Role Of Expiration Dates Of Yeast Sample Viability

1154 Words5 Pages
Role of Expiration Dates in Yeast Sample Viability Nasser Almoteb Kathryn Knackstedt 12/9/2015 Biology 2040, 1003 Abstract Yeasts consume organic compounds (e.g. sugar) to make ATP in a process called fermentation, creating ethanol and carbon dioxide. Dried yeast samples are in a quiescent state; that is, the yeast are in a state of arrested cell growth. Given the differing expiration dates of our yeast samples, we hypothesized that the yeast nearest to their expiration dates would take the longest to produce carbon dioxide. We used the gaseous carbon dioxide product of yeast’s fermentation reaction to observe the length of time our yeast samples (with four different expiration dates) took to undergo fermentation, by…show more content…
These organic compounds, such as sugars, are used by yeasts as reactants in a process called alcoholic fermentation. During alcoholic fermentation, yeast produces two ethanol molecules and two carbon dioxide (C02) molecules from one molecule of glucose; the equation for alcoholic fermentation is: C6H12O6 → 2 C2H5OH + 2 CO2. In our experiment, we used the gaseous property of CO2 at STP to measure the activity of alcoholic fermentation among store-bought yeasts with different expiration dates in the presence of sugar. We hypothesized that the yeast nearer their expiration dates would rise more slowly, or not at all, when compared to the yeast that were farther from the expiration dates listed on their packages. This experiment is important, because yeasts are commonly used subjects of many scientific research studying genes, cell life cycles and responses; and, as such we need to understand how to determine and assure yeasts’ viability. (Gancedo, J. M.1998 and Váchová, L. et al., 2012) Methods To test our hypothesis that yeast closer to their printed expiration dates were less likely to undergo alcoholic fermentation than yeast farther from their printed expiration dates, we used store-bought yeast with different expiration dates, meaning that our yeast varied in age. In addition, we tested our hypothesis using four bags of store-bought yeast, each with different expiration dates. To observe whether each bag underwent fermentation,
    Open Document