Antioxidant additives in food

Oxidation is a not a process exclusive to the human body. It occurs in every living organism and biological system, such as food products. Food oxidation may result in altered flavor, color, nutritional value, and texture, as well as create toxic compounds.

Therefore, antioxidant compounds are one of the most important conservation technologies used by the food industry with their main function being the prevention of oxidative induced degradation of foods.

Antioxidant is a molecule stable enough to donate an electron to a rampaging free radical and neutralize it, thus reducing its capacity to damage. These antioxidants delay or inhibit cellular damage mainly through their free radical scavenging property. The applications of antioxidants have been widespread in the food industry for decades; and are in use in preventing lipids from oxidative degradation. Antioxidants protect cells against the effects of harmful free radicals.

Retarding autoxidation delays the appearance of such undesirable qualities as rancidity in foods, loss of elasticity in rubbers, and formation of gums in gasolines. Antioxidants most commonly used are such organic compounds as aromatic amines, phenols, and aminophenols.

Phenolic compounds, besides being associated with antimicrobial activity, are known for their high antioxidant capacity. They are ubiquitous to plants and therefore present one interesting class of antioxidant compounds to be exploited, although other compounds with a strong antioxidant capacity can also be found, such as some vitamins (vitamin C, E, and A), bioactive peptides, polysaccharides, some minerals, and enzymes.
Antioxidant additives in food

Phenolic Compounds

Plant phenolic and polyphenolic compounds, are defined as compounds possessing one or more aromatic rings bearing hydroxyl substituent(s), and are the secondary metabolites of phenylalanine and to a lesser extent tyrosine in plants.

 Phenolic compounds mostly present in various types of foods of plant origin. Natural antioxidants have been extensively found in fruits and vegetables, seeds of many fruits, cereals, berries, wine, tea, olive oil, and aromatic plants. The content of phenolic compounds in foods may change during processing and storage as mediated by light and temperature.

There is now considerable evidence that wine phenolics, particularly resveratrol, inhibit low-density lipoprotein oxidation and reduce platelet aggregation, two major parameters implicated in atherothrombogenesis. This provides a possible explanation for the cardio protective action of wine.

Phenolic compounds such as cafeic acid, chlorogenic, p-coumaric and ferulic are present in parts of plants that are used as spices. The antimicrobial activity of these and other acids as hydroxycinnamic and cinnamic may retard microbial invasion as well as fruit and vegetable putrefaction.

Apart from being naturally present in the raw materials used for foods, phenolic compounds are also added to certain foods and beverages as colorants or as antioxidants. Phenolic compounds have also been successfully employed as the processing aid for texture modification of fish mince and surimi.

The potential value of phenolic compounds as biopreservatives is considered for the safe extension of perishable products shelf life and these substances can be used to delay or inhibit the oxidation and growth of microorganisms. However, in food applications, the phenolic compounds could be influenced by food components, processing and storage.
Phenolic Compounds

Phenolic compounds as food additive

Plant phenolic and polyphenolic compounds, can be defined as compounds possessing one or more aromatic rings bearing hydroxyl substituent(s), and are the secondary metabolites of phenylalanine and to a lesser extent tyrosine in plants.

Polyphenols are the natural antioxidants prevalent in fruits, vegetables, beverages (tea, wine, juices), plants, seaweeds, and some herbs and show antioxidative and antimicrobial activities in different fish and fish products.

These compounds are too directly related to sensory characteristics of foods such as flavour, astringency, and colour.

The use of phenolic compounds also appears to be a good alternative for sulphiting agent for retarding melanosis in crustaceans. Phenolic compounds have also been successfully employed as the processing aid for texture modification of fish mince and surimi.

Phenolic antioxidants such as butylated hydroxyanisole (BHA), butylated hydroxytoluene (BHT) and monotertiary butylhydroquinone (TBHQ) are hindered phenols with antimicrobial activity. The use of phenolic antioxidants in food products is regulated by federal agencies. In general, these compounds are permitted in concentrations up to 200 ppm, based on the fat or oil content of the food product.
Phenolic compounds as food additive

Amines in food

Many of the antioxidants used in commerce occur naturally in foods (e.g., vitamin C, citric acid, amines, and certain phenolics compounds). However, the amines and the phenolics compounds can be toxic to human in low concentrations; therefore, they and the synthetic antioxidants required strict regulations of their use in foods.

