This study describes a screening system for future brewing yeasts focusing on nonSaccharomyces yeasts. The aim was to find new yeast strains that can ferment beer wort into a respectable beer. Ten Torulaspora delbrueckii strains were put through the screening system, which included sugar utilization tests, hop resistance tests, ethanol resistance tests, polymerase chain reaction fingerprinting, propagation tests, amino acid catabolism and anabolism, phenolic off-flavour tests and trial fermentations. Trial fermentations were analysed for extract reduction, pH drop, yeast concentration in bulk fluid and fermentation by-products. All investigated strains were able to partly ferment wort sugars and showed high tolerance to hop compounds and ethanol. One of the investigated yeast strains fermented all the wort sugars and produced a respectable fruity flavour and a beer of average ethanol content with a high volatile flavour compound concentration. Two other strains could possibly be used for pre-fermentation as a bio-flavouring agent for beers that have been postfermented by Saccharomyces strains as a consequence of their low sugar utilization but good flavour-forming properties.
Alcohol-free beer (AFB) is no longer just a niche product in the beer market. For brewers, this product category offers economic benefits in the form of a growing market and often a lower tax burden and enables brewers to extend their product portfolio and promote responsible drinking. Non-Saccharomyces yeasts are known for their flavor-enhancing properties in food fermentations, and their prevailing inability to ferment maltose and maltotriose sets a natural fermentation limit and can introduce a promising approach in the production of AFB (≤0.5% v/v). Five strains isolated from kombucha, Hanseniaspora valbyensis, Hanseniaspora vineae, Torulaspora delbrueckii, Zygosaccharomyces bailii and Zygosaccharomyces kombuchaensis were compared to a commercially applied AFB strain Saccharomycodes ludwigii and a Saccharomyces cerevisiae brewer's yeast. The strains were characterized for their sugar utilization, phenolic off-flavors, hop sensitivity and flocculation. Trial fermentations were analyzed for extract reduction, ethanol formation, pH drop and final beers were analyzed for amino acids utilization and fermentation by-products. The performance of non-Saccharomyces strains and the commercial AFB strain were comparable during fermentation and production of fermentation by-products. An experienced sensory panel could not discriminate between the non-Saccharomyces AFB and the one produced with the commercial AFB strain, therefore indicating their suitability in AFB brewing.
Breads prepared with a (fermented) rootlet inclusion level of up to 10% compared favourably with wholemeal breads from nutritive, technological and textural perspectives. Furthermore, they were well accepted by sensory panellists. Using rootlets as a food ingredient would have the added benefit of increasing this malting by-product's market value.
Non-alcoholic beer (NAB) is enjoying growing demand and popularity due to consumer lifestyle trends and improved production methods. In recent years in particular, research into the application of non-Saccharomyces yeasts to produce NAB via limited fermentation has gained momentum. Non-Saccharomyces yeasts are known to produce fruity aromas, owing to a high ester production. This trait could be harnessed to mask the often-criticized wort-like off-flavor of NAB produced via limited fermentation. Six Cyberlindnera strains were characterized and screened in wort extract. Four of the six strains produced a pleasant, fruity aroma while exhibiting low ethanol production. The strain Cyberlindnera subsufficiens C6.1 was chosen for fermentation optimization via response surface methodology (RSM) and a pilot-scale (60 L) brewing trial with subsequent sensory evaluation. A low fermentation temperature and low pitching rate enhanced the fruitiness and overall acceptance of the NAB. The NAB (0.36% ABV) produced on pilot-scale was significantly more fruity and exhibited a significantly reduced wort-like off-flavor compared to two commercial NABs. This study demonstrated the suitability of Cyberlindnera subsufficiens to produce a fruity NAB, which can compete with commercial NABs. The outcome strengthens the position of non-Saccharomyces yeasts as a serious and applicable alternative to established methods in NAB brewing.
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