Study On Whole Cold-chain And Preservation Technology Of Postharvest Sweet Corn

With the property of high sugar and water content,rich in vitamins and amino acids,and having fresh,crisp,and unique flavor fruit,sweet corn(Gramineae and Zea mays L.)has become one of the popular vegetables.However,due to strong production of seasonal,listed concentration,not resistant to storage,maturation and ageing accelerated by postharvest respiration rate and metabolism,and water loss wilting and serious nutrient loss caused by high temperature,the shelf-life of sweet corn is always very short,such as only 2 days at room temperature.Now,most of the researches reported on refreshing sweet corn always focus on the section of precooling and storage,ingoring the research on the entire cold chain of postharvest sweet corn.So,on the basis of investigating the effects of temperature on the quality of sweet corn,this report examined the effect of different methods,such as precooling,storage,transportation and sales,on the quality of sweet corn,aiming to provide theoretical basis and technical reference for sweet corn fresh-keeping and cold chain logistics.The results of this study are as follows:1.Study on precooling method of postharvest sweet cornBy investigating the effect of ice water cooling,force-air cooling,room cooling on precooling rate,weight loss and nutritional quality of sweet corn by packaging sweet corn in plastic case at 0?,it showed that the corn temperatures of sweet corn by ice water cooling,force-air cooling and room cooling were decreased from initial 28.2? to 3?,and the precooling time were 140,180 and 370 min,respectively.Moreover,weight loss rates of force-air cooling and room cooling were 1.47%and 1.69%,respectively.However,due to short precooling time,no weigh loss,and less nutrient loss,the performance of ice water cooling was better than that offorce-air cooling and room cooling.2.Study of the effect of storage temperature on respiration rate and quality of sweet cornBy examining storage temperature in the range of 0-30?,on the respiration rate and quality of sweet corn,it found that sugar content of sweet corn was higher and the weight loss rate was low under 0? and the respiration rate was inhibited effectively,delaying the postharvest mature and aging,keeping the original quality better,and thus prolonging last period and shelf-life of sweet corn.Comprehensive consideration,the best storage temperature of sweet corn was 0?.3.Study of the effect of different film packages on physiological and biochemical indicators of sweet cornBy examining the effect of different package methods,such as with different kinds of plastic films(0.03mmPE film and microporous film)and without plastic film,on nutrient quality,antioxidant enzymes activity of sweet corn at(0±0.5)?,it could been seen that weight loss rate of sweet corn packaged by film were below 5%,which could retard the decrease of soluble sugar content and other nutrient contents and thus maintain the sweetness and taste.Although the difference of weight loss rate was not obvious between 0.03mmPE fliim and microporous film,sweet corn in microporous film was better than that in 0.03mm PE flim.After 18 days,the sensory evaluations of sweet corn in microporous film and 0.03mmPE flim were 6.4 points and 5.7 points,respectively,still having the commodity value.However,CK had lost its commodity value.So,microporous film has the best property of keeping fresh sweet corn and extending last period effectively.4.Study on simulation of different transportation methods of sweet cornSweet corns were transported when the core temperatures of sweet corns dropped to about 0? by forced-air cooling,using polystyrene foam box packaging and cooler box under normal temperature,polystyrene foam box packaging and microporous film with carton box packaging under 0? to simulate four transportations.The effects on quality of sweet corn were studied.The results showed that the weight loss rates of sweet corns which were transported by using polystyrene foam box and cooler box under normal temperature after 3 days were 2.18%and 1.44%,respectively,and sensory evaluations were 5.3 points and 6.4 points,respectively.And the core temperatures of sweet corns increased from 0? to near ambient temperature 20.8?after 21 hours and 30 hours,respectively.Cooler box could effectively prolong 9 hours.With microporous film with carton and polystyrene foam box packaging under 0? transportation,the weight loss rates of sweet corns after 12 days were 1.75%and 2.26%,respectively.And sensory evaluations were 5.9 points and 5.3 points,respectively.Microporous film with carton box under 0? transportation of sweet corn was best,which reduced total soluble solids,soluble sugar,Vc,soluble protein and other nutritional quality loss and improved the commodity value.5.Study on simulation of different retail methods of sweet cornThe effects of 1 day transportation with polystyrene foam box packaging and microporous film with carton box packaging at 0?,2 days retailing packaged with and without stretch polyvinylchloride(PVC)film in 4 and 20? on the quality of sweet corn were studied.The results showed that sweet corn with PVC film packaging had lower weight loss rate and nutrient quality losses either in 4? or 20?,making appearance moist,fresh and attractive to consumers.In the four retailing methods,the property of sweet corn packaged with PVC film at 4? was best,having the minimum weight loss rate,soluble solids,soluble sugar,Vc and soluble protein content losses and highest sensory evaluation score.