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Nutrient damage caused by heat treatment
Release time:
Mar 12,2021
Heat treatment has both positive and negative effects on the nutritional value of food. Heating causes protein denaturation and the unfolding of peptide bonds. It also causes starch granules to swell, making them more susceptible to digestive enzymes, thereby increasing digestibility. Heating destroys enzymes in fresh food and kills microorganisms, which helps prevent the oxidation, decomposition, and loss of nutrients. Additionally, heating destroys naturally occurring toxic proteins in food. Raw egg whites contain avidin, which can be destroyed by heat. Raw soybeans contain trypsin inhibitors, phytohemagglutinin, and other harmful substances, and prolonged cooking can further reduce the biological value of soybean protein.
Heat treatment has both positive and negative effects on the nutritional value of food. Heating causes protein denaturation, peptide bonds to unfold, and it can also cause starch granules to swell, making them more susceptible to digestive enzymes, thereby increasing digestibility. Heating destroys enzymes in fresh food and kills microorganisms, thus protecting nutrients from oxidation, decomposition, and loss. Heating also destroys naturally occurring toxic proteins in food. Raw egg whites contain avidin, which can be destroyed by heating. Raw soybeans contain trypsin inhibitors, phytohemagglutinin, and other harmful substances; prolonged cooking time can also reduce the biological value of soybean protein. Therefore, mastering the heating time for legumes is key to improving the biological value of protein.
The adverse effects of heating are reflected in the destruction of amino acids and vitamins. Some essential amino acids such as lysine, cysteine, threonine, and arginine are easily destroyed by heat. Lysine is most severely affected; the ε-amino group of lysine reacts with reducing sugars in the Maillard reaction, forming ε-N-deoxyketose lysine, which cannot be absorbed and utilized by the human body, thus reducing the biological value of protein. When pastries are baked at 200°C for 15 minutes, lysine, phenylalanine, proline, tyrosine, and serine are destroyed by 5-17%, reducing the biological value of protein, and the loss rate increases when milk is added to pastries.
Starch gelatinizes when heated, which is beneficial for digestion, but when starch cools, it will retrograde and age, making aged starch difficult to digest. The destruction of vitamins by heating is most significant, and the loss of vitamin B1 in grains during re-cooking is shown in the table below.
During the heat treatment of canned vegetables and fruits, the loss of vitamin C is 13-16%, vitamin B1 is 2-30%, and vitamin B2 is 5-40%. Short-term high-temperature losses are less than long-term low-temperature losses, and rapid cooling after heat treatment can reduce losses. The most significant losses in milk during heating are vitamin B1 and vitamin C.
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