Browning of foods

Sapers GM. 1993. Browning of foods. Control by sulfites, antioxidants and other means. Food Technol 47 75-84. 

Discoloration, browning. — See also Maillard reaction. Studies of browning of food and related materials were indexed at this heading. 

Kato, H. Studies on nonenzymic browning of foods. Nippon Nogei Kagaku Kaishi 1968, 4, R9-15. 

There are two main types of mechanism by which browning of food occurs, depending on whether the process is mediated by enzymes or not. The division is not precise and, in a specific case, it is usually difficult to rule out one or the other mechanism, unless conditions are such, for instance, during heat processing, that enzymes would have been inactivated. 

The simplest member of the fructose-amino acid series is the glycine derivative, N-(l -carboxy)-methyl-l-amino-l-deoxy-D-fructose (7). Substances of this type are produced in the so-called chemical browning of foods and they have been isolated and characterized from hog liver. They may be obtained synthetically by heating the appropriate amino acid with a very large excess of D-glucose. Several workers have observed... 

Aldoses undergo the Amadori rearrangement and subsequently turn into caramels, the natural brown food colorants, and/or heteroaromatic compounds — derivatives of pyrrole, imidazole, and pyrazine. Ketoses react similarly into ketosylamino acids or ketosylamines, which, in the first step, undergo the Heyns rearrangement (5.17-5.23). These rearrangements are the first steps of either thermal or enzymatic (the Maillard reaction) reactions resulting in the browning of food and the aroma of roasted, baked, or fried foodstuffs. 

Hodge stimulated research on these l-amino-l-deoxy-n-fructoses, not only by his fundamental contributions, but even more by his review, which mentioned the problems encountered during crystallization, and formulated questions about possible intermediates. Their basic role in the nonenzymic browning of foods (Maillard reaction) is another aspect of the biochemical importance of these products in Natiu-e, which has been proved by later work on the stimulation of protein synthesis and the analysis of liver tissues. ... 

Maillard products, associated with the browning of foods, could also provide some carbohydrate for intestinal bacteria. 

As we discussed in Chapter 4, oxidation is the loss of electrons in a chemical reaction, and reduction is the gain of electrons. (Section 4.4) Thus, oxidation-reduction (redox) reactions occur when electrons are transferred from an atom that is oxidized to an atom that is reduced. Redox reactions are involved not only in the operation of batteries but also in a wide variety of important natural processes, including the rusting of iron, the browning of foods, and the respiration of animals. 

Recent efforts to characterize thiol adducts formed during enzymatic and nonenzymatic browning of foods are described in the references (77-80). 

Phenolic compounds are also involved in the enzymatic and non-enzymatic browning of food products. The occurrence of browning reactions is often disadvantageous in the majority of fruit processing operations. Chlorogenic acid and catechin serve as the principal substrates for the phenolase complex that is responsible for the enzymic browning exhibited by many fruits and vegetables. 

Tyrosinases are ubiquitous oxidative enzymes that use molecular oxygen to convert phenols into quinones. These quinones are reactive intermediates that undergo further reactions with various nucleophiles. In nature, tyrosinase-catalyzed reactions are responsible for the browning of food(16), the setting of mussel ghxe(5-I0) and the hardening of insect shells(77-79/... 

M. Sakaguchi and T. Shibamoto, Agric. Biol. Chem., 1979, 43, 667, and J. Agric. Food Chem., 1978, 26, 1179 I in model system for browning of food j... 

Products that may require oxidation reactions (e.g., browning of foods) to develop desired quality parameters cannot be dried in superheated steam. However, it may be possible to consider a two-stage drying process (e.g., steam drying followed by air drying). For drying of silk cocoons, for example, such a process appears to yield a higher quality product. 

Supers GM. 1993. Browning of Foods Control by Sulfites, Antioxidants, and Other Means. Food Technol. 47 75-84. 

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