Flavor enzyme role

It is often necessary to purify a particular protein to better understand its role in the nutritional value and physicochemical properties of food. Similarly, many enzymes have been purified to study their effect on the texture, color, flavor, and nutritional value of foods. The purification and characterization of protein-based microbial toxins has been necessary to better understand their mechanisms of action and their roles in food-borne disease. 

Studies on the functional significance of MFGM-associated enzymes have been restricted largely to their involvement in degradative events that affect processing properties or flavor, or for their use as markers of adequate pasteurization. Obviously, enzymes that can produce product defects are of great concern to the dairy industry. Unfortunately, the biological roles... 

Lipolysis plays an important role in providing the characteristic flavor of many milk products. In particular, the ripening of most cheese varieties is accompanied by lipolysis due to microorganisms or to added enzyme preparations, and, in raw milk cheese, to the milk LPL. Lipolysis is not extensive, but is more pronounced in some cheeses (e.g., blue-veined and hard Italian varieties), than in others. Excessive lipolysis renders the cheese unacceptable (Fox and Law, 1991 Gripon et al., 1991). 

Clearly, more research is required to clarify the somewhat confused picture regarding the role of enzymes in the oxidation of milk lipids. However, the key factor affecting the susceptibility of milk to oxidation appears to be its relative content and distribution of pro-oxidants and antioxidants. Bruhn and Franke (1971) reported that spontaneous oxidation is directly proportional to the copper content and inversely proportional to the a-tocopherol content of milk. Charmley et al. (1991) showed that intramuscular injection of cows with a-tocopherol may overcome a spontaneous oxidized flavor problem caused by low levels of a-tocopherol in milk. In general, milk from pasture-fed cows is less susceptible to oxidation due to a higher content of tocopherols than milk from cows given dry feed (Bruhn and Franke 1971 Urbach, 1989, 1990). 

Giinata, Z., Dugelay, 1., Sapis, J.C., Baumes, R., Bayonove, C. (1993). Role of the enzymes in the use of the flavour potential from grape glycosides in winemaking. In P. Schreier P. Winterhalter (Eds.), Progress in flavor precursors studies (pp. 219-234). Carol Stream Ils. AUured Publishing. 

Flavor formation in fruit products has also extensively been reviewed (10), A distinction can be made between the primary aroma components, which are biosynthesized by the whole fruit and secondary aroma compounds (e.g. hexanal, 2-hexenal), formed after disruption of the cells during processing or chewing (11). The Importance of the peel for aroma formation has also been stressed by several authors (12). An extensive literature on the respiration climacteric (13), the role of ethylene (14) and the enzymes and substrates required for biosynthesis is available (15). 

The heat treatment of cream plays a decisive role in the butter-manufacturing process and the eventual quality of the butter. It is important that milk and cream be handled in the gentlest possible way to avoid mechanical damage to the fat, a serious problem in continuous manufacture (Fritz process) of butter (80). Cream is pasteurized or heat treated for the following reasons to destroy pathogenic micro-organisms and reduce the number of bacteria, to deactivate enzymes, to liquify the fat for subsequent control of crystalhzation, and to provide partial elimination of undesirable volatile flavors. 

Because minerals are an integral part of many enzymes, they play an important role in food processing, e.g., in alcoholic and lactic fermentation, meat aging, and dairy food production. Many compounds used as food additives or for rheological modification of some foods contain metallic cations in their structure. A number of these compounds function as antimicrobials, sequestrants, antioxidants, flavor enhancers, and buffering agents, and sometimes even as dietary supplements (Table 4.4). 

Gunata, Z. et al., Role of enzymes in the use of the flavor potential from grape glycosides in wine-making, in Progress in Flavor Precursor Studies, Schreier, P. and Winterhalter, P., Eds., Allured Publishing Corp., Carol Stream, IL, 1992, p. 219. 

Although methanethiol is most noted for its role in distinctive sulfurous aromas and flavors, other more subtle involvements of methanethiol in flavors occur which deserve attention in developing concepts for controlled enzymic generation of flavors. The flavors and aromas of some fruits and fruit... 

Another important, low molecular weight flavor compound is acetaldehyde. This material plays a significant role in the flavor of yogurt and certain fruit flavors, such as orange. A procedure was patented in 1984 for the conversion of ethanol to acetaldehyde (17) using the enzyme alcohol dehydrogenase (ADH). 

Proteins play many roles in foods, the most important one being nutritional. Another one is flavor binding, and so is flavor formation during processing and storage. The activities of the proteins called enzymes are of obvious importance. Two main groups of physicochemical functional properties of proteins can be distinguished ... 

Oxidation of Phenolic Compounds. Phenolic compounds are widespread throughout the plant kingdom and are prevalent in fruits where they are important contributors to color and flavor (46). Phenolic compounds, particularly flavonoids and derivatives of chlorogenic acid, play a crucial role in the development of a number of postharvest disorders through their oxidation to brown compounds that discolor many fruits and vegetables and substantially reduce their quality. A number of enzymes catalyze the biosynthesis or oxidation of phenolic compounds, among them phenylalanine ammonia lyase (PAL), tyrosine ammonia lyase (TAL), cinnamic acid-4-hydroxylase (CA4H), polyphenol oxidase (PPO), and catechol oxidase (CAO). The chemistry... 

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