Fruits respiration rates

All fruits respire oxygen and, in doing so, start to decay. If the oxygen concentration can be reduced, the rate of respiration will be slowed and the storage life maybe extended. The maintenance of a low partial pressure of oxygen requires a gas-tight structure to prevent diffusion. Such controlled atmosphere stores are carefully constructed and sealed to achieve this, and are generally termed gas stores. 

Neotropical bats Desmodus rotundus, Artibeus literatus, and Phyllostomus discolor) are very sensitive to butanoic acid their detection threshold lies between 1.5 x 10 ° and 1.5 x 10 mol/1 (Schmidt, 1975). The short-tailed fruit bat Carollia perspicillata) has detection thresholds for 18 odorants ranging from 3.6 x 10 to 2.7 X 10 ° molecules/cm air. The animals were most sensitive to fruit-typical compounds such as ethyl butyrate (5.4 x 10 °molecules/cm ), w-pentyl acetate (2.8 X 10 °molecules/cm ), andlinalool(1.8 x 10 molecules/cm ), suggesting nutritional specialization of chemoreception (Laska, 1990). The bats increased their respiration rate from a basal rate of 2-4 Hz to as much as 12 Hz when confronted with an odor of high concentration. 

Using this procedure, there was a decrease in respiration rate with less loss in fruit weight. There was less decay and the color development was similar to fruit treated by continuous degreening. 

Reducing the 02 concentration around fresh fruits and vegetables reduces their respiration rate to an extent that varies with temperature, commodity, cultivar, and physiological age at harvest. Below a minimum of about 1 to 2% 02, a shift from aerobic to anaerobic respiration occurs with a concomitant increase in CO2 production Q0). The reduction in aerobic metabolism associated with reduced 02 levels is apparently not mediated by cytochrome oxidase, which has a K , value of 10"8 to 10 7 M 02 (11.12). It is more likely that reduction of aerobic respiration results from diminished activity of other oxidases such as ascorbic acid oxidase, polyphenol oxidase (FFO), and glycolic acid oxidase, whose affinities for 02 are 5 to 6 times lower than that of cytochrome oxidase (12). 

A recent trend in marketing fresh fruits is to wrap each fruit individually. It should improve the fruit s appearance and minimize abrasion between fruits. However, this would require finding a film with the optimal permeability for air, water vapor, ethylene and carbon dioxide between the fruit and the surrounding atmosphere so as to slow down the fruit s respiration rate, and to maintain the proper relative humidity. If irradiation and a fungicidal agent can be incorporated into the process and packaging, it should further extend the shelf-life of the fruit substantially. 

The respiration rate during ripening of fruit and vegetables is not uniform and changes depending on plant species. Respiration rate changes can distinguish... 

The respiration rate of fresh fruits and vegetables can be expressed as the rate of O2 consumption and CO2 production rate. The usual methods for determining the concentration of respiration are static or closed system, continuous flow system, and permeable system. The respiration rate is measured in permeable system, in other words, the product is within the dimensions and permeability of packaging film known (Beaudry, 1993 Joles et al., 1994 Lakakul, Beaudry, Hernandez, 1999 Lee, Song, Yam, 19% Piergiovanni, Fava, Ceriani, 1999 Smyth et al., 1998). The concentrations of O2 and CO2 are determined and stable mass balance is done on the system in order to estimate respiration rates. 

Fonseca, S. C., Oliveira, F. A. R., Brecht, J. K (2002). Modelling respiration rate of fresh fruits and vegetables for modified atmosphere packages a review. Journal of Food Engineering, v. 52, p. 99-119. 

The respiration rate is affected by the development stage of the fruit. A rise in respiration rate occurs with growth. This is followed by a slow decrease in respiration rate until the fruit is fully ripe. In a number of fruits ripening is associated with a renewed rise in respiration rate, which is often denoted as a climacteric rise. Maximal CO2 production occurs in the climacteric stage. De-... 

Climacteric and nonclimacteric fruits respond differently to external ethylene (Fig. 18.10). Depending on the ethylene level, the respiratory increase sets in earlier in unripe climacteric fruits, but its height is not influenced. In contrast, in nonclimacteric fruits there is an increase in respiration rate at each ripening stage which is clearly dependent on ethylene concentration. 

A significant reduction in respiration rate takes place as the oxygen level is reduced below 21%, especially below 10%. Besides, the production and action of ethylene (CjH ) that plays a central role in ripening of the fruits can be inhibited at low... 

Maintenance of product quality through reduction of respiration rate, browning reactions, fruit softening, and decay,... 

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