Assessment of quality of raw bovine milk sold in Kampala City: A cross sectional study

Abstract

Background: Recently there has been increasing reports concerning the safety of certain foods consumed in Uganda. Milk and meat sold on the Ugandan market have been reported to be contaminated with chemicals or adulterants and microorganisms. Objective: To assess the quality of raw bovine milk sold in Kampala City market by determining the presence of unacceptable chemical residues, adulterants and selected microorganisms. Methods: A cross sectional study was conducted in three administrative divisions of Kampala City namely; Nakawa, Kawempe and Rubaga between October 2018 and March 2019. A total of 120 samples each containing about 500ml of raw milk were collected from 120 dairy outlets using the random sampling method. Four (4) samples were rejected and 116 samples were analysed. The adulterants and chemical residues of interest included; extraneous water, starchy matter, colouring matter, nitrates, antibiotic drug residues (Beta lactam, tetracycline and desfuroylceftiofur), formalin, hydrogen peroxide, carbonates and bicarbonates. Volumetric analysis methods and immune-chromatographic rapid test strips were used to determine presence of chemical residues and specific gravity was determined using a lactometer. The microorganisms of interest were Salmonella species and Staphylococcus aureus that were cultured on selective growth media. Phenotypic colony characteristics and biochemical tests were used to confirm the isolates. After data collection, a database was designed using Epi data 3.1 (EpiData Association, Odense, Denmark, 2004). The data were then exported to STATA 12.0 (Strata Corp., 702 University Drive East College Station, Texas) for data analysis. Categorical variables were described by percentages, ranges, and proportions and continuous variables were described by mean colony forming units. A P-value < 0.05 was considered to declare a result as statistically significant in this study. Results: Of the samples analysed, fourteen samples (12.1%) tested positive for formalin, nitrates, carbonates & bicarbonates residues. No sample was positive for either colouring matter or hydrogen peroxide. Six samples (5.2%) had Salmonella species contamination while 112 samples (96.6%) had Staphylococcus aureus load above permissible limits. Conclusions: The presence of chemical residues, Salmonella species and Staphylococcus aureus in the milk samples is a perfect indicator that this product is mostly not safe for human consumption. Therefore, urgent action by regulators in the milk sector is required to remedy this situation.