1. a) Tempe fermentation and yogurt fermentation are two different type of fermentation. Discuss both procedures and highlight the contribution of microorganism during fermentation.

Tempe fermentation- tempeh is fermented soy foy which fermented with the mold of Rhizopus Oligosporus.- tempeh is prepared by using soaked,dehulled and boiled soy beans. Inoculate with Rhizopus sp. Or “tempeh starter”, pack and incubate at room temperature for 26-48 hours. Tempeh can be packed either in perforated plastics or using natural tree leaves.1. Hydrate the soybeans overnight at room temperature in acidified soak water,beans:water,1:3 (1% of 85% lactic acid added)2. Dehull in abbrasive vegetable peeler3. Remove hulls in running water4. Boil cotyledons in acid soak water 90 minutes5. Drain and cool to 37°C6. Inoculate (1 g spores grown on wheat bran/kg cotyledons)7. Incubate at 37°C (stainless steel covered cake pans with 0.3cm holes at 5cm intervals) bean layers 3-5 thicks.

Yogurt fermentation

-Milk is fermented by a mixture of Streplococcus salivarius sp thermophilus and Lactobacillus bulgaricus.- often these two are co-cultured with other lactic acid bacteria for taste or health effect(probiotics)- acid produced from the fermentation causes the protein in the milk (casein) to coagulate into a semisolid curd.- flavour may be added after the yogurt is made.

1. Heat 1 liter (approximately 1 quart) of milk in a beaker slowly to 85 ºC and maintain at that temperature for 2 minutes. This step kills undesirable contaminant microorganisms. It also denaturizes inhibitory enzymes that retard the subsequent yogurt fermentation. If you are attempting this procedure at home with a sauce pan, use caution so as not to allow the milk to boil over and make a mess on your kitchen stove. See Note 1.

2. Cool milk in a cold water bath to 42-44 ºC. The cooling process should take about 15 minutes.

3. Add 5 g of starter culture to the cooled milk and mix with a glass rod. See Note 2.

4. Cover the container to minimize the possibility of contamination. Incubate at 42ºC for 3 to 6 hours undisturbed until the desired custard consistency is reached. Yogurt is set when the mixture stops flowing as the container is tipped slowly. Fluid yogurt results if the mixture is stirred as the coagulum is being formed. See Note 3.

5. The fresh made yogurt is ready for consumption when it is set. However, you may want to refrigerate it first if you are not accustomed to warm yogurt. Refrigeration also stops the growth of the lactic acid culture, which is thermophilic. (Thermophilic cultures grow best at high temperatures.)