Studies on Sensitivity of Vegetables to Low Oxygen (Part II). Effect of Low Oxygen Atmosphere on Respiration of Several Vegetables.

A pressure swing adsorption-modified air system (PSA-MAS) ·CO₂ evolution analyzer was developed to determine the effects of low oxygen atmosphere on respiration of harvested fruits and vegetables. The respiration rates of cauliflower, celery, komatsuna, lettuce, broccoli and cabbage were measured with the PSA-MAS·CO₂ evolution analyzer and the gas separation membrane-modified air system (GSM-MAS) ·CO₂, evolution analyzer which was previously developed, The respiration rates were determined by measuring the rate of CO₂, evolution from vegetables under air, 1 % O₂, 4 % O₂, 7 % O₂ and 10% O₂ atmospheres at 10°C. The respiration rates were lower under the low oxygen atmosphere as compared to the air control in all vegetables. Distinctive differences in the respiratory response after exposure to low oxygen conditions were observed among commodities. These differences were divided into three groups. The first group showed that the respiration rate decreased immediately after exposure to a low oxygen condition and then the respiration rate stabilized to a steady, remained constant until the end of treatment. The second group showed that after exposure to the low oxygen condition, the respiration rate decreased slightly slower than the first group but then the respiration rate settled down to a steady rate and remained constant until the end of treatment. The third group showed that the respiration rate gradually decreased until the end of treatment after exposure to a low oxygen condition. Vegetables of the first group included cauliflower and celery. Vegetables of the second group included komatsuna and lettuce. And vegetables of the third group included broccoli and cabbage. There was a linear correlation between the oxygen concentration in the atmosphere and the respiration rates of cauliflower and lettuce. Compared to the air control, the respiration rates of cauliflower and lettuce were considerably decreased even at a 10% oxygen atmosphere. In other vegetables, however, respiration rates were slightly decreased under 7 % or more oxygen conditions. Below 7 % oxygen level, respiration rates were obviously reduced at the lower oxygen levels as compared to the air control.