Question

1.Yogurt

a.)Outline the protocol used of making yogurt in a lab. Describe the process of the symbiotic relationship of the two bacterial organism S. thermophilus and L. Bulgaricus in yogurt making.

b.) Discuss the similarities and dissimilarities of making yogurt at home and in the lab.

Answer 1

(a) Yoghurt manufacture from the milk fermentation is an old practice that involves the combination of two and more cultures such as the Streptococcus thermophilus and the Lactobacillus bulgaricus. Gram-positive thermophilic species convert lactose into lactic acid by glycolysis process. The lactic acid makes yogurt creamy, avoids the spoilage and discourages the development of pathogen. Lactic acid also creates a solid curd that results in a thick structure with the main milk protein, casein.

Glucose and galactose together make lactose as a disaccharide molecule. Among the two starters Streptococcus thermophilus and the Lactobacillus bulgaricus, L. bulgaricus have the capability to metabolize glucose which leads to galactose accumulation that adds yogurt sweetness.

Materials:

1. ½ Gallon whole fat or non fat cow/goat/plant based milk.
2. 5 to 10 gm starter culture (Contains Lactobacillus bulgaricus, Lactobacillus acidophilus, and Streptococcus thermophilus). These are Yogourmet freeze dried starter.
3. Ice water bath
4. Thermometer
5. 3-Gallon Pot with lid
6. Spatula
7. Spoon
8. Small bowl
9. Whisker
10. Glass Mason Jar Containers and lids
11. Plastic wrap

Protocol:

1. At first ½ gallon of milk put into 3 gallon pot.
2. Then slowly heat the milk to a temperature of 82 to 90 degree C with constant stirring. Keeping this on mind that milk should not be over boiled.
3. After turning off the milk lid should be put on the container and rest the milk for 10 minutes. During this resting phase occasionally whisking the milk to prevent skin formation over the milk.
4. Then transfer the heated milk into a pan with ice and cool water to cool down the milk to 43 to 46 degree C.
5. Then add 5-10 gm starter mix into a small bowl of milk and mix the mixture to dissolve completely. Then this milk adds to the rest milk container and mixes it well.
6. After that this milk mixture is poured into a glass mason jar and covered the mouth with plastic wrap. Make sure to create couple of holes on the plastic wraps to minimize the condensation.
7. Then put the lid over the plastic on the jar to make it secure during the incubation period.
8. Then incubate the whole glass jar for minimum period of 6 to 12 hours at 43 to 46 degree C.
9. After incubation period, place the jar into the freeze for 2 weeks.

In this way, yogurt has made in lab.

(b) Dissimilarities of making yogurt at home and in the lab are:

Characteristics	Yogurt making at Lab	Yogurt Making at Home
Starter	In lab high quality starter culture has used	Instead of using excellent starter culture, leftover yogurt is used as a starter.
Incubator	To incubate the milk and starter mixture, it is important to keep the mixture continuously into a warm temperature and this will ferment the mixture very well. So in lab incubator is used to ferment the mixture.	At home, mixture islet to sit at room temperature for overnight.

Similarities of making yogurt at home and in the lab are:

In both cases, the general making procedure is same. In both cases, milk is boiled first and let it cool to prevent dying of bacteria. Then add the starter and mix it well. After that leave it for incubate.

This simple method is followed in both the cases but in lab there are lots of factors are followed.