Threshold aldehyde

Aldehydes, enals, dienals, ketones, and hydrocarbons, which are responsible for disagreeable odors, generally bok at lower temperatures than fatty acids. Analysis showkig a free fatty acid concentration of less than 0.05% is an kidication that deodorization is sufficientiy complete. Some of the dienals have very low odor thresholds and sensory evaluation of the finished ok is a judicious quaHty assurance step. 

Diacetyl, acetoin, and diketones form during fermentation. Diacetyl has a pronounced effect on flavor, with a threshold of perception of 0.1—0.2 ppm at 0.45 ppm it produces a cheesy flavor. U.S. lager beer has a very mild flavor and generally has lower concentrations of diacetyl than ale. Diacetyl probably forms from the decarboxylation of a-ethyl acetolactate to acetoin and consequent oxidation of acetoin to diacetyl. The yeast enzyme diacetyl reductase can kreversibly reduce diacetyl to acetoin. Aldehyde concentrations are usually 10—20 ppm. Thek effects on flavor must be minor, since the perception threshold is about 25 ppm. 

No studies have been conducted to evaluate the reproductive effects of endrin aldehyde or endrin ketone in humans or animals via the inhalation, oral, and dermal routes of exposure. Additional animal studies and further human case studies are needed to determine the potential reproductive hazard and to determine threshold levels for effects that may exist via all three of these routes of exposure. 

All aldehydes increased during storage (Fig. 3), but none exceeded their flavor threshold (Fig. 4). 

Strecker aldehydes (Figs. 3 and 4). All 5 aldehydes increased during storage, but none exceeded more than 4.3% of their respective flavor thresholds. 

Furfural (a heat exposure indicator). This aldehyde increased more than 2-fold but reached only 1% of its flavor threshold. 

The increase after 12 weeks for most aldehydes was significant (16-fold for furfural, 7-fold for 2-methylpropanal) however, no aldehyde approached its respective flavor threshold. 

Goal. Using a newly optimized derivatization and solid-phase microextraction (SPME) process, low-level aldehyde concentrations in beer stored for 4, 8, and 12 weeks at 30 °C were monitored. Although all aldehydes increased in concentration, no aldehyde exceeded its flavor threshold. (126 words)... 

None of the analyzed aldehydes exceed their flavor threshold in beer. (Adapted from Vesely et ah, 2003)... 

Fig. 17.2. Properties profile of the products in the oxazolidine library formed with all available reagents (blacKj and after filtering the reagents (grefl based on the product properties with GLARE. The multi-objective thresholds are illustrated by the dashed vertical lines. The initial library is formed by 651 x 637 x 143 products and the filtered library by 144 x 143 x 92 products (aminoalcohols x aldehydes x sulfonyl chlorides).

Bassette and Keeney (1960) ascribed the cereal-type flavor in dry skim milk to a homologous series of saturated aldehydes resulting from lipid oxidation in conjunction with products of the browning reaction. The results of Parks and Patton (1961) suggest that saturated and unsaturated aldehydes at levels near threshold may impart an off-flavor suggestive of staleness in dry whole milk. Wishner and Keeney (1963) concluded from studies on milk exposed to sunlight that C6 to Cn alk-2-enals are important contributors to the oxidized flavor in this product. Parks et al. (1963) concluded, as a result of quantitative carbonyl analysis and flavor studies, that alk-2-4-dienals, especially... 

The intensity of undesirable sensory notes has been positively correlated with the content of carbonyl compounds formed through lipid autoxidation reactions. In general, the carbonyl compounds present have the greatest impact on flavor owing to their low flavor thresholds in comparison with hydrocarbons, substituted furans, and alcohols. Aldehydes are major contributors to the loss of desirable flavor in meats because of their rate of formation during lipid oxidation and low flavor threshold. Thus, an alternative approach for monitoring the extent of lipid oxidation in fats and oils is to measure... 

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