WHO/Food Add./24.65
FAO Nutrition Meetings
Report Series No. 38A
SPECIFICATIONS FOR IDENTITY AND
PURITY AND TOXICOLOGICAL EVALUATION
OF SOME ANTIMICROBIALS AND
ANTIOXIDANTS
The content of this document is the result of the deliberations of the
Joint FAO/WHO Expert Committee on Food Additives which met 8-17
December 1964a
a Eighth Report of the Joint FAO/WHO Expert Committee on Food
Additives, Wld Hlth Org. techn. Rep. Ser., 1965, 309; FAO
Nutrition Meetings Report Series 1965, 38.
CONTENTS
INTRODUCTION
GENERAL PRINCIPLES GOVERNING THE ESTABLISHMENT OF SPECIFICATIONS
Source and nature of impurities
SUBSTANCES STUDIED
GENERAL PRINCIPLES GOVERNING THE TOXICOLOGICAL RE-EVALUATION
NOTES ON THE SPECIFICATIONS CONTAINED IN THE MONOGRAPHS
Note to the reader
ACCEPTABLE DAILY INTAKE ZONES FOR MAN OF SOME ANTIMICROBIALS AND
ANTIOXIDANTS
THE MONOGRAPHS
APPENDIX A. METHODS
APPENDIX B. TEST SOLUTIONS
INTRODUCTION
The Joint FAO/WHO Conference on Food Additivesa which met in Geneva
in 1955 recommended that the two organizations collect and disseminate
information on food additives. As a result, a Joint FAO/WHO Expert
Committee on Food Additives was established. This Committee has met
eight times and issued the following reports: (i) "General principles
governing the use of food additives: First Report";b (ii) "Procedures
for the testing of intentional food additives to establish their
safety for use: Second Report;c (iii) "Specifications for identity
and purity of food additives (antimicrobial preservatives and
antioxidants): Third Report";d (iv) "Specifications for identity and
purity of food additives (food colours): Fourth Report;e (v)
"Evaluation of the carcinogenic hazards of food additives: Fifth
Report";f (vi) "Evaluation of the toxicity of a number of
antimicrobials and antioxidants: Sixth Report";g (vii)
"Specifications for the identity and purity of food additives and
their toxicological evaluation: emulsifiers, stabilizers, bleaching
and maturing agents: Seventh report";h (viii) "Specifications for the
identity and purity of food additives and their toxicological
evaluation: food colours and certain antimicrobials and antioxidants:
Eighth Report".i
a FAO Nutrition Meetings Report Series, 1956, 11; Wld. Hlth Org.
techn. Rep. Ser., 1956, 107.
b FAO Nutrition Meetings Report Series, 1957, 15; Wld Hlth Org.
techn. Rep. Ser., 1957, 129.
c FAO Nutrition Meetings Report Series, 1958, 17; Wld Hlth Org.
techn. Rep. Ser., 1958, 144.
d These specifications were subsequently revised and published as
Specifications for identity and purity of food additives, vol. I,
Antimicrobial preservatives and antioxidants, 1962, Rome, Food
and Agriculture Organization of the United Nations.
e These specifications were subsequently revised and published as
Specifications for identity and purity of food additives, vol.
II, Food colours, 1963, Rome, Food and Agriculture Organization
of the United Nations.
f FAO Nutrition Meetings Report Series 1961, 29; Wld Hlth Org.
techn. Rep. Ser., 1961, 220.
g FAO Nutrition Meetings Report Series, 1962, 31; Wld Hlth Org.
techn. Rep. Ser., 1962, 228.
h FAO Nutrition Meetings Report Series, 1963, 35; Wld Hlth Org.
techn. Rep. Ser., 1963, 281.
i FAO Nutrition Meeting Report Series, 1965, 38; Wld Hlth Org.
techn. Rep. Ser., 1965, 309.
