Respiration Rate Of Slices Research Articles

Physiological responses of fresh-cut apple slices under high CO2 and low O2 partial pressures

Abstract The physiological responses of ‘Delicious’ apple slices to 0–30 kPa CO2 at 0–10 kPa O2 partial pressures at 5°C have been studied. Increasing CO2 partial pressures from 0 to 30 kPa at 0.5, 1 and 10 kPa O2 reduced respiration rates and ethylene production of the slices. The inhibitory effect of CO2 on respiration rate of slices was best explained by an enzyme kinetics model that combined competitive and uncompetitive types of inhibition. Browning increased during storage and was reduced by CO2 to only a limited extent. CO2 levels of 15–30 kPa resulted in about a 50% reduction in acetaldehyde, ethanol and ethyl acetate concentrations in tissues under both anaerobic and low-O2 atmospheres compared with slices kept in CO2-free atmospheres. Elevated CO2 might provide a mechanism to reduce accumulation of fermentation products but sensory quality of slices needs be studied before recommending its use.

The measurement of the fraction of oxygen carried by facilitated diffusion.

Evidence has been presented that the cytochrome P-450 in the endoplasmic reticulum can facilitate the diffusion by oxygen through tissue (Longmuir, 1970). This hypothesis is based on the observation that the respiration rate of liver slices as a function of ambient oxygen tension more closely fits a model equation based on purely passive diffusion. However, the fit is not perfect at higher oxygen tensions, and it seems highly improbable that there can be no passive diffusion proceeding concomitantly. The respiration rate of a slice in which there is only passive diffusion would rise as the square root of the ambient oxygen tension, whereas if transport is purely by carrier, the respiration rate would show “saturation” kinetics. That is, the rate of rise would fall off rapidly, becoming asymptotic to a maximum rate. Thus it seems certain that both passive and facilitated diffusion are proceeding simultaneously. That this is the case can be shown by the application of specific inhibitors to tissue slices.KeywordsRespiration RateOxygen TensionPassive DiffusionLiver SliceOxygen FractionThese keywords were added by machine and not by the authors. This process is experimental and the keywords may be updated as the learning algorithm improves.