How Does Alcohol Affect Yeast Fermentation

Ever since ancient times, humans have been exploiting the fermentation process to produce alcoholic beverages and other acid-based foods. Alcohol has been a valuable item for thousands of years which has had a central place in the markets of ancient civilizations. Alcohol has been a prime influencer of human culture from the very beginning, fuelling the development of things such as the arts and religion. Fermentation itself precedes human history. Rice wine has been consumed in China for at least 9,000 years; a chemical residue found in a jar is the oldest known proof of a deliberately fermented beverage (Penn Museum, 2017). But the influence of alcohol and fermentation most likely extends even deeper into prehistory. In today’s modern world

As the temperature increases, so does the rate of reaction (Worthington, 2018). Figure 3 shows the typical change in an enzyme's activity with increasing temperature. The enzyme activity gradually increases with temperature up to around 37ºC, or body temperature. Then, as the temperature continues to rise, the rate of reaction falls rapidly as heat energy denatures the enzyme. The fermentation rate at high temperatures will be low because high temperatures are lethal to yeast. Therefore, the optimum temperature for fermantion is around 37C, anything lower than 37C and the enzymes haven’t achieved their maximum possible activation energy but anything higher than 37C and the enzymes move too fast and denature. Fermentation is also affected by pH levels. Yeast preforms better in more acidic conditions, in specific its optimum pH is around 5 (ALevelNotes, 2016). This is due to the fact that yeast has evolved to digest the sugars that are found in nature (Biology Online, 2006) . Most natural sugars are found in fruits, which also contain acids such as citric acid. Thus, yeast cells have evolved to favour a slightly acid medium and fermentation progresses best in the pH range 4.5 to 5.5. Increasing or decreasing the pH too much causes the enzymes to stop comepletly and denature. Therefore, slightly acidic conditions are more favourable to fermantion due to yeasts preferring acidic conditions. Another factor that affects fermantion is the structure and type of the sugar present. Glucose would be the most efficient sugar due to the fact it doesn’t require any additional energy to convert it and can be directly used in the glycolysis cycle. This means that monosaccharides are more efficient at fermantion due to the fact that they are easily broken down into glucose. Thus, this would imply that sugars that have a polysaccharides structure are the least