Evaluating the effects of pre-packaging, packaging and varying storage environment treatments on the quality of avocados (Persea americana mill.)

M. Sc. Agri. Eng. University of KwaZulu-Natal, Durban 2013.

Avocados are characterized as climacteric fruit and are vulnerable to rapid physiological deterioration. Maintaining avocado fruit quality requires proper integrated postharvest technologies. Thus, the primary aim of this study was to evaluate the effects of combined postharvest treatments and storage conditions on the physical, chemical and subjective sensory quality parameters of the ‘Hass’ avocado. The study was divided into two experiments. Experiment I investigated the combined effects of postharvest handling treatments and fixed temperature (5°C or 10°C) and relative humidity (85% or 90%) on the quality of avocados for a storage period of 12 days. Experiment II focused on the combined effects of postharvest treatments and temperature-varying storage conditions (5.5°C ± 0.01°C for two days, 5°C ± 0.01°C for six days and 4.5°C ± 0.01°C for 20 days and 95% relative humidity), by simulating a realistic avocado cold chain for 28 days. A Randomised Complete Block Design with pre-packaging (hot water and Avoshine® wax coating), packaging (low density polyethylene (LDPE) and corn starch biodegradable films) and storage conditions (as mentioned above and ambient) with three replications was used in both experiments. The quality parameters that were evaluated included physiological weight loss (PWL), respiration rate, marketability, skin colour, firmness, puree colour, puree viscosity, moisture content (MC), dry matter (DM), pH, total soluble solids (TSS) and total titratable acidity (TTA). The storage conditions and the storage period significantly (P≤0.001) affected the quality parameters that were evaluated in both experiments. Low temperature storage offered the greatest benefit in maintaining high marketability, reduced PWL and delayed the peak in respiration, compared to ambient conditions in both experiments. Control samples exhibited increased rates of ripening, which was evident in increased PWL, reduced firmness, darkened skin colour, rapid decline in pH as well as increased TTA and TSS. The Avoshine® coating, combined with LDPE packaging, was favourable in maintaining a lower PWL, higher marketability, higher MC and lower DM indicative of delayed ripening. Hot water treatment promoted the darkening of the skin, decreased pulp firmness and lowered the marketability. The findings show that cold storage, combined with Avoshine® and LDPE packaging improved the shelf life by two weeks and preserving the quality of avocados during short and extended storage durations, compared to control samples.