Etiket Arşivleri: Lactic acid fermentation

Making Yogurt – Lactic Acid Fermentation

žMaking yogurt

žLactic Acid Fermentation      

žIntroduction

žYogurt production demonstrates fermentation by Streptococcus thermophilus and Lactobaacillus bulgaricus

žHeated milk is inoculated and maintained at a given temperature causing bacteria to grow and ferment lactose, the suger in milk

žThe bacteria produce lactic acid which causes the milk to coagulate

žMateriales

žFood grade containers, washed

žFood grade thermometer

žHotplate

žBeaker tongs

ž2 cup of milk

ž1/3 cup nonfat dry milk

ž2 table spoons yogurt

žpH meter

žProcedure

žCombine milk with nonfat dry milk and heat in water bath to 87ºC

žHold at that temperature for 10 to 20 minutes

žCool to 46ºC and record the pH of the mixture

žPlace the plain yogurt in jar and gradually blend in the warm milk

žCover and place in oven or incubator at  45ºC

žAllow to stand undisturbed until the mixture is firm when the jar is gently wiggled

žThis may take as long as 6 to 8 houres


Fermentation Lab Sheets‎ > ‎Cucumber Pickling ( FE 411 )

PURPOSE

To practice the production of cucumber pickling. By the way, to measure some parameters of the pickle.

THEORY

Pickle is a product that produced from vegetables and fruits are fermented by lactic acid bacteria in a brine has a specific salt concentration or in their self juice. Any kind of vegetables and fruits can be used for pickling. But, in whole world the most known and manufactured pickle type is cucumber pickle.

Lactic acid fermentation is the most important step occurs in the pickling. The fermentation occurs in anaerobic conditions, generally at 18-20 OC, for 2-8 weeks according to pickle’s content. While fermentation occurs, there is a transition between brine and raw material. The salt in brine passes into raw material and various compounds in raw material like minerals, sugars, and nitrogenous substances pass into brine. Lactic acid bacteria ferment the sugars.

Lactic acid bacteria ferment sugars with different pathways. Homofermentative lactic acid bacteria (Lactobacillus plantarum etc.) which are dominant in fermentation use the EMP pathway and produce only lactic acid. This kind of bacteria forms almost all lactic acid and end the fermentation. Heterofermentative lactic acid bacteria (Leuconostoc mesentereoides etc.) which generally start the fermentation use the HMP pathway and produce lactic acid, ethanol, CO2, acetic acid. Thanks to other compounds exception lactic acid by formed these bacteria; the pickle gets its taste and flavor.

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