GENERAL PRINCIPLES GOVERNING THE ESTABLISHMENT OF SPECIFICATIONS
Whereas a natural food may vary in composition, sometimes to a
considerable degree or in undefined ways, considerations of public
health dictate that, as a matter of principle, additives to food
should be of known composition and purity. In fact, modern methods
make it possible to produce chemicals of greater purity and uniformity
by synthesis than is usually achieved by derivation from substances of
natural origin. The adoption of official specifications for food
additives would give assurance to the consuming public that substances
meeting established standards of purity are available for use in food.
At the present time most food legislation merely indicates by name the
substances which may be used in a particular food. It is a well-known
fact that chemicals am produced in a variety of technical and refined
grades. Toxicological evaluation, which is a costly and
time-consuming procedure, must be related to the particular grade or
quality of chemical intended for use in food. The adoption of
specifications of purity of food additives would provide a means of
accurate identification of the additive for regulatory purposes and
would limit the known undesirable ingredients or contaminants to
acceptable tolerance levels.
The existence of specifications, agreed upon by qualified specialists,
serves to ensure a degree of reproducibility and of conformity to
criteria of quality which are acceptable to both chemical
manufacturers and food processors. Furthermore, established
specifications might well act as a guide in the development of new
chemicals of quality suitable for food use. It is important that
specifications for identity and quality of food additives should be no
more stringent that necessary to accomplish their purpose and that
they should be reasonably attainable by the producing industries.
Otherwise, the consuming public would ultimately bear an unnecessary
additional cost of production and control.
One of the most important areas in which specifications of purity
would be of particular value is the determination of the safety for
use of food additives. It is essential to know the identity and
concentration of the major component or components of a food additive
before carrying out an effective toxicological investigation of its
properties. Even small differences in composition of a compound may
materially alter the results of toxicity tests. The investigator must
also know the nature and quantity of the important impurities.
Toxicologists have frequently emphasized that impurities or minor
constituents may have a significant importance far greater than their
amounts might indicate. Information relating to physical properties
such as solubility is also essential.
In many animal tests, particularly with some of the relatively inert
food additives, large amounts of the chemical are required and
therefore the investigator must be certain that he has sufficient
material of a uniform nature or a reliable source of the material of
the same composition. In certain instances, years of animal studies
have been discarded because the composition of the food additive
changed during the test period. Furthermore even if tests demonstrate
beyond any reasonable doubt that a particular substance is safe for
use, their value is impaired when the food additive used commercially
differs significantly from the material tested.
The results of a single investigation are not likely to answer for all
time the question of the safety for use of a particular material. The
Joint FAO/WHO Expert Committee on Food Additives stated at its first
session that permitted additives should be subjected to continuing
observation for possible deleterious effects under changing conditions
of use and should be reappraised whenever indicated by advances in
knowledge. Specifications based on the material used in previous
tests would therefore be of great value in making certain that a
comparable product was employed in such reappraisals. The divergent
results which are occasionally encountered in the toxicological
investigation of the same product may conceivably be due to variations
in the composition of batches of the material under test.
SOURCE AND NATURE OF IMPURITIES
The purity of a food additive, as the term is here employed, refers to
its freedom from substances other than those named in specifications.
"Foreign substances" or "impurities" not included in the
specifications may be, for example, simple inorganic salts or other
substances not necessarily deleterious from the functional or safety
standpoint.
Impurities my arise from the raw materials used in the manufacture of
chemicals (especially when they are complex natural substances), from
substances used in processing steps, from solvents used in extraction
or crystallization and from equipment. They may also be unreacted
intermediates or by-products formed in the course of processing, such
as incompletely esterified acids or isomeric derivatives. Products of
decomposition during storage, such as may result from oxidation,
hydrolysis or polymerization, are likewise regarded as impurities.
However, the constituents of polymeric or other mixtures of
reproducible composition are not regarded as impurities if they
contribute to the functional properties of the substance as a whole
and are not deleterious.
