Title: Antioxidants in Food Processing

Key words: Antioxidants, food processing, shelf-life, propyl galleate, BHA, BHT, TBHQ

Date: Feb 1999

Category: 4. Food Data

Type: Article

Author: De Van Rhijn

 

Antioxidants in Food Processing

The role of synthetic and natural antioxidants in food processing.

 

Introduction

The food industry utilises antioxidants, whether natural or synthetic, to preserve the quality1 and to prolong the shelf-life2 of foods. Antioxidants are therefore becoming very important in our consumer society. Their nature, mechanisms of action and safety in food processing are discussed below.

Role of Antioxidants

The main role of antioxidants in food processing is to help to prevent staling, drying, microbial spoilage, enzymatic changes and oxidation of products. Meats, fruits, nuts, cereals, oils and lipids (especially unsaturated) are particularly prone to oxidation by exposure to light, temperature and minerals. This results in rancidity and the loss of flavour, odour, colour and nutritional quality of foods.

Types and Mechanisms of Antioxidants

Antioxidants can be divided either into naturally occurring or synthetic compounds.

The former includes substances such as Vitamin A, E & C, lecithin and citric acid. Vitamin A (b -carotene) is too unstable to use as a food antioxidant. Vitamin E derivatives (especially a -Tocopherols and tocotrienols) are naturally present in vegetable oils, commercial free-ol forms and are efficient antioxidants. Vitamin C (ascorbic acid) is an excellent oxygen scavenger, metal chelator and regenerator of Vit E.

The synthetic group consists mainly of butylated hydroxyanisole (BHA3), butylated hydroxytoluene (BHT), tertiary butyl hydroquinine (TBHQ) and propyl galleate. They are usually added to fats and oils in food processing, or incorporated into the packaging.

Requirements of Antioxidants

Quality antioxidants must adhere to certain criteria to be useful in processed foods, for example be fat-soluble (BHA), dispersible (TBHQ), easily applied and incorporated. Synthetic antioxidants must be able to inhibit oxidation for one year at 20-30oC , be stable to heat (200 0C) during cooking and not impart colour, odour or flavour to the product. Research in fish4 and fish oil (ESR spectroscopy) have shown a reduction of free radicals by adding antioxidants. Most importantly, they must be safe (class 3 status FDA, USA), which is established by long term histopathological animal testing and the study of metabolites.

Natural antioxidants tend to be more expensive and less widely applied compared to synthetic ones, but are used increasingly often because they have a broader range of action and are perceived as innocuous regarding safety. The antioxidant components of Rosemary oil (carnosol and carnosic acid 5,6) are receiving particular interest.

Safety

BHT is not permitted in various western countries, due to the suspected cancer7 risk as found in numerous studies on animals (rodent8 forestomach9). The levels of usage (0.02% by weight of oil) are closely controlled, and set at 0.05 mg/kg/day for the synthetic antioxidants.

More research is required on synergistic10, 11, 12 combinations, safety and effective concentrations as food additives. Vigilance is also required regarding the safety of newly proposed natural antioxidants (thymol, carvacrol and 6-gingerol 13), and there is evidence of potential pro-oxidants effects of vitamins14, 15, 16.

Conclusion

Oxidation of food is a great hazard risk to health if not prevented by antioxidants, but stringent criteria as to the safety of natural and synthetic antioxidants should be applied.

 

References

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  2. Buck, D.F. and Edwards, M.K.. Anti-oxidants to prolong shelf-life. In Food Technology International. 1996; pp. 29 – 33.
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