Controlling Oxidation
Oxidation is the major cause of deterioration of food and feed products which contain fats and oils, because it is one of the main causes of rancidity in these products. Oxidation is a "weak point" of almost all fats and vegetable oils, even those containing natural antioxidants.
The factors to consider, when discussing deterioration of fats and oils and methods of prevention, include biochemical processes (enzyme caused deterioration), chemical processes (oxygen caused deterioration or auto-oxidation), nature and condition of substrates, required storage time, light, temperature, etc.
Three types of additives are commonly used to prevent the deterioration of fats and oils: antioxidants, their synergists, and preservatives (antimicrobial agents). It should be noted that antioxidants and preservatives act independently of each other. Amalfi's major products are antioxidant formulations, however, formulations containing preservatives are also available.
Antioxidants are added to fats and oils in minute quantities, because of cost factors and regulatory requirements. Another reason is inversion; when an excess of antioxidants acts in the opposite way and actually promotes oxidation. Antioxidants provide an alternate path for oxidation which does not involve the substrate, e.g. fats and oils. The antioxidant does not function indefinitely; it is destroyed in the process.
Peroxide value is one of the most important criteria used to monitor the oxidation process. In the course of oxidation, the peroxide value first increases very slowly (the induction period). When this period ends, the peroxide value starts growing very rapidly, and signs of deterioration become evident. The efficacy of antioxidants can be expressed as a protective factor (PF):
Induction period with antioxidant
PF = -------------------------------------------------
Induction period without antioxidant
This formula shows that the role of antioxidants is to extend the induction period and thus prolong the product's shelf life.
The induction period varies for different fats and oils depending on their chemical composition. Even for the same fats and oils, it can vary, depending on such pro-oxidative factors as light, temperature, metal traces, size of contact surface between air and fats, etc.
Very often, when added in allowable concentration levels, antioxidants fail to protect fats and oils from oxidation. Fortunately their action can be improved by the addition of synergists.
Synergists have little or no activity alone, but enhance the activity of true antioxidants. The most common synergists are phosphoric acid, citric acid, ascorbic acid and ascorbyl palmitate. The main function of synergists is to form complexes with the pro-oxidative metal traces that are found in the most fats and oils. Some synergists also may participate in regeneration of exhausted antioxidants. The antioxidative action is not reduced until both antioxidant and synergist are completely consumed.
Obviously, there is no magical antioxidant formulation to solve the oxidation problem for all fats and oils. Amalfi Ingredients utilizes its many years of experience in the industry, latest scientific data and modern technology to develop custom formulations. Our advanced combinations of these antioxidants with different synergists, solvents and solubilizers fulfill all industry needs for antioxidant formulations. Among the antioxidants we manufacture and use in our formulations are: BHA ,BHT , Ethoxyquin, Propyl Gallate , TBHQ and Tocopherols
THE USE OF ANTIOXIDANTS AND ANTIMICROBIALS
IN FOOD PRESERVATION
The are two basic ways in which food products can spoil, or undergo an unwanted chemical change:
1. spontaneous oxidation by atmospheric oxygen
2. chemical reactions catalyzed by microbes
These can include all of biochemistry, hydrolysis, reduction, and not surprisingly oxidation as well (Hius in't Veld, Leninger).
Food preservation strategies follows the same logic. Some methods prevent oxidation by adding antioxidants to be product, others act by eliminating the microbes by heating, irradiation or antimicrobials. The best methods are those which address both sides of the problem: hermetic sealing of sterilized food and freezing. The last two strategies provide a way to prevent chemical changes for a long time, but tend to be expensive. Since ancient times humanity learned many ways to address the two sides of food preservation issue inexpensively: if milk is going to sour anyway - control the process and find uses for sour milk. Fruit will both oxidize and rot - preserve it by increasing the concentration of acid or sugar (or both) until neither reaction occur anymore. However in the process, instead of preserving the original substance, a new food was created. This is not always an option. A more balanced way of preserving food can be found using modern knowledge of chemistry.
Antioxidant use alone provides no antibacterial action. Moreover, antioxidants improve the environment for bacterial action, because reactive oxygen species are harmful to microorganisms (Kim et al, Hayashi et al, stephens et al). Addressing both sides of the food spoilage problem, addition of a natural antimicrobial substance may not only help prevent bacterial growth but increase the effectiveness of the antioxidant. Coca Cola company is adding Phosphoric acid to its trademark beverage for that reason.
When an abundant source of food is encountered, bacteria may form communities within a matrix secreted by the bacteria. More than one species may be included. This biofilm provides a relatively protected environment for the bacteria (March et al). One of the goals of food preservation is to prevent the formation of dense bacterial populations. Isolated pockets of bacterial growth may degrade food even if most of the food is clean and adequately treated with antioxidants. This is another reason why initial antimicrobial treatment of food and antioxidation alone may not be sufficient. A combination of antioxidant and bacteriostatic additives provides an optimal solution to the problem of preservation of sensitive substances such as fat and oils.
References
BHA / BHT / Ethoxyquin / Propyl Gallate / TBHQ / Tocopherols
Refrences
Coel, M., "Ethoxyquin: Science vs. Marketing",
Petfood Industry, Sept.-Oct. 1995:8.
Sherwin, E. R., "Antioxidants for Vegetable Oils",
J. Am. Oil Chem. Soc., 53:430 (1976).
Cort, W. M.,
"Antioxidant Activity of Tocopherols,
Ascorbyl Palimate and
Their Mode of Action", J. Am. Oil Chem.
Soc. 51:322 (1974).
Allen, J. C. and Hamilton R. J., Rancidity in Foods",
Applied Science, Elsevier (1989).
Hudson B. J. F., "Food Antioxidants", Applied Science, Elsevier (1990).
Leninger textbook of biochemistry
Iowa State University food safety consortium web site: www.foodsafery.iastate.edu
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