Flavor Threshold Values Research Articles

Determination and comparison of flavor (retronasal) threshold values of 19 flavor compounds in Baijiu.

Nineteen compounds, including ten esters, six acids, and three alcohols, were characterized and considered as significant tastants and aromas in Baijiu (Chinese Liquor). The flavor (retronasal) threshold values (FTVs) of these 19 compounds were determined by the 10 samples test method in hydroalcoholic solutions (46%v/v in ethanol). The FTVs of the compounds were calculated based on the best estimate threshold method. All the FTVs determined by the professional Chinese Baijiu tasters were lower than those by the nonprofessional tasters. For instance, the detection (2.31mg/kg)andrecognition(11.74mg/kg)valuesofethyl hexanoate determined by the nonprofessional group were higher than the respectively corresponding values 0.44 and 3.80mg/kg determined by the professional group. All of the odor activity values (OAVs) of ethyl valerate (OAV: 1176.00 to 2321.17), ethyl octanoate (OAV: 6841.20 to 7851.60), and 1-butanol (OAV: 26.78 to 39.72) in Gujinggong Baijiu were more than 10-fold larger than their dose-over-threshold values (DoTs), for which the DoTs of ethyl valerate, ethyl octanoate, and 1-butanol were 92.84 to 183.25, 180.03 to 206.62, 1.18 to 1.75, respectively. On the contrary, the OAVs of ethyl heptanoate (OAV: 3.60 to 5.70) and isoamyl alcohol (OAV: 1.18 to 1.57) were lower than their corresponding DoTs at 152.62 to 241.63 and 12.26 to 16.41. The results demonstrated that it is necessary to consider and compare their DoTs and OAVs simultaneously on evaluating the contribution of flavor compounds in Baijiu. PRACTICAL APPLICATION: Sensory evaluation of threshold values of various flavor compounds could be significantly affected by their existing matrix. Most of the published results of the flavor threshold value of compounds were determined from the matrix such as beer, whiskey, red wine, rather than Chinese Baijiu. The results of this work not only could provide valuable information for flavor studies of Chinese Baijiu but also give useful information for the Baijiu industry to quality control.

Analysis of Headspace Volatile Compounds in Cold-stored and Freeze-dried Krill Eupausia superba

Abstract Headspace volatile compounds of cold-stored and freeze-dried Krill Eupausia superba were analyzed to investigate their flavor qualities using a system combining a dynamic headspace isolator, an automatic thermal desorber, and a gas chromatograph-mass-selective detector. Levels of oxidation products of polyunsaturated fatty acids such as aldehydes, alcohols, and ketones, which are known to give seafood a nasty smell because of their low flavor threshold values, increased during cold storage of krill. Notably, levels of 2-methylpropanal, 3-methylbutanal, 2-methylbutanal and 2-butanone increased during its storage. They can be considered index compounds of off-odor according to freshness degradation during storage. By contrast, in freeze-dried krill powder, levels of aldehydes, ketones, and aromatic compounds decreased rapidly. Only alcohols, which did not greatly affect the food flavor, were isolated in large amounts. It was confirmed that levels of oxidized compounds of krill increased during cold storage, but decreased in freeze-dried krill.

The Contribution of 4-Hydroxyfuranone Derivatives to the Aroma of Commercial Beers and Malts

Analysis of hot water extracts from a range of commercial malts showed that 2,5-dimethyl-4-hydroxy-3(2H)furanone (DMHF) varied from undetectable (lager malt) to 4.2 mg/litre (crystal malt), a concentration twenty-six times the flavour threshold in water. 5-Methyl-4-hydroxy-3 (2H)furanone (MHF) was detected in all samples except one but was always well under its flavour threshold value. 2(or 5)-Ethyl-5(or 2)-methyl-4-hydroxy-3(2H)furanone (EMHF) was not detected in any of the samples. Fermentation of lager, ale and crystal malt extracts with an ale strain of yeast led to the appearance of EMHF in all cases as well as additional DMHF. The greatest increases in both compounds was with the ale malt. Both increases and decreases occurred in MHF concentration as a result of fermentation but final levels were always well below the flavour threshold value. Analysis of ten commercial beers found DMHF in all the samples and in five cases levels exceeded twice the flavour threshold value in beer with flavour units from 2.4 to 9.1. A flavour panel noted that in four of these cases the beer had a distinctly sweet/caramel aroma which is typical of DMHF. EMHF was undetectable in six samples, detectable, but unquantifiable, in three cases but at about 80% of the flavour threshold value in the remaining sample. MHF was found in all samples but at insignificant levels. The results show that DMHF is an important flavour compound in British ales and EMHF may make a contribution in a limited number of situations. The contribution of malt type, brewery processing and yeast strain in determining the concentration of the two 4-hydroxyfuranones in beer remains uncertain.

