Flavor formation, in food processing

Proline is the second most abundant amino acid (13-18%) contained in wheat gluten, and plays a very in rtant role in flavor formation during food processing. A great deal of work has been carried out by Tressl et aL (5) on the volatile conponents generated in proline-specific Maillard reactions. The most abundant proline-specific Maillard reaction products arc 2,3-dihydro-IH-pyrrolizines. 

Low-molecular-weight peptides play an important role in the flavor intensity of meat and beef broth (27b). A beefy meat peptide isolated of beef imparts desirable sensory properties and has potential as a flavor enhancer in heat-processed foods (27c,d). Peptides released in dry-cured ham during processing were evaluated by HPLC and related to the ham flavor formation (27e,f). 

With several foods it has now become evident that only a few compounds are actually involved in the aroma [4-6]. Therefore, the main goals of modern flavor chemistry are (i) to identify those compounds predominantly contributing to a food flavor (ii) to characterize their precursors in the raw materials and (iii) to clarify the reaction pathways governing their formation during food processing and storage. Such data are prerequisites for the improvement of food flavors as well as the inhibition of off-flavors by technological steps. 

The flavors of foods such as wheat, peanuts, and sesame, after being cooked, are quite different from those of the raw materials. Flavor formation from flavor precursors in the processed foods is primarily via the Maillard reaction, caramelization, thermal degradation, and lipid-Maillard interactions. 

A second distinguishing factor of thermal oxidations is their more random nature than typical room temperature oxidations. Very high temperatures make more sites available on the fatty acid for oxidation to occur. Thus a wider range in end products (volatile flavor components) will occur. So even though the same chemical mechanisms are involved in flavor formation in deep fat fried foods, the flavor developed is unique to this process. 

Biochemical Processes of Flavor Compound Formation in Food and Potential of LAB... 

The aroma of fmit, the taste of candy, and the texture of bread are examples of flavor perception. In each case, physical and chemical stmctures ia these foods stimulate receptors ia the nose and mouth. Impulses from these receptors are then processed iato perceptions of flavor by the brain. Attention, emotion, memory, cognition, and other brain functions combine with these perceptions to cause behavior, eg, a sense of pleasure, a memory, an idea, a fantasy, a purchase. These are psychological processes and as such have all the complexities of the human mind. Flavor characterization attempts to define what causes flavor and to determine if human response to flavor can be predicted. The ways ia which simple flavor active substances, flavorants, produce perceptions are described both ia terms of the physiology, ie, transduction, and psychophysics, ie, dose-response relationships, of flavor (1,2). Progress has been made ia understanding how perceptions of simple flavorants are processed iato hedonic behavior, ie, degree of liking, or concept formation, eg, crispy or umami (savory) (3,4). However, it is unclear how complex mixtures of flavorants are perceived or what behavior they cause. Flavor characterization involves the chemical measurement of iadividual flavorants and the use of sensory tests to determine their impact on behavior. 

The flavor quality of food is a primary factor involved in a consumer s decision to purchase a food item. Therefore, food technologists require a thorough understanding of how flavor deteriorates if they are to prepare products that consumers will purchase repeatedly. This knowledge is particularly important in meat and meat products, since the deterioration of meat flavor is a serious and continual process (1-4) that involves both the loss of desirable flavor components 4,5) and the formation of off-flavor compounds (6-9) many of which are associated with lipid oxidation (10). 

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