Literature data on odour thresholds of volatile food constituents, and, in particular on their odour quality, may differ significantly. In order to obtain more reliable sensory data, the odour thresholds of eighty-four compounds previously characterised as key food odorants were re-evaluated and compared to literature results. In addition, the odour thresholds of ten odorants are reported here for the first time. On the basis of a distinct protocol, also the aroma attributes of the odorants were evaluated in order to define an aroma language, which can be used for specific purposes, e.g., training of panellists for GC-Olfactometry.

Re-investigation on odour thresholds of key food aroma compounds and development of an aroma language based on odour qualities of defined aqueous odorant solutions

Flavor is an important quality attribute which relates to the organoleptic characteristics of meat. Although perception of flavor is a complex phenomenon, odor is the most important single factor contributing to the overall characteristics of flavor. A large number of compounds have been identified in the volatile fraction of red meats and poultry. An overview of the chemical constituents present in the volatiles of beef, pork, mutton, and chicken is presented according to species and arranged by chemical class--hydrocarbons, alcohols, acids, aldehydes, ketones, sulfides, heterocyclic compounds, etc. The volatile components of cured and uncured pork are compared. The field of meat flavor is assessed in terms of what has been accomplished and the direction in which it may proceed. Techniques for analysis of these volatiles are briefly described.

Meat flavor volatiles: A review of the composition, techniques of analysis, and sensory evaluation

The formation of flavor in fermented beverages is due to various biosynthetic mechanisms. In wine, flavors arise as the result of compounds: 1. Originating from the native fruit (grap) 2. Which are formed or altered during the various processes employed in production 3. Which are developed or transformed by yeast during fermentation 4. Arise during the aging process In this review the results of investigations on the development of flavors in grape and wine will be discussed. Special attention will be devoted to the effects of specific processes in winemaking on the development of flavor.

Flavor composition of wines: a review.

Determination of food authenticity is one of the most crucial issues in food quality control and safety. The introduction of new sophisticated techniques, in conjunction with greater consumer demands and expectation for safer products, gives a tremendous impetus to food quality assurance. Wine adulteration, mainly in terms of varieties and regions of origin (geographical), has been very widespread. Therefore, apart from novel experimental techniques, the need emerged for a more comprehensive statistical data analysis. Multivariate analysis comprising principal component analysis (PCA), discriminant analysis (DA), canonical analysis (CA), cluster analysis (CLA), has, in most cases, been effectively employed in wine differentiation and classification according to geographical origin.

Application of quality control methods for assessing wine authenticity : Use of multivariate analysis (chemometrics)

Analysis of phenolic acids and flavonoids by high-pressure liquid chromatography☆

SUMMARY— Stepwise discriminant analysis for classifying food samples (known independently to differ in flavor) is illustrated by computer analysis of gas chromatograms from roasted coffee and potato chips. Four lots of coffee prepared so as to differ in flavor were scored organoleptically, steam distilled, and the distillate examined gas chromatographically. By calculating all possible ratios among peak heights and subjecting these ratios to discriminant analysis, the coffee could be classified into the four flavor categories from the gas chromatographic data. The discriminant analysis procedure was set to select the ratio most critical in differentiating among the chromatograms, then move on to the next most efficient ratio until the samples were classified. The same thing was done for potato chips except headspace volatiles were used for the gas chromatographic analysis.



Not only does the procedure described enable flavor to be correlated with gas chromatographic data, but the efficiency values for each ratio are useful. A compound devoid of flavor can conceivably be highly correlated with flavor; however, there is a good chance that a compound highly correlated with flavor is a flavor substance itself.

Stepwise Discriminant Analysis of Gas Chromatographic Data as an Aid in Classifying the Flavor Quality of Foods

SUMMARY— The flavor threshold concentrations were determined for 23 compounds composing an artificial peach beverage base. The threshold levels ranged from 52 ppm to 0.4 ppb. The threshold values were used in sub-threshold, additive sub-threshold, and concentration trials. Sub-threshold and additive sub-threshold effects resulted from only a few of the flavor combinations tried. Change in concentration of one compound in a mixture of six compounds was not readily detectable organoleptically. The difference in concentration could be detected gas chromatographically, but only if the mixtures were extracted with pentane and concentrated.

