Reduction of Bioburden by Optimizing Gamma Dose for Enhancing Export Value of Pakistani Peaches

Master's Thesis from the year 2014 in the subject Chemistry - Bio-chemistry, grade: A, , course: Biotechnology, language: English, abstract: Peach is the most commonly eaten stone fruit which grows in the temperate regions ofthe world. These are also among the most exported fruits in term of volume and value.Peaches, being perishable and susceptible to microbial spoilage, have a short shelflife.The goal of this study was to determine the effect of gamma irradiation on themicrobiological and organoleptic properties of peaches and secondly, to determine theeffects of irradiation on shelf-life of the fruit. The fruit (local variety, No.4), at propermaturity stage was collected and irradiated with 0.25, 0.5, and 0.75kGy dose, storedunder refrigerated (4oC) conditions for a period of three weeks. Total viable count,Gram negative Enterobacteriaceae count, Salmonella-Shigella count, yeast and moldcount, loss in weight and decay percentage was evaluated after 7, 14 and 21 days ofstorage (4oC). Data obtained from microbiological and sensory evaluations ofirradiated peaches was compared with the observations obtained from unirradiated(control) samples. Microbial evaluation of the fruits revealed the presence ofSalmonella sonnie on SS agar and non fermentor spp. on macConkey agar. Ten typesof yeasts were isolated on potato dextrose agar and analyzed microscopically. Studiesshowed total bacterial, yeast and molds significantly decreased with increasing doselevel. The sensory evaluation of the fruits revealed that irradiation preserves thetexture and appearance of fruit. The gamma-irradiation dose of 0.75kGy proved to beeffective in reducing weight loss and significantly (p=0.05) delaying the decaying ofthe fruit by 7 days under refrigerated (4oC) conditions. Statistical studies were carriedout using Duncan's multiple range test (DMRT) and means were separated by LSD at5 %. It is hoped that this particular type of research will help in improving exportquality of peaches.