcherrima identified as the dominant species, comprising approximately 70% of the yeast population. Among 163 isolated strains, 20% demonstrated killing activity, with Saccharomyces cerevisiae exhibiting the strongest killing efficiency, as well as Pichia anomala and M. pulcherrima showing broad-spectrum antagonistic activity. This study identified dsRNA-encoded killer phenotypes in S. cerevisiae, S. paradoxus, and Torulaspora delbrueckii, revealing multiple distinct killer toxin types. The biocontrol potential of wild berry-inhabiting yeasts was demonstrated in a real food system, grape juice, where the S. cerevisiae K2-type killer strain significantly reduced fungal contaminants. The selected H. uvarum, M. pulcherrima, S. cerevisiae, and S. paradoxus yeast strains representing both berries were applied for VOC analysis and identification by gas chromatography-linked mass spectrometry. It was revealed that the patterns of emitted volatiles are yeast species-specific. Statistically significant differences between the individual VOCs were observed among killing phenotype-possessing vs. non-killer S. paradoxus yeasts, thus revealing the involvement of killer systems in multi-level biocontrol enablement. The performed studies deepen our understanding of potential yeast biocontrol mechanisms, highlight the importance of produced antimicrobials and volatiles in ensuring antagonistic efficacy, and prove the relevance of isolated biocontrol yeasts for improving food safety.

Microbial interactions and dynamic changes of volatile flavor compounds during the fermentation of traditional kombucha

This study aims to explore the core microbiota of kombucha and to discover potential correlations between microbiota and volatile flavor compounds. The total acidity and microbial colony numbers changed dramatically in different fermentation periods of kombucha. Microbial analysis based on high throughput sequencing technology showed that the bacteria of Komagataeibacter, Pseudomonas, Burkholderia, Ralstonia, Halomonas, Sphingomonas and fungi of Dekkera, Saccharomyces cerevisiae, Botryotrichum, Monascus, Pichia were the dominant genera. In addition, the correlation coefficients between the bacteria and fungi were different. The volatile flavor compounds of alcohols, acids, esters, aldehydes, ketones, phenolics, and terpenes were identified using headspace solid-phase microextraction combined with gas chromatography coupled with mass spectrometry. Typically, the concentrations of ethanol, acetic acid, and ethyl acetate was 71.59-248.23 μg/L, 97.73-849.00 μg/L, and 44.52-181.59 μg/L, respectively, during fermentation. This study is helpful to understand the dynamic changes of microbial communities and volatile flavor compounds during the fermentation of kombucha.

Optimization of the Fermentation Conditions of Huaniu Apple Cider and Quantification of Volatile Compounds Using HS-SPME-GC/MS

The fermentation process and composition of volatile compounds play a crucial role in the production of Huaniu apple cider. This study aimed to optimize the fermentation conditions of Huaniu apple cider and quantify its volatile compounds using headspace solid-phase microextraction-gas chromatography-mass spectrometry (HS-SPME-GC/MS). The optimal fermentation parameters were determined using response surface methodology (RSM). The optimal fermentation temperature was 25.48 °C, initial soluble solids were 18.90 degrees Brix, inoculation amount was 8.23%, and initial pH was 3.93. The fermentation rate was determined to be 3.0, and the predicted value from the verification test was 3.014. This finding demonstrated the excellent predictability of a RSM-optimized fermentation test for Huaniu apple cider, indicating the reliability of the process conditions. Moreover, the analysis of volatile compounds in the optimized Huaniu cider identified 72 different ingredients, including 41 esters, 16 alcohols, 6 acids, and 9 other substances. Notably, the esters exhibited high levels of ethyl acetate, ethyl octanoate, and ethyl capricate. Similarly, the alcohols demonstrated higher levels of 3-methyl-1-butanol, phenethylethanol, and 2-methyl-1-propanol, while the acids displayed increased concentrations of acetic acid, caproic acid, and caprylic acid. This study provides the essential technical parameters required for the preparation of Huaniu apple cider while also serving as a valuable reference for investigating its distinct flavor profile.

