FLAVOR SAFETY

V. FLAVOR SAFETY

A. General Considerations

Flavors are part of food, so they must be wholesome and safe. The concern of consumers and the responsibility of flavor manufacturers make safety aspects topics of utmost interest and importance. Various publications by R. L. Hall reflect this concern (47–51).

Since the authorities simply demand that flavors be innocuous, various approaches have been chosen to verify the safety of flavoring substances. In 1972, a number of toxicol- ogists and pharmacologists from Belgium, Denmark, France, Germany, Italy, Japan, the Netherlands, Switzerland, the United Kingdom, and the United States met in Geneva and

Any flavoring substance may be placed, by expert judgement, on a spectrum of confidence regarding safety-in-use, ranging from one extreme to the other. At the extreme of greatest confidence may be placed those substances which fulfill the following descrip- tion:

• They belong to a group of substances simple in chemical structure and closely related, several of which have been studied toxicologically, and have been found not to possess significant toxicity at levels higher, by a suitable safety factor, than those which could reasonably be encountered in the diet of man.

• They are known, or can, with confidence, be assumed, to be metabolized to safe products or excreted by known mechanisms. By ‘‘metabolized to safe products’’ is implied absence of appreciable tissue accumulation and biotransformation to products that are not considered to constitute any contradiction to the use of the parent compound as a flavoring.

• They are used, or are proposed for use, at defined and very low levels in the diet. • They occur widely and naturally, in foods, at amounts generally closely related to the present or proposed use.

At the other extreme, where confidence is lacking, are these compounds, which are • Complex, unusual, or unknown in chemical structure

• Not closely related to substances whose safety has been demonstrated or are related to substances of toxicological concern • Used at high dietary levels, especially when this use is in special risk groups, such as children • Not known to occur, and probably do not occur, naturally in food

At the extreme of high confidence, a low priority for testing is, at present, required, although additional requirements arising from knowledge may be imposed at any time. There is also less need for analytical methodology today, except in those instances in which production figures lead to the suspicion that the levels of use, and the varieties of uses, create a total dietary burden that substantially exceeds that attainable from natural sources.

At the other extreme of low confidence, the full range of toxicological and metabolic studies will be required as well as suitable methods for analysis of the substance in food. An intermediate position of confidence should carry appropriate graduated interme- diate evaluation and testing requirements. The hundreds of different flavoring materials make it difficult to establish levels of confidence for each one of them. To arrive at reasonable and acceptable priority settings, certain assumptions had to be made to make the problem less complex:

Complex mixtures of natural aromatic raw materials that have always been used in foods are regarded as safe for the present time as long as analytical results indicate no presence of foreign materials such as pesticides, heavy metals, or other known or unknown contaminants.

Under these conditions, it can be assumed with good probability that such aromatic

Consequently, nature-identical flavoring substances are considered, by some authori- ties, as being safe, as long as they are not used in food in concentrations signifi- cantly higher than in the natural complex mixture.

Artificial flavoring substances are considered by some authorities as potentially haz- ardous as long as their innocuousness has not been fully established in extensive and suitable tests.

From these considerations, which used to be common thinking 20 years ago, two conclusions became evident: artificial flavoring substances represent the class of highest risk, and some means had to be found to assess the risk involved with natural or nature- identical flavoring substances in order to set priorities for further testing. The latter point,

a setting of priorities, was still not possible or attainable on the basis of these recommenda- tions. This situation is well phrased in Chapter 8 of the Council of Europe’s book (42): ‘‘Indeed, the prolonged use of a substance, with visible harmful effects, does not prevent that substance from contributing to a marked degree towards the morbidity of the popula- tion exposed to it.’’

The safety evaluation of flavorings is as well a topic for JECFA. In its 17th report (53), it stated that the safety of flavorings cannot be evaluated by simply applying the procedures traditionally used for other food additives. In its 20th report (54), JECFA con- sidered the large number of flavoring raw materials and concluded that a priority list for testing should be established. In a later report, JECFA (55) acknowledged that it would not be possible to carry out full toxicological testing with all substances used in the flavor trade.

