Aroma changes

Odorants that cause aroma changes, e.g. olf-flavours, may be detected by a comparative AEDA of fresh and deteriorated samples. Studies on storage defects of soybean oil [22, 51], buttermilk [52], boiled cod [53], dry parsley [54] and black and white pepper [55] are examples. 

The most important precursors for lipid oxidation are unsaturated fats and fatty acids like oleic (18 1), linoleic (18 2), linolenic (18 3) and arachidonic acid (20 4). The more unsaturated ones are more prone to oxidation. Lipid peroxidation and the subsequent reactions generate a variety of volatile compounds, many of which are odour-active, especially the aldehydes. That is why lipid oxidation is also a major mechanism for thermal aroma generation and contributes in a great measure to the flavour of fat-containing food. Lipid oxidation also takes place under storage conditions and excessive peroxidation is responsible for negative aroma changes of food like rancidity, warmed-over flavour, cardboard odour and metallic off-notes. 

Food Off-flavour/aroma change Odorant(s) involved Reference... 

Garlic develops its aroma from enzymatic reactions, as described before. When garlic slices are deep fried, microwave heated, or oven baked, the aroma changes (Yu et al., 1993) and contributes a different kind of garlic flavor to foods. A novel... 

As the optimum fermentation is achieved, the leaf mass is dried or fired to inactivate the enzymes and halt the fermentation. Continuous driers are usually used, in which hot air is generated by electrical heater or coal furnace. In this process, the leaf turns dark brown or black, the aroma changes to floral, and the moisture is reduced to less than 6%. 

The loss of natural flavor compounds in aseptically processed and packaged milk and cream and the aroma changes in the headspace of UHT milk were monitored during storage. The concentration of methanal, propanal, butanal and nonanal decreased over six months for two processes (138°C for 20.4 s and 149°C for 3.4 s). Total... 

In this paper we will discuss the effect of UHT processing and storage on the loss of natural flavors in milk and cream and on the aroma changes in the headspace of aseptically processed and packaged milk during storage. 

Holscher W. and Steinhart H. (1992b) Aroma changes during roasted coffee ageing. Lebensmittelchemie 46(5), 106-11. 

The structure of the food matrix is also known to affect the release of volatile compounds having an impact on flavors and aroma. Changes in flavor result from the interactions of lipid-derived carbonyl compounds by aldolization with the amino groups of proteins. Undesirable flavors are produced when beef or chicken are fried in oxidized fats by the interaction of secondary lipid oxidation... 

Kirsch F, Beauchamp J, Buettner A (2012) Time-dependent aroma changes in breast milk after oral intake of a pharmacological preparation containing 1,8-cineole. Clin Nutr... 

Peroxidases (EC 1.11.1.3) induce undesirable aroma changes in plant foods. In green beans, enzyme inactivation reached 88% in 10 min after pressure treatment at 900 MPa. At pressures above 400 MPa (32 °C), the activity of this enzyme in oranges fell continuously... 

Aroma interactions with lipids, proteins and carbohydrates affect the retention of volatiles within the food and, thereby, the levels in the gaseous phase. Consequently, the interactions affect the intensity and quality of food aroma. Since such interactions cannot be clearly followed in a real food system, their study has been transferred to model systems which can, in essence, reliably imitate the real systems. Consider the example of emulsions with fat contents of 1%, 5% and 20%, which have been aromatized with an aroma cocktail for mayonnaise consisting of diacetyl, (Z)-3-hexenol, (E,Z)-2,6-nonadienol, allyl isothiocyanate and allyl thiocyanate. The sample with 20% of fat has the typical and balanced odor of mayonnaise (Fig. 5.32 a). If the fat content decreases, the aroma changes drastically. The emulsion with 5% of fat has an untypical creamy and pungent odor since there is a decrease in the intensities of the buttery and fatty notes in the aroma profile (Fig. 5.32 b). In the case of 1% of fat, pungent, mustard-like aroma notes dominate (Fig. 5.32 c). 

There have been a number of reports on the essential oil composition of O. sanctum [1-9] however, there are no reports on the characteristic aroma-active components of the fresh herb and distilled essential oil. Furthermore, no study has specifically addressed the volatile changes that occur during cooking of the herb or during manufacture of the distilled essential oil. The following investigation was conducted to identify compounds responsible for heat-induced aroma changes in holy basil herb. 

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