The amines are an extensive class of organic compounds of general formula RNHi (primary), RR'NH (secondary), and RR'R"N (tertiary). Their chemical and chromatographic properties are determined by the presence of a basic functional group and active hydrogen atoms in the molecule. Amines occur widely as constituents or additives in foods.

Nitrosamines are formed by the reaction of nitrites with secondary amines. The amines are common, naturally occurring component of many foods. Nitrite is a food additive use in the curing of meats, but majority of nitrite entering the gastrointestinal tract arises from other sources, such as water, plants, nitrogen oxides in polluted air and open flames used in some types of food processing and saliva.

Large amounts of amines are present in cheese, chocolate, wines, beer; yeast extracts and fish products. They are also present in certain fruits and vegetables and the levels increase as the fruits ripens.
Amines in food

Citric acid as antioxidants

While various acids can function to inactivate prooxidant metals in fats, citric acid has been used to fill most needs. It is very effective in retarding the oxidative deterioration of lipids in foods and is commonly added to vegetables oils after deodorization.

Citric acid

Citric acid was studied in the 1940s an 1950s as a food antioxidant useful in butterfat, vegetable oils, shortenings, lard, fats and the phospholipid portion of milk.

Citric acid functions as a synergist with other antioxidants in a various vegetables oils. Some linoleate-containing oils such as soybean oils, crambe, mustard oil and rape oil are effectively stabilized by the addition of 0. 01% of citric acid.

In palm oil, TBHQ and citric acid treatment significantly reduced oxidation and improve bleachability. Other foods that commonly use citric acid as an additive include ice cream and sorbets, caramel, soda, cider, beer and wine, cheese, many canned and jarred foods, baked goods and cake mixes, frozen fish, many processed sweets and precut and packages fruits and vegetables.
Citric acid as antioxidants

Tocopherols as antioxidant in food

The tocopherols are optically active, liquid alcohols and only the D-isomers occur in nature. The tocopherols are antioxidants. They are fat soluble and are added to fats and oils to delay or prevent rancidity.

Tocopherols are a group of chemically related compounds occurring naturally in plant tissues especially in nuts, seeds, fruits and vegetables which show both antioxidant and vitamin E activity. Vegetable oils are the most important sources of tocopherols.

Wheat germ oil and cottonseed oil are the best source of vitamin E (α-tocopherol). The tocopherols include α, β, γ and 𝛿 homologs and the corresponding tocotrienols. The basic structural unit in all the homologs is a hydroxylated benzene ring system and a isoprenoid side chain.
Tocopherols as antioxidant in food

Antioxidant TBHQ

Antioxidants are a group of food preservatives that delay or prevent the deterioration of foods by oxidative mechanisms. This includes tertiary butylhydroquinone (TBHQ). Its molecules act by scavenging freed radicals or oxygen, or by inhibiting enzymes that facilitates oxidation.

TBHQ is regarded as the best antioxidant for protecting frying oils against oxidation. It provides good carry through protection similar to that of BHA and BHT. TBHQ widely used as antioxidants in cosmetics, food lipids and health products.

It is added in animal fats, fish oils, fats and oils used in the manufacture of heat-treated foods and frying fats. TBHQ also used in cereal-based snack foods, chewing gum, dehydrated broths, dehydrated meat, dehydrated potatoes, dehydrated soups, processed nuts, sauce, and seasoning and condiments.

TBHQ is adequately soluble in fats and does not complex with iron or copper, as observed for propyl gallate; therefore, it does not discolor the treated products.
Antioxidant TBHQ

Butylated hydroxytoluene

Butylated hydroxytoluene or BHT (3,5-di-tert-butyl-4 hydroxytoluene) is a synthetic antioxidant which prevents oxygen-induced lipid deterioration by acting as a ‘chain breaker’ in a series of free-radical reactions.

It has a molecular structure and performance similar to BHA. Both BHA and BHT are extremely soluble in edible fats and oils and have practically no water solubility. It is susceptible to loss by volatilization and distillation under, certain food processing conditions, such as frying.

