EFFECT OF GAMMA RADIATION ON AFLATOXIN LOAD, AMINO ACID AND FATTY ACID COMPOSITION OF ORYZA SATIVA L.

Abstract

Crops which are stored for more than a few days become a potential target for mould growth and mycotoxin formation by the species Aspergillus. The present study investigated an effective extraction, clean up and analysis methodology for aflatoxins, amino acids and fatty acid methyl esters (FAME) in rice (Oryza sativa L) samples collected from Faisalabad Division, Pakistan The extraction solvent (acetonitrile & water) gave ≥ 85% recovery in spiked cereal samples using a MycoSep-226 column. The sensitivity (LOD) of HPLC (FLD) was higher as compared to HPLC UV/Vis after derivatization of sample extract with trifluoroacetic acid (TFA). After treatment with γ-irradiation (0, 2, 4, 6 kGy), more than 95% reduction in AFB1 was observed in the samples. Effectiveness of γ-irradiation in rice samples contaminated with high concentrations of aflatoxin (AFB1) and total aflatoxins produced by Aspergillus flavus and Aspergillus parasiticus was significantly (p<0.05) dependant on radiation dose. Initial fungal population of rice samples was evaluated at 2.4 x 106 CFU g-1 while maximum reduction percentage was observed at radiation dose 6 kGy (6.4 CFU g-1) when compared to the control sample. Amino acid profiles remained predominantly unchanged except for an increase (p<0.05) in leucine at 4 kGy. Rice fat, after irradiation, showed minor changes in the composition of fatty acid methyl esters. Effect of dose on palmitic (16:0), stearic (18:0), linoleic (18:2), linolenic (18:3) and arachidic (20:0) acids was statistically non significant whereas, olenic acid showed a significant change in concentration. The results indicate that γ-irradiation is a good technique for removing contaminants such as aflatoxins from cereal commodities. The total biomass (CFU/g) showed linear behaviour as dose level of gamma irradiation was increased.