By dividing the respective threshold values into the amount of each compound present in the beverage, a factor was calculated, called the “unit flavor base,” which indicated the relative importance of each compound as a flavor substance in the peach beverage. By dividing the gas chromatographic peak heights by the respective threshold values, gas chromatographic response was weighted for flavor importance. When the unit flavor base and weighted gas chromatographic response were converted into logarithms, the relation between the values was nearly linear. The correlation coefficient was 0.8691 (significant @ 0.01).

Determination of Flavor Threshold Levels and Sub‐Threshold, Additive, and Concentration Effects

SUMMARY

Solutions of glycine, glutamic acid, lysine, methionine, and phenylalanine adjusted to pH 6.5 were reacted separately with glucose, fructose, maltose, and sucrose at 100 and 180°C. Some of the aromas generated were reminiscent of foods, whereas others were distinctly unpleasant. Ethanal, propanal, acetone, isobutanal, aerolein, butanal, 2-butanone, 2,3-butane-dione, erotanal, 2-pentanone, and heptanal were identified as end products in one or more of the 20 mixtures. The glutamic acid-glucose mixture was also heated at 100 and 180°C after being adjusted to pH 5.0 and 8.0. Of the compounds above, isobutanal and heptanal were not formed. Pentaual was formed at 100° but not at 180°C. A synthetic potato medium containing glucose and glutamic acid heated at 100°C yielded ethanal, propanal, acetone, butanal, 2-butanone, 2,3-butanedione, and crotonal. A potato extract heated at 180° differed from the synthetic potato medium heated at 100° in the products formed. Not formed were 2-butanone and 2,3-butauedione; pentanal, heptanal and hexen-l-al were formed. In all, 85 carbonyls were detected in the various mixtures or substrates.

Effects of pH and Temperature on the Carbonyls and Aromas Produced in Heated Amino Acid-Sugar Mixtures

SUMMARY

Gas chromatographic methods were developed for the separation of apigeninidin compounds, pelargonidin, cyanidin, delphinidin, petunidin, and malvidin. Protocatechuie, p-hydroxybenzoic, gallie, vanillie, and syringic acids–which are useful for the identification of particular anthocyanidins–were also amena-able to gas chromatographic analysis. Phlorglucinol could likewise he measured. Separation of rhamnose, ribose, xylose, fructose, ga-lactose, and glucose was good. Except for fructose, the others are common glycosidie sugars and aid in differentiating anthocyanins. Retention times were determined for the monogluco-sides of delphinidin, petunidin, pelargonidin, and malvidin; for a delphinidin glycoside extracted from wild grape hyacinths; and for arhutin, hesperidin, rutin, and quercitrin. Betanin likewise was volatile as the silyl ether. Rhamnetin, catechin, and quercetin yielded good gas chromatographic waves. Phenolphthalein and naphthorescoreinol were sometimes used as internal standards. The silyl ethers or esters above were prepared in pyridine or dimethyl sulfoxide. The data suggest that gas chromatography might he used for preparative as well as for identification purposes.

Gas Chromatographic Determination of Anthocyanins and Other Flavonoids as Silyl Derivatives

Cottonseed oil containing 0, 2.5, 5 and 10% added moisture was heated to simulate food-frying conditions. The volatile carbonyls from the heated oil were crystallized as 2,4-dinitrophenylhydrazones and then regenerated for separation by gas-liquid chromatography. Nineteen peaks were observed for the dry oil; oil with added moisture had fewer peaks. Oil containing added moisture produced more total carbonyl by weight than did dry oil. Maximum production of carbonyls occurred in the oil with 2.5% added moisture.

Elizabeth S. Keith

Papers

Stepwise Discriminant Analysis of Gas Chromatographic Data as an Aid in Classifying the Flavor Quality of Foods

Determination of Flavor Threshold Levels and Sub‐Threshold, Additive, and Concentration Effects

Effects of pH and Temperature on the Carbonyls and Aromas Produced in Heated Amino Acid-Sugar Mixtures

Gas Chromatographic Determination of Anthocyanins and Other Flavonoids as Silyl Derivatives

Effect of moisture level on volatile carbonyls in cottonseed oil heated to 210C