Sensory analysis flavor dilution

Table 5 shows the sensory evaluation by Schieberle et al. (30) of the different kinds of butter, namely, Irish sour cream (ISC), cultured butter (CB), sour cream (SC), sweet cream (SwC), and farmer sour cream (ESC). It revealed ISC butter and ESC butter with the highest overall odor intensities. Table 5 shows that 19 odor-active compounds were detected by aroma extract dilution analysis (AEDA) in a distillate of the ISC butter. The highest flavor dilution (ED) factors have been found for 5-decalactone, skatole, i-6-dodeceno-y-lactone, and diacetyl followed by trany-2-nonenal, cw,c -3,6-nonadienal, c/i-2-nonenal, and l-octen-3-one. 

It is well known that the aroma extract dilution analysis (AEDA) is a nsefnl method for the recognition of the odor quality and odor intensity of each component." Especially the AEDA is a useful method for the identification of trace amonnts of the component that significantly affects the flavor of tea drinks. The odor intensity of the flavor component is expressed by the flavor dilution (ED) factor, that is, the ratio of the concentration of the flavor component in the initial extract to its concentration in the most dilnte extract in which odor was detected by gas chromatography-olfactometry (GC-0). Therefore, hereafter, from the viewpoint of sensory evalnation, the change in the flavor of tea drink dnring heat processing by AEDA will be mainly discnssed. Furthermore, in order to inhibit flavor deterioration of tea drink, the stndy of flavor precnrsor in a variety of foods, including tea drinks, will be proposed. 

Food flavor, taste, and texture sensations are perceived over time during consumption, and intensity of flavor perception can change over time. The temperature of the product, after time, equilibrates with the mouth temperature. Physical manipulations such as tongue movements, mastication, and salivary dilution affect the product and its sensory characteristics over time. The classic methods of descriptive sensory analysis do not take into account this temporal dimension. For that purpose, dynamic methods such as time-intensity analysis were developed [13]. 

The analysis of aroma compounds starts with the isolation of the volatile fraction from the food. Techniques used in the preparation of flavor extracts from foods have recently been reviewed [7-9], The most important task in the choice of the isolation procedure is to test whether the flavor of the extract is identical or at least similar to the flavor of the food itself. This has to be checked by a sensory evaluation of the food extract (e.g., after dilution with an appropriate medium like water or oil) before a time consuming chemical analysis is performed. 

Bisulfite addition products are readily formed at wine pHs (1, 23, 24). The bisulfite addition product is thought to be a more sensory-neutral compound and may be exploited by winemakers as a means of decreasing the aldehydic character of wines (1). Bisulfite addition has also been used to mask the stale flavor of beer which is thought to be largely due to the formation of trans-l-noneml (25). Kaneda et al. (25) used HPLC with fluorescent detection of an o-phthalaldehyde derivative to quantitate and identify individual aldehyde-bisulfite products, however, only acetaldehyde-bisulfite adducts were observed in commercial beers with this method. Hydrolysis of the adducts occurs at pHs greater than 8, therefore by adjusting the pH prior to analysis, total aldehydes (free plus bisulfite bound) can be estimated. At low pHs accurate estimation of free aldehydes is complicated however, by analysis conditions which alter the equilibrium between bound and free forms (temperature, dilution, solvent extraction, analysis time, etc.). 

Sensory Evaluation of the contribution of identified compounds to the aroma In order to identify those compounds mainly contributing to the characteristic flavor of the Black Truffle, the odor of the individual components of the headspace analysis were tested by a panel of eight judges (trained in sensory evaluation of truffles). The compounds tested were diluted in vegetable oil, in a range of concentrations from 30 to 300 ppm. 5 point scales (5 = exceptionally good full truffle aroma, 1 = not different from solvent) were used for flavor imitation and intensity. 

Recent studies of photooxidized butter and butter oil identified by aroma extract dilution analysis, 3-methylnonane-2,4-dione, a potent volatile compound derived from furanoid fatty acids (see Section C.4) (Figure 11.7). Six different furanoid fatty acids were established as dione precursors, and were found in various samples of butter made from either sweet cream (116 76 mg/ kg), or from sour cream (153-173 mg/kg), or from butter oil (395 mg/kg). Similar precursors of the dione were identified in stored boiled beef and vegetable oils. This flavor defect arising by photooxidation of butter or butter oil is apparently different from the light-activated flavor in milk,that involves the interaction of sulfur-containing proteins and riboflavin. However, more sensory comparisons are needed to distinguish between these two flavor defects due to light oxidation. 

UV-Vis may be used in the QA laboratory to either determine the concentration of a particular component in an incoming ingredient (quantitative analysis) or to obtain an overall spectrum (scan from 200-700 nm). An overall spectrum has value in providing a profile for future reference of either new batches of an incoming ingredient or a newly made finished flavor. These determinations are often made on dilutions that are used for sensory testing and require only 30 sec to obtain. 

In recent studies, potent aroma compounds have been identified using various gas chromatography-olfactometry (GCO) techniques, such as Charm Analysis and aroma extract dilution analysis (AEDA) (7,8). The flavor compounds that are identified by these methods are significant contributors to the sensory profile. In some cases, these sensory-directed analytical techniques have enabled the discovery of new character impact compounds. However, in other instances, key aroma chemicals have been identified that, while potent and significant to flavor, do not impart character impact. For example, in dairy products, chocolate, and kiwifmit, these flavor types appear to be produced by a complex blend of noncharacterizing key aroma compounds. 

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