Flavour Profiles

Like enzymes, whole cells are sometime immobilized by attachment to a surface or by entrapment within a carrier material. One motivation for this is similar to the motivation for using biomass recycle in a continuous process. The cells are grown under optimal conditions for cell growth but are used at conditions optimized for transformation of substrate. A great variety of reactor types have been proposed including packed beds, fluidized and spouted beds, and air-lift reactors. A semicommercial process for beer used an air-lift reactor to achieve reaction times of 1 day compared with 5-7 days for the normal batch process. Unfortunately, the beer suffered from a mismatched flavour profile that was attributed to mass transfer limitations. 

The volatile compounds of juices made from freshly cut pineapple fruits from different cultivars from Costa Rica, Ghana, Honduras, Cote d Ivoire, the Philippines, Reunion, South Africa, and Thailand were studied in comparison to that of commercial water phases/recovery aromas, juice concentrates as well as commercially available juices [12]. The qualitative pineapple fruit flavour profile showed several methyl esters, some characteristic sulfur-containing esters, and various hydroxy esters were responsible for the typical pineapple flavour profile. 

The maximum permitted temperature for the production of process flavours is around 180 °C, as defined by legal regulations, but in general, the temperatures actually used are much lower in order to be able to reach a broad variety of different flavour profiles, such as cooked, boiled, fried, roasted and shallow-fried notes. The pressure during the reaction is usually below 10 bar (10,000 hPa). 

In these cases, masking flavours can be used together with a rebalancing of the flavour profile to cover the changes in perception. The use of sweet inhibitors such as lactisol (6, Fig. 21.3) can help to reduce the lingering aftertaste in some cases. 

After extraction of the whole paprika, including seed and stems, the obtained colour-value of the extract is relative low, about 350 to 500 ASTA, but the extraction yield can reach 15 to 17 wt.%. High-quality Hungarian paprika species like Sweet Paprika Excelsior give an extract with a colour value between 1,500 and 1,800 ASTA, and a good flavour profile. 

The characterisation of a fruit type or variety will be reflected in the flavour profile of its volatile components. Analytical techniques can produce an accurate peak profile using gas chromatography, but in simpler terms the sensory receptors of most individuals can quickly differentiate between fruit varieties. We have four basic taste senses, sometimes described as sweet, sour, acid and bitter, and these are identified by taste receptors situated mainly on the tongue. The key component of flavour differentiation, so-called top-notes and the like, is detected not so much by taste as by aroma in the nasal cavity. Thus, during the process of eating and drinking, the release of aroma volatiles can be identified and an assessment of their value arrived at. 

It has been reported to be synergistic with intense sweeteners such as aspartame and acesulfame K and, when used at low levels (0.2%), improves certain flavour profiles (Eriknauer, 2003 LFRA, 2001). The relative sweetness of tagatose is 0.92. On ingestion, 20% of tagatose is absorbed in the small intestine and the rest is metabolised by the microflora of the colon. Dose-response studies indicate a prebiotic effect at 10 g/day (Eriknauer, 2003). 

For carbonated products, for which heat treatment is not required, the level of carbonation at the time of consumption is likely to be important to the mouth-feel and flavour profile. Therefore, measuring carbonation levels during a realtime storage trial or even a shortened trial made at elevated temperatures (i.e. 35-40°C) will be an important part of the package validation protocol. 

Joshi, V. K. and Sandhu, D. K. (2009). Flavour profiling of apple vermouth using descriptive analysis technique. Nat. Prod. Rad. 8(4), 419 25. 

Table 17.3. Flavour profile of star anise volatile oil.

The chemistry of the flavour of milk fat and butter is very complex, involving a large number of compounds contributing to the overall aroma and taste. Approximately 200 volatile compounds have been identified in milk fat (Schieberle et al., 1993). However, many of the volatile compounds are present at concentrations below their individual flavour threshold level, and the extent to which these compounds contribute to the overall flavour profile is not known fully. The perceived flavour of milk fat can be altered by a change in the concentration of individual volatile compounds. The principal factor that can change the concentration of the volatile compounds is the feeding regime of the cow (Bendall, 2001). 

Lflly, M., Lambrechts, M.G. Pretorius, I.S. (2000). Effect of increased yeast alcohol acetyltrans-ferase an activity on the flavour profile of wine and distillates. App. Environ. Microbiol., 66, 744-753. 

Lflly, M., Bauer, F.F., Styger, G., Lambrechts, M.G., Pretorius, l.S. (2006b).The effect of increased branched-chain amino acid transaminase activity in yeast on the production of higher alcohols and on the flavour profiles of wine and distillates. FEMS Yeast Res., 6, 726-743. 

The occurrence of many of these reactions depends on the presence of appropriate precursor in the grape must and together with the concentration of precursor and the ability of the yeast to (i) produce an appropriate extracellular enzyme for non-transportable precursors, (ii) take up the precursor, and (iii) transform the precursor different combinations of yeast and grape variety can lead to small or large differences in the aroma and flavour profile of the wine. 

In addition to the choice of yeast strain, the method of inoculation can be used to modulate wine flavour in ways not readily achievable with conventional yeasts, which are typically used in monoculture. A combination of alternative yeast species and inoculation strategies can lead to wines with very different chemical and flavour profiles, such as greater complexity and diversity of flavours, and enhanced mouth-feel and persistence of flavour (Table 8D.4). 

Allowing musts to ferment with indigenous yeasts can potentially produce a high diversity of flavours but the flavour profile is dependent on the yeast species and numbers present in the must, as well as the physico-chemical and nutrient composition. Although, from a microbiological perspective, depending on indigenous... 

Apart from the already described processes, another method of distillative technology has found application, especially for lime fmits. Here entire fruits are submitted to steam distillation which, due to the exposure to thermal and acidic influences, results in the so-called distilled lime oil. The overall flavour profile of these oils differs considerably from that of cold-pressed lime oil. 

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