Obviously contaminants like dirt, soot, rust, lubricants and insect
fragments must be avoided in manufacture, packaging and storage of
food additives. Whereas their presence is generally revealed in the
application of the tests given in the second part of this manual, no
specific tests for the detection and identification of these
contaminants are included.
From the foregoing discussion it is obvious that, depending on the
original materials and manufacturing procedure, impurities may be
volatile or non-volatile, organic or inorganic, deleterious or
non-deleterious. The important factors to be considered are:
(a) Is the impurity one which might jeopardize the safe use of the
food additive?
(b) Is the amount of impurity sufficient to affect the activity or
usefulness of the food additive?
(c) Can the impurity be reduced in amount or avoided by good
manufacturing practice?
(d) Is the impurity of sufficient consequence to justify a limitation?
Whereas food additives are usually employed in relatively small
quantities and traces of impurities may pose no serious health
hazards, prudence dictates that reasonable limits be established for
impurities, consistent with good manufacturing practice as judged by
modern standards. For this reason it will be noted that a general
tolerance limit is placed in the monographs on arsenic and lead, which
my occur in traces as they do in naturally derived food additives and,
indeed, in foods themselves, even under optimum conditions. Lower
tolerance levels are established in the case of those additives which
are employed in relatively large proportions in foods. In particular
cases, tolerance levels for other elements may be given.
It should be emphasized that these specifications are drawn up only
for purposes of identification of each substance and with a view to
the establishment of a satisfactory level of purity for substances
used as food additives.
The principles guiding the work of the Joint FAO/WHO Expert Committee
on Food Additives have been extensively dealt with in the previous
reports of this Committee mentioned above. It may be, however, useful
to restate here the objectives aimed at in establishing specifications
for food additives. These objectives are:
(a) to identify the substance that has been subjected to biological
and toxicological testing;
(b) to ensure that the substance is of the quality required for safe
use in food;
(c) to reflect and encourage good manufacturing practice.
SUBSTANCES STUDIED
The eighth meeting of the Joint FAO/WHO Expert Committee on Food
Additives had before it a list of antimicrobials and antioxidants
which had been considered at its sixth meeting, but for which no
specifications for identity and purity were available at that time.
It was agreed that it would be advisable to delete from this list any
substance that was not known to be in use as a food additive, or on
which the information available to the Committee was insufficient for
compilation of specifications or for toxicological evaluation. On
this basis the following three substances were not considered:
(a) Distearyl thiodipropionate. According to information available to
the Committee, this antioxidant is not on any of the permitted lists.
(b) Gum guaiac. This additive being a natural substance, does not
lend itself to precise definition.
(a) Isopropyl citrate mixture. This additive is a product of a single
company, which has a use patent, and the specifications have not been
made available to the Committee.
The substances for which the Committee has prepared specifications
are:
Potassium nitrate o-Phenylphenol
Sodium nitrate Sodium o-phenylphenol
Potassium nitrite Formic acid
Sodium nitrite Thiodipropionic acid
Diphenyl Dilauryl thiodipropionate
In addition, the toxicological data for the following compounds were
evaluated:
Butylated hydroxytoluene Sulfur dioxide
Hexamethylenetetramine Sodium sulfite
Propyl Sodium metabisulfite
Octyl and dodecyl gallates Sodium hydrogen sulfite
Nordihydroguaiaretic acid Tartaric acid
Phosphoric acid
The detailed specifications for these compounds are to be found in the
publication Specifications for Identity and parity of food
additives, vol. I, Antimicrobial preservatives and antioxidants,
Food and Agriculture Organization, Rome, 1962. However, for
convenience, an abbreviated specification is reproduced here
immediately preceding the toxicological evaluation.
With regard to the purity tests, the following was re-emphasized:
The nature of impurities that might be present in a food additive has
already been discussed. In the case of arsenic and lead, limits of 3
and 10 mg/kg respectively may be considered as acceptable unless
otherwise stated in the specifications. It is stressed that those
limits are established to ensure food manufacturing practice and not,
in most cases, because of any great toxicological concern, since food
additives are commonly used in relatively low concentrations.
