Cucumber fruit

Srilaong V and Tatsumi Y. 2003. Changes in respiratory and antioxidative parameters in cucumber fruit (Cucumis sativus L.) stored under high and low oxygen concentrations. J Jap Soc Hort Sci 72(6) 525—532. 

The fruit of the cucumber plant Cucumis sativus) is mainly eaten raw or as pickle. Approximately 30 volatile compounds have been detected in the volatile fraction of cucumber, with aliphatic alcohols and carbonyl compounds being most abundant [35]. Fresh cucumber flavour develops as a result of enzymatic degradation of linoleic and linolenic acid rapidly after the tissue is disrupted (Scheme 7.2), by which ( ,Z)-2,6-nonadienal and ( )-2-nonenal mainly are formed [184]. ( ,Z)-2,6-Nonadienal is the main flavour volatile of cucumber fruit, with ( )-2-nonenal as the second most important compound (Table 7.7) [185, 186]. 

Uses fungicide, cucumbers, fruit, onions, tomatoes... 

Mansour, S.A., Belal, M.H., Abou-Arab, A.A.K., Gad, M.F. Monitoring of pesticides and heavy metals in cucumber fruits produced from different farming systems. Chemosphere 75, 601-609 (2009)... 

Since hydroperoxide lyase was first identified in non-green tissues, watermelon seedling (14) and cucumber fruit (9,22), the occurrence of the enzyme has been reported in various non-green and green plant tissues. Non-green tissues in which hydroperoxide lyase occurs include etiolated seedlings of watermelon (14), cucumber (17), and alfalfa (17), soybean seed (21,23), fruits of cucumber (9,22,24),... 

Hydroperoxide lyase was found first in the 12,000 g supernatant of watermelon seedling extracts (14). On the other hand, Galliard et al reported that cucumber fruit hydroperoxide lyase was associated with a particulate fraction and was solubilized with Triton X-100 ( ,22). Galliard et al also used Triton X-100 to extract hydroperoxide lyase effectively from cucumber fruit (24), tomato fruit (32) and kidney bean leaf (27). Wardale et al attempted to determine the subcellular localization of hydroperoxide lyase in cucumber fruit by sucrose density gradient centrifugation (30). 

Optimum pH ranges from 5.5 to 8 for hydroperoxide lyase fran green and non-green tissues. Km values for VI and VII range from 2 x 10"5 - 2 x 10-3 M (5,9,23,24,25,26,28). Hydroperoxide lyase from cucumber fruit (28), watermelon seedling (14) and tomato fruit (25) was inhibited by p-chloromercuribenzoate, But not the enzyme from tea leaf (28). This observation indicates that chloroplastic and non-chloropTastic hydroperoxide lyase may differ in structure. 

Compound identifications were based on comparison of mass spectral data and co-chromatography of plant components with standards as reported (8,9). A sample of 3,6-nonadien-l-ol was isolated from melon (10) whereas 8,11—heptadecadienal and 8,11,14-heptadecatrienal were obtained from cucumber fruit (11). Of primary interest in the present study is the identification of Cg aldehydes and alcohols including nonanal and nonanol which are effective promotors of wheat rust spore germination. The unsaturated Cg compounds have not been evaluated for activity but their close structural relationships to nonanal and nonanol make them candidates for germination promotors. 

The relative ratios of alcohols and carbonyls for the six-, eight- and nine-carbon volatiles in fish (23-24) and oysters (26) parallel those encountered in cucumber fruits (37) and mushrooms (27, 56) if the two systems are combined. Therefore, the use of plant-based enzyme systems for the controlled generation of fresh seafood flavors and aromas has been under consideration in our laboratory as a means to overcome some of the self-inactivating problems associated with fish lipoxygenases. 

Flavor-generating systems have included those from mushrooms (mascreated Agaricus bisporus) and cucumber fruits (mascreated Cucumis sativus) which were each added to surimi at 1%. Additionally, single geranium leaves (either crushed or uncrushed Pelargonium sp.) were placed into 100 gm of surimi. 

Demethylation of pectin has been the most obvious change observed in cell wall structure, both in the chilling injury of fresh cucumbers ( 7, 29) and during fermentation ( ). Bell et al. (30) showed that cucumber plants contain pectinesterase in all parts of the plant, including the fruit. As part of a series of studies of chilling injury in cucumber fruits, Fukushima and Yamazaki (29) found that a decrease in hot, water-soluble, high... 

Galliard and Matthew (5) have reported the biogenesis of C15, C14, C13 and C12-saturated fatty aldehydes from palmitic acid in cucumber fruits. However, that of the unsaturated Cn-aldehydes such as (Z, Z, Z)-8,11,14-heptadecatrienal, (Z, Z)-8, 11-heptadecadienal and (Z)-8-heptadecenal had not been studied so far. Thus, the enzymatic formation of the long-chain aldehydes from unsaturated fatty acids in a green seaweed, U. pertusa, was explored. 

E,Z)-2,6-N. (violet leaf aldehyde) bp. 88 °C (1.3 kPa), LD50 (rat p.o.) >5 g/kg fatty-green odor of violet leaves in which it was first detected in 1925, ( ,Z)-structure assigned in 1944. It also occurs in vegetable flavors ( impact compound in cucumber), fruit flavors (guava, melon, mango), meat, and seafood flavors. For synthesis, see Lit.. ... 

As shown in Fig. 3, the initial products from the 9- and 13-hydroperoxides of linoleic acid are the volatile aldehydes c/j-3-nonenal and hexanal and the corresponding C9 and C12 0x0 acid fragments. Analagous volatile products from linolenic acid are cw-3,c/s-6-nonadienal and cw-3-hexenal. However, in most plants, an isomerase enzyme converts the cis-3-enals to the trans-2 isomers (see Fig. 3). Such an enzyme cis-Z, trans-l-emA isomerase has been partially purified from cucumber fruits (Phillips et al., 1979). 

The hydroperoxide cleavage enzyme from cucumber fruit is optimally active at pH 6.5, is very heat-labile, and attacks both 9- and 13-hydroperoxide isomers with equal facility. Subcellular localization studies have shown that the enzyme is associated mainly with the plasmalemma, Golgi body, and endoplasmic reticulum membranes (Wardale et al., 1978). 

Miller A.R., Kelley,T.J., Mujer C.V. Anodic peroxidase isoenzymes and polyphenol oxidase activity from cucumber fruit tissue and substrate specifity. Phytochemistry, 29 705-709 (1990). 

Cucumber fruits were studied by using the same analytical approach as they contain only five key volatiles and their concentration in cucumber tissue seems to be less variable than in tomato (see, for example. Ref. 12). Table 4 shows the El and API correlations for the five compounds each one could be attributed to a single ion mass on the API, and calibration with authentic standards allowed conversion of the ion signal into concentration units (parts per billion by volume). The amount of the Cg volatiles present in the macerated tissue was estimated by microwaving a sample of cucumber to inactivate the enzyme system that produces Cg and Cg volatile compounds. Inactivation was confirmed by APIMS analysis of the headspace above the treated samples. Microwaved samples were macerated after spiking them with known amounts of the Cg volatiles, then measuring volatile compound release in the blender apparatus. The values obtained from the spiked standards were then compared with the release traces from cucumber samples and the amounts of nonenal and nona-2,4-dienal estimated as 5 and 8mg/kg fresh tissue, respectively. These values compare well with the... 

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