Hydrogen Sulfide (H2S), is a negative off aroma produced during yeast fermentation and is common in cider and leads to consumer rejection. H2S has a very low odor detection threshold (ODT) and is often described as "rotten egg". H2S is produced when juice is deficient in yeast nutrients, such as amino acids and yeast assimilable nitrogen (YAN), which is a common problem in apples since they naturally low in nutrients. The purpose of this research was to investigate the effects of yeast nutrient addition to cider fermentation by adding four different nitrogen-rich supplements and evaluating the effects on H2S production, fermentation kinetics, and aroma quality during cider. Three yeast strains (M2, EC1118 and ICV OKAY), four yeast nutrients (Fermaid K, Fermaid O, Experimental Nutrient, and DAP) and single addition versus split addition of nutrient were tested. For single addition, all nutrient was added pre-fermentation and for split additions, the first addition was pre-fermentation and the second at one-third total soluble solid (TTS) depletion as measured by °Brix. Sensory evaluation was conducted on selected treatments. The greatest H2S was produced by M2 yeast strain (525 .63 ± 53.31 µg mL-1) while the least H2S on average was produced by EC1118 (118.26 ± 26.33 µg mL-1) and ICV OKAY produced an intermediate amount of H2S (209.26 ± 31.63 µg mL-1). Significant differences were observed between treatments and total H2S production within yeast strains. Yeast strain had the largest effect on H2S production. The second largest effect was yeast nutrient type. Classical text analysis of descriptions of cider aroma were evaluated and 25 attributes were chosen to describe the ciders. Check- all-that-apply (CATA), a rapid sensory technique that askes panelists, revealed that there was no clear pattern between variables tested. This work demonstrates that yeast nutrient type and yeast strain affect H2S production during cider fermentation. These findings provide a basis for improving the effectiveness of strategies used to prevent H2S production in cider fermentation. / Master of Science in Life Sciences / Cider, an alcoholic beverage made from fermenting apple juice, has grown in popularity and production in the United States in recent years. With increased in production and sales there is increase demand for high quality cider, but cider is prone to sensory faults. A common fault in cider aroma includes negative off aromas know as volatile sulfur compounds (VSCs). These aromas are often described as "rotten eggs", or "cabbage" and lead to consumer rejection of the product. One of the most recognized VSCs is hydrogen sulfide (H2S) which has a characteristic smell of "rotten eggs". These negative off aromas are thought to be produced during yeast fermentation under nutrient lacking conditions. Apples, depending on cultivar, ripeness, and other factors, naturally lack yeast assimilable nitrogen, vitamins, amino acids, and other nutrients needed for a successful yeast fermentation leading to off aromas. Yeast nutrients can be added to apple juice to increase nutrient availability, but little research has been focused on nutrient addition and timing of additions to prevent H2S production in cider. Most research focused on H2S production has been studied in wine must or grape juice. This knowledge may be limited when applying practices to apple juice due to differences in juice chemistry. Providing cider makers with specific scientific strategies to prevent off aromas, such as H2S, is important to the continued growth of the cider industry. This research is focused on exploring aroma quality and H2S prevention strategies in cider by evaluating how yeast nutrient addition via four exogenous nitrogen rich yeast nutrient and timing of yeast nutrient addition affect H2S production, fermentation kinetics, and consumer perception of aroma in cider fermentation.

