Temperature effects on the internal lower oxygen limits of apple fruit.
Yearsley, C. W.; Banks, N. H.; Ganesh, S.;
Postharvest Biology and Technology Year: 1997 Vol: 11 Issue: 2 Pages: 73-83 Ref: 27 ref.
1997
บทคัดย่อ
Exposure of packaged fresh produce in modified atmospheres (MA) to elevated temperatures can cause the partial pressure of O2 inside the produce (piO2) to fall below internal lower O2 limits (LOLis), resulting in fermentation and loss of quality. In this study, 2 types of LOLi were estimated from steady-state external chamber atmospheres: the anaerobic compensation point (ACPi), and the fermentation threshold based on the respiratory quotient (FTiRQ) and on ethanol (EtOH) accumulation (FTiEtOH). Mean estimates of LOLis of apple cultivars Cox's Orange Pippin and Braeburn ranged between 0.5 and 1.0 kPa internal partial pressure of O2 (piO2) for ACPi; 0.8 and 1.7 kPa piO2, for FTiRQ, and 0.5 and 2.0 kPa piO2 for FTiEtOH, for fruit temperatures between 0 deg and 28 deg C. Values for ACPi estimated at 32 deg were higher than those between 0 deg and 28 deg . In general, estimates of dissolved O2 concentration at ACPi and FTiRQ tended to decrease with increasing temperature for Braeburn apples, changed
little for Cox's Orange Pippin apples, but increased again for ACPi at 32 deg . On average, estimates of LOLis were higher for Braeburn than Cox's Orange Pippin apples. The effect of temperature on diffusion coefficients and solubility were considered unlikely to contribute significantly to variation in LOLis except for solubility at higher temperatures, but differences in tissue porosity may have influenced differences in LOLis between cultivars. Results of the current study indicate temperature effects on LOLis would not be significant except for MA packages destined for markets with ambient temperatures in excess of 28 deg . On the other hand it seems that to assume that ACPi is independent of temperature may be too simplistic, particularly if fruits are exposed to a very wide range of temperatures. LOLis were relatively constant compared with lower O2 limits based on package atmospheres, and can be used to estimate optimum MA package atmospheres that account for fruits within a population with the highe
st respiration rates and lowest permeance to O2.