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Spirulina is a highly nutritious microalgae commonly used as a food additive. During fermentation, different adjuncts are incorporated to act as a nutrient source for yeast and fortify or modify the sensory attributes of the final product. In this study, the effect of Spirulina on the characteristics of controlled yeast fermentation and the production of volatile organic compounds (VOCs) was analyzed. Spirulina was added to malted barley during mashing and fermented under standard conditions. An unaltered mash (negative control) and yeast extract (positive control) were also fermented. The addition of Spirulina resulted in an increased fermentation rate (~14% faster) and bigger yeast cells (~34% larger) in comparison to the negative control. There were differences in color (determined as SRM) between treatments; however, there were only minor differences in VOCs, with no statistical differences observed between chemical compound groups. No differences were observed in the pH, total number of yeast cells, or final attenuation between treatments. The primary mechanism for the observed differences is believed to be an increase in amino acids available to yeast that were contributed by the Spirulina. This shows both that Spirulina has a high potential as a fermentation adjunct and that the amino acid profile of an adjunct can significantly impact fermentation. [ABSTRACT FROM AUTHOR]

The exploration of space is becoming more feasible, and with this comes the possibility of performing fermentations in microgravity. Our study explores the potential effects of microgravity on a standard brewing model fermentation. As the fermentation of barley wort has been studied for centuries, there is an established foundation of knowledge with which to compare any changes that occur under microgravity. A modified ASBC miniature fermentation protocol (Yeast-14) was conducted within a Yuri 2.0 microgravity chamber to examine the response of Saccharomyces pastorianus to simulated microgravity conditions. Our findings reveal that yeast exhibited accelerated growth rates under microgravity compared to standard conditions. Additionally, the microgravity environment led to significantly lower levels of volatile compounds such as isoamyl acetate and 2-phenethyl acetate in the final product. Further genetic analysis showed significant downregulation of the ATF2 gene in the control group, potentially the mechanism behind the observed decrease in volatile compounds. These results show that while fermentation under microgravity is likely to eventually be commonplace, there may be changes in rate and gene expression that are beneficial or detrimental to the final product depending upon the desired characteristics. [ABSTRACT FROM AUTHOR]

Berries and their products can enhance the antioxidant profile, color, and sensory characteristics of beverages, resulting in competitive, value-added products. However, a complete overview of how fermentation affects these compounds is lacking. The American black elderberry, Sambucus canadensis, is an excellent candidate for studying how berry juices are affected during fermentation due to high concentrations of color compounds, anthocyanins, and volatile compounds. Gravity, pH, titratable acidity, total anthocyanins, color, and GC-MS analyses were performed on two varieties of elderberries to examine the physical and chemical qualities of elderberry juice before and after wine fermentation. A commercial product with elderberry adjuncts added post fermentation was also analyzed. The concentration of anthocyanins degraded by ~40% as the color of the elderberry wine shifted from blue to red after fermentation. Products that added elderberries post fermentation did not see the same degradation, however, also did not incorporate the same changes to volatile compounds as observed in the fermented wine. The fermentation industry can use this study's findings to decide how best to use fruits to improve commercial products. [ABSTRACT FROM AUTHOR]

Belgian Saisons and Lambics are two well‐known examples in the brewing industry of mixed fermentations, combination of two or more yeast and/or bacteria strains. The purpose of this study was to determine the impact different pitch rates of Saccharomyces cerevisiae (traditional brewing yeast) and S. cerevisiae var. diastaticus (a variant associated with Belgian styles) had on the fermentation kinetics and concentration of the volatile compounds in the finished beers. A series of brews were performed utilizing ratios of S. cerevisiae and diastaticus. The fermentations were heavily monitored, and a model was used to fit fermentation variables. It was found that mixed fermentations produced behaviors that were predictable and proportional to the mixture ratios. As expected, the pure cultural fermentations of diastaticus had a slower fermentation midpoint (M) at 45.45 h versus 28.28 h for S. cerevisiae with the mixed ones falling in between the two. Flavor and aroma play a key role in the acceptability of beer. The mixed fermentations showed a combination of the two different yeast strains aromatic profiles. When combined, there was a strong linearity between alcohols (R2 = 0.94), esters (R2 = 0.89), and the overall total (R2 = 0.91) volatile compounds. Practical Application: Modeling is a widely utilized tool in several different fields. The purpose of this research is to apply modeling techniques to describe the fermentation speed and flavor profile of a mixed fermentation between S. cerevisiae and diastaticus. The equations from this data can be used by brewers for product development purposes to make beers with certain flavor profiles within a desired timeframe. [ABSTRACT FROM AUTHOR]

This research aimed to assess how the partial removal of carbon dioxide affects fermentations to provide a better understanding of how the manipulation of carbon dioxide concentration can be used to optimize industrial fermentations. To achieve this, fermentation kinetics, fermentation metabolic products, and yeast stress indicators were analyzed throughout ongoing brewing fermentations conducted under partial vacuum with atmospheric pressure controls. The partial vacuum reduced the solubility of carbon dioxide in the media and decreased the time necessary to reach carbon dioxide saturation. The effect was an increased rate of fermentation, and significantly more viable cells produced under vacuum pressure compared to controls. Ethanol, glycerol, and volatile organic compound concentrations were all significantly increased under partial vacuum, while indicators of yeast stress (trehalose) were reduced. Additionally, as the number of yeast cells was higher under partial vacuum, less sugar was consumed per volume of yeast cell. This study measured fermentation kinetics, metabolic products, and yeast health to holistically assess the effect of partial vacuum during a batch fermentation and found significant differences in each that can be individually exploited by researchers and industry. Summary An exploration of batch yeast fermentation in a low-pressure environment, with a focus on the health and productivity of the yeast cells. [ABSTRACT FROM AUTHOR]