A comparative study of the effect of bacteria and yeasts communities on inoculated and spontaneously fermented apple cider

Understanding bacteria and yeasts communities can reduce unpredictable changes of apple cider. In this study, apple juice inoculated with Saccharomyces cerevisiae WET 136 and fermented spontaneously were compared, the relationships of bacteria, yeasts, organic acids, and volatiles were analyzed. Results showed that microbial diversity affected the fermentation, organic acids and volatiles in apple ciders. In the first four spontaneous fermentation days, LAB (lactic acid bacteria) multiplied and reached 7.89 lg CFU/mL, and then triggered malolactic fermentation (MLF), leading to malic acid decreased by 3880.52 mg/L and lactic acid increased by 4787.55 mg/L. The citric, succinic and fumaric acids content was 2171.14, 701.51 and 8.06 mg/L lower than that in inoculated cider, respectively. Although the yeasts multiplied during spontaneous fermentation, it did not reach 7.50 lg CFU/mL until the 5th day, which led to a long lag period, as well as later and lower production of acetaldehyde and higher alcohols. The inoculated yeast inhibited LAB, acetic acid bacteria, Rahnella, and non-Saccharomyces. Yeasts were the key to produce citric acid, acetaldehyde and 3-methyl-1-butanol in apple cider; while bacteria were closely related to the formation of lactic acid, acetic acid and ethyl acetate. It suggested that low higher alcohols and acetaldehyde can be realized by selecting yeasts, and Leuconostoc pseudomesenteroides can work as candidate to reduce L-malic and citric acids in apple cider.

Sensory descriptive analysis of hard ciders from the Northeast and Mid-Atlantic United States

Although alcoholic or "hard" cider is a beverage of growing popularity throughout the Northeastern and Mid-Atlantic United States (US), the industry lacks a consistent language for describing the sensory quality of its products. The main objective of this research was to explore the sensory attributes that can be used to describe a large representative sample (N = 42 samples) of ciders from Virginia, Vermont, and New York, using classical descriptive analysis (DA). The secondary objective of the research was to determine if cider samples' sensory attributes differ based on extrinsic factors, such as style, packaging, and apple varieties. The study was conducted using a standard DA: 8 panelists were trained for 13 h to develop a lexicon of aroma, taste, and mouthfeel descriptors for 42 cider samples (15 single varietal ciders, 27 blended ciders). Then, subjects evaluated each cider in duplicate for all descriptive attributes in standard sensory-evaluation conditions. Results were analyzed to determine overall differences among the individual cider samples, geographic origins, cider styles, and packaging formats, as well as significant differences across individual attributes. Herein, we report on 29 attributes that can be used to discriminate cider samples, as well as a subset of attributes which differentiate ciders based on extrinsic product variables. These results provide a framework for describing ciders from the Northeast and Mid-Atlantic regions of the US, which may be further generalizable to other North American ciders. As well, these results highlight the potential for more descriptive, sensory-based style guidelines may inspire future research related to cider production practices and terroir.

A Preliminary Study of Yeast Strain Influence on Chemical and Sensory Characteristics of Apple Cider

During the fermentation of apple juice, yeast metabolism creates complex biosynthetic pathways which produce a range of compounds responsible for the organoleptic qualities of cider. In this study, basic cider quality parameters were measured to investigate the influence of six yeast strains on cider made from three apple varieties (‘Pink Lady’, ‘Sturmer’, and ‘Bulmer’s Norman’). Measurement of pH, titratable acidity, and total phenolic content revealed that yeast can influence cider attributes, albeit variety and season dependent. Descriptive sensory analysis using a trained sensory panel was conducted on cider made from ‘Pink Lady’ apples and the same six yeast strains. The sensory panel significantly differentiated the yeast strains on the attributes of ‘fresh apple’, ‘earthy’ and ‘pear’. Identifying the variety specific influence of individual yeast strains on chemical and sensory characteristics of apple cider will provide cider makers with an enhanced understanding when choosing yeast strains.

In Vitro Biological Control of Aspergillus flavus by Hanseniaspora opuntiae L479 and Hanseniaspora uvarum L793, Producers of Antifungal Volatile Organic Compounds

Aspergillus flavus is a toxigenic fungal colonizer of fruits and cereals and may produce one of the most important mycotoxins from a food safety perspective, aflatoxins. Therefore, its growth and mycotoxin production should be effectively avoided to protect consumers' health. Among the safe and green antifungal strategies that can be applied in the field, biocontrol is a recent and emerging strategy that needs to be explored. Yeasts are normally good biocontrol candidates to minimize mold-related hazards and their modes of action are numerous, one of them being the production of volatile organic compounds (VOCs). To this end, the influence of VOCs produced by Hanseniaspora opuntiae L479 and Hanseniaspora uvarum L793 on growth, expression of the regulatory gene of the aflatoxin pathway (aflR) and mycotoxin production by A. flavus for 21 days was assessed. The results showed that both yeasts, despite producing different kinds of VOCs, had a similar effect on inhibiting growth, mycotoxin biosynthetic gene expression and phenotypic toxin production overall at the mid-incubation period when their synthesis was the greatest. Based on the results, both yeast strains, H. opuntiae L479 and H. uvarum L793, are potentially suitable as a biopreservative agents for inhibiting the growth of A. flavus and reducing aflatoxin accumulation.

