Browsing by Author "Rathnayake, R.M.N.P."

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    Effect of Gamma Irradiation on Histamine Content of Yellowfin Tuna (Thunnus albacares) Fish Muscle
    (Uva Wellassa University of Sri Lanka, 2018) Surendra, I.H.W.; Edirisinghe, E.M.R.K.B.; Rathnayake, R.M.N.P.
    Food irradiation is a process that has proven to be successful, due to its high effectiveness in inactivating pathogens without deteriorating product quality. Histamine is a causative agent for scombroid foodborne poisoning which effects on the quality of fish products. Therefore present study was conducted to evaluate the effect of gamma irradiation on histamine content in Yellowfin tuna fish fillets. Fish flesh was treated by Co-60 source at doses of 1, 3, 5, 7 and 10 kGy. Initial determinations were made just after irradiation and second determinations were made after storing control and irradiated samples for 24 hours at room temperature (30 °C). The concentration of histamine was detected by using High Performance Liquid Chromatography (HPLC) method. Total bacterial count (TPC) was performed according to the ISO 4833:2003 standard. The highest increment was detected in control sample after 24 hours of storage period and rate of increment of histamine is 9.97%. After 24 hours of storage, irradiated samples showed 2.40, 2.00, 3.00, 8.69 and 7.31% of increment in histamine at 1, 3, 5, 7 and 10 kGy irradiations respectively. However, no any significant difference found between any treatments. As revealed by results of TPC, highest amounts were found in control samples (3.03 x 105 cfu/g initially and 1.44 x 108 cfu/g after 24 hours storage period). In spite of increment in bacterial count in 1 kGy irradiated sample (7.4 x 105 cfu/g), all other samples were not exceeded the maximum level of acceptance in bacterial count (5 x 105 cfu/g) either after 24 hours of storage. The TPC results showed significant reduction after irradiation and within the storage time respect to the control. The results revealed that the low dose (3 kGy) irradiation can implement for the better safety of Yellowfin tuna fish fillets according to the changes in the histamine content and bacterial count.
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    Impact of Gamma Irradiation on Control of Microorganisms in Export Oriented Moringa (Moringa oleifera) Powder and Flakes
    (Uva Wellassa University of Sri Lanka, 2019) Karunanayake, K.M.S.P.L.; Rathnayake, R.M.N.P.; Ranasinghe, R.D.R.; Wijesinghe, W.A.J.P.
    Moringa (Moringa oliefera) has a growing demand in export market mainly due to its health benefits. The study was carried out to evaluate the effect of different gamma irradiation doses to 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 at dose rate 5.3 Gy min-1. Under physical parameters, water activity, moisture content, color and infusion color (∆E value based on L*, a*, b* in Hunter color scale) were measured for each of the treatment. Under microbial safety, total plate count, yeast and mold count and coliform counts were done. All treatments were replicated in three times. 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 color and infusion color of irradiated Moringa powder and flakes were not significantly different (P<0.05) with the control sample. The average total plate count in control sample of powder was 1.29×107±2.47×105 CFU g-1 and flake was 4.5×105±3.71×105 CFU g-1, both irradiated Moringa samples showed significant reduction in dose dependent manner. No Yeast and Mold counts were observed in all the treated samples. Escherichia coli were identified in 0 kGy and 2 kGy samples only. It is concluded that the 6 KGy was better for Moringa flake and 8 kGy was better for Moringa powder for microbial safety, while preserving the physical quality.