Question

Yeast fermentation lab help please ?

rate of fermentation decreases after 20 min. Provide one reason why this may happen?

Answer 1

Many possibilities

Explanation:

If you are using yeast and sugar in a liquid solution then one reason could be because the alcohol created from the yeast is toxic to yeast at certain levels. Alcohol is what is used frequently to kill bacteria and sterilize things, so it makes sense. However, I do not think there would be enough alcohol in there after 20 minutes to decrease fermentation.

Another reason could be that fermentation does not really start for a couple of hours to a day or two after being combined with the other "ingredients." It really depends on the type of yeast used (baker's, champagne, brewer's, etc.).

Another reason could be that the yeast is not at the ideal temperature. Different yeasts can survive in different temperature ranges, and if the temperature is not ideal it would be very likely that the yeast would begin to die off and fermentation would barely occur.

A final obvious reason would be that the lab equipment wasn't sterilized before use and some bacteria killed the yeast.