Authentication Using Volatile Composition: A Proof-of-Concept Study on the Volatile Profiles of Fourteen Queensland Ciders

Although relatively small, the Australian cider industry has experienced significant growth in recent years. One of the current challenges in the industry is the lack of research specific to Australian ciders. Establishing baseline volatile organic compound (VOC) profiles of Australian cider is paramount to developing a better understanding of the industry. This understanding may ultimately be utilized for both the categorization and authentication of existing ciders, and the targeted modification of cider volatiles for the development and improvement of cider quality. This study utilized gas chromatography, coupled with mass spectrometry, to identify key VOCs present in 14 ciders sourced from four different manufacturers in Queensland, Australia. A total of 40 VOCs were identified across the ciders, with significant variation depending on the flavor and manufacturer. Principal component analysis indicated that the ciders were well-separated based on the manufacturer, supporting the prospect of using the volatile composition to discriminate between cider manufacturers. Furthermore, hierarchical cluster analysis highlighted the commonalities and differences in cider composition between different manufacturers, which may be indicative of the varying ingredients and manufacturing processes used to create the ciders. Future studies profiling the volatile composition of larger numbers of Australian ciders are recommended to support the use of this analytical technique for authentication purposes. Likewise, exploration of the relationship between specific processes and VOCs is recommended to fortify an understanding of how to optimize cider production to improve consumer satisfaction.

Freely Behaving Mice Can Brake and Turn During Optogenetic Stimulation of the Mesencephalic Locomotor Region

A key function of the mesencephalic locomotor region (MLR) is to control the speed of forward symmetrical locomotor movements. However, the ability of freely moving mammals to integrate environmental cues to brake and turn during MLR stimulation is poorly documented. Here, we investigated whether freely behaving mice could brake or turn, based on environmental cues during MLR stimulation. We photostimulated the cuneiform nucleus (part of the MLR) in mice expressing channelrhodopsin in Vglut2-positive neurons in a Cre-dependent manner (Vglut2-ChR2-EYFP) using optogenetics. We detected locomotor movements using deep learning. We used patch-clamp recordings to validate the functional expression of channelrhodopsin and neuroanatomy to visualize the stimulation sites. In the linear corridor, gait diagram and limb kinematics were similar during spontaneous and optogenetic-evoked locomotion. In the open-field arena, optogenetic stimulation of the MLR evoked locomotion, and increasing laser power increased locomotor speed. Mice could brake and make sharp turns (~90°) when approaching a corner during MLR stimulation in the open-field arena. The speed during the turn was scaled with the speed before the turn, and with the turn angle. Patch-clamp recordings in Vglut2-ChR2-EYFP mice show that blue light evoked short-latency spiking in MLR neurons. Our results strengthen the idea that different brainstem neurons convey braking/turning and MLR speed commands in mammals. Our study also shows that Vglut2-positive neurons of the cuneiform nucleus are a relevant target to increase locomotor activity without impeding the ability to brake and turn when approaching obstacles, thus ensuring smooth and adaptable navigation. Our observations may have clinical relevance since cuneiform nucleus stimulation is increasingly considered to improve locomotion function in pathological states such as Parkinson's disease, spinal cord injury, or stroke.

An Overview of the Factors Influencing Apple Cider Sensory and Microbial Quality from Raw Materials to Emerging Processing Technologies

Given apple, an easily adapted culture, and a large number of apple varieties, the production of apple cider is widespread globally. Through the fermentation process, a series of chemical changes take place depending on the apple juice composition, type of microorganism involved and technology applied. Following both fermentations, alcoholic and malo-lactic, and during maturation, the sensory profile of cider changes. This review summarises the current knowledge about the influence of apple variety and microorganisms involved in cider fermentation on the sensory and volatile profiles of cider. Implications of both Saccharomyces, non-Saccharomyces yeast and lactic acid bacteria, respectively, are discussed. Also are presented the emerging technologies applied to cider processing (pulsed electric field, microwave extraction, enzymatic, ultraviolet and ultrasound treatments, high-pressure and pulsed light processing) and the latest trends for a balanced production in terms of sustainability, authenticity and consumer preferences.

