BIOCHEMICAL CHARACTERIZATION OF BACTERIA AND FUNGI ISOLATES ASSOCIATED WITH POST-HARVEST SPOILAGE OF AVOCADO PEAR (PERSEA AMERICANA) SOLD IN TWO FRUIT MARKETS IN THE BENIN CITY METROPOLIS, NIGERIA

Abstract

Persea americana is a major and cheap source of nutrients-containing protein fruit and commonly referred to as Avocado pear. It is a green-skin, fleshy body and may be spherical or pear-shaped and ripens easily after harvest, significantly reducing its shelf-life. The average storage time before spoilage is 3-6 days. The fruit is highly cherished by many and as such a significant dietary contribution, in developing countries. However, the poor shelf-life of the fruit has led to its high perishability, huge post-harvest losses and market glut during harvest. In this study, fresh, undamaged, firm, healthy-looking, ripe avocado fruits purchased from Oba Market and New-Benin market were left free of dust and insects under room temperature for between 5-6 days to undergo a natural process of spoilage. A homogenate of each of the sample was achieved by blending 25 grams of the sample in 225 ml of sterile 1.5 % peptone water with a sterile glass blender. Serial dilutions of up to 10^-1 - 10^-5 were made and 1 ml of each of the dilutions were transferred into sterile Petri dishes and respectively mixed with 15 ml of an appropriate sterile media and incubated at a temperature of 37 ^oC for 48 hours, while the Sauboraud dextrose agar (SDA) was left at room temperature for 5 days. After incubation, bacterial and fungal colony-forming units were counted and used to determine the total aerobic viable counts (TAVC), total coliform counts (TCC), Escherichia coli counts (EC), Staphylococci counts (SC) and total fungi counts (FC). Representative colonial isolates were subsequently subcultured on nutrient agar slants and stored at a temperature of 4 ^oC prior to characterization. Phenotypic identification of microbes was performed according to standard methods. The present study revealed that the coliform bacteria (TCC = 2.42 x 10³ cfu/g and 2.06 x 10³ cfu/g) accounted for a significant fraction of the total bacterial population (TAVC = 2.75 x 10⁴ cfu/g and 9.68 x 10³ cfu/g) isolated from spoiled pear produce. Hence, Erwinia and Klebsiella aerogenes of genus of Enterobacteriaceae, were the main spoilage bacteria; while Phytophthoras species (FC = 1.73 x 10⁴ cfu/g and 1.02 x 10⁴ cfu/g) was the main spoilage fungus of pear produce sold in the two Nigerian markets. The isolation of pathogenic organisms also calls for a public health concern.