Effect of Storage Temperature on Postharvest Quality, Ripening and Marketability of Marula Fruits (Sclerocarya birrea subsp. caffra)

A laboratory experiment was undertaken to investigate the effect of storage temperature on storage life and quality of marula fruits. The experimental design was a completely randomized design with three replicates. Marula tree landraces growing around Sebele area of Gaborone were used for the study. The storage temperatures were 0, 4, 8 and 12±1°C (90-95% RH). Some fruits were also left at room temperature (25±3°C) as control. The results of the study showed that storage temperature and duration of storage significantly (p ≤ 0.05) affected the incidence and severity of chilling injury in marula fruit. Chilling injury developed in all the fruits stored below 12°C, though the severity of chilling injury significantly (p ≤ 0.01) varied with storage temperature. The marula fruit stored well for 25 days at 12°C without the development of physiological disorders and decay incidence. The fruit underwent normal ripening process with colour (carotenoids and anthocyanins) development (increased from 10.7 to 598 nmoles/cm2 of fruit skin), high total soluble solids (increased from 10.3 to 12.2%) and low titratable acidity (decreased from 30.2 to 17.4 mg/100 ml juice) after removal from storage (12°C) and held for seven days at room temperature to simulate marketing conditions. It was concluded that shelf life extension and marketing of marula fruits could be attained at a temperature of 12°C and 90-95% RH. This is due to the fact that the fruit will not suffer from chilling injury and will undergo normal ripening process.