Evaluation of autochthonous Saccharomyces bayanus strains under stress conditions for making ice ciders

Mosaic Genome of a British Cider Yeast

Hybrid formation and introgressions had a profound impact on fermentative yeasts domesticated for beer, wine and cider fermentations. Here we provide a comparative genomic analysis of a British cider yeast isolate (E1) and characterize its fermentation properties. E1 has a Saccharomyces uvarum genome into which ~102 kb of S. eubayanus DNA were introgressed that replaced the endogenous homologous 55 genes of chromosome XIV between YNL182C and YNL239W. Sequence analyses indicated that the DNA donor was either a lager yeast or a yet unidentified S. eubayanus ancestor. Interestingly, a second introgression event added ~66 kb of DNA from Torulaspora microellipsoides to the left telomere of SuCHRX. This region bears high similarity with the previously described region C introgression in the wine yeast EC1118. Within this region FOT1 and FOT2 encode two oligopeptide transporters that promote improved nitrogen uptake from grape must in E1, as was reported for EC1118. Comparative laboratory scale grape must fermentations between the E1 and EC1118 indicated beneficial traits of faster consumption of total sugars and higher glycerol production but low acetic acid and reduced ethanol content. Importantly, the cider yeast strain produced high levels of fruity ester, including phenylethyl and isoamyl acetate.

New Ciders Made by an Exhaustion Method: An Option to Val-Orise Subproducts from the Making of Ice Ciders

Cryo-extraction (pressing of frozen apples), is one of the two freeze-enrichment systems allowed for the making of ice juices. Its ciders are often described as more complex and aromatic, however, the production yield is quite low. The Exhaustion method associated with the previous one proposes the valorisation of the discarded apple juice fractions for the making of new ciders. Three types of apple juices and three species of yeasts (S. bayanus, C6; S. cerevisiae, Levuline-CHP, and T. delbrueckii, Biodiva-TD291) have been used to evaluate the Exhaustion method. The ciders obtained were analysed for chemical and volatile composition as well as sensory characteristics. The yield (%) of the Exhaustion process ranged between 24 and 37%. The yeasts promoted the fermentation at different rates, providing ciders with alcoholic degrees between 9 and 12 (%v/v), and low volatile acidities. The yeast strain significantly influenced most of the parameters analysed, whereas the raw apple juice influenced the perception of the attributes fruity, apple and butter. Although the ciders produced by Exhaustion presented significantly lower concentrations of all the volatile compounds analysed than the corresponding ice ciders obtained by Cryo-extraction, the S. bayanus C6 and T. delbrueckii TD291 gave highly valued ciders from the sensory point of view.

A high-throughput screening method for the discovery of Saccharomyces and non-Saccharomyces yeasts with potential in the brewing industry

Both Saccharomyces and non-Saccharomyces yeast strains are of great importance for the fermentation industry, especially with the flourishing of craft breweries, which are driving current innovations. Non-conventional yeasts can produce novel beverages with attractive characteristics such as flavour, texture, and reduced alcohol content; however, they have been poorly explored. A new method for screening the fitness of conventional and non-conventional yeast libraries utilising robotic platforms and solidified media representing industrial conditions is proposed. As proof of concept, a library formed of 6 conventional and 17 non-conventional yeast strains was distributed in 96, 384 and 1536 arrays onto a YPD agar medium. Following this, the library was replicated in different conditions mimicking beer and cider fermentation conditions. The colony size was monitored over time, and fitness values measured in maximum pixels/h and maximum biomass were calculated. Significant differences in growth were observed in between the different strains and conditions. As examples, Candida milleri Y-7245 displayed good performance in wort conditions, and Kazachstania yakushimaensis Y-48837 stood out for its performance in apple juice. The method is proposed to be used as a pre-screening step when studying vast yeast libraries. This would enable interested parties to discover potential hits for further study at a low initial cost. Furthermore, this method can be used in other applications where the desired screening media can be solidified.

Apple Fermented Products: An Overview of Technology, Properties and Health Effects

As an easily adapted culture, with overloaded production in some parts of the globe, apples and their by-products are being redirected to pharmaceutical, canning and beverages industries, both alcoholic and non-alcoholic. Fermentation is generally considered to increase the bioavailability of bioactive compounds found in apple, by impacting, through a high degree of changes, the product’s properties, including composition and health-promoting attributes, as well as their sensory profile. Probiotic apple beverages and apple vinegar are generally considered as safe and healthy products by the consumers. Recently, contributions to human health, both in vivo and in vitro studies, of non-alcoholic fermented apple-based products have been described. This review highlighted the advances in the process optimization of apple-based products considering vinegar, cider, pomace, probiotic beverages and spirits’ technologies. The different processing impacts on physical-chemical, nutritional and sensory profiles of these products are also presented. Additionally, the harmful effects of toxic compounds and strategies to limit their content in cider and apple spirits are illustrated. New trends of fermented apple-based products applicability in tangential industries are summarized.

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.

Genomic Adaptation of Saccharomyces Species to Industrial Environments

The budding yeast has been extensively studied for its physiological performance in fermentative environments and, due to its remarkable plasticity, is used in numerous industrial applications like in brewing, baking and wine fermentations. Furthermore, thanks to its small and relatively simple eukaryotic genome, the molecular mechanisms behind its evolution and domestication are more easily explored. Considerable work has been directed into examining the industrial adaptation processes that shaped the genotypes of species and hybrids belonging to the Saccharomyces group, specifically in relation to beverage fermentation performances. A variety of genetic mechanisms are responsible for the yeast response to stress conditions, such as genome duplication, chromosomal re-arrangements, hybridization and horizontal gene transfer, and these genetic alterations are also contributing to the diversity in the Saccharomyces industrial strains. Here, we review the recent genetic and evolutionary studies exploring domestication and biodiversity of yeast strains.

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.