What is Acrolein
Production
Acrolein derives from the catabolism of GLYCEROL [esterified with fatty acids in triglycerides (lipids)] and is significantly produced during:
- The thermal overcoming of the "smoke point" of food fats and oils during cooking
- The burning of the cigarette (smoking)
- Incorrect fermentation of the must in the wine sector; this reaction is catalyzed by the enzymes of lactic bacteria (in case of processing error) which, starting from the GLYCERINE contained in the must, release acrolein.
NB. It is also possible to CHEMICALLY reproduce the dehydration of glycerol into acrolein by means of Synthesis of Skraup1.
Toxicity
Acrolein is a highly polluting and harmful contaminant for man; it constitutes 5% of atmospheric aldehydes2 and, more than FORMALDEHYDE (50% of the TOT), it represents the most dangerous molecule. Some studies conducted by Kane Alare in 1978 they demonstrated that acrolein and formaldehyde act synergistically as COMPETITIVE AGONISTS, therefore the production and severity of mucosal irritations due to atmospheric exposure are ESPECIALLY due to THEIR concentration (acrolein + formaldehyde) rather than the total presence of volatile aldehydes.
Despite being quantitatively less present than formaldehyde, acrolein has a significantly higher irritant potential; it, even at low concentrations, causes inflammation of the conjunctive mucous membranes of the eyes and the mucous membranes of the airways. Continuous exposure to acrolein determines:
- Worsening of mucous irritation
- Reduction in respiratory rate
- Bronchoconstriction induced by stimulation on the cholinergic reflex
- Enzymatic imbalances attributable to hepatic suffering: increase in alkaline phosphatase + increase in transaminases = increase in cortisol secretions (pituitary-adrenal feedback)
NB. If present in the circulation, acrolein is also potentially toxic for the kidney and certainly highly irritating to the mucous membrane of the bladder and ureter. This irritation can develop into erythematous-type rashes3.
Professional protection
A 2008 research carried out by Lupoping et al. has shown that formaldehyde (but certainly also "acrolein) is a potentially carcinogenic molecule for both the nasal and esophageal mucosa, as well as being probably responsible for leukochemias. By virtue of the results obtained, the "Italian Cancer Research Association (AIRC) has classified these molecules as"HARMFUL for occupational exposure"(see working figures in contact with formaldehyde and acrolein).
Acrolein in the oil for frying
Foods with a high acrolein content are especially those fried or violently cooked on the plate or in a pan. Acrolein accumulates in extra-used and often already exhausted oils, therefore, the richest food source of acrolein is undoubtedly made up of FRIED foods and served in collective catering (takeaways, restaurants and fast-food restaurants).
The formation of acrolein in food is determined by exceeding the smoke point, that is, the temperature above which the oil begins to:
- Releasing gray smoke
- Losing its nutritional values
- Releasing TOXIC catabolites
After the smoke point, the production of acrolein is greater in vegetable oils with a prevalence of unsaturated, especially in those with a good quantity of polyunsaturated fatty acids (soy, flax, grape seeds, walnut, etc. for this reason not recommended for frying) .
The oil that releases less acrolein in cooking is undoubtedly PEANUT oil, because it contains 35% polyunsaturated fats, followed by that of sunflower seeds (55%). NB. Sunflower seeds intended for the production of "oil are genetically mutated to increase the concentrations of oleic acid, consequently raising the smoke point; therefore sunflower oil is a potential genetically modified organism (GMO - Skoric D. et al., Can J Physiol Pharmacol 2008)!
However, what needs to be specified is that all seed oils (including peanut oil) undergo significant acrolein release after just one frying, so they should NOT be used multiple times. On the contrary, virgin (or extra virgin) olive oil is also distinguished by a good smoke point (thanks to the prevalence of monounsaturated fatty acids) and seems to be able to withstand even 2-3 consecutive frying; this characteristic is justified from the high content of antioxidants that strongly limit the presence of acrolein in the oil.
NB. Seed oils do NOT contain the same amount of antioxidants because during industrial processing they are treated with chemical solvents, such as hexane, butane, propane etc. (Indart A et al. Free Radic Res 2002).
Ultimately it is advisable to limit the frequency of consumption of fried foods to a minimum, especially if PURCHASED elsewhere; moreover, to prevent the formation of acrolein at home, it is advisable:
- Respect the smoke point
- If using peanut or sunflower oil, use it for a single frying
- Prefer virgin or extra virgin olive oil
Bibliography:
- Chemistry of pharmacologically active heterocyclic compounds - D. Sica, F. Sulfur - Piccin - pag-81: 83
- Treatise on forensic medicine and related sciences - G. Giusti - pages 151-152
- Oncological medicine - G. Bonadonna, G. Robustelli Della Cuna, P. Valagussa - Elsevier Masson - page 1764.