However, it was agreed that it is always desirable to keep the level
of arsenic and lead in the food as low as possible.
The question of tolerance limits for mercury, calcium, selenium and
fluorine was also considered. As traces of these elements in food
additives may arise only in rare cases, it was agreed to fix limits
only when these elements may be introduced through raw materials or
conditions of manufacture. The methods to be used for the detection
and determination of the elements, unless given in the monographs, are
shown in Appendix A.
GENERAL PRINCIPLES GOVERNING THE TOXICOLOGICAL RE-EVALUATION
The Joint FAO/WHO Expert Committee on Food Additives was requested by
a committee reporting to the Codex Alimentarius Commission to
reconsider, in the light of new biological data, some antimicrobials
and antioxidants which had previously been evaluated in the Sixth
Report of the Joint FAO/WHO Expert Committee. These compounds are:
Butylated hydroxytoluene (BHP)
Propyl, octyl and dodecyl gallates
Hexamethylenetetramine
Nordihydroguaiaretic acid (NDGA)
Phosphoric acid
Sulfur dioxide, sodium sulfite, sodium metabisulfite and
sodium hydrogen sulfite
Tartaric acid
The general principles governing the re-evaluation of these additives
were essentially those laid down in previous reports of the Joint
FAO/WHO Expert Committee on Food Additives.a
The meaning of the two zones of acceptability is made clear in the
Sixth and Seventh Reports. The following extract from the Seventh
Reportb is included for clarification:
"The concept of using zones of acceptability was put forward in the
Committee's sixth reportc for several reasons. First, the primary
intention of the Committee is to give guidance to national bodies to
assist them in their choice of food additives which are suitable for
their particular needs, safe in use, and can be regarded as acceptable
for purposes of international trade. Secondly, it is one of the
principles underlying food additive control that the quantity of a
food additive used should not be greater than is necessary to ensure
the technological effect required. Thirdly, the dietary pattern
a FAO Nutrition Meetings Report Series, 1956, 11; Wld Hlth Org.
techn. Rep. Ser., 1956, 107. FAO Nutrition Meetings Report Series,
Wld. Hlth Org. Rep. Ser., 1957, 15. Wld Hlth Org. techn. Rep. Ser.,
1957, 129. FAO Nutrition Meetings Report Ser., 1961. 29; Wld Hlth
Org. techn. Rep. Ser., 1961, 220. FAO Nutrition Meetings Report
Series, 1962, 31. Wld. Hlth Org. techn. Rep. Ser., 1962, 228. FAO
Nutrition Meetings Report Series, 1964, 35; Wld Hlth Org. techn. Rep.
Ser., 1964, 281.
b FAO Nutrition Meetings Report Series. 1964, 35, 10; Wld Hlth Org.
techn. Rep. Ser., 1964, 281, 10.
c FAO Nutrition Meetings Report Series, 1962, 31; Wld Hlth Org.
techn. Rep. Ser., 1962, 228.
differs greatly from one country to another and consequently the
possible benefits and risks may also differ; the final decision on the
use of any particular food additive can only be usefully taken on a
national or regional rather than an international basis.
