Assessment of handling practices and microbial contamination of raw and cooked African walnut (Tetracarpidium conophorum) fruit snacks in Abuja Nigeria markets

Abstract

Microbial contamination of walnut fruits can be of health risk concern. This study assessed the handling practices and the microbial contaminant of raw and cooked African walnuts (Tetracarpidum conophorum Mull. [Arg]), fruits in Abuja, Nigeria. An initial market survey involving the administration of 120 semi-structured questionnaires was conducted. Seventy-two raw walnuts and 72 cooked walnuts samples were collected from Gwagawlada, Bwari and Abuja municipal area councils and bulked separately into 24 composite samples and examined for the total bacterial count. Fifty-two (52.0%) of the traders, preserve the cooked walnuts by submerging them in cold water overnight. The raw ones were preserved by shade-drying monthly for 4-5 hrs and bagging jute sacks by (68.0%) traders. The bacterial colony count in the raw walnut sample ranged from 1.13 x 105- 2.30 x 106 and 1.53 x 105- 6.80 ×106 in the cooked samples. Three Gram-negative bacteria - Pseudomonas aeruginosa, Escherichia coli, and Shigella sonnie, and two Gram-positive bacteria; Staphylococcus aureus and Salmonella spp. were identified biochemically. Staphylococcus aureus and E. coli had the highest incidence of 42.0% and 25.2% in both the cooked and raw samples respectively. Thirty-three (67%) of the raw samples were in the satisfactory level while 83% of the cooked samples were in the satisfactory category when compared to the ICMSF food standard. Since some ready-to-eat cooked samples contained notable pathogenic microbes that are harmful to humans, this indicated a health risk concern.