Microbial and heavy metal contamination of pineapple products processed by small and medium scale processing enterprises in Rwanda

Abstract

Fruit products are increasingly consumed but highly prone to microbial deterioration if not adequately processed and stored. The present study was conducted to evaluate the microbial and heavy metal concentrations of packed pineapple nectars, syrups and jams processed by 10 Small and Medium scale pineapple processing Enterprises (SMEs) over a storage duration of 12 months. Collected samples were analysed to determine whether the levels of microbial and heavy metal concentrations were in line with maximum permissible limits set by Codex Alimentarius Commission (CAC), East African Standards (EAS) and Rwanda Bureau of Standards (RBS). The samples were tested for yeasts and moulds, total plate counts, Faecal coliforms, total coliforms, Escherichia coli, Salmonella, Shigella and Staphylococcus aureus using tested International Organization for Standardization (ISO) microbial determination methods. Quantitative determination of heavy metals: zinc, iron, lead, copper, cadmium and aluminium was carried out by Atomic Absorption Spectrophotometer (AAS). Pineapple products were free from most of the microorganisms but only nectars from 30% of SMEs were highly contaminated above the permissible Codex and RBS limits with total plate counts >300 CFU/ml  and yeasts and mould counts >300 CFU/ml. The mean levels of zinc, iron, copper and aluminium were within the acceptable recommended Codex and RBS standard values but the levels of lead and cadmium were above those permissible standard values. These results indicated that some fruit processors in Rwanda may not be observing good manufacturing and hygienic practices, leading to a need for improved post-harvest and processing guidelines, better monitoring and enforcement, and additional research into heavy-metal ingress in the manufacturing process.

Keywords: Pineapple,  juices,  jams, microbial contamination,  heavy metal, Rwanda.

African Journal of Biotechnology, Vol 13(39) 3977-3984