The zone of acceptability represents the limits of intake that can be
regarded as presenting no significant hazard to health on the basis of
the evidence available. However, the problems that may arise from the
introduction of a food additive into the diet may be complex and may
sometimes require further study by experts in nutrition or other
related fields. This is more likely to occur when high levels of
dosage are used or if the food additive is to be used in foods mainly
consumed by some special group in the community, such as children. It
is for this reason that many countries tie proposed levels of a
permitted substance to a specified use or uses. The Committee felt,
however, that any attempt to tie zones of acceptability to specified
use would be too restrictive at an international level, and some other
solution of this problem was therefore sought. To ensure that expert
opinion would be consulted whenever higher dosage levels of certain
food additives were used or when special circumstances might arise,
the Committee decided to split the zone of acceptability into two
parts in selected cases. The first part has been termed the
unconditional zone of acceptability and this represents levels of use
that are effective technologically, at least for some purposes, and
can be safely employed without further expert advice. The second part
consists of a conditional zone of acceptability and represents levels
of use that can be employed safely, but at which it is thought
desirable that some degree of expert supervision and advice should be
readily available. The unconditional zones of acceptability are
therefore intended mainly to help developing countries that may not be
able to call upon appropriate experts to guide them in the handling of
particular problems in the field. The conditional zones of
acceptability, on the other hand, are more likely to be of interest to
those countries that have a more elaborate organization for dealing
with food policy and the health hazards to the consumer. It must be
emphasized that the whole zone of acceptability may be safely
employed, that it provides for an adequate margin of safety, and that
it is based on a careful consideration of the evidence available. The
added caution imposed by restricting levels of use to the
unconditional zone of acceptability is only necessary in the special
circumstances already described."
From the foregoing statement it should be quite clear that the
inclusion of a food additive in the conditional zone only does NOT
mean that this additive is considered unsuitable for use in food.
As with the evaluation of all food additives, it has been difficult to
assess the significance of certain experimental findings. As was
stated in the Fifth Report, there is still no general agreement on the
proper assessment of subcutaneous sarcomas. The relationship between
the mutagenic effects of food additives on micro-organisms or on
insects and possible genetic hazards from their use in human food is
still under discussion and no agreed solution has been reached. A
similar situation exists in the field of teratogenesis in spite of the
intensive studies in progress in many countries. These considerations
have raised difficulties, especially in the evaluation of
hexamethylenetetramine.
The observation of a relative increase in liver weight in the absence
of detectable histological change is also difficult to interpret and
requires further studies on the mechanism of this effect. This
problem gives special difficulties in the evaluation of the toxicity
of butylated hydroxytoluene and butylated hydroxyanisole.
Work on the augmentation of toxicity under the influence of stress,
such as partial starvation, has shown that toxic effects can be
detected by these methods at dietary levels considerably lower than
those that reveal toxicity in the unstressed animal in conventional
tests. The assessment of these new methods is difficult at present
because of lack of comparative data with different food additives.
Toxicological evaluations of gum guaiac and of isopropyl citrate
mixture were presented in the Sixth Report.d The Committee has now
reconsidered these two additives but is unable to prepare
specifications (see "Substances studied", page 5). The previous
evaluations, therefore, are only valid for the materials actually used
by the investigators concerned.
After careful consideration of the new evidence put before it and
reconsideration of the data available at the time of the Sixth Report,
the Committee decided to change the evaluation of only one of the
additives, namely tartaric acid, although several of the comments have
been modified. The other evaluations of acceptable daily intakes
remain the same as in the Sixth Report.
d FAO Nutrition Meetings Report Series, 1962, 31, 51-53 and 65-67;
Wld Hlth Org. techn. Rep. Ser., 1962, 228, 51-53 and 65-67.
NOTES ON THE SPECIFICATIONS CONTAINED IN THE MONOGRAPHS
The most effective way of using the information contained in the
monographs has been described in detail in the Sixth and Seventh
Reports.a,b The following supplementary information is given on the
conventions adopted in the specifications and on the evaluation of
toxicological data.
Nomenclature
The title of each monograph contains the name by which the substance
is most commonly known in food manufacture. Where other recognized
names exist, they are listed as synonyms. For the technical names,
the recommendations of the International Union of Pure and Applied
Chemistry (IUPAC) and the usages of the various national chemical
societies have been taken into consideration. Where the structure or
composition of a food additive has not been clearly elucidated, a
description of its chemical nature is given instead of the chemical
name.
Formulas
A chemical formula is given for each inorganic substance, and
empirical and structural formulas are shown, where known, for each
organic substance. All formulas represent the pure compounds and
serve only a descriptive purpose.
