Other Natural Plant Volatiles

Some natural plant volatiles, such as methyl jasmonate, trans-anethole, carvacrol, cinnamic aldehyde, eugenol, linalool, and thymol, have been used as antimicrobials in reducing microbial contamination and extending shelf life of fruits and vegetables [129]. Methyl jasmonate (MJ) is known for its properties to enhance resistance to chilling temperature of fruits and vegetables [130]. MJ vapor, in combination with modified atmosphere packaging, can reduce loss of firmness, fungal decay, and development of chilling injury and increase retention of organic acids in papayas [131]. MJ vapor from a 10_4 or 10"5 mol source in a 1 l container also retarded deterioration of celery sticks for 2 weeks at 10°C and reduced the bacterial load by approximately 3 logs after 1 week storage [130]. Wang [132] reported that postharvest quality of raspberries was enhanced with treatments of MJ, AITC, tea tree oil, or absolute ethyl alcohol during storage at 10°C. Wang and Buta [133] also found that 2.24 to 22.4 ^/lMJ vapor maintained good quality of fresh-cut kiwifruit for up to 3 weeks, as did absolute ethanol and isopropyl alcohol.

Weissinger et al. [108] evaluated nine natural volatile compounds for their ability to destroy salmonella on alfalfa seeds and sprouts. In this study, vapor-phase acetic acid, AITC, trans-anethole, carvacrol, cinnamic aldehyde, eugenol, linalool, MJ, or thymol were applied to inoculated alfalfa seeds at 1000 mg/l of air concentration for 1,3, and 7 hours at 60° C. Only acetic acid, cinnamic aldehyde, and thymol caused significant reductions in salmonella populations (>3 log CFU/g) compared to the untreated control (1.9 log CFU/g) after treatment for 7 hours. Treatment of seeds at 50°C for 12 hours with acetic acid (100 and 300 mg/l) and thymol or cinnamic aldehyde (600 mg/l) led to a 1.7 log CFU/g reduction of salmonella on seeds without affecting germination percentage. Treatment of seeds at 50°C with AITC (100 and 300 mg/l) and cinnamic aldehyde or thymol (200 mg/l) did not significantly reduce populations compared with the untreated control. Seed germination percentage was largely unaffected by treatment with gaseous acetic acid, AITC, cinnamic aldehyde, or thymol for up to 12 hours at 50°C. Acetic acid at 200 and 500 mg/l reduced an initial population of 7.50 log CFU/g of alfalfa sprouts by 2.33 and 5.72 log CFU/g, respectively, within 4 days at 10°C, whereas AITC at 200 and 500 mg/l reduced populations to undetectable levels. However, both treatments caused deterioration in sensory quality. Treatment of sprouts with 1 or 2 mg/l AITC also adversely affected sensory quality and did not reduce salmonella populations after 11 days of exposure at 10° C.

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