Expert: Walter Hintz - 5/25/2010

Question
QUESTION: Hi Walter,

I would appreciate some info on the following. I am researching in waste fruit disposal systems and one of our intention is to retrieve waste fruits, rotten fruits, fruit peels, etc and before we process them into fertilizers, we would like to use a crusher to squeeze all available juices out and store them in closed tanks. My question is:

Will the sugars in the fruit juice degrade and what is the final chemical components it will finally degrade to given all the different types of bacteria expected to be present in these waste products? I've read something about pyruvates or lactic acid, but I'm not quite sure.

I look forward to your useful reply. Thanks.

ANSWER: In the presence of oxygen some of the glucose will break down into pyruvic acid. When you store the juices into closed tanks you will have anaerobic conditions and fermentation occurs and the glucose breaks down into alcohol and carbon dioxide
 C6H12O6  >>>>>>  2(CH3CH2OH)  +  CO2

If exposed to oxygen bacteria will convert the alcohol to acetic acid C2H4O2

---------- FOLLOW-UP ----------

QUESTION: Thank you for your reply. I have a follow up question. What would be the best way to preserve these large quantities of stored fruit juices so that the sugars (i.e. glucose, frustose, etc) do not degrade into alcohol or pyruvic acid? And should we use open or closed tanks?

Answer
You cannot stop the degradation of fruits and fruit juices. Bacteria and yeasts will bring about a breakdown. We are talking about the Law of entropy here. Besides it seems to me that you want it to break down. I am not sure what kind of  a fertilizer you are looking for. The main component of fertilizer is Nitrogen. Fruits contain very little protein.