B. Correlation of Flavor Consumption with Total Food Consumption

Whereas JECFA provided no priority settings, the FAO/WHO Codex Alimentarius Com- mission (56) concluded that the consumption ratio proposed by J. Stofberg (57) would

be a useful tool for determining priorities as to which substances should be investigated first. The consumption ratio is defined as the ratio between the amount of a particular flavoring substance consumed as a natural ingredient of basic and traditional food and the quantity of the same substance consumed as a component of added flavors by the same population and over the same period of time.

If the consumption ratio for a given material is larger than 1, it can be concluded that the intake of this material is predominantly derived from natural sources. If it is zero, we are dealing with an artificial flavoring material that does not occur naturally in food. The proposal to use the consumption ratio as a means to determine priorities for safety testing is still the only logical and generally accepted procedure. Stofberg and Stoffelsma (58,59) have published quantitative data on naturally occurring flavoring substances. The IOFI, its member associations, and the flavor industry support this approach by sponsoring the Dutch CIVO/TNO publication of annual literature reviews on quantitative data of flavoring substances in food, by encouraging independent researchers to collect such data, and by encouraging efforts of the individual flavor companies to compile such information from their existing files or through additional analytical investigation (60).

The next step, as foreseen in the Stofberg proposal, will be to assign priorities to the numerous flavoring substances according to their consumption ratio. Substances with low consumption ratios would then be selected by the application of a protocol similar to the decision tree approach, as proposed by Cramer et al. (61) for appropriate safety

C. Safety Assessment of Flavors

1. Laboratory Studies There is no scientific foundation for the common assumption that natural foods and flavors

are safe. Moreover, there are no available test methods where ‘‘absolute safety’’ can be determined by what is being consumed. It is also difficult to foresee the availability of such test methods in the future. The major drawback on toxicological tests is the inaccuracy of extrapolating animal laboratory test results to humans. Not only are humans vastly differ- ent in their metabolism compared to test animals, but the differences among humans in their response to various foods and nutrients is another major variable.

Hall (4) defined safety in food ingredients as ‘‘the practical certainty that injury will not result from the substance when it is used in the manner and quantity proposed for its use within the lifetime of the individual.’’ Another definition for safety can be indirectly extracted from the U.S. Food Additive Amendment, where an acceptable food additive is defined as follows:

A substance which is generally recognized among experts qualified by scientific training and expertise to evaluate safety, as having been adequately shown through scientific procedures or expertise based on minimum use of food to be safe under the conditions of its intended use.

Present methodology of high-level toxicological animal testing does not provide conclusions with a reasonable degree of confidence for judging safety for humans. There- fore, the safety of the FEMA GRAS materials was determined by its Expert Panel using judgment based on technical information provided on these materials. On the other hand, some authorities have adopted the position that all flavoring materials are subject to critical reevaluation before their final legal status is confirmed.

Some of the toxicological test methods used to establish the safety of an additive or flavoring material are discussed next.

a. Acute Toxicity.

A group of test animals, usually consisting of ten mice, are given

a dose of the substance to be tested. The dose levels, consumed by test animals for 2 weeks, are set to establish the median lethal dose, the dose from which half of the animals in the group die. The results are then expressed as LD 50 in milligrams of the test substance per kilogram of body weight of the test animal. Acute toxicity is usually used for prelimi- nary investigations, and the results provide some information on the metabolic degradation and actions of metabolites of the substance. The need for further testing will be determined by the results of the acute toxicity study.

