Development of Oxidized Odor and Volatile Aldehydes in Fermented Cucumber Tissue Exposed to Oxygen

Abstract

Changes in volatile compounds in fermented cucumber tissue during exposure to oxygen were investigated by purge and trap sampling, followed by GC-MS. Hexanal and a series of trans unsaturated aldehydes, (E)-2-pentenal, (E)-2-hexenal, (E)-2-heptenal, and (E)-2-octenal, increased in fermented cucumber slurries exposed to oxygen. Sensory evaluation of oxidized odor was correlated with the increase in aldehyde concentrations. Other identified volatile components present after fermentation did not show major changes during exposure to oxygen. There was no decrease in the formation of aldehydes in fermented cucumber samples that were heated to inactivate enzymes before exposure to oxygen. These results indicated that the formation of aldehydes in oxygen was due to nonenzymatic reactions.

Oxidative metabolism and the physiological age of seed potatoes are affected by increased α‐linolenate content

“…1994, Panavas and Rubinstein 1998) that cleave PUFAs from membrane phospholipids (phospholipases). The catabolism of free PUFA by lipoxygenase (LOX) and subsequently through various enzymatic and non‐enzymatic pathways (Fobel et al. 1987, Grechkin 1998, Zhou et al.…”

“…Increased peroxidative damage to membranes during ageing and in response to high unsaturated fatty acid content may be reflected in the activities of various lipolytic enzymes (Borochov et al 1994, Panavas andRubinstein 1998) that cleave PUFAs from membrane phospholipids (phospholipases). The catabolism of free PUFA by lipoxygenase (LOX) and subsequently through various enzymatic and non-enzymatic pathways (Fobel et al 1987, Grechkin 1998, Zhou et al 2000 generates lipid hydroperoxides, oxy-free radicals, short-chain (C 6-9 ) aldehydes, alcohols, epoxycompounds, etc. Phospholipase activity in potato is dominated by patatin, a 42-kDa storage protein (Senda et al 1996) that accounts for as much as 40% of tuber soluble protein (Strickland et al 1995).…”

Processing of Non-Fermented Sour-Sweet-Slices of Cucumbers (Cucumis Sativum L)

“…Softening of cucumber tissue may occur because of a low content of calcium and may be reduced using calcium because demethylation of fresh Ca-pectates that improves cell wall rigidity and improved resistances against polygalacturonase [13]. The relation between polygalacturonase was hyperbolic and that means that log10 versus time is a straight line [14]. A low content of Calcium may result in a lower firmness.…”

“…A low content of calcium may result in low firmness [11]. Both calcium and NaCl prevented both enzymatic [14] and non-enzymatic softening of cucumber [8].Polyphenol oxidase (Tyrosinase) catalyses hydroxylation of monophenols and promote oxidation of the O-diphenoles to O-quinones that may cause severe browning of cucumber tissue [15].Enzymatic browning of fruits and vegetables is therefore mostly related to oxidation of endogenous phenolic compounds that ulti-mately leads to the formation of dark brown polymers of a quinoidal nature. That situation requires blanching of cucumbers in order to avoid a serious loss in consumer qualities.…”

“…The onset of browning was delayed for about 2 days, although the length of the lag period was dependent on the amount of molecular oxygen in the headspace of the reaction system. The lag period was not observed when a pre-oxidized solution of ascorbic acid was used, suggesting that a product of ascorbic acid oxidation is responsible for the onset of browning [13].Ascorbic acid was a very efficient antioxidant against formation of hexanal, (E)-2-penenal, (E)-2-hexenal, (E)-2-heptenal, and (E)-2octenal when slurries of fermented cucumber tissue were exposed to oxygen and most of these oxidative was efficiently prevented at 1755 ppm [14].Non-chemical browning of cucumber includes interactions of amino acids and sugars at various levels of pH that could affect the colour of cucumber by non-enzymatic browning through several kinetic reactions that would reduce the contents of amino acids and sugars [11,20]. Model experiments showed that the level of 5-hydroxymethylfurfural (5hmf) at pH 3.5 from fructose was 31.2 times faster than glucose, whereas sucrose was 18.5 times faster than glucose [21].…”