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Antioxidants:

Regulatory Status

Fereidoon Shahidi and Ying Zhong

Memorial University of Newfoundland,

St. John’s, Newfoundland, Canada

1. INTRODUCTION

Oxidation of unsaturated lipids is a major cause of food quality deterioration by

giving rise to the development of off-ﬂavor compounds and loss of nutritional value

of food products (1). Although it has been known for a long time that lipid oxida-

tion can be induced by catalytic systems such as light, temperature, enzymes,

metals, and metalloproteins; the mechanism of oxidation reactions remained uncer-

tain until the 1940s when free radicals and reactive oxygen species were found to be

involved in oxidation processes by the pioneering work of Farmer et al. (2), Bolland

and Gee (3), and Bateman et al. (4– 6). Furthermore, antioxidants were found to

protect lipids against oxidation either by quenching free radicals or scavenging

oxygen, among others (6). Antioxidants are substances that, when present in foods

at low concentrations compared with that of an oxidizable substrate, markedly

delay or prevent the oxidation of the substrate (7). Antioxidants that ﬁt in this deﬁ-

nition include free radical scavengers, inactivators of peroxides, and other reactive

oxygen species (ROS), chelators of metals, and quenchers of secondary lipid

oxidation products that produce rancid odors (8). Antioxidants have also been

Bailey’s Industrial Oil and Fat Products, Sixth Edition, Six Volume Set.

Edited by Fereidoon Shahidi. Copyright # 2005 John Wiley & Sons, Inc.

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ANTIOXIDANTS: REGULATORY STATUS

used in the health-related area because of their ability to protect the body against

damage caused by ROS as well as reactive nitrogen species (RNS) and those of

reactive chlorine species (RCS) (9).

Antioxidants can be broadly classiﬁed by their mechanism of action as primary

antioxidants, which break the chain reaction of oxidation by hydrogen donation and

generation of more stable radicals, and secondary antioxidants, which slow the oxi-

dation rate by several mechanisms, including chelation of metals, regeneration of

primary antioxidants, decomposition of hydroperoxides, and scavenging of oxygen,

among others. These substances may occur naturally in foods, such as tocopherols

and ascorbic acid; however, natural antioxidants are often, at least partially, lost

during processing or storage, thus exogenous antioxidants are intentionally added

to products or their precursors participate in the formation of antioxidants during

processing. Although there are many of compounds that have been proposed to

inhibit oxidative deterioration processes, only a few can be used in food products

(10). Antioxidants for use in food processing must be inexpensive, nontoxic, effec-

tive at low concentrations (0.001–0.02%), capable of surviving processing (carry-

through), stable in the ﬁnished products, and devoid of undesirable color, ﬂavor, and

odor effects. In general, the selection of antioxidants depends on products, compati-

bility, and regulatory guidelines (11). In this chapter, the properties and applications

of antioxidants in foods as well as their regulatory status are discussed.

2. SYNTHETIC ANTIOXIDANTS

Although the use of antioxidants dates back to ancient times when herbs and spices

were used in food preservation, modern antioxidant technology is only about

60 years old. Since free radicals were found to be responsible for lipid oxidation,

hundreds of natural and synthetic compounds have been evaluated for their efﬁcacy

as radical scavengers or for their other inhibitory effects. Among them, only four

synthetic antioxidants are widely used in foods; namely, butylated hydroxyanisole

(BHA), butylated hydroxytoluene (BHT), propyl gallate (PG), and tert-butylhydro-

quinone (TBHQ) (7, 12). Scientists are attempting to develop novel synthetic anti-

oxidants aimed at retarding the effects of free-radical-induced damage in various

food products as well as in the human body cells (13). Synthetic antioxidants

used in the food industry can be added as direct additives or indirectly through

diffusion from packaging material (6).

All antioxidants have points of strengths and weaknesses. Therefore, certain

points, such as thermal stability, effective concentration, and synergism, should

be taken into consideration when selecting antioxidants for use in particular foods.

Regulatory status is another factor that cannot be ignored, especially for some anti-

oxidants that have been reported to show potential adverse health effects. Synthetic

antioxidants have been tested for safety and approval for use in food at low concen-

trations on the basis of complex toxicity studies (10). Allowable limits for use of

antioxidants vary greatly from country to country, and depend on the food product

under consideration (11).

