Bacterial Composition of Biofilms of a Local Tigernut Drink Processing Unit in Yenagoa, Nigeria

Abstract

Microorganisms grow and form biofilms on surfaces of equipment employed in food processing. These biofilms are considered as the major sources of contamination in the food industry. The study determined the bacterial load and composition on surfaces of equipment and utensils employed in tigernut drink production, from a vendor with a production unit located in an open market in Yenagoa, Nigeria. Swabs were taken from different sampling points made of varying materials—the grinding machine (metal), the collection bowls, water storage containers (thick plastic) and retail bottles (light plastic). These were analysed for total heterotrophic bacterial counts (THBC) and bacterial diversity using standard procedures. The THBC of water used in the drink production was also determined. The THBC of the sampling points ranged from log 3.28±0.06 cfu/cm2 to log 5.18±0.05 cfu/cm2, and log 5.13±0.07 cfu/ml for the water sample. The grinder and water recorded higher bacterial load with a statistically significant difference (P<0.05). The retail bottles had the least bacterial count. Shigella spp. were the most isolated (27.451%), then Salmonella spp. (21.568%) and E. coli (15.686%). Streptococcus spp., Staphylococcus spp. and Vibrio spp. were the least isolated (11.765% each). Shigella and Salmonella species occurred at all sampling points but not on the retail bottles. E. coli was present in the water collection bowls and retail bottles while Streptococcus, Staphylococcus and Vibrio were found only in the retail bottles. On diversity, four bacterial genera (39.216%) were isolated from the retail bottles, three (25.490%) from the water storage containers and two (17.647%) from the grinder and collection bowls. The microorganisms possibly had preference for attachment to the surfaces based on the material makeup and nutrient availability. Their occurrence and high numbers reflect the low level of hygiene employed prior to drink production. This could be of public health concern.