2- preparación para hacer yogurt

[1]

List of Reagents and Instruments

A. Equipment

  Beakers
  Heat source
  Incubator, 43ºC
  Thermometer 

B. Reagents

  Milk
  Starter culture (lactobacilus culture ? )or plain yogurt from local stores 

Procedures

 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.) See Note 4.
 6- Use of Lactobacillus acidophilus: Grind 4 yogurt tablets (about 1 g) into fine powder. Repeat Steps 3-5.
 7- For entrepreneurs or simply hungry/thrifty students: You can recycle a small part of the finished product as the starter culture for the next batch. Theoretically, you can multiply or maintain your supply of yogurt indefinitely. However, in actuality, extended recycling is not recommended because the composition of the mixed culture will gradually deviate from the ideal one, and hence the flavor.