Effect of Gamma Irradiation on the Bacteriological, Sensory and Physicochemical Qualities of Peanut Butter

Aims: This study investigated the effect of gamma irradiation on the bacteriological and sensory qualities as well as some physicochemical properties of peanut butter irradiated at different doses.

Methodology: Peanut butter samples were pre-packaged and sealed in plastic jars with each jar containing 500 g of peanut butter. The samples were exposed to 0, 2, 3, 4 and 5 kGy absorbed doses of gamma radiation and bacteriological, sensory and physicochemical qualities were evaluated.

Results: The TVC of the irradiated peanut butter ranged between 3.33 and 2.0 cfu/g and Staphylococcus aureus count ranged between 2.63 cfu/g to below detection limit. A dose of 2 kGy resulted in a 0.93 log reduction whilst maximum dose of 5 kGy used resulted in a 1.33 log reduction in the total viable counts of the irradiated samples. E. coli and Salmonella sp were not detected in both the irradiated and unirradiated peanut butter. No significant effect was observed in the sensory properties of the irradiated peanut butter. Peroxide value (PV) and Malonialdehyde (MDA) content were observed to range between 42.00±2.83-44.00±0.00 (meq/kg) and 6.89 x 10-7 ± 2.26x10-8 -1.12x10-6±5.44x10-8(M) respectively.

Conclusion: The MDA concentration increased significantly with increasing dose though no significant differences were observed between the measured values for doses of 2 and 3 kGy as well as 4 and 5 kGy. Gamma irradiation proved effective in reducing microbial load in the peanut butter without significantly affecting the sensory attributes as well as the peroxide value.