This behavior is technologically useful in food processing because the products of rancidity produce an offensive flavor, decrease the nutritional value of food, and may have deleterious health consequences when ingested.

In negative aspect of BHT, is that it may give a yellow coloration due to the formation of stilbenequinone in the presence of iron.

First patented in 1947, BHT was initially used as an industrial antioxidant in the petroleum and adhesive industries and later in the 1950s as a food and cosmetic additive. In foods, BHT may be used to a 0.02% concentration, whereas in cosmetics it is used in a 0.01% to 0.1% concentration.
Butylated hydroxytoluene

Antioxidant of propyl gallate

The gallates used as food antioxidants include propyl, octyl and dodecyl esters of gallic acid. Propyl gallate (n-propyl-3,4,5-trihydroxybenzoate) is used in vegetable oils and butter. It is also used as antioxidant in ethers, emulsions, waxes and transformer oils.

This antioxidant is used to prevent rancidity in meat products such as rendered fats or pork sausage.

Structure of propyl gallate

It is an effective antioxidant for shelf-life improvement of vegetable oils at usages levels of 100 to 200 ppm, or the FDA and USDA permitted levels; however, its usage is hampered by solubility problems, discoloration and poor heat stability.

Propyl gallate is less soluble in fats and oils than BHA and BHT and has significant solubility in water. The low oil solubility of propyl gallate makes this antioxidant difficult to incorporate into fats and oils and its solubility in water makes it more likely to complex with iron and iron salts, which causes dark discoloration in some applications.
Antioxidant of propyl gallate

Butylated hydroxyanisole (BHA)

The self propagation of free radical reactions can be prevented by antioxidants. Some such as α-tocopherols and their congeners and ascorbic acid occur naturally.

The most widely used and highly effective synthetic antioxidants are butylated hydroxyanisole (BHA), butylated hydroxytoluene (BHT), gallates, and tertiary butyl hydroquinone (TBHQ).

BHA is used as an antioxidant for oils and fats either alone or with a gallate and a synergist, such as citric or phosphoric acid.

Butylated hydroxyanisole

It is a mixture of two isomers: 2-tert-butyl-4-hydroxyanisole (2-BHA) and 3-tert-butyl-4-hydroxyanisole (3-BHA); the commercial compound contains over 90% of the3-isomer.

Butylated hydroxyanisole is prepared by alkylating p-methoxyphenol with isobutylene or tert-butyl alcohol in the presence of phosphoric acid as a catalyst.

It occurs as a white or slightly yellow, waxy solid having a faint characteristic odor. It is insoluble in water but is freely soluble in alcohol and in propylene glycol. It melts between 49° and 63°.

BHA is used in a wide variety of products, including beverages ice cream, candy, baked foods, gelatin, soup bases, potatoes, glazed fruits, potato flakes, dry breakfast cereals, dry yeasts, dry mixes for desserts and beverages, shortening, smoked dry sausages and emulsions as stabilizers for shortenings.
Butylated hydroxyanisole (BHA)

Food Additives as anticaking, free flow agents and antioxidants

Food Additives as anticaking, free flow agents and antioxidants
These are compound that are added to dry ingredients such as salt, powdered sugar and finely ground spice blended to keep the product free flowing during storage and use.

The compound added, such as calcium stearate, has the ability to preferentially tie up moisture, therefore maintaining the free flow properties of the dry product and minimizing the problems of caking, lumping and agglomeration.

While for antioxidants traditionally, these food additives have been added to fats, oils, and fat containing foods to prevent oxidation from occurring , which in turn can result in product rancidity.

Both naturally occurring compounds such as vitamins A and C as well as synthetic antioxidants typified by butylated hydroxyanisole (BHA) and butylated hydroxytoluene (BHT) have been utilized due to their ability to tie up free oxygen before it can react with the unsaturated portion of fatty acids.

Due to potency of some synthetic antioxidants, maximum usage levels are enforced. It should be noted that antioxidants are intended to retard but not to prevent product deterioration and discoloration.
Food Additives as anticaking, free flow agents and antioxidants