Virginia is the largest apple producing state in the Southeast region of the United States and ranks 10th in most cideries in the US. Natural, or un-inoculated, fermentation methods are of interest to cider producers due to the potential for generating unique and complex aromas and flavors via fermentation with naturally present microbiota. The objective of this study was to determine the effect of common pre-fermentation sulfite addition and pH adjustment on cider chemistry and sensory outcomes for naturally fermented high- and low-tannin apple cultivars. Four treatment conditions were applied to both the high- and the low- tannin cultivars: acidification only, sulfites only, acidification and sulfites, and a control with no pre-fermentation juice chemistry adjustment. The eight experimental ciders were fermented using the Pied de Cuve (PDC) method for natural fermentation. Cider chemistry and sensory parameters were determined, and the treatments imparted key differences in both. Key findings were analyzed for pH, titratable acidity, volatile acidity, malic acid, free/total SO2, yeast assimilable nitrogen (YAN), total polyphenols, residual sugars, and ethanol. For the acidified condition, the pH was lowered to 3.2 using malic acid. Cider pH ranged from 3.36 ± 0.04 to 3.72 ± 0.07, reflecting a general trend toward rising pH over the course of fermentation. Juice tannins were 0.244 ± 0.003 g/L for Harrison and 0.12 ± 0.01 g/L for GoldRush. Tannins decreased during fermentation; however, Harrison ciders maintained a higher range compared to GoldRush. Sensory characteristics were determined using a Descriptive Analysis (DA) with a trained panel which produced 28 descriptors. Results were examined via analysis of variance (ANOVA) and significant differences for apple cultivar, acid adjustment, and sulfite use were found for both chemistry and sensory parameters. The interaction between high- and low- tannin content and sulfite use had the most impact on the cider chemistry and sensory attributes. This study helps to shed light on the extent to which pre-fermentation pH adjustment and/or sulfite additions can influence the outcomes of natural cider fermentation in both high- and low-tannin cultivars. / Master of Science in Life Sciences / Cider, also known as "hard cider," is an alcoholic beverage fermented from apples. Virginia is the 6th largest apple producing state in United States and ranks 10th in number of cideries. Natural fermentation uses microorganisms that are present in the environment to ferment cider. This type of fermentation is of interest to the cider industry due to the unique aromas and flavors produced by this method. The objective of this study was to determine the effect of common fermentation management strategies: pre-fermentation sulfite addition and acid adjustment, on cider chemistry and sensory outcomes for naturally fermented high- and low-tannin apple cultivars. Eight experimental ciders were fermented using the Pied de Cuve (PDC) method, which is a type of natural fermentation. Cider chemistry and sensory outcomes were evaluated. The experimental treatments and their interactions imparted key differences in both chemical and sensory outcomes. Cider pH ranged from 3.36 ± 0.04 to 3.72 ± 0.07 reflecting a general trend toward rising pH over the course of fermentation. Juice tannins were 0.244 ± 0.003 g/L for Harrison and 0.12 ± 0.01 g/L for GoldRush. Tannin concentration generally decreased during fermentation; however, Harrison ciders maintained a higher range compared to GoldRush. Sensory characteristics of each cider were determined using a Descriptive Analysis (DA) study, a with a trained panel which produced 28 descriptors, 19 of which were significant. The interaction between high- and low- tannin content and sulfite use had the most impact on the cider chemistry and sensory attributes. This study helps to inform cider producers regarding the impacts of pre-fermentation acid or sulfite additions on natural fermentation, and how those impacts may vary among high- and low-tannin apple cultivars.

Though the cidermaking process is very similar to that of winemaking, there is a lack of scientific knowledge as to how orchard management practices and fruit storage affect the quality of the resulting cider. This research examined how both varying harvest maturities and post-harvest storage temperatures and durations in apple cultivars Dabinett, Brown Snout, and York impacted fruit quality as well as the chemistry of the juice and cider. Harvest intervals of two weeks before maturity, at maturity, and 2 weeks after maturity resulted in significant differences in fruit quality and juice chemistry, but few of these differences persisted in cider chemistry. Nonetheless, differences in concentration of some individual polyphenols determined by UPLC-MS were observed in ciders made from fruit harvested at different stages. For example, cider made from optimally mature Dabinett had over 250% the concentration of procyanidin B5 that was found in cider made from fruit harvested earlier or later. The storage treatments also resulted in substantial differences in fruit and juice chemistry, but fewer differences in cider chemistry. As with the harvest maturity experiment, differences in individual polyphenols were detected, with ciders made from cv. York having 20% higher epicatechin concentration when stored for 6 weeks at 1°C rather than 10°C. Finally, the accuracy of the Folin-Ciocalteu (FC) assay, commonly used for quantification of total polyphenols in fruit juices and fermented fruit beverages was critically evaluated. Reducing sugars in the sample matrix did not affect the results of the FC assay, whereas the presence of the amino acid tyrosine resulted in significant overestimation of total polyphenols in fruit juice by the FC assay. / Master of Science in Life Sciences / Cider production and consumption in North America has increased rapidly in recent years. Though cidermaking is in many ways similar to winemaking, there is a lack of scientific knowledge as to how orchard management practices and fruit storage affect the quality of cider. This study examined how varying the harvest date and the ways in which apples are stored after harvest but before cidermaking can affect cider quality. This work was conducted using the apple cultivars Dabinett, Brown Snout, and York. We found that differences in fruit maturity at harvest as well as post-harvest storage parameters impacted fruit, juice and cider quality. However, the differences observed in cider quality as a result of these treatments were much more subtle than the observed differences in fruit and juice quality. This work indicates that in order to accurately assess the impact of orchard management and post-harvest treatments on cider quality, cider should be made and evaluated, rather than assuming that the differences observed in fruit and/or juice will directly translate into cider quality differences.

