At present the EU-permitted range of food additives classed as antioxidants for food systems covers what could be seen as a bewildering wide range of possible choices to the food technician. From this wide array the challenged food technician is expected to make the most effective, economical, and these days, label-friendly choice for the application in hand. But how is this choice made and wher does one begin?

Although todays food processing techniques control many of the potential causes of oxidation due to improvements in processing, packaging, storage and delivery of foods to store, in many cases these improvements are still not enough and as a result antioxidants play an increasingly important role in food quality. 

SYNTHETIC AND NATURAL ANTIOXIDANTS

In mainstream food markets the traditional use of antioxidants has, for over 60 years, been based on the use of rather well known chemical antioxidant systems such as Butylated Hydroxytoluene (BHT) and Butylated Hydroxylanisole (BHA), Propyl Gallate (PG) and Tert-Butylhydroquinone (TBHQ).

To compound this possible confusion to the user, there are also numerous so-called natural or botanicals with so-called biological (in-vivo) and non-biological (in-vitro) antioxidant capacity, some of which possess EU pending additive status or can be simply ingredients offering useful side capacity as antioxidants (table 1).

Table 1: Classification and economic choice of so-called natural antioxidants

In effect there needs to be a distinct, clear divide made between antioxidants that offer capacity for quality protection in the food system, and those antioxidants associated with and applied for their health giving benefits.

When choosing a more natural solution or a cleaner label declaration to extend shelf-life, we should not consider tocotrienols (palm oils), flavonoids (wheat), isoflavones (soya) and polyphenols (grape fruit), since they have a low-cost efficiency on the protection of the food. They also do not offer additional benefits that cannot be gained from other more commercially accepted natural antioxidants with food protection capacities such as rosemary, green tea and tocopherols from soya bean oil. 

A NATURAL MIXED TOCOPHEROL COULD BE A SENSIBLE CHOICE ECONOMICALLY

In most commercial situations, the choice of using a natural mixed tocopherol (E306, a tocopherol with a composition in the main of the homologues delta, gamma, alpha and beta tocopherol) would seem a sensible one in that the ascending order of performance in-vitro would be delta, gamma, beta, and alpha.

Tocoblend L70IP from Vitablend is an example of a natural mixed tocopherol high in the naturally occurring homologues delta and gamma, the antioxidant power packs as far as antioxidant protection goes.

Certainly, natural mixed tocopherols that are from a non-GM and certified source demonstrate a cost-effective performance against the traditional use of synthetic antioxidants. Such products can be added to any food source at quantum satis level.

These can have a GRAS status (generally regarded as safe) and can be used in high temperature processes (up to 200 deg C) such as frying oils. Being available in powder (water dispersible and oil soluble) or oil soluble liquid forms would also offer a very versatile natural material offering excellent protection possibilities for oxidative stability. Natural tocopherols find economic use in vegetable oils, cereals, frying oils, fish oils, soft gel manufacture and even cosmetics.

If possible we should also consider fat-soluble vitamin-based antioxidants such as ascorbates which when presented in a fat-soluble form as ascorbyl palmitate are a versatile compound for synergistic use in combination with tocopherols and rosemary.

In addition, consideration to the capability of vitamin E classes such as DL alpha tocopherol and natural sunflower source alpha tocopherol should be made. Using natural source sunflower tocopherols is gaining increased attention to avoid association to soya and allergens.

ROSEMARYS EConOMIC NATURAL ANTIOXIDANT COMPOUNDS

With the recent green light towards the safety of rosemary extracts by the EFSA for use in foods, these extracts now offer a further expanding role with options outside of their traditional use as a flavouring in meats.

Rosemary offers two potent economic natural antioxidant compounds carnosol and carnosic acid which, approved for food use, are readily utilised in synergistic combinations with other natural antioxidants or utilised alone.

Rosemary is already well known for its high temperature stability, its GRAS status and its ready dispersion into both oil and water phases if the correct form of rosemary is chosen. This versatile compound also now offers lowered residual rosemary odour through more advanced processing, leading it to a broader acceptance and option as an alternative to the use of synthetic antioxidants.

Both rosemary and natural mixed tocopherols as well as natural vitamin E therefore already offer suitable options to satisfy the application and economic needs for the food industry in replacing traditional synthetics. 

THE SYNERGY BETWEEN NATURAL AND VITAMIN baseD ANTIOXIDANTS FOR COST REDUCTION

Synergy between natural and vitamin-based antioxidants also plays an interesting role in this selection and one that warrants closer inspection to determine the exact partnership for the best economic return. The aim of synergy for the user is to drive the synergy in such a way that costs to the end user are reduced, as otherwise there appears little point to the extra formulation.

It is this approach that is bringing natural and vitamin based synergistic formulations to the price level of traditional synthetic antioxidants. Work on the relationships between tocopherols, rosemary, vitamin E and ascorbates are providing information on optimisation of the synergy that can be achieved as antioxidants.

Antioxidants that act in food are divided into three types; primary, secondary and tertiary, based on their different modes of action and it is combining these classes that can be useful starting points for synergistic action.

Primary antioxidants are considered as the phenolic compounds that are oxidised instead of the oil for example BHA, BHT, TBHQ and tocopherols. Secondary antioxidants are the compounds that inactivate oxygen, e.g. ascorbic acid, ascorbyl palmitate. Tertiary antioxidants are, for example, chelators and compounds that remove iron and copper traces e.g. citric acid, EDTA.

Oxidation increases at not only higher ambient temperatures but also by the presence of heavy metal ions, especially copper and iron. Careful thought towards the use of formulations of antioxidants in combination with certain acids such as citric acid (CA) or ethylene diamine tetra acetic acid (EDTA) dependant on the food to be treated, can achieve extra shelf-life benefits at little extra cost.

We have thoroughly examined the potential of synergy between different antioxidants for cost efficiency. In many cases an antioxidant mix containing a combination of either rosemary and tocopherols or tocopherols and ascorbates, can produce cost effective results in the extension of many classes of oil as compared to utilising single ingredients.

CAREFUL ANTIOXIDANT SELECTION CAN GIVE LONG-TERM BENEFITS

Careful selection of the correct antioxidant or antioxidant system can result in long-term benefits. There are always several possibilities and the choice will depend on the manufacturer’s own economics and labelling preferences and preferences such as whether to use natural or semi-natural options in replacing synthetic antioxidants.

It is often too simple to make a quick decision without reference to substantiation. As an antioxidant provider, it is important to put a strong emphasis on formulation and application work, and present several antioxidant system options to the manufacturer so that they can make the most appropriate decision for the protection of their food suitable to their own preferences.