Apple aroma substance

Besides the medicinally used herbal mixtures, there arc also the so-called household teas which are preferred by people who are sensitive to coffee or who do not wish to drink a caffeine-containing beverage on a regular basis. Household teas are made up from drugs which, apart from small amounts of tannins, have only aroma substances and possibly also plant acids bramble leaves, raspberry leaves, hibiscus flowers, hips and haws, and apple skins arc frequent components of such teas [4]. 

Apple flavor The sometimes marked differences between aromas of individual varieties of apples are mainly due to quantitative variations in the composition of apple flavor substances. Key components are ethyl (+)-2-methylbutanoate and other esters of 2-methylbutanoic acid, in addition to ethyl and hexyl bu-tanoates, hexyl acetate, (E)-2- and (2)-3-hexenyl acetates (see fruit esters) and j3-damascenone. ( )-2- Hexenal, ( )-2- hexen-l-ol, and hexanal (see alka-nals) play a special role in A. f. These are trace aroma substances in intact apples. When the fruit cells are destroyed, the concentration of the Cg units increase strongly due to enzymatic processes. They are the main aroma components of apple juice. Accordingly, the aromas of fresh apples and apple juice differ markedly. Apricot flavor The typical aroma is due to the combined effects of numerous components with flowery and fruity characters these include linalool, 1-ter-pinen-4-ol, a-terpineol (see p-menthenols), 2-phen-ylethanol, a- and )8- ionones, /5- damascenone, and (Z)-jasmone for the flowery part together with fruit esters and lactones, e. g., 4-octanolide, 4- and 5-deca-nolide, 4-dodecanolide (see alkanolides), hexyl acetate and hexyl butanoate for the fruity part, rounded off by benzaldehyde. 

To handle dehydration of fruit juices, a technology called slush drying was proposed and tested with apple juice for the potential loss of volatile flavor and aroma substances (Chandrasekaran and King 1971 Lowe and King, 1974). The principle of this method stems from the dependence of the freezing point on the concentration of dissolved solids (Figure 20.1). It boils down to the fact that drying takes place from an ice-liquid mixture (slush) in which 20% to 70% of the water present in the fruit juice is frozen (the... 

The mixture in Fig. 5.2, c gives a new odor profile because definite features of the decenal (stale, paint-like, rancid) and the hexenal (like apples, almonds, sweet) can no longer be recognized in it. The examples show clearly that the aroma profiles of foods containing the same aroma substances can be completely dissimilar owing to quantitative differences. For example, changes in the recipe or in the production process which cause alterations in the concentrations of the aroma substances can interfere with the balance in such a way that an aroma profile with unusual characteristics is obtained. ... 

Fruits and vegetables (e. g., pineapple, apple, pear, peach, passion fruit, kiwi, celery, parsley) contain unsaturated Cn hydrocarbons which play a role as aroma substances. Of special interest are (E,Z)-l,3,5-undecatriene and (E,Z,Z)-1,3,5,8-undecatetraene, which with very low threshold concentrations have a balsamic, spicy, pinelike odor. It is assumed that the hydrocarbons are formed from unsaturated fatty acids by P-oxidation, lipoxygenase catalysis, oxidation of the radical to the carbonium ion and decarboxylation. The hypothetical reaction pathway from linoleic acid to (E,Z)-l,3,5-undecatrieneis shown in Formula 5.25. 

The aroma substances that comprise flavors are found in nature as complex mixtures of volatile compounds. A vast majority of volatile chemicals that have been isolated from natural flavor extracts do not provide aroma contributions that are reminiscent of the flavor substance. For instance, n-hexanal is a component of natural apple flavor (1) however, when smelled in isolation, its odor is reminiscent of green, painty, rancid oil. Similarly, ethyl butyrate has a nondescript fruity aroma although it is found in strawberries, raspberries, and pears, it does not uniquely describe the aroma quality of any of these individual fruits. It has long been the goal of flavor chemists to elucidate the identity of pure aroma chemicals that have the distinct character impact of the natural fruit, vegetable, meat, cheese, or spice that they were derived from. Often, these are referred to as character impact compounds (2). 

In some instances crop plants were also selected for a higher content of certain types of secondary products. Cultivated apples, pears and other fruits have a better aroma, i.e., contain more volatile secondary substances, and in addition to a higher sugar content are much more attractively colored than their wild progenitors. The pigments (E 5.5.2) and scent volatiles are usually nontoxic for humans, in contrast, for example, to the tanning substances which many of the wild forms of our cultivated fruits contain. 

In contrast, the retention of water-soluble aromas, as in apples, is not as advantageous, since the microwave energy generates many vapor bubbles, so that the volatile aromas have a large surface to evaporate. Nevertheless, the low pressures limit the product temperatures to lower values, as long as a certain amount of free water is present and this helps to retain temperature sensitive substances like vitamins, colors, etc. So in some cases, the high quality of the products could make this relative expensive process, economical also. 

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