Yeast Fermentation Case Study

1. Why is pretreatment necessary for fruits and vegetables prior to freezing? Discuss.

Fruits and vegetables have seasonal and perishable nature and subjecting them to some form of preservation helps them be available for later consumption (Lin & Brewer, 2005). According to Wu et al., freezing helps keep food taste, and nutritional value, better than any other conservation technology. However, after freezing-thawing, food presents some drastic changes and cumulative, gradual, and irreversible quality loss, mainly shown in drip loss (which is due to cell damage), texture alteration (loss of turgor during thawing, thus resulting in flaccidity and shrinking), lower volume and, in some cases, change in color , taste and aroma . During freezing,

What is the role of yeast in fermentation? Does the type of yeast affect the process? Explain

Yeast plays a vital role in the production of all alcoholic beverages and the selection of suitable yeast strains is essential not only to maximise alcohol yield, but also to maintain beverage sensory quality. The yeast species that dominates in the production of alcoholic beverages worldwide is Saccharomyces cerevisiae, and the particular strains of this species employed in fermentation exert a profound influence on the flavour and aroma characteristics of different beverages (Stewart & Walker, 2016) . In the case of brewing fermentation, there two main types of yeast that are commonly used, the top-fermenting ale yeast and bottom-fermenting lager yeast. These yeast types are so named because of their tendency to form clumps or flocculate near the top or the bottom of the fermenter before dropping out of solution at the end of fermentation. Each of these types has different characteristics that affect the flavor, aroma, and mouthfeel of the end product (A Perfect Pint, 2016). Ale is top-fermented, meaning the yeast is applied to the top of the wort, and at a higher temperature. Top-fermenting is the oldest method and Saccharomyces cerevisiae is the yeast usually involved. Top-fermenting tends to yield more flavor, as esters (a byproduct of both kinds of fermenting) are more pronounced in warm fermenting, as are phenols (which include things like tannin). Lager, on the