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SYNTHETIC ANTIOXIDANTS

C(CH 3 ) 3

OCH 3

3–isomer

Figure 1. Chemical structures of BHA molecules.

2–isomer

2.1. BHA (Butylated Hydroxyanisole) and BHT (Butylated

Hydroxytoluene)

Phenolic and polyphenolic compounds are the most active dietary antioxidants (14).

The structural variation of phenolic antioxidants directly inﬂuences their physical

properties, resulting in differences in their antioxidant activity. BHA and BHT are

examples of phenols, in which the aromatic ring contains alkyl groups (hindered

phenols), which are extremely effective as antioxidants (11).

Chemically, BHA is a mixture of two isomers (2-tertiary-butyl-4-hydroxyani-

sole and 3-tertiary-butyl-4-hydroxyanisole) (Figure 1). The 3-isomer is generally

considered to be a better antioxidant, and accounts for 90% of the commercial

BHA (12). BHA is a white, waxy solid that is sold in the form of ﬂake or tablet.

It is a highly fat-soluble monophenolic antioxidant that is extensively used in bulk

oils as well as oil-in-water emulsions (10–12). It is effective in animal fats and rela-

tively ineffective in vegetable oils. Demonstrating considerable effectiveness in

controlling the oxidation of short-chain fatty acids, BHA is frequently used for the

preservation of coconut and palm kernel oil in cereal and confectionery products

(10). BHA is good in baking because of its stability to heat and its mild alkaline

conditions, although its application in frying is limited due to its volatility (11).

However, it can be added to packaging materials to provide protection to food pro-

ducts inside the package through volatilization (12). BHA is particularly useful in

protecting the odor and ﬂavor of essential oils (10). Furthermore, BHA has been

reported to possess antimicrobial activity (15–17) and is known to act synergisti-

cally with other antioxidants such as BHT.

BHT (3,5-di-tert-butyl-4-hydroxytoluene) (Figure 2) is a white crystalline solid

with properties similar to BHA (12). It is appropriate for thermal treatment but not

as stable as BHA (11). Being able to regenerate BHA, BHT is commonly used in

(CH 3 ) 3 C

C(CH 3 ) 3

CH 3

Figure 2. Chemical structure of BHT.

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ANTIOXIDANTS: REGULATORY STATUS

combination with BHA to provide greater antioxidant activity (18). BHT does not

have an optimum concentration; usually, BHA/BHT mixtures are added to foods at

levels of up to 0.02% (10, 11). Both BHA and BHT have a slight phenolic odor, and

may impart undesirable odor in foods when used at high temperature for an

extended period of time (10, 11).

Although synthetic antioxidants have widely been used in the food industry,

there are some arguments about their safety (19). The use of BHA and BHT in

foods has been decreased due to their potential action as promoters of carcinogen-

esis (20). In addition to the carcinogenicity of BHA in the forestomach of rodents,

BHA and BHT have been reported to be cytotoxic (21–23). Furthermore, a sugges-

tion has been made that BHT be withdrawn from use in all foods because of its

possible adverse effects on the kidney and liver as well as lung tissues of rat

(24, 25). However, some scientists have noted that the metabolism of BHT in rat

and man are too widely different to allow a proper hazard assessment of BHT in

humans (26). It is generally considered that permitted food antioxidants, such as

BHA and BHT, have a considerable safety margin; for instance, the dose for

enhancement of carcinogenesis is at least 1500-fold greater than that in human

exposure (27, 28). Meanwhile, BHA and BHT have been reported by some

researchers to pose no cancer hazard to humans and, on the contrary, have health

beneﬁts related to their anticarcinogenic and antimutagenic properties as well as

inhibition of cholesteral oxidation (29–32).

Despite positive and negative reports of these synthetic antioxidants on human

health, their use is subject to regulation, in the United States, under the Food and

Drug Administration (FDA) and the U.S. Department of Agriculture (USDA); in

Canada, the Food and Drug Regulations (National Health and Welfare); in Europe,

the European Economic Community (EEC); and in Japan, the Food Sanitation Law.

Many other countries have adopted regulations similar to those used in the United

States, with signiﬁcant differences existing both in the antioxidants approved and in

their application and level of usage (10, 11). According to the existing food additive

regulations published by the FDA, BHA and BHT are lawful for use individually or

in combination at a maximum level of 0.02%, or 200 ppm, based on the lipid con-

tent of food products, as speciﬁed by the Code of Federal Regulations (CFR) (6, 7, 12).

