Croplife-B with nitrous oxide or carbon dioxide extends shelf life of green beans (Phaseolus vulgaris L.) at ambient temperatures

摘要

Croplife-B is said by the manufacturer to stimulate the production of phytoalexins and to reduce fungal growth in sprayed plants. To investigate the effects of Croplife-B preharvest sprays and increased postharvest carbon dioxide (CO sub(2)) and nitrous oxide (N sub(2)O) concentration on pod quality and shelf life, off-season green bean plants, winter-grown in the warm Jordan Valley, were sprayed twice at a rate of 270 ml/ha Croplife-B. Green bean pods were kept after harvest in 100 kPa N sub(2)O, 20 kPa CO sub(2) or 60 g dry ice (frozen CO sub(2)) in 120-litre barrels for twenty days. Results indicated that Croplife-B accelerated the production time and reduced mold appearance and development during and after storage when used alone or in combination with CO sub(2), N sub(2)O or dry ice treatments. Croplife-B did not affect firmness, total soluble solids, pH, titratable acidity, color, volume or moisture-content loss of green bean pods stored at 23-16 degree C, maximum-minimum ambient temperatures and 88% relative humidity. Nitrous oxide and CO sub(2) treatments resulted in decreased water loss from the pods and maintained regular pod shape throughout the storage period, with N sub(2)O being the most efficient treatment. Nitrous oxide and CO sub(2) resulted in improved bean pod coloration at the end of storage time. Firmness and titratable acidity decreased while the pH increased more when beans were treated with N sub(2)O and CO sub(2) during the storage period than in the dry ice treatment or control. White mold did not appear for 20 days on pods treated with N sub(2)O and CO sub(2) when stored at 16-23 degree C and 88% relative humidity. With dry ice treatment the white mold appeared at 10 days of storage. Dry ice treatment reduced the appearance of mold, maintaining it at under 50% for 20 days. The beneficial effect of N sub(2)O and CO sub(2), coupled with Croplife, in inhibiting the mold continued for 10 days after the bean pods were removed from storage on Day 20. The results of these experiments are consistent with Croplife-B acting as an elicitor of phytoalexins.