Microbiological Comparative Studies of Crude Aqueous Extracts from Arabica and Robusta Coffee

Abstract

The aim of the present study was to determine the degree of microbial contamination of aqueous extracts of green and roasted coffee originating in India. The samples used in this analysis were obtained by two extraction methods: hot extraction and cold extraction. If a microbial load of samples was found, the same extracts were filtered using sterile 0.22 μm pore size filters from PES (Polyester) for decontamination. The working methodology was based on the Standard SR EN ISO 21149/2017 which provides general guidelines for counting and detecting mesophilic aerobic bacteria using as a medium for isolation, cultivation and counting of microorganisms (bacteria and fungi) the non-differential environment. The experimental results obtained showed microbial contamination of all samples. The level of microbial contamination is different for the extracts taken under study, depending on the type of coffee used, green or roasted, but also on other conditions, such as wet or dry processing. Roasted coffee is much less contaminated compared to green coffee, due to a thermal (incomplete) sterilization by the roasting procedure. The working conditions used, the temperature of the distilled water used to prepare the extracts, their non-sterile handling, but also the type of coffee used, are the factors that determined the microbial contamination.