Nitric oxide degradation in oxygen atmospheres and rate of uptake by horticultural produce

Fumigation of horticultural produce for a few hours with low concentrations of nitric oxide (NO) has been previously shown to extend postharvest life, but treatments have been carried out in an atmosphere with very low oxygen (O-2) due to the known rapid oxidation of NO. This study examined the rate of loss of 30 mul l(-1) NO from atmospheres containing 0.3-21% O-2 and found that the rate of loss was much lower than expected with the half life of NO ranging from about 16 h in 0.3% O-2 to 3.5 h in 21% O-2. Exposure of ten types of produce to 30-100 mul l(-1) NO showed that the rate of loss of NO was greater at higher concentrations and was much greater than in air only, the difference indicating uptake of NO by produce. The rate of uptake of NO by produce varied considerably, with a 130-fold range from about 90 mmol min(-1) per 100 g in lettuces to about 1 mmol min(-1) per 100 g in lime. When calculated on a surface area basis, the range was only 15-fold varying between about 1 and 13 mmol min(-1) per 100 cm(2), but with no obvious pattern that could be related to produce characteristics. NO thus may be sufficiently stable at the concentrations and fumigation times required for produce to be treated in normal air, although surface area and other as yet unknown physical characteristics of produce need to be taken into account as these affect the quantity of gas absorbed. (C) 2002 Elsevier Science B.V. All rights reserved.