Low temperature storage is a widespread technology to prolong the shelf life of fruits.
The removal of C2H4 from the surrounding atmosphere during cold storage of avocados has been proposed by Zauberman and Fuchs (1973) to prevent chilling injury (CI). Moreover, CI occurrence increases when avocados cv.
Fuerte stored at low temperatures are treated with 100 ppm C2H4 (Lee and Young, 1984).
On the biochemical aspect, C2H4 is related in avocado with the synthesis of several cell wall degrading enzymes involved in fruit softening and with enzyme activities of the C2H4 synthesis pathway.
In general, the protein pattern of Hass fruits is correlated with the C2H4 evolution during the postharvest period (Christoffersen et al., 1982), and the levels of several mRNAs that change during ripening of avocados was clearly affected by pulses of propylene, an C2H4-like factor (Starret and Laties, 1991).
Since C2H4 appears to affect the synthesis of enzymes related with the CI symptoms of avocado (atypical respiration and C2H4 production rates, and failure to soften properly upon warming) we have studied the CO2 and C2H4 production, flesh firmness and protein profile of Hass fruits stored at 7C with or without C2H4 removal.
Fruits were stored in cold store rooms at 90% RH. External CO2 and C2H4 production was measured by gas chromatography on avocados placed in respiratory chambers.
In a batch of fruit, C2H4 was removed from the chamber by chemisorption.
One sachet (10 g of Green Keeper, manufactured by Pro-market SA, Spain) per kg of fruit was placed into the correspondent respiration chamber.
Flesh firmness was measured using an Instron 1140 Testing machine, fitted with a double plateprobe.
In order to avoid coring effects, samples were taken by cutting three peeled fruit halves into pieces.
The pieces were immediately frozen in liquid N2, randomized and ground to a fine powder with a coffee mill.
Water soluble proteins were extracted according to Kanellis et al. (1989) with minor modifications, and subjected to SDS-PAGE using 10 to 15% gradient polyacrilamide gels.
Silver stained gels were scanned with the Biolmage system (Millipore Corporation).
The rates of CO2 and C2H4 production were clearly reduced by low temperature.
The respiration pattern was similar between both conditions, showing an irregular behavior during the first 25 days of storage.
After this breaking point a slow increase was observed.
Ethelene production was more affected by the temperature, being always below 1.5 μl/kg/hr.
The treatment with C2H4 removal reduced these levels and the peaks on C2H4 evolution were smoothed.
Softening of fruit during storage shows that delay of ripening was not affected by the treatment with C2H4 removal.
This suggests that induction of the synthesis of softening related enzymes should not solely be attributed to