Flavor Chemicals, Test Methods for

This section provides the test methods by which certain flavor chemicals listed in the preceding tabular section are to be analyzed. 

Proceed as directed under GC Assay of Flavor Chemicals. The composition of the polar column and the conditions of analysis may be varied at the discretion of the analyst, provided that such changes would result in equal or improved separations and/or quantification as would be obtained by use of the particular column material and test conditions specified therein. 

M-2a Aldehydes—Hydroxylamine tert-Butyl Alcohol Method 

Hydroxylamine Solution Dissolve 45 g of reagent-grade hydroxylamine hydrochloride in 130 mL of water, add 850 mL of tert-butyl alcohol, mix, and using a pH meter, neutralize to a pH of 3.0 to 3.5 with sodium hydroxide. 

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Specifications for Flavor Chemicals. .. 517 Test Methods for Flavor Chemicals. .. 630 Gas Chromatographic (GC) Assay of Flavor Chemicals. . . 635... 

Note 6 (Assay) Assay requirements are specified as minimum values (unless a range of assay values is given) and are stated in weight percent unless otherwise indicated. References to assay methods are indicated by citations in parentheses, e.g., (M-1 a), to methods provided under Test Methods for Flavor Chemicals. 

In addition to the previously mentioned chemical tests, methods based on the carbonyl content of oxidized fats have also been suggested (Henick et al 1954 Lillard and Day 1961) as a measure of oxidative deterioration. The procedures determine the secondary products of autoxidation and have been reported to correlate significantly with the degree of off-flavor in butter oil (Lillard and Day 1961). The methods, however, are cumbersome and are not suited for routine analysis. 

Thin-layer chromatography remains one of the main methods for class fractionation and speciation of lipids [23,24] and is used increasingly to determine the botanical origin, potency, and flavor potential of herbs and spices [25-27]. In the pharmaceutical industry, it is used for the analysis of complex and dirty samples with poor detection characteristics and for stability and content uniformity testing [28-31]. It continues to be widely used in the standardization of plant materials used as traditional and modem medicines. In addition, it retains an historic link with the characterization of dyes and inks and the control of impurities in industrial chemicals. 

Testing for flavor-impact chemicals in fermented pickles was compared using solid-phase extraction (SPE), purge-and-trap (P T) on Tenax, and SPME (5). Determination of which chemicals were the most significant flavor-impact chemicals was made by olfactometry experiments employing the detection frequency method (for details, see Chapter 12) and by recombination studies (i.e., adding suspect flavorants to an artificial salt brine solution to determine which potential flavorant and/or combination of flavorants most closely matched the flavor of the pickle brine). 

Knowledge of chemical structure, pharmacokinetics, and metabolic pathways provides a method to assess the safety of flavoring substances that lack a full safety testing profile using data from structurally related substances which have been adequately tested for toxicity. 

It is often too expensive to have or maintain an inhouse descriptive sensory panel. Therefore, other ways of measuring flavor need to be developed. Off-flavor in many foods have been measured by using gas chromatography to assess the level of lipid volatiles associated with off-flavor development Chapters 5, 6, 9) such as hexanal or by direct chemical determination of thiobarbituric acid reactive substances Chapters 5, 6) as a marker of the degree of lipid peroxidation. A new method being tested for use in the assessment of food qu ity is impedance technology. This method is showing promise for use in the seafood industry Chapter 20),... 

Regardless of the official specifications for soybean oil and its products, the ultimate proof of the pudding is in the eating that is, sensory evaluation of the odors and flavors of soybean oil and its products is the ultimate method to assess oil quality and stability. Sensory evaluation cannot be replaced fully by any chemical or instrumental analysis, although some methods can correlate fairly well with sensory results. Sensory evaluation of oils usually is done by a panel of experts or a trained panel, and often the method recommended by the American Oil Chemists Society (300) is used. During the evaluation, the panel is asked to score the overall flavor quality, as well as the intensity of many individual off-fiavors. Although chemical and physical tests are more reproducible and less time consuming than sensory evaluations, oxidative rancidity and off-flavor evaluation of soybean oils are best done by sensory tests. Correlations established between sensory evaluation scores and... 

Another approach to the detection of adulteration has been to determine whether a pure chemical has been synthesized from petroleum-based chemicals or from recent plant metabolism [25]. AU recent plant tissues contain some C due to HU in the CO2 of the atmosphere (nuclear testing). The only way for a flavor compound to show no C is if it has been synthesized from petroleum sources. C has a half-life of about 5,730 years and thus is depleted in crude oil. An obvious weakness of this method is it does not distinguish synthetic chemicals made from plant starting materials from truly natural materials. 

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