Impact of gamma irradiation on microbiological and physical properties of butterfly pea tea (Clitoria ternatea)

Abstract

Butterfly pea flower tea is a caffeine-free herbal fusion made from flowers of the Clitoria ternatea plant and is rich in antioxidants. It is difficult to clean large quantities before processing as butterfly pea tea is made from small flowers. In consequence, microorganisms can be present in the final product. This product has a good demand in the foreign market and is expected to increase in the future. Large-scale production is more profitable and efficient if contamination is reduced. Gamma irradiation can be used as an effective treatment to destroy microorganisms. Samples collected from an exporter were irradiated 3 days after processing at different target doses of 3kGy, 5 kGy and 7 kGy and non-irradiated sample was used as the control. Co-60 gamma irradiator was used with the rate of 0.15Gys-1. Total Plate count, total coliform and fecal count and yeast and mold count of butterfly pea were determined according to modified ISO standard methods. Water activity, moisture content %, powder color and infusion color (∆E value based on L, a, b in Hunter color scale) were measured for each treatment under physical parameters. All treatments were done within a week after irradiation and replicated three times. The highest microbial contamination was observed in the non-irradiated sample. The total plate count dramatically decreased with increasing irradiation doses. Escherichia coli were identified in the control sample. There were no yeast and mold count, total coliform and total fecal count observed in all the treated samples. The average water activity and moisture % of control samples were 0.263±0.00 and 7.860±0.18% whereas irradiated butterfly pea tea samples were 0.31±0.01 and 7.37±0.20% respectively. The mean ∆E values of powder and infusion of the irradiated samples were not significantly different (P>0.05) from the control sample. The study shows that 3kGy is the possible dose to eliminate microbial contamination and has no considerable effect on the physical parameters of butterfly pea.