Evaluation of Volatilomic Fingerprint from Apple Fruits to Ciders: A Useful Tool to Find Putative Biomarkers for Each Apple Variety

Aroma is a crucial criterion to assess the quality of apple fruits, juices, and ciders. The aim of this study was to explore similarities and differences in volatile profiles among apple fruits, juices, and ciders from different apple varieties (Festa, Branco, and Domingos) by headspace solid-phase microextraction gas chromatography–mass spectroscopy (HS–SPME/GC–MS). A total of 142 volatile organic compounds (VOCs) were identified, but only 9 were common in all analysed matrices and apple-tested varieties. Esters, alcohols, and aldehydes presented a higher concentration in apple fruits and juices, whereas esters, alcohols, and acids were dominant in ciders. Moreover, there were unique VOCs for each matrix and for each variety, highlighting the importance of the selection of apple varieties as an important factor to obtain good sensory and quality ciders, multiple benefits, and legal protection against the misuse of local products.

Effect of Saccharomyces cerevisiae and Schizosaccharomyces pombe strains on chemical composition and sensory quality of ciders made from Finnish apple cultivars

Composition of volatile compounds and concentrations of sugars and organic acids were studied in apple ciders produced with Saccharomyces cerevisiae and Schizosaccharomyces pombe yeasts using eleven different Finnish apple cultivars. Moreover, sensory quality of selected ciders was studied using check-all-that-apply test with untrained panelists. Seventy-seven volatile compounds were detected in the samples using HS-SPME-GC-MS. In general, the ciders had higher concentrations of higher alcohols, aldehydes, and acetals whereas the juices contained higher contents of C6-alcohols. Simultaneously, fermentation using S. pombe resulted in lower concentrations of malic acid, ethyl pentanoate, ethyl hexanoate, and volatile acids and higher concentrations of residual sugars compared to S. cerevisiae. Ciders made using S. cerevisiae were characterized as 'alcoholic' and 'yeasty' while S. pombe ciders were more frequently described as 'sweet', 'honey-like', and less rated as sour. Besides the strong effect by the yeasts, apple cultivars had significant effects on the compositional and sensorial properties of apple ciders.

The Effect of Apple Juice Concentration on Cider Fermentation and Properties of the Final Product

European legislation overall agrees that apple juice concentrate is allowed to be used to some extent in cider production. However, no comprehensive research is available to date on the differences in suitability for fermentation between fresh apple juice and that of reconstituted apple juice concentrate. This study aimed to apply freshly pressed juice and juice concentrate made from the same apple cultivar as a substrate for cider fermentation. Differences in yeast performance in terms of fermentation kinetics and consumption of nutrients have been assessed. Fermented ciders were compared according to volatile ester composition and off-flavor formation related to hydrogen sulfide. Based on the results, in the samples fermented with the concentrate, the yeasts consumed less fructose. The formation of long-chain fatty acid esters increased with the use of reconstituted juice concentrate while the differences in off-flavor formation could not be determined. Overall, the use of the concentrate can be considered efficient enough for the purpose of cider fermentation. However, some nutritional supplementation might be required to support the vitality of yeast.

Identification of Apple Varieties Using a Multichannel Hyperspectral Imaging System

This paper reports the nondestructive detection of apple varieties using a multichannel hyperspectral imaging system consisting of an illumination fiber and 30 detection fibers arranged at source–detector distances of 1.5–36 mm over the spectral range of 550–1650 nm. Spatially resolved (SR) spectra were obtained for 1500 apples, 500 each of three varieties from the same orchard to avoid environmental and geographical influences. Partial least squares discriminant analysis (PLSDA) models were developed for single SR spectra and spectral combinations to compare their performance of variety detection. To evaluate the effect of spectral range on variety detection, three types of spectra (i.e., visible region: 550–780 nm, near-infrared region: 780–1650 nm, full region: 550–1650 nm) were analyzed and compared. The results showed that the single SR spectra presented a different accuracy for apple variety classification, and the optimal SR spectra varied with spectral types. Spectral combinations had better accuracies for variety detection with best overall classifications of 99.4% for both spectral ranges in the NIR and full regions; however, the spectral combination could not improve the results over the optimal single SR spectra in the visible region. Moreover, the recognition of golden delicious (GD) was better than those of the other two varieties, with the best classification accuracy of 100% for three types of spectra. Overall, the multichannel hyperspectral imaging system provides more spatial-spectral information for the apples, and the results demonstrate that the technique gave excellent classifications, which suggests that the multichannel hyperspectral imaging system has potential for apple variety detection.