Although BHA and BHT are effective at low concentrations, they become pro-

oxidant at high levels in foods (11, 33). As speciﬁed in 21CFR, 172.100, and

172.115, limitations for BHA and BHT, alone or in combination for speciﬁc pro-

ducts, are as follows: 10 ppm in potato granules; 50 ppm in dehydrated potato

shreds, dry breakfast cereals, potato ﬂakes, and sweet potato ﬂakes; and 200 ppm

in emulsion stabilizers for shortenings (11). BHA and BHT are not allowed in ﬁsh

products (5). The summery of regulations, applications, and properties of BHA and

BHT are shown in Tables 1 and 2.

The daily dietary intakes of BHA and BHT have been estimated in many coun-

tries. The daily intakes of BHA and BHT in Japan in 1998 were 0.119 and

0.109 mg/d/person, which reﬂect 0.5% and 0.7% of the acceptable daily intake

(ADI), respectively (35). The estimates of theoretical maximum daily intake

(TMDI) of BHA and BHT in Brazil published in 2001 were in the range of

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SYNTHETIC ANTIOXIDANTS

TABLE 1. Properties, Applications, and Regulations of BHA.

NAME:

Butylated hydroxyanisole (BHA)

CATEGORY:

Antioxidant

FOOD USE:

Bakery products/Meat products/Spices/Cereals/Dehydrated

mashed potatoes/Beverage mixes/Dessert mixes/Nuts/Vita-

mins/Yeast/Vegetable

oils/Animal

fats/Processed

cheeses/

Margarine/Essential oils/Chewing gum base

SYNONYMS:

Mixture of two isomers: 3-tertiary butyl-4-hydroxyanisole and

2-tertiary butyl-4-hydroxyanisole/(1,1-dimethylethyl)-4 meth-

oxyphenol/E320/ Antracine 12/Embanox/Nipantiox/Sustane

BHA/ Sustane 1-F/Tenox 4B/ Tenox 5B

FORMULA:

(CH 3 ) 3 CC 6 H 3 OCH 3 OH

MOLECULAR MASS:

180.25

PROPERTIES AND

APPEARANCE: White waxy ﬂakes or tablets

MELTING RANGE IN C: 48–55

FLASH POINT IN C: 130

PURITY %: Not less than 98.5 of 2-isomer and not less than 85 of 3-isomer

SOLUBILITY % AT VARIOUS TEMPERATURE/pH COMBINATIONS:

in water:

at 20 C

Insoluble

at 25 C

in vegetable oil:

30% cottonseed oil

40% coconut, corn, peanut oils

50% soybean oil

100% at 25 C

in ethanol solution:

> 25%

in propylene glycol:

at 20 C

70%

FUNCTION IN FOODS:

Antioxidant preservative by terminating free radicals formed

during autoxidation of unsaturated lipids. It also possesses

antimicrobial activity as a phenolic compound.

ALTERNATIVES:

BHT; PG; TBHQ

SYNERGISTS:

BHT; propyl gallate; methionine; lecithin; thiodipropionic acid;

citric acid; phosphoric acid

FOOD SAFETY ISSUES:

This antioxidant has not been subjected to great criticism of

safety. However, suspected for tumor formation in animals with

forestomach.

LEGISLATION:

USA: Maximum usage level approved for general use; FDA

0.02% and USDA 0.01% of weight of fat.

Special applications include:

Chewing gum base: 0.01% by weight of chewing gum base

Active dry yeast or dry material

Emulsion stabilizer: 0.02% by weight of emulsion, shortenings,

stabilizer

Potato ﬂakes, sweet potato ﬂakes: 0.005% by weight, dry

breakfast cereal, of food material, packaging material

Potato granules: 0.001% by weight of potato granules

Dry mixes for beverages: 0.009% of material and desserts

Beverages and desserts, prepared from dry mixes: 0.0002%

Dry diced glazed fruits: 0.0032%

Flavor substances: 0.5% of essential oil content

U.K. and EUROPE: approved

CANADA: approved

AUSTRALIA/PACIFIC RIM and JAPAN: approved

Adapted from (34).

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