By cooking food, nutritional changes are induced which mainly concern the health and hygiene-food aspects of the food itself. Among the changes affecting the various macronutrients, those of lipids are predominantly negative; let's see them in detail.
Hydrolysis of fats - a positive aspect
Cooking food fats involves a "hydrolysis (or partial digestion) of the lipids themselves.
This is a modification that mainly concerns i glycerides, or the "complex" fats formed by a molecule of glycerol + 1-3 attached side chains (for example fatty acids). After digestion and absorption, most of the glycerides (triglycerides) are used for the production of ATP, both through the B-oxidation of fatty acids (fatty acids) and through the neoglucogenesis of glycerol.
Fatty acids are nutrients that provide more than double the calories compared to sugars but, on the other hand, they are extremely slow to use both because of the long cellular oxidation process and because of the considerable digestive, absorption and metabolic effort.
By virtue of this "slowness", the hydrolysis by cooking the fats (or breaking the bond between the fatty acids and glycerol with the release of water) would certainly represent a positive aspect, since it speeds up digestion and consequently limits the time. overall usage for the body.
Fat peroxidation - a downside
Physico-chemical modifications of lipids by means of cooking mainly concern the peroxidation of the polyunsaturated fatty acids (PUFA). Cooking PUFA fat determines the absorption of molecular oxygen with production of peroxides, or chemical compounds containing the "structural unit" -O-O- "which" deactivate "the starting fatty acid and all its functions; the first peroxides to be released are the hydroperoxides, which inevitably involve the production of free radicals. Peroxidation is a negative aspect of cooking fats as, in addition to significantly changing the color, smell and taste of the foods involved, it triggers free radicals (possibly blocked by antioxidants) and cancels the specific function of the PUFAs. interested.
Exceeding the smoke point - a downside
To cook fats it is essential to avoid exceeding the relative smoke point. Obviously, by following the rules of cooking systems, this inconvenience is easily avoided ... but in the eventuality, what could be the inconveniences in exceeding the smoke point? The smoke point is defined as the maximum temperature at which we can cook the lipids; not all greases have the same smoke point and some are more suitable for heat treatment than others. When the smoke point is exceeded, acrolein and formaldehyde are released immediately, two catabolites of the glycerol extremely toxic to the liver. Acrolein is visible in the form of white smoke and is potentially stinging for the mucous membranes of the eyes, nose and respiratory tract. Being catabolites of free glycerol, the production of acrolein and formaldehyde (such as peroxidation) also depends primarily on hydrolysis primary which breaks down glycerides into fatty acids + glycerol.
NB: the production of acrylamide also occurs during the cooking of fats that exceed the smoke point; in particular, its release occurs during the heat treatment of sugars and is correlated to the temperature and inversely proportional to the concentration of water in the food. The production of acrylamide increases particularly during the cooking of fats since in such circumstances such high temperatures are easily reached (see fries, fried croutons, etc.) as to allow their release.
Ultimately, cooking fats involves numerous structural alterations. Compared to cooking proteins and cooking sugars, cooking lipids has fewer positive implications, which are limited to the hydrolysis of the energy molecules called glycerides. This molecular simplification process can increase the digestibility of the fats involved but, on the other hand, promotes the degradation of PUFA fatty acids by peroxidation and free radicals release, and determines the conversion of glycerol into acrolein or formaldehyde; last but not least, it has been shown that frying sugars in fats (since very high temperatures are reached) favors the production of acrylamide, a toxic and carcinogenic chemical compound of carbohydrates.