Impact of the Physicochemical Composition and Microbial Diversity in Apple Juice Fermentation Process: A Review

Fermented apple beverages are produced all over the world with diverse characteristics associated with each country. Despite the diversifications, cider producers are confronted with similar issues and risks. The nature of the raw material, also known as the fermentation medium, plays a key role in fermentation. A well-defined composition of apples is, therefore, required to produce cider with good quality. In addition, ferment and its metabolism are important factors in the fermentation process. The producers of cider and other alcoholic beverages are looking in general for novel yeast strains or for the use of native strains to produce "authentic" and diversified beverages that are distinct from each other, and that attract more and more consumers. Research articles on cider production are infrequent compared to wine production, especially on the impact of the chemical composition and microbial diversity of apples on fermentation. Even though the processing of fermented beverages is close in terms of microbial interactions and production, the study of the specific properties of apples and the production challenges of cider production is advantageous and meaningful for cider producers. This review summarizes the current knowledge on apple composition and the impact of the must composition on fermentation and yeast growth. In addition, the microbial diversity of cider, activities, and its influence on fermentation are reviewed.

Aromatic, olfactometric and consumer description of sweet ciders obtained by cryo-extraction

Nine ciders obtained by cryo-extraction were analysed for chemical, olfactometric and sensory characteristics. Three types of ice apple juices and three autochthonous yeast strains were evaluated. The quantitative volatile profile is mainly influenced by the apple juice. Regarding the olfactometric profiles of the ice ciders, 23 odorants not previously found in Spanish still ciders, and described as sweet, spicy, fruity and floral were observed. Among these, it is worth mentioning 5 high-boiling point compounds found in an olfactometric zone where heavy, phenolic odours predominate in still ciders. The sensory descriptions obtained by Check-All-That-Apply classified the ice ciders mainly by their sweet taste and smoothness, these attributes being the most influential in the assessment of the overall quality of the ciders. The most highly valued ciders were described as the sweetest, most fruity ones, in agreement with their having the highest values for the ratio between total sugars and total acidity.

Analysis of Volatile Compounds and Sugar Content in Three Polish Regional Ciders with Pear Addition

Aroma plays important part in cider acceptability to the consumer. In this study, techniques such as headspace solid-phase microextraction (HS-SPME), which has been coupled with gas chromatography and mass spectrometry, have been used to assess what changes in the volatilome occur during fermentation of three apple cultivars (Cortland, Gala, Idared) with and without addition of pear (Konferencja) juice addition. Analysis of volatiles has shown that temperature of fermentation, apple variety and pear juice addition have significant influences on the volatile compositions of the acquired ciders. Ciders prepared in laboratory conditions fermented at 15 °C were characterized by a greater share of esters, such as ethyl hexanoate, ethyl decanoate and ethyl dodecanoate, in volatile profile (66.24–79.58%) than ciders fermented at 20 °C (58.81–77.22%). Ciders fermented at a higher temperature were characterized by a greater share of alcohols, such as phenylethyl alcohol and hexan-1-ol (18.34–36.7%) than ciders fermented at a lower temperature (16.07–25.35%). In the ciders prepared from pear (20% w/w) and apple (80% w/w) juice, the presence of esters, such as ethyl (2E, 4Z)-deca-2,4-dienoate, characterized by a pear aroma, could be noted.

Properties of Potato Starch Roasted with Apple Distillery Wastewater

This study aimed to produce starch esters by roasting potato starch with apple distillery wastewater at various temperatures and aimed to determine the effects of esterification conditions on selected properties of the modified preparations. Apple distillery wastewater was concentrated, mixed with starch (30 g of dry matter per 100 g of starch), dried, and roasted at temperatures of 110, 130 or 150 °C for 3 h. The resulting preparations were rinsed 30 times with a 60% ethanol solution, dried, and disintegrated. After that, the following analyses were performed: content of substituted acids (after alkaline de-esterification) with high performance liquid chromatography (HPLC); thermal characteristics with differential scanning calorimetry (DSC); swelling power and solubility in water at 80 °C; color changes with a colorimeter; rheology of the pastes based on the plotted flow curves; and the pastes’ resistance to amyloglucosidase. Starch treatments with apple distillery wastewater at 130 and 150 °C caused significant changes to its properties when compared to the control samples of native starch and starch roasted without wastewater, including: a lower temperature and heat of pasting, lower swelling power and solubility in water, darker color, higher resistance to amyloglucosidase, and the formation of pastes with a lower viscosity.

