Flavor changes

Other examples are glycine — formaldehyde, alanine — acetaldehyde, valine — isobutyraldehyde, phenylalanine — phenylacetaldehyde, and methionine — methional (106). Products such as dried skim milk, dried eggs, and dehydrated vegetables and fmits are particularly susceptible to deteriorative flavor changes ascribed to this reaction (Table 10). 

The natural moisture of the cocoa bean combined with the heat of roasting cause many chemical reactions other than flavor changes. Some of these reactions remove unpleasant volatile acids and astringent compounds, partially break down sugars, modify tannins and other nonvolatile compounds with a reduction in bitterness, and convert proteins to amino acids that react with sugars to form flavor compounds, particularly pyrazines (4). To date, over 300 different compounds, many of them formed during roasting, have been identified in the chocolate flavor (5). 

Tea Beverages. Uncoated aluminum is not compatible with tea beverages since direct contact causes discoloration and undesired flavor changes during storage. When the water contains dissolved iron, it can react with the tannin in the tea and cause darkening in the presence of air. Dissolved air in the beverage or in the headspace of the can should be... 

Lepton flavor-change, electron electric dipole moment, 242-243... 

Some esters play a central role In flavor changes during beer aging. (Adapted from Vesely et ah, 2003)... 

Flavor changes that occur in citrus juices are the result of heat input into the product over time i.e., they are a function of temperature and time. It is for this reason that canned and bottled juices are generally less preferred by consumers than other processed citrus juices, e.g., frozen concentrates or chilled juices. The canned juices receive more heat input during pasteurization and they remain at relatively high temperatures for extended periods of time because they are discharged from the water coolers at temperatures near 40°C to facilitate drying and to inhibit rusting of the cans. It is well known that the rate of flavor deterioration increases with temperature, so canned juices are stored at a temperature as low as is economically practical before distribution at the retail level to extend their shelf life as much as possible. 

Berry et al. (54) evaluated foam-mat dried instant orange juice and determined that its flavor was acceptable over 26 weeks when stored at 21.1°C. At 29.4°C flavor changes were observed after two to four weeks with samples in the pH range of 4 to 6. The flavor stability of the instant orange powder was directly related to pH when stored at 29.4°C. Stability was improved by using more acidic juices, addition of acid, or removal of sugar. 

Table I shows that an increase of Amadori compounds occurs parallel with an increase of isovaleraldehyde formed by Strecker degradation of the amino acid leucine (18 ). It becomes evident from Table I that the flavor impression "burnt arises if certain concentrations of isovaleraldehyde are exceeded this flavor change is increased by increasing isovaleraldehyde concentrations. By this means an analytical control of undesirable sensory changes caused by the Maillard reaction in carrots is available.

According to Table V the tolerable limits of iso-valeraldehyde concentration seem to be variety dependent while "Rubika" containing 1.8 ppm isovaleralde-hyde does not exhibit distinct undesirable flavor changes, "Rubin" having the same isovaleraldehyde concentration and "Pariser Markt" with an even lower amount of isovaleraldehyde already show a burnt flavor character. These findings may be attributed to the fact that... 

There is increasing evidence that the interaction of lipids with the Maillard reaction is relevant to the generation of flavor in many cooked foods. For instance, the removal of lipids from coconut has been shown to cause flavor changes in the roast material (12). Uncooked coconut contained significant amounts of lactones as the main aroma components on roasting pyrazines, pyrroles and furans were also found in the aroma volatiles which added a strong nut-like aroma to the sweet aroma of the unroasted coconut. When ground coconut was defatted and then roasted, the sweet aroma due to lactones disappeared and the product possessed a burnt, nut-like aroma. A marked increase in the number and amount of Maillard reaction products, in particular pyrazines, was found. 

A flame photometric detector specific for sulfur compounds revealed a mixture of sulfur compounds in the cooked meat extract which quantitatively changed with storage. Three nuyor sulfur compounds were identified as markers for flavor changes, namely methional, methyl sulfone, and benzothiazole. 

Flavor Profiles of Foods Added MSG. The effects of MSG on a variety of foods were qualitatively and quantitatively investigated using the Semantic Differential (9, 39). The aim of the study was to make clear how people in general, not specialists in food science, respond to the flavor changes of foods. 

Gremli, H. (1996). Flavor changes in plastic containers. A literature review. Perfum. Flav. 21, 1-8. 

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