In this study the combinatory effect of several extrinsic factors on reduced (vacuum) pressure fermentations was explored. Specifically, the pressure, temperature, and FAN levels of high gravity Saccharomyces cerevisiae fermentations were manipulated, while yeast morphology was assessed using automated multivariate image analysis. Fermentation attributes including yeast growth, viability, and ethanol production were monitored using standard methods. Across all FAN and temperature levels, reduced pressure (vacuum pressure) fermentations resulted in a greater than or equal number of cells in suspension, higher average viability, and greater ethanol production in comparison to atmospheric pressure fermentations; however, the magnitude of the effect varied with extrinsic factors. The image analysis revealed that while yeast size was extremely variable across all fermentations, the ratio of vacuole to cell area consistently decreased over each fermentation and could be used to predict the point where the yeast experienced a sharp decline in viability ending the fermentation. This study showed that a combination of traditional measurements and novel automated analyses can be used by brewers to anticipate performance and endpoints of their fermentations, and that reduced pressure can have significant effects upon the rate and final ethanol concentration of variable industrial fermentations. [ABSTRACT FROM AUTHOR]

Beer is traditionally brewed using barley, hops, water, and yeast. Historically, fruit has been utilized in brewing operations as a source of carbohydrates, color, and/or flavor. This practice has been increasing in recent years due to economic and market factors. While many scientific studies have shown that it is both possible and desirable to include fruits in brewing operations, there is little research published on how to properly evaluate their potential for use in brewing. This review aims to introduce and discuss the ways in which fermented products are impacted by the addition of fruit with respect to the following characteristics of the fruit and final product: sugars, volatiles, color, product identity, and microbial factors. To support this review, a case study is included in which peaches were evaluated for potential use as a fruit additive in a commercial brewing application. The peach juice, pre-addition beer, and final product were assessed based upon processing characteristics, sugar content and composition, color, volatile profile, and economic suitability for various applications in fermented beverages. This paper details the methods used to evaluate fruit as a guide for considering fruit as an addition to brewing formulations. [ABSTRACT FROM AUTHOR]

The kinetics and success of an industrial fermentation are dependent upon the health of the microorganism(s) responsible. Saccharomyces sp. are the most commonly used organisms in food and beverage production; consequently, many metrics of yeast health and stress have been previously correlated with morphological changes to fermentations kinetics. Many researchers and industries use machine vision to count yeast and assess health through dyes and image analysis. This study assessed known physical differences through automated image analysis taken throughout ongoing high stress fermentations at various temperatures (30 ◦C and 35 ◦C). Measured parameters included sugar consumption rate, number of yeast cells in suspension, yeast cross-sectional area, and vacuole cross-sectional area. The cell morphological properties were analyzed automatically using ImageJ software and validated using manual assessment. It was found that there were significant changes in cell area and ratio of vacuole to cell area over the fermentation. These changes were temperature dependent. The changes in morphology have implications for rates of cellular reactions and efficiency within industrial fermentation processes. The use of automated image analysis to quantify these parameters is possible using currently available systems and will provide additional tools to enhance our understanding of the fermentation process. [ABSTRACT FROM AUTHOR]

Recently there has been an increased interest in characterising the rates of alcoholic fermentations. Sigmoidal models have been used to predict changes such as the rate of density decline. In this study, three published sigmoidal models were assessed and fit to industrial fermentation data. The first is the four-parameter logistic model described in the ASBC Yeast-14 method. The second model is a nested form of the four-parameter logistic function, adding an extra parameter, creating the 5-parameter logistic equation., where an additional parameter was added to allow for asymmetry. The final model is a three-parameter logistic equation which describes the change in the Apparent Degree of Fermentation with time. The three models were compared by fitting them to industrial data from Australian and Canadian lagers, American and Scottish ales and Scotch Whisky fermentations. The model fits were then compared to one another with a technique developed by Akaike and a nested F-test. The Akaike information criterion compares the models and accounts for both the goodness of fit, and the number of parameters in the model. Finally, consideration was given to the establishment of prediction bands (that enclose the area that one can be 99% sure contains the true datapoints). Calculation of these bands was "challenging" but successful as the industrial fermentation data was heteroscedastic. [ABSTRACT FROM AUTHOR]

Understanding yeast dynamics during fermentation is important for quality control, whether monitoring fermentation consistency or identifying aberrant events, such as premature yeast flocculation (PYF). Previous models of fermentation dynamics tend to be parameter rich and require large time series, which are rare in industry. This research investigates five simpler models to 1) describe fermentation dynamics, 2) refine quality control sampling regimes to improve model fit, and 3) identify PYF fermentations. The ability of these models to describe yeast dynamics was evaluated using model fitting with time series data and Akaike Information Criterion (AIC) model selection. Data simulated from large time series was used with this model fitting approach to improve sampling schedules without increasing sampling effort. Lastly, PYF was identified in fermentations of fungal-contaminated malt using linear discriminant analysis (LDA). For large data sets, a four-parameter extension of the normal curve performed best while smaller data sets were better described by the 2-parameter gamma model. Moving sampling effort nearer the population peak improved model fits. Lastly, all models detected PYF, however the two-parameter gamma model provided a simple metric for distinguishing PYF. This research provides guidelines on appropriate model use, improving sampling regimes, and identifying PYF. [ABSTRACT FROM AUTHOR]