Gamma Irradiation of Export Oriented Moringa Leaf (Moringa oleifera) Powder and Flakes for Microbial Safety

Abstract

Gamma irradiation is a well-accepted innovative technology. This study was carried out to evaluate the effect of different gamma irradiation doses on physical parameters, and microbial quality of export oriented Moringa powder and flakes in Sri Lanka. Homogenized Moringa samples were collected from a particular exporter. Samples were irradiated at doses of 0 kGy, 2 kGy, 4 kGy, 6 kGy, 8 kGy and 10 kGy by industrial Co-60 gamma irradiator. Under physical parameters, water activity, moisture content, colour and infusion colour (in Hunter colour scale) were measured for each of the treatment. Under microbial safety total plate count (TPC), yeast and mold count and coliform counts (total coliform, fecal coliform and E. coli) were measured. All treatments were triplicated. Average moisture content of irradiated Moringa powder and flakes were 6.32±0.04% and 6.09±0.03% respectively. Average water activity of irradiated Moringa powder was 0.41±0.00 and irradiated Moringa flakes was 0.44±0.03. Mean values of colour and infusion colour of irradiated Moringa powder and flakes were not significantly different (P<0.05) with the control sample. The average TPC in control sample of Moringa powder was 1.29×10⁷±2.46×10⁵ CFU/g and Moringa flake was 4.20×10⁵±3.71×10⁵ CFU/g, where irradiated samples show drastic reduction with the dose. The average Yeast and Mold counts in the control sample of Moringa powder was 3.11×10²±6.80×10¹ CFU/g and Moringa flake was 2.30×10²±2.06×10² CFU/g, where irradiated samples show sterilized conditions. E. coli were identified in 0 kGy and 2 kGy samples only. All irradiated samples showed significant reduction (p<0.05) of TPC, yeast and mold and coliform counts in both Moringa powder and flakes. It is concluded that the 6 KGy is better for Moringa flake and 8 kGy is better for Moringa powder for microbial safety while preserving the physical and chemical properties.

Keywords: Moringa, Gamma irradiation, Dose, Microbial safety, Quality changes