Studies Of Irradiation Effect On Quality Of Fresh-cut Vegetables

As a non-thermal processing technology, food irradiation can not only play important role indecontamination of food, but also maintain good quality of food as well. In order to develop irradiatedfresh-cut vegetable products, the effects of irradiation technology on nutritive quality (soluble solidscontent, Vitamin C content and nitrate content), physical and chemical quality (texture, color and weightlose), decontamination effect and sensory quality of fresh-cut vegetables are studied using lettuce,balsam pear, cucumber, summer radish, color pepper, cherry tomatoes and purple cabbage asexperimental materials in this study. And the changes of fresh-cut vegetable products packaged duringstorage at4℃by different methods were also analyzed. The main results are shown below.(1) γ-irradiation could effectively decrease the contamination in fresh-cut vegetables. To reducethe TBC of fresh-cut vegetables, the D10value of TBC in fresh-cut lettuce, balsam pear, cucumber,summer radish, color pepper, cherry tomatoes, purple cabbage were measured as0.30,0.27,0.31,0.33,0.40,0.36and0.40kGy, respectively. To decrease the risk of potential pathogens in fresh-cut vegetables,the D10value of Salmonella enteritidis in fresh-cut balsam pear, lettuce, color pepper were0.24,0.22and0.22kGy, respectively. The D10value of Listeria innocua in fresh-cut balsam pear, lettuce, colorpepper were0.22,0.20and0.21kGy. Based on hygienic standard of irradiatied fresh-cut vegetablesafter storage6days, it was summaried that the minimum effective dose of mixed vegetable salad is0.52kGy.(2) γ-irradiation on physical and chemical of fresh-cut vegetables showed difference with theincrease of irradiation dose. There were no significant difference (5%level) between the experimentalgroup and control group on color and weight lose at the dose lower than2.32kGy during8d storage,while the marked differences on texture between the treated samples and the control was observed at thedose of2.22～2.32kGy.(3) γ-irradiation on nutritive elements and sensory evaluation were also different. The detaillustrated that with the treated doses below2.32kGy, the differences (5%level) between the treatedsamples and the control on soluble solids content and nitrate content were not noticeable. In addition,the effects of irradiation to fresh-cut vegetable in sensory characteristic including color, odour, texture,taste and totally acceptability were not significant at the dose below2.32kGy. However, it should bepointed out that the content of vitamin C in fresh-cut vegetables was reduced by irradiation at abovementioned dose. It was summarized from parts (2) and (3) that the maximum tolerance dose of mixedvegetable salad is1.81kGy.(4) Different packaging methods (ordinary packaging, vacuum packaging, plastic box packagingand simple modified atmosphere packaging) on fresh keeping of fresh-cut vegetables were studied.Consideration of the changes of nutrition indicators, physical and chemical indicators, microbiologicalindicators and sensory quality of fresh-cut vegetables, simple modified atmosphere packaging showed abetter storage effects than others.(5) A processing procedure of fresh-cut vegetables salad was developed: selection of the varieties of vegetables, classification, cleaning, segmentation, dehydration, packaging and irradiation.Confirmation experiments show that irradiation at1.38kGy, combined with simple modified atmospherepackaging can extended the shelf-life of fresh-cut vegetables at least6days at the condition of originaltotal bacteria counts (TBC) less or equal to105cfu/g.It is concluded that food irradiation could apply on the preservation of fresh-cut vegetables, canensure the safety and prolong the shelf life at the same time. Irradiation treatment of fresh-cutvegetables can also meet the demand of special groups such as diabetes who have strict hygienerequirements on food.