Molecular weight
For the purpose of information and description, the molecular weights
of the compounds are given where known. These have been calculated
from the table of atomic weights approved by the Commission on Atomic
Weights of the International Union of Pure and Applied Chemistry in
1961.
Temperature
All temperatures are given in degrees centigrade.
Solubility
The solubilities of the substances contained in the monographs are
given without reference to possible chemical changes. Unless
otherwise stated, the standards adopted are room temperature and
normal atmospheric pressure.
a FAO Nutrition Meetings Report Series, 1962, 31; Wld Hlth. Org.
techn. Rep. Ser., 1962, 228.
b FAO Nutrition Meetings Report Series, 1964, 35; Wld Hlth Org.
techn. Rep. Ser., 1964, 281.
Solvents
Unless otherwise stated, reference to water in the monographs presumes
distilled water. The term "ethanol" is used as referring to 95% v/v
ethyl alcohol, and the term "absolute ethanol" for solvent containing
not less than 98% v/v alcohol. Other v/v concentrations of ethanol
may be specified in individual cases.
Assays
The assay methods described for the compounds are those that are
considered to be the most suitable. A second method is included if
the preferred procedure requires instrumentation not widely available.
Methods
Procedures for the determination of loss on drying, sulfated ash and
physical constants and tests for the presence of certain metals are
presented in Appendix A.
Test solutions
All reagents referred to in the identification and purity testa and in
the assays are assumed to be analytical grade, unless otherwise
specified.
Test solutions (TS) are given in alphabetical order in Appendix B. In
general solutions are brought to approximate normality or to a simple
multiple or fraction of normality. When the normality or percentage
composition of acids is not indicated, the concentrated form should be
used. When the use of a test solution as indicator is specified in a
test or assay, 3 drops of the solution should be added, generally as
the endpoint is approached, unless otherwise directed.
NOTE TO THE READER
Any comments relating to specifications should be addressed to: Food
Science and Technology Branch, Nutrition Division, Food and
Agriculture Organization, Rome, Italy. Any comments relating to
biological data and their evaluation should be addressed to: Nutrition
Unit, World Health Organization, Palais des Nations, Geneva,
Switzerland.
ACCEPTABLE DAILY INTAKE ZONES FOR MAN OF SOME ANTIMICROBIALS, ANTIOXIDANTS
Substances considered Unconditional Conditional
(mg/kg body-weight)
Butylated hydroxytoluene - 0-0.5
Formic acida - 0-5
Propyl, octyl and dodecyl gallates 0-0.2 0.2-0.5
Gum guaiac See "Substances studied"
Hexamethylenetetramineb - -
lsopropyl citrate mixture See "Substances studied"
Nitrates of sodium and potassiuma 0-5 5-10
Nitrites of sodium and potassiuma 0-0.4 0.4-0.8
Nordihydroguaiaretic acidc - -
o-phenylphenol 0-0.2 0.2-1
Sodium o-phenylphenol 0-0.2 0.2-1
Phosphoric acida 0-5 5-15
Sulfur dioxide 0-0.35 0.35-1.5
Sodium sulfite 0-0.35 0.35-1.5
(calculated as SO2)
Sodium metabisulfite 0-0.35 0.35-1.5
(calculated as SO2)
Sodium hydrogen sulfite 0-0.35 0.35-1.5
(calculated as SO2)
Tartaric acida 0-6 6-20
Thiodipropionic acid 0-3 3-15
Dilauryl thiodipropionate 0-3 3-15
Distearyl thiodipropionate See "Substances studied"
Diphenyl 0-0.05 0.05-0.25
a Naturally occurring substances; the estimated acceptable intakes
listed above do not include the amounts occurring naturally.
b Not considered suitable for use in food pending the result of work
now in progress.
c Available scientific evidence inadequate for evaluation.
See Also:
Toxicological Abbreviations