Quantitation of potent odorants of virgin olive oil by stable‐isotope dilution assays

The potent odorants of four olive oil samples differing in flavor were quantitated, and their odor activity values (OAVs) were calculated by dividing the concentrations of the odorants in the oil samples by the flavor threshold values in the oil. The odorants with higher OAVs were contrasted with the different notes of the flavor profiles of the olive oils. It was concluded that the following compounds contributed mainly to the flavor notes given in parentheses: (Z)‐3‐hexenal (green), ethyl 2‐methylbutyrate, ethyl isobutyrate, ethyl cyclohexanoate (fruity), (Z)‐2‐nonenal (fatty) and 4‐methoxy‐2‐methyl‐2‐butanethiol (black‐currant‐like). The results showed that the calculation of OAVs is an approach to objectify the flavor differences of olive oil samples.

Dihydro‐1,3,5‐dithiazines: Unusual flavor compounds with remarkable organoleptic properties

Abstract 5,6‐Dihydro‐2,4,6‐trialkyl‐4H‐1,3,5‐dithiazines play an important role in food flavors and particularly in heated food products. They are formed from thermal interaction of aldehydes, hydrogen sulfide, and ammonia resulting from degradation components of lipids, amino acids, and thiamin. Many of them have interesting organo‐leptic properties and relatively low flavor threshold values, and deserve particular attention. This review describes all alkyl‐substituted and bicyclic 1,3,5‐dithiazines identified in the flavor of foodstuffs as well as in model systems. Furthermore, this review provides a general description of the sensory properties of 1,3,5‐dithiazines and additionally reports on new results and recent research developments in order to update information in the area of this hitherto almost overlooked chemical class of flavor compounds.

Effect of Various Direct Ultra-High Temperature Heat Treatments on Flavor of Commercially Prepared Milks

Grae A milk (3.25% fat) was direct UHT processed at 132.2, 143.3, and 137.2°C with 2min preheating and at 137.2°C without preheating for 12s and aseptically packaged in 246-ml Brik Pak cartons in a commercial plant. Samples from each treatment were stored at 25 and 2°C for 24 wk.Changes in acid degree value paralleled the development of stale flavor most closely with a correlation coefficient higher than any of the other tests. Dissolved oxygen might have affected rate of flavor change for UHT milks stored at room temperature. Increases in acidity were slightly greater in UHT samples stored at room temperature than under refrigeration. A combination of acid degree value, dissolved oxygen, and titratable acidity correlated most closely to stale flavor. There was little difference in flavor and concentration of volatile compounds among various heat treatments. Concentrations of acetaldehyde, propanal, n-hexanal, 2-pentanone, 2-hexanone, and 2-heptanone increased more at room temperature than in refrigerated storage; in general, these increases paralleled the stale flavor. Concentrations of the carbonyl compounds measured were far below flavor threshold values when UHT milks were criticized as stale. However, a combination of acetaldehyde, acetone, 2-pentanone, and 2-heptanone were related most closely to stale flavor and could have had an effect on the flavor when all were present.

Development of an HPLC-Method for the Determination of E-2-Nonenal in Beer using Column Switching Techniques

Abstract E-2-nonenal is an important compound formed during ageing of beer. It has a flavour threshold value of about 0.1 μg/l. A method is described for isolation of E-2-nonenal from beer by solid phase extraction. After extraction E-2-nonenal is derivatized with dansylhydrazine and analyzed with reversed phase HPLC using column switching techniques. The combination of on-line preconcentration of the derivative and heartcutting enables the analysis of E-2-nonenal in beer at natural levels.

