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Saturday, August 4, 2012

Yoghurt / Yogurt Production: Procedure, Role of bacteria in yoghurt & Therapeutic Value of yoghurt

Yoghurt / Yogurt is a fermented milk with clustered like consistancy, Flavoured or Non-Flavoured product fermented by Lactobacillus bulgaricus Streptococcus thermophilus. Yoghurt has higher nutritive value compared to other fermented products of milk because of its higher milk solid contents.

Production of yoghurt
Yoghurt / Yogurt

Yoghurt / Yogurt is produced by the controlled fermentation of milk by the two species of bacteria. Bacillus Sps.& Streptococcus Sps. The sugar, Lactose in milk is fermented to lactic acid and that it causes the formation of curd. This acid also restricts the growth of food poisoning bacteria & some other bacteria that causes the spoilage of food. So milk is potential source and yoghurt is safer and can be kept for up-to ten days under proper storage conditions.
                                         The correct balance between the two bacteria's are important for good quality of yoghurt. In practice a dried culture can be obtained and this can be grown on pasteurized milk & can be kept in a refrigerator. A part of the master culture can be used everyday for a week & the last part can be re-inoculated into milk to form new starter culture. This method can be continued for several months provided good hygiene. But eventually undesirable bacteria will contaminate the culture & it must be replaced.
                                        If a pure culture is not available, it is possible to add one or two spoonful of commercial yoghurt as starter culture. This can be done everyday. Finally it is possible to add part of yoghurt production to a new batch of milk the following day, there is a greater risk of contamination using this method. Yoghurt can be either stirred or set. Yoghurt is fermented in bulk, stirred and then dispensed into pot. Fruits and nuts can be added into each type but care should be taken to avoid contamination. In some countries layers of fruit syrup is added on the set yoghurt.

yoghurt fermentation
Large Scale Production of Yoghurt
                                                              Image Source
Yoghurt Production Procedure
Yoghurt can be easily produced in small scale, the procedure is as follows:
  1. Collect milk carefully in a cleaned covered vessel.
  2. Pasteurize the milk at 80oC for 15 to 20 mins.
  3. Cool the milk to 40 to 45oC as soon as possible.
  4. Added starter culture and mix well.
  5. Keep the milk in an incubator at 40 - 45oC for 3 - 4 hrs.
  6. Specific coloures and flavours can be added if required.
Process of yoghurt production

Role of Bacterial Culture in Yoghurt / Yogurt Production
In the production of yoghurt, the two yoghurt cultures excerts synergetic action during the initial incubation of Streptococcus thermophilus grows luxuriously because of the liberation of numerous aminoacids from the casein produced by Lactobacillus bulgaricus which stimulate growth of Streptococcus thermophilus.
It is demonstrated that acid production by L.bulgaricus is enhanced by formate & CO2 produced in yoghurt during acidification has been proposed. S.thermophilus grows faster during early part of incubation due to stimulatory effect of amino acids liberated by L.bulgaricus there by removing oxygen and producing the CO2 and formate in milk. After the growth of S.thermophilus it is slowed by increasing concentration of lactic acid. The more acid tolerant L.bulgaricus increases the effect of compounds generated by Streptococci.

Therapeutic Value of Yoghurt / Yogurt
  1. Yoghurt has been used as a biomedicine in treating the patients suffering from gastrointestinal disturbances.
  2. The yoghurt bacteria stops the anaerobic spore formation in the large intestine thus prevents petrification process taking place in alimentary canal.
  3. It is used as refreshing beverage.
  4. Yoghurt is rich in amino acids, Vitamins & Minerals.
  5. Improves Lactose intolerance.
  6. Boost immune system.
  7. High in Calcium, Potassium and Protein.