Acid Value Flavor Chemicals

A persistent idea is that there is a very small number of flavor quaUties or characteristics, called primaries, each detected by a different kind of receptor site in the sensory organ. It is thought that each of these primary sites can be excited independently but that some chemicals can react with more than one site producing the perception of several flavor quaUties simultaneously (12). Sweet, sour, salty, bitter, and umami quaUties are generally accepted as five of the primaries for taste sucrose, hydrochloric acid, sodium chloride, quinine, and glutamate, respectively, are compounds that have these primary tastes. Sucrose is only sweet, quinine is only bitter, etc saccharin, however, is slightly bitter as well as sweet and its Stevens law exponent is 0.8, between that for purely sweet (1.5) and purely bitter (0.6) compounds (34). There is evidence that all compounds with the same primary taste characteristic have the same psychophysical exponent even though they may have different threshold values (24). The flavor of a complex food can be described as a combination of a smaller number of flavor primaries, each with an associated intensity. A flavor may be described as a vector in which the primaries make up the coordinates of the flavor space. 

Malonaldehyde, a major product of autoxidatlon of polyunsaturated fatty acids is a very reactive substance and reacts with amino acids, proteins and other chemical substances present in meats. Its concentration is generally determined by the 2-thlobarblturlc acid (TEA) test. Malonaldehyde may be used as an indicator for evaluation of the oxidative state of cooked meats. It has been reported that warmed-over flavor in beef is generally perceived when TEA number of cooked meats exceed numerical values of 0.5 to 1.0 (31). Malonaldehyde has also been implicated as having mutagenic and perhaps carcinogenic effects (32). Its presence further affects the rheological properties and texture of cooked meat products. Despite these, malonaldehyde has very little or no... 

Anisidine Value. Anisidine value is a measure of secondary oxidation or the past history of an oil. It is useful in determining the quahty of crude oils and the efficiency of processing procedures, but it is not suitable for the detection of oil oxidation or the evaluation of an oil that has been hydrogenated. AOCS Method Cd 18-90 has been standardized for anisidine value analysis (103). The analysis is based on the color reaction of anisidine and unsaturated aldehydes. An anisidine value of less than ten has been recommended for oils upon receipt and after processing (94). Inherent Oxidative Stability. The unsaturated fatty acids in all fats and oils are subject to oxidation, a chemical reaction that occurs with exposure to air. The eventual result is the development of an objectionable flavor and odor. The double bonds contained in the unsaturated fatty acids are the sites of this chemical activity. An oil s oxidation rate is roughly proportional to the degree of unsaturation for example, linolenic fatty acid (C18 3), with three double bonds, is more susceptible to oxidation than linoleic (C18 2), with only two double bonds, but it is ten times as susceptible as oleic (C18 l), with only one double bond. The relative reaction rates with oxygen for the three most prevelent unsaturated fatty acids in edible oils are ... 

DHA can be reduced to RAA by chemical agents, such as hydrogen sulfide or enzymatically, by dehydroascorbic acid reductase. The conversion of DHA to diketogulonic acid (DKG) is irreversible and occurs both aerobically and anaerobically, particularly during heating. This reaction results in loss of biological activity. The total oxidation of RAA may result in the formation of furfural by decarboxylation and dehydration. With subsequent polymerization, the formation of dark-colored pigments results. These compounds affect the color and flavor of certain foods, such as citrus juices, and decrease nutritive value. 

Table III gives the physical and chemical properties of the M. oleifera oil. Some of the properties of the oil depend on the extraction medium. The M oleifera oil is liquid at room temperature and pale-yellow in colour. Electronic nose analysis shows that it has a flavor similar to that of peanut oil. The melting point estimated by differential scanning calorimetry is 19°C (15). The chemical properties of the oil depicted in Table III below are amongst the most important properties that determines the present condition of the oil. Free fatty acid content is a valuable measure of oil quality. The iodine value is the measure of the degree of unsaturation of the oil. The unsaponifiable matter represents other lipid- associated substances like, sterols, fat soluble vitamins, hydrocarbons and pigments. The density, iodine value, viscosity, smoke point and the colour of Moringa oil depends on the method of extraction, while the refractive index does not. Varietal differences are significant in all physical characteristics apart from refractive index and density (2). The heating profile of the M. oleifera seed oil using the differential scanning calorimetry (DSC) conventional scan rate shows that there is one major peak B and, two small shoulder peaks A and C...

Although they are not methods of preparative value in a chemical sense, cysteine, cystine, N-acetylcysteine, 4-thiazolidinecarboxylic acid and cysteine methyl ester when heated in soybean oil at 200 °C produce many sulfur-containing heterocycles among which are found vanishingly small amounts of various 1,2,4-trithianes <76MI 620-01). The reaction is termed the Maillard reaction and is widely employed in laboratories in the flavor industry. 

The production of water-free tetrahydrofuran is possible using this method 28], but this is only a model reaction. No one will produce a bulk chemical like tetrahydrofuran in a microreactor. But products with higher value have similar reaction behavior, for example the esterification of end-terminated long-chain hydroxycar-bon acids. An inner ester forms by cyclization leading to macrocydic compounds, which can be used in the flavor and fragrance industry. 

The oxidative dehydrogenation of alcohols represents key steps in the synthesis of aldehyde, ketone, ester, and acid intermediates employed within the fine chemical, pharmaceutical, and agrochemical sectors, with allylic aldehydes in particular high-value components used in the perfume and fiavoring industries [1]. For example, crotonaldehyde is an important agrochemical and a valuable precursor for the food preservative sorbic acid, while citronellyl acetate and cinnamaldehyde confer rose/fruity and cinnamon flavors and aromas, respectively. There is also considerable interest in the exploitation of biomass-derived feedstocks such as glycerol (a by-product of biodiesel synthesis from plant or... 

The mode of operation (batch, continuous) and the use of a dedicated or a multipurpose plant is crucial for the choice of an appropriate ISPR configuration. The successful production of bulk products such as lactic acid requires an optimized dedicated system. This production plant has special equipment and advanced control strategies and is not very flexible. Generation of additional by-products has to be avoided. High added value, low volume products such as fine chemical or natural flavors are mostly produced in multipurpose plants. Investment in additional equipment or modifications of the reaction vessels is more difficult to justify, if just a few products need the application of ISPR. In this case, the less complex ISPR configurations 1 and 3 are preferred. Fiuthermore, the outlet of the production should also be easily adjustable to the market demand. 

The excellent review by Freeman and coworkers predicted a shift of the application of ISPR techniques from bulk products to high added value, low volume products such as fine chemicals, food additives, or high molecular products [3]. This shift has occurred to a certain extent however, as seen beforehand there is still a lot of research going on for bulk products such as lactic acid. It seems that there is still a need for dedicated ISPR facilities, that use robust equipment and that do not generate a lot of unwanted by-products. A reason for the failure of many previous ISPR projects was the addition of an extension that was too complex. Another requirement for a successful ISPR introduction is certainly the use of a flexible and broadly applicable multipurpose plant. It should be possible for instance to enhance the production of several different flavors with the same ISPR configuration, or at least with minor modifications. Thus, a compromise is needed for the choice of separation (e.g., choice in the type of hydrophobic resin, solvent, or membrane) between high selectivity for one single product or a less selective, but broad applicable solution. 

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