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.

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The effect of various levels of moisture content of dehydrated potato on the relationship of ‘total’ and ‘free’ sulphur dioxide contents has been studied and the influence of these relationships on the development of non‐enzymic browning has been noted. The use of ‘in‐package’ desiccants to reduce moisture contents reduces the rate of loss during storage of the total sulphite previously added to the potato. Free sulphur dioxide is also found to decrease during storage until the moisture content reaches a critical low value. At or below this moisture level, loss of ‘free’ sulphur dioxide is prevented, and in fact at moderate temperatures of storage it may actually increase. It is suggested that for potatoes of the variety and condition tested, the onset of non‐enzymic browning would be delayed beyond 52 weeks by ensuring that ‘free’ sulphur dioxide levels were maintained at not less than 250 p.p.m.

Whole and skimmed milk spray dried powders have been gas packed by two methods, and the chemical and physical changes taking place during storage at 17 and 37 °C for two years have been measured. The conventional method of double gas packing with nitrogen, with an interval of several days for desorption, was used as a control for a new method employing a single gas packing with a mixture of nitrogen (90 %) and hydrogen (10 %) plus the inclusion within the can of a solid catalyst pellet containing palladium.The new system was more effective in removing oxygen and in maintaining an almost oxygen free atmosphere within the cans. Used on a commercial scale it would have several important advantages over the conventional method, and both whole and skimmed milk powders packed in this way would probably be usable after storage for 10 years at normal temperatures. Because of the low general level of oxygen in all the cans packed by both methods and because of the low moisture content there was little difference in the keeping quality of the powders. What little there was, however, was in favour of the new method.The most effective method of extending the storage life of milk powder is to pack it in an airtight container from which the air has been removed and replaced by a chemically inert gas such as nitrogen, the process commonly known as gas packing. This is particularly true for whole milk powder where the storage life is governed by the rate of oxidation of the unsaturated fats and the consequent development of objectionable flavours (Lea, Moran & Smith, 1943). The advantage of gas packing skimmed milk powder of normal moisture content (about 3 %) is much less but it has been found to be worth while in preventing the development of stale flavours, especially where the storage period might be prolonged or the storage temperature high (Henry, Kon, Lea & White, 1948).The technique of gas packing is simple and, so long as the containers are airtight, the oxygen content can easily be reduced from the 21 % present in air to 1 % or less

Results are reported of pilot‐scale experiments on the concentration of beer by freezing and removal of ice and by evaporation at approximately 24° and 50° C., and on reconstitution of concentrates in commercial soft‐drink bottling equipment. Storage life and palatability of concentrates, and effects thereon of various treatments applied to concentrates, of various additions thereto, and of various types of water used for reconstitution are discussed, and consideration is given to the types of beer best suited to the various methods of concentration.