ASSESSMENT OF LOCAL METHODS OF PROCESSING FOR THE PRESERVATION OF THE PHYSICO-CHEMICAL PROPERTIES AND MICROBIOLOGICAL QUALITY OF TWO LOCAL CHEESES IN ILORIN, NIGERIA

Abstract

Nigerian locally produced cheese from milk, commonly known as wara is highly nutritious and highly prone to attack by spoilage and pathogenic microorganisms. Moist heat treatment and salting alone are the common methods used for processing. This study assessed the efficacy of these local processing methods in preserving the physicochemical properties and microbiological quality of wara. Samples were purchased from open markets in Ilorin; processed by boiling in water and with addition of salt; and stored at room temperature (28±2oC) to mimic the local method. The samples were observed at 24 hrs interval for a period of 96 hrs, for changes in pH, color, odor and texture. Microbiological analysis was done following standard methods. The pH of most of the samples increased while the color, odor and texture deteriorated within 48 hrs of storage. The cheese samples were preserved most by boiling with salt. Many spoilage and pathogenic microorganisms were isolated. The bacterial isolates were Lactobaccillus acidophilus, Escherichia coli, Bacillus cereus, Staphylococcus aureus, Proteus vulgaris, Enterococcus feacalis, Aerobacter aerogenes, Klebsiella, Aerococcus, Micrococcus and Streptococcus spp.; while the fungi were Aspergillus flavus, A. fumigatus, A. flavus, Candida tropicalis, Rhizopus arrhizus, Penicillium and Mucor spp. Some of the microorganisms were eliminated during treatments, others survived while some contaminated the samples during storage. Though boiling of wara with salt was shown to improve its keeping quality compared to other methods studied, further treatments such as frying, drying, and roasting; as well as storage at low temperature may significantly increase the shelf life.