Orange aroma value

The fruity note in the aroma profile of both varieties is produced by acetic acid esters. On the other hand, there is a decrease in the ethyl esters, which are more odor active than the acetates (cf. 5.3.2.2) and dominate in some other fruits, e. g., oranges and olives. Hexanal, (Z)-3-hexenal and (Z)-3-nonenal are responsible for the green/apple-like note. (E)-P-Damascenone, which smells of cooked apples, has the highest aroma value in both varieties due to its much lower odor threshold. Eugenol and (E)-anethol contribute to the aniseed-like note which is a characteristic especially of the aroma of the peel of the Cox Orange. 

Methylcyclopentenolone has a strong caramel-like, maple-like or licorice-like aroma (31j, and was found in browned, dehydrated orange juice at the 1 ppm level (43). Its synergistic flavor effect with other compounds, such as 5-methyl-2-furfural and N-ethylpyrrole- 2-carboxyaldehyde, was reported (43). Although it is present at levels five times below its threshold value, it still impacts on the heat-abused flavor of dehydrated orange juice. This ketone probably results from amine-assisted sugar degradation (45). 

Tocopherol was effective and ascorbic acid ineffective in the protection of citrus oils evaluated by aroma (13). In a typical study, 5 g of orange oil was oxidized in 75-mL open brown bottles at 45°C and was evaluated by a panel after 6 d, at which time it was ranked as off-odor, "terpeney. The peroxide value of the initial oil was zero the oxidized material had a PV of 100. As a result, days to reach 100 PV was used as an endpoint. Comparative antioxidant effects on a number of citrus oils and on D-limonene [cyclohexene, l-methyl-4-(l-methylethenyl)-(R)-5989-27-5] are presented in Table X. BHA is the most active while AP has no activity alone but does synergize with tocopherol. 

Figure 2. Those present at appreciably higher intensities in the Valencia will have positive values and those from the Early-Mid oil will have negative values. Noticeably absent from Figure 2 are major orange oil aroma components such as ethyl butyrate, octanal and linalool as they have almost the same intensity in both sample types. As might be expected the five aldehydes discussed earlier (peaks 1, 13, 14, 17 md 28) are present. Other major aroma differences were due to two ketones, wine lactone (peak 29) and P-damascenone (peak 23). Wine lactone was completely absent in the Early-Mid oil as compared to being a major aroma peak in Valencia oil. P-damascenone (peak 23) was one of the most intense aroma peaks in the Early-Mid oil and completely lacking in the Valencia sample.

Figure 1 Quantitative descriptive analysis configuration of the aroma in orange juice samples. The average intensities for the various attributes are graphed on lines radiation outward from a value of 0 at the center point to a value of 9 at the outward perimeter.

The aromatic properties of essential oils are perhaps the most conspicuous and account for a wide range of traditional applications. Many terpenoids have characteristic odors, some of them are presented in Tables 96.3 and 96.4 [55-57]. The odor thresholds however may vary greatly and depend on the matrix. (—)-Limonene with citrus-like aroma is a key odorant of orange juice and neral/ geranial the key odorants of lemons. l-p-Menthene-8-thiol present in grapefruit juice and responsible for the grapefruit aroma has with 0.02 ng/L one of the lowest odor threshold values [42]. 

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