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IMPROVING THE SUPPLY, QUALITY,AND UTILITY OF PROTEINSSoichi AraiDepartment of Agricultural Chemisty, The University of TokyoBunkyo-Tokyo 113, JapanABSTRACTFood proteins inevitably undergo deterioration preharvest and postharvest.The deterioration may jeopardize efficient supply of proteins to any section ofthe world and their usefulness for human consumption. A solution to this problemrequires basically the use of up-to-date methods for minimizing the factorsinvolved in the deterioration and, at the same time, for maximizing desirableprotein properties. The sophisticated methodology currently available for thispurpose, emphasizes the potential of novel enzymic modification of proteins. Thesubtlety and versatility of protein structures permit their intentionalmodification in the form of covalent attachment of suitable amino acid esters withthe aid of a protease action. Examples are given of recent work on improving thenutritive value of soy protein by attachment of L-methionine ethyl ester, and ofendowing hydrophilic proteins (e.g., gelatin) with a greater surface action byattachment of lipophilic L-leucine n-alkyl ester. The utility of enzymicallymodified proteins and future research strategies are discussed.KEYWORDS: enzymic modification: flavor: functional property; gelatin; lipid;methionine supplementation; pigment; plastein reaction; protease; soy protein.INTRODUCTIONAs the requirement for high quality foodstuffs increases, it becomesimperative to improve the supply, quality, and utility of conventional as well asnon-conventional proteins. The less affluent sections of the world criticallyneed protein foodstuffs. Any of the currently available proteins, however, haslimitations for use as human food. All are deficient in one or more of theessential amino acids. Many suffer from lack of ideal functional properties, andseveral contain undesirable chemical components. These deficits can be totally orpartly minimized by use of modern methods of modifying the properties of foodproteins. Although proteins are fundamentally important as nutrients, theypossess subtle and versatile chemical and physical properties that make them keyfunctional ingredients of food. As the world's need for high quality proteinsbecomes more acute; more and more of this need can be met only by intentionalmodification of the properties of proteins in order to increase their utility forhuman consumption. This is one of the main reasons why studies on the intentionalmodification of food proteins has been stressed in recent years.383