b. Mutagenicity Tests (62,63). These are usually the second phase of testing, where gene mutations of bacteria or animal cells are observed in vitro (tissue cell cultures). Some investigators believe that if a substance causes mutation, it should be considered unsafe. However, the disagreement in this area among scientists is based on the fact that while it appears that all carcinogens are mutagenic, there is no reason to believe that all mutagens are in fact carcinogens. In some cases, a mutagenicity test is run in vivo.

c. Metabolic and Pharmacokinetics Studies. In this type of experiment, radioisotopes may be used to determine the distribution kinetics and biochemical fate of the test sub- stance. As an example, if an ester is investigated, it should hydrolyze in vivo tests to the c. Metabolic and Pharmacokinetics Studies. In this type of experiment, radioisotopes may be used to determine the distribution kinetics and biochemical fate of the test sub- stance. As an example, if an ester is investigated, it should hydrolyze in vivo tests to the

e. Subchronic Studies. Subchronic studies are used to provide information on dose- response, characteristics, and to determine dosage levels for chronic feeding studies. Nor- mally, subchronic studies are carried out with two animal species over a span of 90 days. Preferably one of the test animals should be a nonrodent.

f. Reproduction and Teratogenicity Studies. Although only rarely used by the flavor industry, these studies include the exposure of test animals for their life span and for two or three generations. The objectives are to determine whether the test substance affects the reproduction of the animal. The test animals are usually rodents.

g. Chronic Toxicity and Carcinogenicity Studies. The objective of these tests is to dem- onstrate the absence of carcinogenesis induced by the test material in low doses over most of the animal’s life span. The test animals are usually rodents. In order to exclude nonspe- cific chronic toxic effects, it was suggested that a level of 5% of the test material not be exceeded in the feed.

Flavors in dosage levels of up to 5% pose a number of problems. Possibly dosed to their high sensory capabilities, test animals normally reject such food. If the products were encapsulated, the ingestion of at least five times are much carrier material would be required, resulting in a increase to 20% of the total feed.

2. Interpretation and Evaluation of Results Flavoring materials, before undergoing toxicological tests, are assessed to determine the

extent to which toxicity tests are needed. Flavor manufacturers, in preliminary evaluation, examine the following information:

The chemical and physicochemical properties to assess purity The chemical structure in order to assess its simplicity or complexity and the occur-

rence of ‘‘suspicious’’ components, such as epoxides Similarity to other related substances, the toxicity or metabolism of which is known Maximum use level, consumption data, and the type of food in which the substance

will be used Occurrence in nature Past experience of food consumption in which this material was applied

Another proposal in risk assessment is to consider the assumption that nature-identi- cal substance might be relatively safer than artificial chemicals. If this assumption is used along with knowledge of the nature of the chemical structure, substances can be classified into four general categories providing a maximum safe dosage in foods as follows:

Safe Maximum Dosage in Food (ppm) Nature-identical

Simple structure

Complex structure

Artificial Simple structure

Complex structure

It was also suggested by Givaudan Roure that using a safety factor* of 5000 instead of the traditional factor of 100 in the preliminary toxicological testing of the four categories might provide some insurance of safety or indicate the necessity of further studies using more stringent toxicological testing.

Besides assessing risk and establishing safety for flavoring materials, toxicological data are also used to establish acceptable daily intake data. The ADI is expressed for humans in milligrams of a substance per kilograms of body weight by the Joint Expert Committee of FAO/WHO. An ADI of ‘‘no upper limit’’ is assigned to materials when no risk could be assessed after extensive testing. When sufficient proof is available to exclude possible risk to consumers with incomplete data, a temporary ADI is assigned until more information is available.

The ‘‘no effect level’’ (NEL) is the dosage for which test results have demonstrated that ingested material exhibits no visible harm. However, it should be noted that science might never be capable of assuring absolute safety Human beings are not created with equal metabolisms, and even when a certain type of food is scientifically considered safe, some of the population may have adverse reactions to it. Individuals with no allergy are the exceptions rather than the rule, and even these individuals might have very slow, nonapparent, adverse reactions.