Aroma Investigation of New and Standard Apple Varieties Grown at Two Altitudes Using Gas Chromatography-Mass Spectrometry Combined with Sensory Analysis

The aromatic profile of apples constitutes important information for the characterization and description of local products. Apple flavor is determined by perception in mouth and aroma; while the first is mainly defined by sugars and organic acids, aroma is a complex mixture of many volatile organic compounds (VOCs) whose composition is often specific to the variety. Headspace-solid phase microextraction gas chromatography coupled with mass spectrometry (HS-SPME-GC-MS) allows for the detection of detailed information of volatile constituents. In this study, eleven apple varieties (Braeburn, Fuji, Gala, Golden Delicious, Coop 39-Crimson Crisp^®, Dalinette-Choupette^®, Fujion, CIV323-Isaaq^®, Coop43-Juliet^®, SQ159-Natyra^®, UEB32642-Opal^®) grown in two pedoclimatic locations at different altitudes in South Tyrol (Italy) (ca. 225 m and ca. 650 m a.s.l.) were investigated. Thirty-eight VOCs were identified and combined with sensory analysis results (from 11 trained panelist) to characterize the aroma of new and standard apple varieties with a special focus on pedoclimatic location differences. The study shows strong diversification of the varieties based on their VOC profiles and sensory attributes, as expected. Moreover, investigating how the pedoclimatic location at different altitudes can influence the apple aroma profile, we identified twelve VOCs involved in these differences and provided a deeper investigation on how different altitudes can influence the apple aroma composition and perceptions combining the analytical and sensory parameters.

Monitoring Cider Aroma Development throughout the Fermentation Process by Headspace Solid Phase Microextraction (HS-SPME) Gas Chromatography–Mass Spectrometry (GC-MS) Analysis

Volatile organic compounds (VOCs) play a crucial role in cider quality. Many variables involved in the fermentation process contribute to cider fragrance, but their relative impact on the finished odor remains ambiguous, because there is little consensus on the most efficient method for cider volatile analysis. Herein, we have optimized and applied a headspace solid phase microextraction gas chromatography–mass spectrometry (HS-SPME GC-MS) method for the chemical analysis of cider VOCs. We determined that the 30 min exposure of a divinylbenzene/carboxen/polydimethylsiloxane (DVB/CAR/PDMS) solid phase microextraction (SPME) fiber at 40 °C yielded detection of the widest variety of VOCs at an extraction efficiency >49% higher than comparable fibers. As a proof-of-concept experiment, we utilized this method to profile cider aroma development throughout the fermentation process for the first time. The results yielded a very practical outcome for cider makers: a pre-screening method for determining cider quality through the detection of off-flavors early in the fermentation process. The aroma profile was found to be well established 72 h after fermentation commenced, with major esters varying by 18.6% ± 4.1% thereafter and higher alcohols varying by just 12.3% ± 2.6%. Lastly, we analyzed four mature ciders that were identically prepared, save for the yeast strain. Twenty-seven key VOCs were identified, off-flavors (4-ethylphenol and 4-ethyl-2-methoxyphenol) were detected, and odorants were quantified at desirable concentrations when compared to perception thresholds. VOCs varied considerably following fermentation with four novel strains of S. cerevisiae, evidencing the central importance of yeast strain to the finished cider aroma.

Immobilization of Saccharomyces cerevisiae on Apple Pieces to Produce Cider

Three yeasts (Saccharomyces cerevisiae var. boulardii, a commercial probiotic yeast; S. cerevisiae W13, a wild yeast able to remove ochratoxin A; and S. cerevisiae 17, a wild yeast with promising probiotic traits) were screened for their ability to adhere on apple pieces as a function of different contact times (15–30 min). Then, apple pieces were stored at 4 °C for 15 days, and the viable count of yeasts was periodically assessed. Yeasts were able to adhere on apple pieces after 15 min (7 log cfu/g) and retained their viability throughout the refrigerated storage. In a second step, apple pieces with S. cerevisiae W13 were used to produce cider on a small scale. The variables under investigation were (a) the recycling of pieces up to 10 times and (b) the preliminary storage of pieces at 4 °C before use. Pieces used immediately after yeast immobilization could be successfully used again 10 times and gained a fermentation performance (in terms of yeast amount in cider and ethanol after 24 h) similar to that achieved by free cells. In addition, the preliminary storage of pieces at 4 °C did not affect their performances as reusable starter carriers.