Anti-oxidants

Anti-oxidants are substances which retard the onset and progression of oxidative rancidity in fats. They may be useful to extend the storage life of fats, before use in biscuits, and also to extend the shelf life of biscuit products.

The most commonly used anti-oxidants in biscuit manufacturing are BHA (butylated hydroxyanisole), BHT (Butylated Hydroxytoluene), Propyl Gallate and TBHQ (tertiarybutylhydroquinione). They are thought to work by preventing the formation of free radicals that initiate and propagate auto-oxidation.

BHA is effective in animal fats but relatively ineffective in vegetable fats and it provides a good carry through from dough to baked goods. It is insoluble in water.

BHT is cheaper than BHA but is similar in properties.

Propyl gallate imparts good stability to vegetable oils but is heat sensitive decomposing at about 148°C (NB the centre temperature of a biscuit during baking reaches only about 105°C). It has poor carry through characters to baked products and is not very soluble in either oil or water.

TBHQ, is the most effective anti-oxidant for most fats, especially vegetable fats. It has good carry-through properties and is fat soluble.

Anti-oxidants are generally incorporated into food by being added to fats. They work best if added at an early stage so they should be added by the fat supplier at the end of the refining process. Adding at the stage of dough mixing generally does not give a good dispersion and the fat may already have started to be oxidised.

Anti-oxidants are classed as additives and therefore their use is controlled. BHA, BHT, propyl gallate and TBHQ are permitted in most countries for use individually or in combination at a level not to exceed 0.02% based on the weight of the fat. The exception is that TBHQ and propyl gallate may not be used in combination in many countries.

It is best not to rely on anti-oxidants to extend shelf life. Good housekeeping of the handling of fats is an important requirement. Use clean tanks, do not keep fat for too long, never agitate warm fat, use, quickly, fat from boxes which have been damaged and the fat has soaked into the cardboard outer.

Lauric fats, coconut and palm kernel oils, commonly used for biscuit creams, are very stable to oxidative rancidity so do not need additions of anti-oxidants. Anti-oxidants are ineffective in preventing hydrolytic rancidity.

There is some evidence that sucrose in the biscuit acts as a mild anti-oxidant. It may be that sugar masks the taste at the onset of rancidity but if it is true, clearly additions of anti-oxidants to cracker formulations, where there is little or no sugar, will be more important than for other biscuit types.