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The phenolic composition of two commercial liquid smoke emulsions has been determined by gas chromatography-mass spectrometry of the free phenols and their trimethylsilyl ethers. The phenolic fraction of smoked bacons derived from the liquid smoke emulsions has been determined similarly and compared with the phenolic fraction of traditional kiln-smoked bacon. A preliminary examination of phenol penetration in smoked bacon has beenmade on a sample prepared from a liquid smoke emulsion by electrostatic spraying.

Non-enzymic browning involves a complex of chemical reactions with few identifying common features other than the involvement of carbonylic intermediates, the production of brown pigments (melanoidins) and the effect of sulphites in either inhibiting or retarding the development of the melanoidins. In general, amine compounds (amines, amino acids, peptides, proteins) are important in reactions, usually with carbohydrates, which (a) produce highly reactive carbonylic intermediates and (b) involve condensation with these intermediates to produce highly coloured pigments. These reactions occur in many foods and, where they are undesirable, may usually be controlled more or less successfully by the addition of sulphites. This effectiveness of a single additive in controlling a variety of chemical pathways is probably due to the number of different reactions which sulphite can enter into with, for example, reducing sugars, simple carbonyls, uj?-dicarbonyls, /3-hydroxycarbonyls, ab-unsaturated carbonyls and with the melanoidins. It is known that in exerting its anti-browning effect in food, the amount of measurable sulphite decreases and there is some evidence that amongst the products derived from sulphite in a rat diet there is at least one toxic factor. Information is only recently available about the nature of some of the more stable products (e.g. sulphonated deoxyosuloses) arising from sulphite-loss and further investigation of the biological properties of these products seems necessary. With increasing concern about the total dietary intake of sulphite it is becoming more necessary to identify the uses of this additive where there is no adequate alternative and the most effective ways of employing it where it is essential in food processing; further advances in the chemistry of sulphites in relation to food will be important in achieving this.

Nitrosation of the phenolic components of liquid smoke preparations has been shown to take place in model systems simulating gastric digestion of smoked bacon. The major products isolated have been shown to be o-nitrophenols formed by oxidation, in the meat system, of the corresponding nitroso derivative. Similar compounds have been shown to be formed in actual samples of liquid smoked and traditionally smoked bacon during processing, frying and simulated digestion.

Twenty three UK commercially produced ammonia caramels and eight experimentally produced ammonia caramels have been analysed by a range of physical and chemical tests, which include solids content, nitrogen levels, colour intensity and pH. A statistical treatment of the results is reported.

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The apparent total N-nitroso content of foods can be measured by a procedure based on chemical denitrosation and chemiluminescent detection of the eliminated nitric oxide. Procedures have been established which substantially reduce the 'apparatus blank' response to the denitrosating agent and allow total nitroso contents down to 10 micrograms (N-NO)/kg to be measured reproducibly on a 1-g sample. Typically, duplicate analyses of samples containing 10-1000 micrograms (N-NO)/kg differ by less than 15% of their mean. Potentially the method can be subject to some interference from compounds other than N-nitroso compounds, but at least in some commodities these interfering compounds do not exist in measurable amounts.