Arun Maama, am still not convinced that looking at turmeric as a digestion
inhibitor is the only way to look at it. We do not split things into
individual attributes or alkaloids and reduce the subject to just one of
its aspects. It has so many anti inflammatory antioxidant boosting
properties that it seems to have more benefits
<http://authoritynutrition.com/top-10-evidence-based-health-benefits-of-turmeric/>on
the whole which science is slowly learning about.

Also, it takes a whole lot of turmeric to keep foods from spoiling. I don't
think we ever use it in those quantities. If there is empirical evidence
that x quantity of turmeric inhibits digestion of y quantity of food. I
would like to learn more.

Dear Nisha, 
I am glad that you posed this issue online. I would like to take it and post it on different links that I am involved in and enable more opinions of people. First and foremost, I declare and submit that I am not an authority on the subject of health and I am not qualified to advise you or any one on this subject. But my conviction is based on solid grounds like basic principles of Natural Hygiene and my own personal experience of over four decades.Eat food without turmeric or oil and you will see that the food has been digested from your stomach sooner and you feel the lightness of the body. Eat foods with turmeric and feel that the food is still in the stomach for a long time giving us a heavy feeling in the stomach. 
Many of us get confused with the major two concepts 
 1. the medical approach of treating disease as an entity that is alien to our life and the need to fight it and remove it.by means of anti bodies called  medicines - whether it is an inorganic chemical or an organic herb. Tulasi, Turmeric, garlic, and ever so many in that category . Their role is to stop life's way of dealing with toxins in our body. inflammation,(septic) fever, cough, cold, diarrhea, vomit and the like - acute crisis. Any herb like turmeric which stops these symptoms are considered very valuable in this concept . whooping cough may stop for some time if one takes a glass of warm milk treated with turmeric. But it will not remove the cause of coughing.
 2. The Natural Hygiene concept which considers all these acute symptoms as favorable to life as they were initiated by life itself to maintain high level health. This vigorous activity initiated by the body should be supported first by accepting it as good and then by encouraging it by following stricter measures of discipline following a more natural life style. 
We do not need any anti-septic or anti inflammatory materials in our food. Our body needs food which will be only food and should be digested well. What is a food? One which can be eaten independently eaten as breakfast, lunch or dinner without causing any complication. Compare it with carrots, beets, or other Satvic vegetables. We cannot eat even one spoon of turmeric powder alone. So it is not food and could not be used in our food. When compared to other colloidal condiments which give us a flavor, but will get eliminated as roughage. Continuous intake of turmeric wil leave a stain in our intestines, and liver which is hard to clean up. 
We do not need turmeric and we have plenty of very nutritious  vegetables which furnish all our needs. It is not possible to convince any one who does not want to be convinced. I am stating all this only to clear my own thoughts. It is up to you if you believe in what I say. 
After all I do not know every thing.Do tell me if there are things you know and I will try to learn. thank you for the dialogue .