Interaction of Food Components During Processing

Abstract

The major chemical reactions that take place during food processing, as would be expected, occur between the main food components—the carbohydrates, proteins, fats and vitamins. These components can react with each other and with various food additives such as nitrites, sulphite, aldehydes and alkali: to give food products of lower nutritional value; to produce desirable and undesirable browning and flavours; and very occasionally to produce toxic materials.

Proteins are the most reactive of the food components and they can combine with sugars, fats, polyphenols, vitamin B₆ and with various chemical additives. The Maillard reaction between protein and reducing sugars is perhaps the most important and the most widely studied reaction. During early Maillard reactions reducing sugars combine primarily with the essential amino acid lysine to form a biologically unavailable deoxyketosyl compound; this reaction is very important in milk products, which can lose a large proportion of their lysine content during processing and storage without any visible changes in colour. The later Maillard reactions lead to the brown pigments; they further reduce the nutritional value but also produce many desirable flavours and odours, which have been reported to be at least partly responsible for the flavours and odours of freshly baked bread, coffee, cocoa, beer, cooked meats and cooked vegetables. The Maillard flavours have been divided into four main groups, the most important being the N-heterocyclics (responsible for roasted, nutty and baked flavours) and cyclic enolones responsible for caramel flavours.

The reactions of fats and alkali with proteins, the destruction of certain vitamins, and some results obtained during our investigations into protein-formaldehyde and protein-polyphenol reactions will also be briefly discussed.