Edible oils are produced by extracting oilseeds, not out of thin air, so some harmful substances in the oil itself will be brought into the produced oil due to imperfect processes and technical defects. There are some common harmful substances in the oil, such as: glucosinolate, erucic acid and gossypol.
Canola belongs to the Brassicaceae plant, and it contains considerable content of glucosinolate. Due to the presence of glucosidase in plants, glucosinolates are hydrolyzed by the effects of glucosidase, and the hydrolysate contains sulfur compounds such as thiocyanate and isothiocyanate and nitrile. Among them, thiocyanate and isothiocyanate can prevent the absorption of iodine from the body’s thyroid gland, which will cause the body’s thyroid hypertrophy. Nitrile can inhibit the growth of animals and cause animal death. It also has certain effects on the human body and has strong toxicity. Even some glucosinolates will be cyclized under certain conditions to form oxazolidinethione due to their own structure, which is quite detrimental to human health. Most of these sulfides are volatile, so they can be eliminated by heating in production and life.
Canola oil contains 20% -50% erucic acid. The chemical formula of erucic acid is CH3 (CH) 7 = CH (CH) 11COOH, which is a kind of fatty acid. Studies shows that animal eating a considerable amount of erucic acid can cause a large amount of triglycerides to accumulate in the heart muscle of animals. The main component of triglycerides is erucic acid. Long-term infiltration of myocardial monocytes can cause myocardial fibrosis and even pericardial effusion. In addition, erucic acid can cause liver sclerosis, which adversely affects human health.
The following measures can be used to reduce or even eliminate the effects of erucic acid on the human body:
1. Limit the erucic acid content in edible oils by formulating relevant legal standards to reduce it to a level beneficial to the human body
2. Improve the conventional vegetable seed varieties and reduce the erucic acid content. This new variety has appeared on the market now;
3. Reduce the harm of erucic acid to human body by adding appropriate saturated fatty acids.
Cottonseed used to extract cottonseed oil contains a considerable amount of gossypol, and gossypol is toxic. The harmful effects of gossypol are mainly combined with the proteins and amino acids in cottonseed meal, reducing the effectiveness of proteins and amino acids, especially lysine; gossypol entering the intestine can stimulate the gastrointestinal mucosa and cause gastroenteritis; after entering the body, it damages the heart, liver, kidney, nerves and other tissues and organs; gossypol also binds to functional proteins in the body, making it inactive, and iron binding causes iron deficiency anemia; serious illness can also cause reproductive damage, which has severely harmed people’s health.
In order to make cottonseed oil reach the standard that people can eat normally, the free gossypol content needs to be reduced. The general treatment method is as follows: after steam cooking, pressing the cottonseeds, it is necessary to perform alkali refining for the pressed oil. The alkali refining can reduce the gossypol content and make its content within the limit of the content standard set by China.
Hazards and effects of cooking oil reuse
After repeated heating at edible oil, its nutritional value is already quite low, and under high temperature environment, the molecular structure inside the oil will be destroyed, and the fatty acids therein will undergo polymerization. It is extremely toxic and can reduce the metabolism rate of animals, damage liver function, and even cause cancer. With repeated high-temperature use, more and more polymers in edible fats will cause greater harm to the human body. Therefore, in daily life, repeated use of grease at high temperatures should be avoided to reduce the harm to human health caused by harmful substances.
Improper storage leads to rancidity of oil
When edible oil is stored in a high temperature environment, it will produce a series of biochemical reactions, such as the enzymatic hydrolysis process catalyzed by plant residues and enzymes produced by microorganisms; the other is the hydrolysis process of oil products under air, sunlight, water and other conditions. These reactions will lead to rancidity of the oil. After the rancidity of fats and oils, a severely deteriorated odor will be released, and at the same time, various internal nutrients will be destroyed, which greatly reduces the nutritional value of edible fats, and what’s more, It will also cause a series of harmful oxidation products to the human body, endanger human health, and even cause diseases such as tumors.
In order to prevent the rancidity of fats and oils, the following points would be noticed during production and storage:
1. Strictly implement the process flow, improve the process level, reducing the content of residues in finished oils and thus destroying the conditions under which oxidase are activated in oils and fats, this requirement is often solved by hydration;
2. Try to reduce the moisture in the fat as much as possible, at least 0.2% required by relevant national standards;
3. Usually grease should be placed in a dry, dark and low temperature environment, and it needs to be sealed;
4. Reduce the possibility of microbial pollution by cleaning up the production and storage environment;
5. Reduce the possibility of metal ion pollution during production and storage;
6. It is possible to delay the oxidation of fat and extend the storage time by adding an appropriate amount of antioxidant to the fat. Of course, it is also possible to use a nitrogen-filled fresh-keeping method to extend the storage time.