Oxidation processes aromas

During the oxidation process, leaf color changes from green to copper and a pleasant characteristic aroma develops. In most instances, the proper termination point is deterrnined by the skill of the process supervisor (tea maker) on whose judgment the value of the final product is highly dependent. However, some attempts to control a suitable end point by instmmental techniques have been made. The fermentation step is terrninated by firing (drying). 

The development of both desirable and undesirable fishy flavors has long-been a concern to the seafood and fishery Industry (1-6). Oxidative processes occurring through enzymic and nonenzymlc mechanisms Initiate hydroperoxide formation In fish lipid systems that are responsible for the formation of the short chain carbonyls and alcohols which exhibit distinct flsh-llke flavors and aromas. Because the generation of fresh fish aroma compounds Involves some of the same polyunsaturated fatty acid precursors and oxidative pathways as autoxldatlon. It has been a tedious task to differentiate the mechanisms and aroma compounds... 

Cigarette smoke composition is dependent on two major processes occurring during the smoking of tobacco the direct transfer by vaporization of volatile tobacco components directly to the smoke and the pyrogenesis of smoke components from tobacco components. The pyrogenesis involves a variety of reactions, including oxidation, reduction, aroma-tization, hydration, dehydration, condensation, cyclization, polymerization, depolymerization, etc. 

Novel mixtures of optical isomers of natural and kosher styrallyl alcohol (a-phenylethyl alcohol), and their corresponding acetate esters of styrallyl alcohol (a-phenylethyl acetate) were prepared by multiple fermentation processes and an azeotropic esterification reaction. In the first step, natural acetophenone was produced by bioconversion of cinnamic acid by Pseudomonas sp. (P), Comanonas sp, and Arthrobacter sp. 6). In the first microbial oxidation process, the side chain of cinnamic acid was oxidized to the ketone to form acetophenone that was transiently accumulated in the fermentation broth (P). The current commercial fermentation process yielded >5g/L of acetophenone in the fermentation broth following 2 days of incubation using Arthrobacter sp. The resulting acetophenone was recovered and purified from the fermentation broth by solvent extraction followed by fractional distillation. Acetophenone itself can be used in creating flavor formulations and in enhancement of aroma and taste or both. 

Synthesis of aroma compoimds are generally suppressed by high CO2 and low O2 levels, in part by their action on ethylene sensitivity, but also via action of O2 on oxidative processes, including respiration required for substrate production. But low O2 MAP may suppaess aroma production so consumers perceive reduced quality upon opening the container. 

Wine extracts the quercus lactone (structure cf. S.3.2.3) on storage in oak barrels. The difference in aroma compared with maturation in steel tanks also results fiom oxidative processes, which cause an increase in aldehydes in oak har-... 

Production of compounds which help in development of characteristic aromas of many fmits such as apple, banana and strawberries, and so on can be adversely affected by MAP. The high CO and low may affect the oxidative processes and ethylene perception and suppress aroma production. However, most produce recover from moderate low suppression of volatile aroma production and eventually develop characteristic flavors. Still the aroma of the commodity, when it is just taken out of the low Oj packages may be inferior to the fresh commodity, which can affect consumer appeal (Beaudry, 2000). 

Supercritical fluid extraction combined with high-resolution GC MS proved to be a powerful tool for the analysis of the virgin olive oil aroma [15]. The volatiles identified were compared with those obtained by using the DHS method. Different aromatic profiles were obtained by applying the two extraction procedures. The profiles obtained by DHS-GC-MS corresponded to a genuine extra-virgin olive oil sample in accordance with previous findings [18]. The presence of off-flavors was not detected. In the SFE extracts, however, markers of oxidation processes were identified, since this technique is also suitable for the extraction of semivolatile compounds. These were volatile compounds related to oxidation of linoleic, linolenic, and oleic acids, and in particular aldehydes and acids, which had been previously found in oxidized olive oil samples [19],... 

Alcohohc beverages are made up primarily of ethanol, congeners, and water. Congeners are vaporized with the alcohol in distillation below 190° proof and are developed during the maturation process by oxidation and other reactions. These components contribute to palatability and create the characteristic appearance, aroma, and taste of a particular spidt. When the spirit is distilled at a lower proof, more congeners are present and the spirits possess more character. Congeners are usually reported either as grams per 100 Hters at "as is" proof, or as 100° proof at parts per million or parts per billion. 

Flavor is one of the major characteristics that restricts the use of legume flours and proteins in foods. Processing of soybeans, peas and other legumes often results in a wide variety of volatile compounds that contribute flavor notes, such as grassy, beany and rancid flavors. Many of the objectionable flavors come from oxidative deterioration of the unsaturated lipids. The lipoxygenase-catalyzed conversion of unsaturated fatty acids to hydroperoxides, followed by their degradation to volatile and non-volatile compounds, has been identified as one of the important sources of flavor and aroma components of fruits and vegetables. An enzyme-active system, such as raw pea flour, may have most of the necessary enzymes to produce short chain carbonyl compounds. 

Products of the LOX pathway or compounds formed by autoxidation of fatty acids (Scheme 7.2) are also important for leek aroma [31, 163]. Volatile compounds of the LOX pathway are not pronounced in the aroma profile of freshly cut leeks owing to a high content of thiosulfinates and thiopropanal-S-oxide [30]. In processed leeks that have been stored for a long time (frozen storage), however, these aliphatic aldehydes and alcohols have a greater impact on the aroma profile owing to volatilisation and transformations of sulfur compounds [31, 165]. The most important volatiles produced from fatty acids and perceived by GC-O of raw or cooked leeks are pentanal, hexanal, decanal and l-octen-3-ol (Table 7.5) [31, 35, 148, 163, 164]. 

Following preliminary hypochlorite treatments, a coherent process path was identified and implemented. Corn starch was oxidized with 6.4% (w/w) hypochlorite for two hours and given a combined base-heat gelatinization process (Method A). This base material exhibited excellent physical characteristics (i.e., stable emulsion with 20% db lemon oil incorporation into an aqueous dispersion, low lemon oil vapor phase flux (low headspace content), lack of inherent flavor and aroma) and when finally tested for spray dried lemon oil (20% db) retention efficiency in a lab-scale mini-dryer, the viability of this polymer was ascertained. Nearly 70% of the added lemon oil was retained following the drying of this DE 1.45 starch, a measure of functionality matched only by gum arabic (34). 

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