What is the maximum allowed temperature to cook onions saving the fructooligosaccharides?
Onions are a great source of fructooligosaccharides that are a natural prebiotic that beneficial bacteria of our gut microbiome feed on.
Having read about this I have started eating raw onions but they can be nasty, as for boiled onions - that's kind of easier for me yet nobody likes them anyway, some people actually find it easier to eat onions raw and just find boiled onions disgusting.
So I have ended up seeking a healthy-tasty ways to cook them.
I've found a scientific papers by Roberto Vega and Zuniga-Hansen (http://dx.doi.org/10.1016/j.foodchem.2014.10.119) that says the percent of retention of sc-FOS is greater than 95% at temperatures above 95 °C yet it doesn't seem to make it clear how far above 95 °C can we go.
Olive oil smoke point is 160°C. Is sautéeing onions at near this temperature ok if saving the fructooligosaccharides is what I want?
Best Answer
To give some perspective on FOS (fructooligosaccharides) denaturation characteristics to sucrose (for a baseline since sucrose is a common molecule),
FOS are water-soluble and their sweetness is 0.3-0.6 times that of sucrose, depending on the chemical structure and the degree of polymerization of the oligosaccharide. FOS are highly hygroscopic and their water holding capacity is greater than that of sucros. The viscosity of a FOS solution is higher than that of sucrose at the same concentration because the greater molecular weight of FOS. The enhanced viscosity of the gastrointestinal content may delay the rate of gastric emptying and the digestion and absorption of nutrients. Their thermal stability also is greater than of sucrose. FOS are highly stable in the normal range of food pH (4.0-7.0).
This is comparing the FOS (fructooligosaccharides) to normal sucrose. Specifically, this mentions that the thermal stability is greater than sucrose.
If sucrose has a decomposition temperature of 186°C (367 °F), when it starts to form caramelized onions, then it is safe to assume that you will be able to fry your onions in olive oil with a smoke point of 160°C without denaturing the FOS since FOS has a greater thermal stability.
Source for decomposition temperature of sucrose: https://en.wikipedia.org/wiki/Sucrose
Pictures about "What is the maximum allowed temperature to cook onions saving the fructooligosaccharides?"
At what temperature are onions cooked?
Around 320\xb0F, sliced onions will caramelize without burning, and don't require constant stirring.Does cooking onions reduce quercetin?
The boiling of onion leads to about 30% loss of quercetin glycosides, which transfers to the boiling water. At that time, the effect of additives on the quercetin conjugates is different according to the compounds.How to Sauté Onions
Sources: Stack Exchange - This article follows the attribution requirements of Stack Exchange and is licensed under CC BY-SA 3.0.
Images: Engin Akyurt, Lachlan Ross, Olga Lioncat, Dmitriy Zub