Comparison Effects Of Electron Beam And Gamma Irradiation On Preservation Of Steamed Tofu Rolls

Steamed tofu roll is popular for its good taste, convenience and high nutritive value. Most ofsteamed tofu rolls are sold in sale with the problem of short shelf-life, which confines its commodityproperty. Consumers have to eat it within1or2days without long time storage. Food irradiation is akind of fresh keeping and processing technology which treats food or agro-products with gamma raysfrom Co-irradiator or electron beam at high energy level produced from accelerator. The main purposesof irradiation are sprout inhibition, ripening delay, decontamination, sterilization and fresh keeping.Irradiation has been widely applied on food fresh keeping. Howerver, researches and applications offood irradiation are mainly focused on gamma (GR) irradiation, there is few reports on research ofelectron beam (EB) irradiation because of limitation of device development in China. With thedevelopment of EB Technology, it is technical available to use EB on food irradiation after2010.Comparison study of EB and GR irradiation on foods is needed to make sure the advantages anddisadvantages of both radiation processings clearly.This study focuses on the comparison effects of EB and GR irradiation on decontamination,nutritive elements, sensory evaluation and physicochemical properties of steamed tofu rolls. The maincontents in details as follows:(1) Results of EB and GR irradiation on decontamination in steamed tofu rolls demonstrated thatGR irradiation yielded D10values of0.20,0.24, and0.22kGy for S. aureus, S. enteritidis, and L.innocua, respectively. The respective D10values for EB irradiation were0.31,0.35, and0.27kGy. Thisindicates that GR irradiation is more effective than EB irradiation in reducing possible pathogens insteamed tofu rolls. However, the D10value of GR and EB irradiation for Total bacterial counts (TBC)were0.48and0.43kGy, respectively, which suggests that EB irradiation has a similar positive effect onreducing TBC with GR irradiation.(2) The study compared effects of EB and GR irradiation on nutritive elements and sensoryevaluation. Results showed that EB irradiation at dose of8.8kGy or below or GR irradiation at dose of12.3kGy or below have not significant effect on nutritive and sensory quality of steamed tofu rolls.(3) Results of EB and GR irradiation on physicochemical property showed that GR irradiationwould cause more oxidation in steamed tofu rolls, compared with EB irradiatioin. EB irradiationshowed less negative effect on oxidatioin and slowed down the oxidation process caused by storage.Either EB or GR irradiation could slow down the reduction of pH value caused by storage, and keepsteamed tofu rolls fresh. EB irradiation had more positive effect on it. Neither GR nor EB irradiationhad significant effect on texture of steamed tofu rolls. GR and EB irradiation had significant effect oncolor of steamed tofu rolls, but no obvious regularity with irradiation dose.(4) Effects of different modified atomosphere packaging (MAPC) on preservation of steamed tofurolls were studied. The data showed that vacuum packaging was better than others in slowing down theoxidation speed of steamed tofu rolls which was caused by storage and irradiation.(5) A technique of irradiated steamed tofu rolls to control microflora and extend shelf-life was formed as follows: the minimum effective dose is4.5kGy, and the maximum tolerance dose is8.8kGy;when the original total bacteria counts (TBC) is lower than10~5CFU/g, then EB irradiation at4.5kGycombined with vacuum packaging can extend the shelf-life of steamed tofu rolls to at least30days.