An apple wine produced by Kiviks Musteri AB have an undesirable flavor of yeast. As a step in the development to reduce this off-flavour the wine flavor was analyzed by gas chromatography-mass spectrometry (GCMS) with headspace solid-phase microextraction (HS-SPME). Two other wines without the flavor of yeast where analyzed as references. Samples from the production step prior to clarification where also analyzed. Through matching against mass spectrum library, retention index and in some cases references a total of 37 volatile compounds were identified in the apple wines. Some uncertainty in the relative quantification of a few compounds was caused by insufficient clearance (deadsorption) of the SPME-fiber. When comparing the different wines the compounds were divided into groups: key compounds, ethyl esters, derivatives of 3-methyl-1-butanol, other compounds: group 1 and other compounds: group 2. In each group the percent area for each compound was calculated. Comparing the percent area of each wine showed that the samples prior to clarification contains a higher number of volatile compounds e.g. ethyl esters and 3-methylbutanol derivatives than the final wine products. The comparisons also revealed differences between the wines. The results from the analyses indicated that the compounds that hypothetically contribute to the yeast-flavor could be 2-phenylethanol; 3-methylbutanoic acid; 2-methyl-1-butanol; 2-phenylacetaldehyde och 2-methylthiolan-3-one. The results need to be verified e.g. by an odor panel if they are going to be useful for Kivik Musteri AB in its effort to solve the taste problem in the wine.

Dissolved oxygen has previously been shown to affect the colour and sensory properties of red and white wine during storage. A number of different wines and wine based sparkling ciders are made at Kiviks Musteri AB. The aim of this work is to study the effects of dissolved oxygen and different enological treatments on sensory quality and colour of red wine and sparkling apple cider during storage at different temperatures. The effects of fermentation and fining on foaming ability of pear wine are also studied.   Samples of red wine were taken after different processing steps such as pumping, sulphuration, pasteurization and filling. To evaluate the effects of the processes on the wine, dissolved oxygen, colour and free SO2 were measured in each. Measurements were also made on samples of red wine stored at either 38°C or room temperature for different amounts of time. Sensory evaluations were also made of the wine samples. Colour was measured by measuring absorbance at 420, 520 and 620 nm. Dissolved oxygen was also measured after different processing steps during production of apple cider. To study the effects of dissolved oxygen on cider, three different batches of apple cider were produced, with different concentrations of dissolved oxygen. The samples were stored at either 38°C or room temperature for one week. Measurements of absorbance at 420 nm and free SO2, along with sensory evaluation were made on the cider samples before and after storage. Fermentation and fining of pear wine were made in small scale and the foaming ability was compared to that of large scale factory produced wine.   Pumping and filling had negative impact on the flavour of red wine. Colour intensity increased while free SO2 decreased during storage of red wine. The sensory quality decreased during storage and a higher storage temperature had a distinctive impact on this decrease. Dissolved oxygen had no noticeable effect on changes in sensory properties of neither red wine nor cider during storage. A higher concentration of dissolved oxygen was correlated to a higher increase in colour intensity of red wine though. A higher decrease was also seen in free SO2 in red wine samples with higher dissolved oxygen content when stored at 38°C. Fermentation had a large impact on foaming properties of pear wine. Small scale wine fermentation resulted in much lower foaming ability than large scale fermentation. / Syrehalten i viner har i tidigare studier visat sig kunna påverka både färg- och smakförändringar i vinerna under längre tids lagring. På Kiviks Musteri AB i Skåne produceras en mängd olika sorters vin och vinbaserade cidrar. Målet med den här studien är att studera vilken effekt syrehalten har på smak och färg i viner och cidrar från Kiviks Musteri som får lagras i olika temperaturer. Effekten av olika processteg under produktionen studeras också. Slutligen studeras även hur skumbildningen i päronvin påverkas av jäsning och klarning av vinet.   Prover av rödvin togs efter de olika processtegen vinet genomgår på Kiviks Musteri. Proverna lagrades olika länge i antingen 38°C eller rumstemperatur. Färgstyrka och smak analyserades på proverna före och efter lagringen. Syrehalten analyserades också i proverna direkt efter att de tagits och svavelhalten i proverna analyserades före och efter lagringen för att mäta hur mycket proverna oxiderades under lagringen. Mätningar av syrehalt gjordes även efter olika processteg under produktionen av äppelcider på Kiviks Musteri. Vilken effekt syrehalten har på äppelcider studerades genom att tre olika satser äppelcider med olika syrehalt tillverkades. Prover från dessa lagrades en vecka i antingen 38°C eller rumstemperatur. Därefter analyserades färgstyrka, svavelhalt och smak på proverna. Hur skumbildning i päronvin påverkas av jäsning och klarning studerades genom att päronvin fick jäsa och klarnas antingen i stor skala i musteriets tankar eller i liten skala på ett laboratorium. Skumbildningen mättes genom ett test där vinprover blandades med kolsyrat vatten.   De processer som inverkade starkast på smaken på rödvin var pumpning och tappning, vilka gav tydliga smakförsämringar. När rödvin lagrades så minskade svavelhalten medan färgstyrkan ökade. En försämring av smaken skedde också under lagringen, särskilt när vinet lagrades i 38°C. Syrehalten hade ingen tydlig påverkan på smaken av vare sig rödvin eller äppelcider. Syrehalten i rödvin hade däremot ett svagt samband med ökningen i förgstyrka i rödvin. Syrehalten hade även ett samband med minskningen av svavelhalten i de prover av rödvin som lagrades i 38°C. Skumbildningen i päronvin påverkades väldigt starkt av jäsningen, medan klarningen hade begränsad effekt. Skumbildningen var vesäntligt mycket lägre i päronvin som jäst i liten skala på laboratoriet än i det vin som jäst i musteriets tankar.

