Naked Science Forum

Non Life Sciences => Chemistry => Topic started by: thedoc on 24/05/2016 15:02:36

Title: QotW - 16.05.20 - What role does cooking play in digestion?
Post by: thedoc on 24/05/2016 15:02:36

What role does cooking play in digestion?
Asked by Sol


                                        Find out more on our podcast page (http://www.thenakedscientists.com/HTML/podcasts/naked-scientists/show/1001354/)

 

Title: Re: how does the changes foods undergo during cooking play a role in digestion?
Post by: chiralSPO on 01/04/2016 19:38:20

I don't know too much about cooking chemistry, but I'll share some of what I do know, regarding digestibility...

Proteins have very specific ranges of shapes that they adopt in living organisms, and probably aren't significantly different in fresh, unspoiled, uncooked food. At elevated temperatures (say 50 °C and up, being especially significant above 100 °C) proteins begin to "denature." This doesn't necessarily break any covalent bonds within the protein, but does change how the protein is folded. This can make particularly robust proteins somewhat easier to digest, and it can also decrease toxicity.

For instance many funguses contain a wide variety of enzymes that help them digest their food sources, be it cellulose, lignin, humins (not humans) or animal tissues... Eating raw funguses could lead to a scenario in which they are digesting you while you are digesting them. Once cooked, however, the enzymes completely loose their activity, and are just as harmless and nutritious as eating cooked egg whites. The same goes for polypeptidic toxins contained in animals (various venoms), plants (like ricin in castor) and in funguses (some particularly nasty toxins in amanita funguses are harmless once denatured)

Another class of toxins, cyanohydrins also known as alpha-hydroxy nitriles, release cyanide when digested or when being cooked ("cyanogenic"). These compounds are responsible for a large number of plant-derived foods which are toxic when raw, but harmless when cooked (cassava/yucca/manioc/tapioca, apricot seeds, bamboo shoots; see: http://www.foodsafety.govt.nz/elibrary/industry/Cyanogenic_Glycosides-Toxin_Which.pdf)

Glycosides (some of which are cyanogenic) are also a large class of toxins, of which most are decomposed during the cooking process.

Title: Re: how does the changes foods undergo during cooking play a role in digestion?
Post by: evan_au on 01/04/2016 22:05:37

A recent paper suggests that cooking greatly reduces the mechanical strength and elasticity of food, allowing extraction of far more calories.
The authors of the paper ran experiments which included chewing raw goat meat. Human teeth make almost no impression on it, and you can extract almost no calories from it (but you can get some nutrition by slicing it into small pieces with stone tools).

I assume that cooking breaks open cell walls, and denatures the connective tissues, making it much easier to bite off pieces, chew and swallow. Digestive enzymes would then have easier access.
See: http://www.nature.com/news/food-processing-1.19513