DIMETHYL TRISULPHIDE, ITS MECHANISM OF FORMATION IN HOP OIL AND EFFECT ON BEER FLAVOUR

The precursor of dimethyl trisulphide (DMTS) in hops is destroyed by sulphur dioxide during kilning, but then re-forms slowly during storage. A redox mechanism is suggested and S-methyl-cysteine sulphoxide is postulated as the DMTS-precursor. The effect of DMTS on beer flavour is described. The flavour threshold value for DMTS in a commercial beer has been found to be 0·10μg/litre.

Concentrations of some aliphatic aldehydes and ketones found in raw and roasted spanish and runner peanuts

AbstractCarbonyl compounds in oil cold‐pressed from raw and roasted peanuts were isolated and quantitated as their 2,4‐dinitrophenylhydrazones. Quantitative data were obtained for more than 40 compounds and compared to the flavor threshold values of the compounds in oil. In general, concentrations of aldehydes and ketones in Spanish peanuts were higher than in runner peanuts. Hexanal and octanal and possibly nonanal, 2‐octenal and 2‐nonenal may contribute to the “green‐beany” flavor of raw peanuts. Concentrations of 2‐methylpropanal, 2‐methylbutanal and 3‐methylbutanal vastly exceeded their flavor thresholds and probably contribute significantly to the harsh note of freshly roasted peanuts. Other compounds that could contribute to the flavor and aroma of roasted peanuts are: hexanal, heptanal, octanal, nonanal, dodecanal, 2‐heptenal, 2‐octenal, 2‐nonenal, 2‐decenal and 2,4‐decadienal.

Ester Production by Pseudomonas fragi. III. Synergistic Flavor Interaction of Esters at Subthreshold Concentrations ,

Flavor threshold values were determined for ethyl acetate, ethyl butyrate, ethyl hexanoate, ethyl isovalerate, butyric acid, diacetyl, and dimethyl sulfide in homogenized milk. In addition, flavor thresholds were determined for two component mixtures of these compounds in milk. Synergistic interactions (P<0.01) were observed in the mixtures of ethyl hexanoate-ethyl butyrate, ethyl butyrate-butyric acid, ethyl butyrate acid, ethyl butyrate-ethyl acetate, and ethyl hexanoate-ethyl isovalerate. Diacetyl-ethyl hexanoate and dimethyl sulfide-ethyl hesanoate mixtures did not show significant flavor interactions.

A compound responsible for mushroom flavour in dairy products

SummaryThe ‘mushroom compound’ previously reported as a gas chromatographic fraction of oxidized dairy products has been identified as oct-l-en-3-ol. The alcohol was found to have a flavour threshold value of 1 part in 109 in water, 1 part in 108 in skim-milk, and 1 part in 107 in butterfat. A mechanism for the formation of oct-1- en-3-ol is discussed.

Autoxidation of Milk Lipids. III. Effect on Flavor of the Additive Interactions of Carbonyl Compounds at Subthreshold Concentrations

Summary Flavor threshold values were determined for carbonyl compounds in homogenized milk. Values obtained in parts per million were: propanal, 0.43; n -butanal, 0.19; n -pentanal, 0.13; n -hexanal, 0.049; n -heptanal, 0.12; n -octanal, 0.46; n -nonanal, 0.22; n -decanal, 0.24; n -hex-2-enal, 0.067; n -hept-2-enal, 0.077; n -non-2-enal, 0.004; n -dec-2-enal, 0.092; n -hept-2,4-dienal, 0.049. An additive interaction, defined as the interaction of subthreshold concentrations of carbonyl compounds to give a detectable flavor, was observed in a mixture of the C 9 and C 10 alkanals and of the C 8 and C 10 alkanals. The implications of the additive interaction in flavor of foods are discussed.

A compound responsible for metallic flavour in dairy products: I. Isolation and identification

SummaryThe ‘metallic compound’ previously reported as an important cause of off-flavour in oxidized dairy products has been identified as oct-l-en-3-one. The compound was found to have a flavour threshold value of one part in 109 in butterfat and one part in 1010 in water. This compound was also isolated from oxidized safflower oil.