This master thesis deals with the investigation of selected chemical and sensory characteristics of ciders, which were made from four selected apple varieties. The theoretical part describes the chemical composition of apples, cider, the technology of production and production in the world. The next section describes the analytical methods used to determine chemical characteristics not only in ciders but also in other alcoholic beverages. The experimental part focuses on the determination of chemical characteristics such as the content of organic acids, carbohydrates, total phenolic content, alcohol antioxidant activity and elemental composition. The purpose of the work was to find out how different varieties differ in chemical composition. The produced ciders were subjected to sensory analysis to evaluate the selected cider sensory parameters, which were in the natural state and with the addition of carbon dioxide. The results show that ciders of different varieties differ in chemical composition. Malic acid was the most cider's abundant of the organic acids in the range of 2759 – 4411 mg·l-1. Another acid represented was lactic acid in the range of 166,2 – 288,1 mg·l-1. The glucose content of each cider was determined between 845,3 – 1159,8 mg·l-1and fructose 32,6 – 406,7 mg·l-1. Potassium 944,29 – 1073,98 mg·l-1 was the most represented of all elements. The total phenolic content was determined to be in the range of 164,2 – 214,1 mg of GAE·l-1and the antioxidant activity of 0,192 – 0,318 mg·l-1. These differences in chemical composition were also reflected in sensory evaluation. According to the overall assessment, the best cider was made from the Granny Smith variety, which contained the most organic acids and carbohydrates. It has been found that by adding carbon dioxide, sensory parameters such as colour, taste and smell are altered.

The thesis on the topic: Tracking of quality parameters for apple ciders in the retail network was accomplished at the Department of Post-Harvest Technology of Horticultural Products at the Faculty of Horticulture at the Mendel University in Brno in years 2016/2017. The goal of this thesis was to design and prepare several variations of apple ciders and compare them with products from the retail network. Thesis defines apple ciders, their history and division, legislation, requirements on labelling, technology of production and compares the available products in the czech retail network. In the practical part, the thesis deals with the comparison of produced and purchased apple ciders according to the specified quality parameters and the sensory evaluation.

