Purpose: This study was performed to determine the effect of polyphenol extracts from coffee processing byproductst on the in vitro growth of microorganisms relevant to the food industry.
Methods: Polyphenol extracts were obtained from the coffee mucilage, as a byproduct of coffee processing, using the modified methodology described by Mingo et al. (2016), based on extraction with ethanol 50% (v/v). Dilutions of the extracts, with initial concentrations between 711 and 740 mg/ml, were added to different population densities of: foodborne pathogens Staphyolococcus aureus ATCC 25923, Bacillus cereus ATCC 11778, Salmonella Typhimurium ATCCC 13311 , and Listeria monocytogenes SLCC 4013; of food deteriorating bacteria Pseudomonas ATCC 27853, Alcaligenes UCR 277, Serratia UCR 299, Micrococcus luteus ATCC 4698, and Escherichia coli ATCC 35150; and human gut bacteria Lactobacillus acidophilus CRL730, Lactobacillus casei CRL431, Lactobacillus rhamnosus ATCC 7469, and Lactobacillus plantarumATCC 14917 (human gut bacteria) through plate diffusion. The bacterial growth, as indicated by colony formation, was visually inspected after 24 hours of incubation under aerobic atmosphere at 35°C.
Results: Growth inhibition was observed for B. cereus and Micrococcus sp. in extract concentrations ranging from 30 to 70 and 14 to 70 mg/ml, respectively. While, the strains of Serratia sp., Pseudomonas sp., L. plantarum and L. rhamnosus were not inhibited.
Significance: Though the mechanism of action of the extracts remains to be elucidated, this type of extract could be used in the pharmaceutical or food industry, as natural preservatives of products prone to contamination with low GC% gram-positive bacteria.