Yogurt Fermentation

Yogurt Fermentation Yogurt is made by lactic acid fermentation. The main (starter) cultures in yoghourt are Lactobacillus bulgaricus and strep thermophilus. The function of the starter cultures is to ferment lactose (milk sugar) to produce lactic acid. The cast up in lactic acid decreases pH and causes the milk to clot, or go the kookie gel that is characteristic of yogurt. The fermentation of lactose also produces the odor compounds that are characteristic of yogurt. Lactobacillus bulgaricus and Streptococcus thermophilus are the only 2 cultures needed by law (CFR) to be present in yogurt.Other bacterial cultures, much(prenominal) as Lactobacillus acidophilus, Lactobacillus subsp. casei, and Bifido-bacteria may be added to yogurt as probiotic cultures. Probiotic cultures benefit human race health by improving lactose digestion, gastrointestinal function, and stimulating the resistive system. Lactic acid fermentation is the simplest type of fermentation. Basically, it is a r edox reaction. In anaerobic conditions, the cells primary mechanism of ATP issue is glycolysis. Glycolysis reduces that is, transfers electrons to nicotinamide adenine dinucleotide+, forming nicotinamide adenine dinucleotideH.However, there is only a limited supply of NAD+ available in a cell. For glycolysis to continue, NADH must be oxidized that is, declare electrons taken away to regenerate the NAD+. This is usually done with an electron transport chain in a process called aerophilous phosphorylation. However, this mechanism is not available without oxygen. Instead, the NADH donates its extra electrons to the pyruvate molecules formed during glycolysis. Since the NADH has lost electrons, NAD+ regenerates and is again available for glycolysis.Lactic acid, for which this process is named, is formed by the reduction of pyruvate. The quantity fermentation process to make yogurt is fairly simply. The milk variety is pasteurized at 185F (85C) for 30 minutes or at 203F (95C) f or 10 minutes. A high heat treatment is use to denature the whey (serum) proteins. This allows the proteins to form a more stable gel, which prevents musical interval of the water during storage. The high heat treatment also further reduces the rate of spoilage organisms in the milk to provide a better milieu for the starter cultures to grow.Yogurt is pasteurized before the starter cultures are added to ensure that the cultures go forward active in the yogurt after fermentation to act as probiotics if the yogurt is pasteurized after fermentation the cultures will be inactivated. Next, the combine is homogenized (2000 to 2500 psi) to mix all ingredients thoroughly and improve yogurt consistency. Then, the milk is cooled to 108F (42C) to bring the yogurt to the ideal growth temperature for the starter culture. undermentioned this, the starter cultures are mixed into the cooled milk.Next, the milk is held at 108F (42C) until a pH 4. 5 is reached. This allows the fermentation to p rogress to form a soft gel and the characteristic flavor of yogurt. This process can take several(prenominal) hours. The yogurt is then cooled to 7C to stop the fermentation process. harvest-tide and flavors are added at different steps depending on the type of yogurt. Finally, the yogurt is pumped from the fermentation vat and packaged as desired. Primary artificial lake Yogurt Production. Milk Facts. Cornell University, n. d. Web. 8 Oct 2012.