The dual role of oxygen in avocado fruit respiration: Kinetic analysis and computer modelling of diffusion‐affected respiratory oxygen isotherms

Abstract

Oxygen plays a dual role in affecting the rate of respiration of avocado fruit {Pcrsca atncricana Mill, cv. Hass). The respiration rate 1' . oxygen concentr-ation cut-vc for steady state avocado fruit respiration is biphasic. The curve becomes monophasic, however, when measured under conditions of rapidly changing oxygen concentration in a closed circulating system. The results are interpreted as indicating that oxygen at relatively high concentrations modulates respiration independent of its interaction with the terminal oxidasepresutnably cytochrome oxidase.A cotnputer model is presented which takes into account the effect of diffusion barriers on the kinetics of oxygen utilization as a function of concentration in avocado fruit. The model is used to tnake predictions concerning the apparent A^,,, of the terminal oxidase or oxidases in avocado fruit. It is concluded Ihat Ihe apparent A^, , , of the terminal oxidase of uninhibited avocado fruit is that of eytochrome oxidase, and that the alternative, eyanidc-resistant oxidase of avocado fruit does not contribute appreciably to the uninhibited respiration of preclin-iacteric or climacteric avocado fruit,

Modeling Respiration of Apple Slices in Modified‐Atmosphere Packages

“…Since diffusive resistance of whole fruit resulted in an O 2 partial pressure gradient of only 2 to 5 kPa (Rajapakse et al, 1989), the interior O 2 level was sufficiently high to very nearly saturate the respiratory response (Tucker and Laties, 1985). Thus, the reduced diffusive resistance provided by slicing should not have resulted in an increase in O 2 uptake relative to whole fruit.…”

Avocado Fruit Development and Ripening Physiology

“…Low levels of oxygen decrease overall respiration rate (Tucker and Laties 1985), and also appear to block the ethylene-forming system (Burg and Burg 1967;Beyer 1977). High carbon dioxide concentrations also decrease ripening, possibly by acting as a competitive inhibitor of ethylene (Rhodes 1981).…”

Effect of modified atmosphere packaging (MAP) with low and superatmospheric oxygen on the quality and antioxidant enzyme system of golden needle mushrooms (Flammulina velutipes) during postharvest storage

“…The RRs increased rapidly and reached a peak after 7 days storage, dropped rapidly from day 7-14, and remained relatively stable. The respiration was enhanced during the storage and the breathing peak occurred at day 7; this has also been called "breathing promotion period" [29]. In these high oxygen packs, the RRs of initially oxygen rate of 50 and 80% reached a peak value of 0.093 and 0.043 mg h ¡1 g ¡1 fw on the day 7, respectively.…”