Effects on fat-soluble vitamins during food storage and processing

The most significant losses of vitamins occur in raw materials during storage and as a consequence of handling, food processing and extending the shelf-life of nutritive foodstuffs.

The chemical properties of vitamins dictate the mechanism and extent of losses during processing. Fat soluble vitamins are degraded by a distinctly different set of chemical processes than water soluble vitamins.

In generally fat-soluble vitamin can be affected by physical factors (temperature, sunlight and UV light radiation, oxygen/air) chemical factors (radicals, peroxides, metal ions, Cu2+, Fe3+) and the biochemical factors (enzymes, mainly oxidases, eg.g lipoxygenase).

Fat–soluble vitamins are particularly susceptible to oxidation due to all of these factors and the process is further accelerated by the presence of oxidized fat. The fat-soluble vitamins, particularly A, D and E are sensitive to oxidation during processing and storage. The fat soluble vitamins and vitamin processes (carotenoids and tocotrienes) are destroyed by autocatalytic processes similar to these experienced by unsaturated fatty acids.

The fat-soluble vitamins are generally less heat-labile than the water soluble ones, but they are susceptible to degradation at high temperature especially in the presence of oxygen.

Certain fat-soluble (particularly vitamin A and the carotenoids) experience geometric isomerization upon thermal processing with losses of vitamin value. All the fat-soluble vitamins are lost at a varying degree during thermal processing with the exception of vitamin K.

Vitamin A has little loss during cooking but presence of acid it becomes rancid. No loss during canning and processing.

Effects on fat-soluble vitamins during food storage and processing

Vitamins as antioxidants in processed foods

Vitamins as antioxidants in processed foods
Oxidation, a series of chemical reactions yielding undesirable and products (off odors, colors, and flavors), may occur in many fruits and vegetables and foods high in fat and oil during exposure to air, light, heat, heavy metals, certain pigments or alkaline conditions. Enzymatic browning may occur in some fruits and vegetables, particularly apples, banana, peaches, pear, and potatoes, which contain phenolase enzymes. When these fruits and vegetables are cut or sliced and exposed to air, the phenolases catalyze oxidation of phenolics compounds to ortho-quinone compounds, which then polymerize, forming brown pigments.

Oxidation in lipids (autoxidation) and in fat and oil containing foods, on the other hand, occurs as a result of the susceptibility of fatty acids (building blocks of fats and oils) to oxidations and subsequent formation of reactive compounds referred to as “free radicals”.

The free radicals promote the development of a series of chemical reactions which lead to the production of off-flavors, colors, odors, and rancidity. While both saturated and unsaturated fatty acids are susceptible to oxidation, unsaturated fatty acids are significantly more susceptible than their saturated counterparts at room temperatures and at elevated temperatures.

Antioxidants, as defined by Food and Drug Administration are “substances used to preserve food by retarding deterioration, rancidity or discoloration due to oxidation.” Some oxidations have more than one function. For example, Ascorbic acids may function as a free-radical chain terminator, and oxygen scavenger, or a metal chelator. Under certain conditions, it may act as a promoter for oxidation.
Vitamins as antioxidants in processed foods