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

Author: Abbas F. Al-Jamali ^* and Majde T. Bani Hani

Received 10 September 2008, accepted 11 December 2008.

Abstract

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 (CO₂) and nitrous oxide (N₂O) 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 N₂O, 20 kPa CO₂ or 60 g dry ice (frozen CO₂) 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 CO₂, N₂O 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 23-16ºC, maximum-minimum ambient temperatures and 88% relative humidity. Nitrous oxide and CO₂ treatments resulted in decreased water loss from the pods and maintained regular pod shape throughout the storage period, with N₂O being the most efficient treatment. Nitrous oxide and CO₂ 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 N₂O and CO₂ during the storage period than in the dry ice treatment or control. White mold did not appear for 20 days on pods treated with N₂O and CO₂ when stored at 16-23°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 N₂O and CO₂, 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.

Key words: Croplife-B, organic, carbon dioxide, nitrous oxide, dry ice, green beans, Phaseolus vulgaris L., modified atmosphere, temperature.