The Virginia cider industry has grown rapidly in the past decade, and demands research-based recommendations for cider fermentation. This study evaluated relationships between the unique chemistry of apples and production of hydrogen sulfide (H2S) in cider fermentations. Yeast assimilable nitrogen (YAN) concentration and composition and residual fungicides influence H2S production by yeast during fermentation, but these factors have to date only been studied in wine grape fermentations. This study surveyed 12 Virginia-grown apple cultivars and found that the majority were severely deficient in YAN. The effects of three fungicides on cider fermentation were investigated; elemental sulfur, fludioxonil and fenbuconazole. Fenbuconazole adversely impacted fermentation kinetics. Sulfur and fludioxonil marginally impacted fermentation kinetics. Sulfur increased H2S production, but fludioxonil and fenbuconazole did not affect H2S production. There was no difference in fermentation kinetics and H2S between nitrogen sources arginine (approximating grape), asparagine (approximating apple) and ammonium (YAN supplement). Supplementation with methionine resulted in increased fermentation rate and decreased H2S production. The detrimental effects of fenbuconazole and beneficial effects of methionine were diminished with increasing total YAN. Contrary to previous findings, the most H2S was formed at 153 mg/L YAN which is above the generally recommended minimum to prevent H2S formation. These results indicate that apple juice chemistry may influence yeast metabolism during cider fermentation, in ways that have not been previously studied in grape fermentation. Our findings indicate the need for and contribute to the development of targeted fermentation management practices for cidermaking. / Master of Science in Life Sciences

Hazard Analysis Critical Control Point (HACCP) regulations for juice manufacture require the application of a process that will result in a 5-log reduction (99.999%) of the pertinent pathogen in the juice being processed. The use of ultraviolet (UV) light, as an alternative to traditional thermal processing, has been adopted by some juice processors as a means of meeting the HACCP 5-log performance standard. However, little research had been performed to determine the effect of UV when used in combination with antimicrobial agents that are commonly added to juice products. Therefore, the objectives of this work were (1) to determine if chemical preservatives and ultraviolet light have a combined effect on the reduction of Escherichia coli in apple cider, and (2) to determine the influence of adding chemical preservatives at different points in the processing of juice (i.e., either prior to or after ultraviolet light processing) on the reduction of Escherichia coli in apple cider. In this study, refrigerated (4°C) pasteurized apple cider that contained no added preservatives was inoculated with E. coli ATCC 25922, a surrogate strain for E. coli O157:H7, and exposed to UV (peak output: 254 nm). The following chemical preservatives were added to apple cider either prior to or after UV exposure: dimethyl dicarbonate (75 and 150 ppm), hydrogen peroxide (75 and 150 ppm), potassium sorbate (1000 and 2000 ppm), and sodium benzoate (1000 and 2000 ppm). Following UV exposure and chemical preservative application, inoculated juices were stored at 4°C for 72 hours. Samples were collected prior to and immediately after UV exposure and at 24, 48, and 72 hours of storage. At each sampling point, juice portions (0.1 ml) were serially diluted in peptone diluent (0.1%) and surface plated onto Tryptic Soy Agar (TSA). Counts of the bacterial colonies were made 48 hours after incubating plates at 35°C. Overall, reductions of E. coli were greater in cider treated with preservatives after UV processing than when preservatives were added prior to UV processing (P < 0.05). Furthermore, dimethyl dicarbonate and hydrogen peroxide were more effective than potassium sorbate and sodium benzoate in reducing E. coli populations in conjunction with UV (P < 0.05). When added prior to UV exposure, potassium sorbate was the least effective, allowing for the greatest survival (P < 0.05). This study describes the use of UV in conjunction with hydrogen peroxide and dimethyl dicarbonate as an effective method for producing a 5-log or greater reduction of E. coli O157:H7 in apple cider. / Master of Science

This thesis analyzes data from seven Swedish craft cider entrepreneurs to examine how they respond to challenges within the entrepreneurial contexts–institutional, business, social, and spatial–defined by Welter. Thematic analysis is used to identify the major challenges within each context and then Bourdieusian capital theory is employed to analyze how these artisan entrepreneurs use, convert, and combine capitals to overcome obstacles. Findings reveal that two major challenges are present within the various contexts–cider’s symbolic deficit in Sweden and the formation of a Swedish craft cider community and industry. In the face of these challenges Swedish craft cidermakers demonstrate creativity in using and converting non-economic capitals–social capital in particular.