Temperature is the most important physical parameter in food processing operations. Only in ranges of higher temperatures can microorganisms be killed. The higher the temperature, but also the intensity and time of processing, the greater the loss of nutrients and vital substances (macro- and micronutrients) of the respective processed foods.
Especially the important unsaturated fatty acids in nuts and vegetable oils are subject to oxidation if they are hardened, heated for a long time and strongly during extraction or exposed to sunlight and air without protection. In the presence of oxygen in the air, the unstable unsaturated fatty acids are transformed into toxic compounds – so-called trans fatty acids – that can damage cells and increase the tendency to thrombosis. The content of essential antioxidants – for example, vitamins A, E and beta-carotene – in the original vegetable oils decreases as a result of heating. Their actual task is to protect our body from aggressive oxygen compounds – the free radicals. However, if their number is reduced, oxidation cannot be counteracted and toxic substances – so-called peroxides – are formed, which have a disruptive effect on hormone balance and enzyme functions as well as on fat and protein metabolism. Heat-labile vitamins such as vitamin C, A, B2 and B6 are additionally destroyed. Overheated fats thus increase the need for unsaturated fatty acids and also for vitamin E, since this can be destroyed by atmospheric oxygen. A deficiency of vitamin E increases the toxic effect of oxidation – the risk of developing atherosclerosis (hardening of the arteries) and cancer increases.
The most time-consuming among thermal treatments is sterilization, because the milk is brought to 109 to 115°C for 20 to 45 minutes, for example. As a result, especially the heat-sensitive nutrients and vital substances are affected and are subject to high loss.
Vitamin losses of milk due to:
| Heating process | Vitamin B1 | Vitamin B6 | Vitamin B12 | Folic acid |
| Pasteurize | < 10 % | 0-8 % | < 10 % | < 10 % |
| Sterilize | 20-50 % | 20-50 % | 20-100 % | 30-50 % |
| Ultra High Temperature | 0-20 % | < 10 % | 5-10 % | 5-10 % |
In addition to the listed losses of vitamin B1, B6, B12 and folic acid, vitamin C remains only 10-70%, pantothenic acid 15-70% and vitamin B2 only 30-50%. Occurring protein changes as well as loss of taste during sterilization are also problematic to see.
