Study On Processing Technology Of Fresh-cut Chinese Yam And Its Keeping Quality

In recent years, with the raising of living standard and accelerating of life rhythm, fresh-cut fruits and vegetables have gotten more and more consumers’ interests thanks to its advantages of freshness, health, nutrition, convenience and so on. However, the processings such as peeling and cutting destroyed the membrane integrity which enhanced the respiratory and metabolism and resulted in nutritional lose, microorganism and storage periods shortened, then the development of fresh-cut fruits and vegetables would be directly affected. Effects of heat treatment before processing, different concentrations of chlorine dioxide, different formulations of browning inhibitor, different concentrations of Nisin,different packaging materials,different storage temperatures on storage quality and physiological and biochemical changes of the fresh-cut Chinese yam were studied in this research, the nutritional components and safety factors of fresh-cut Chinese yam were also analyzed and evaluated. Finally, the hazard analysis critical control point of was established. It could provide the technical support and theoretical basis for processing and storage techniques of fresh-cut Chinese yam. The results showed that:1. Heat treatment before processing could obviously inhibit the browning and increasing of total phenolic content, reduce the respiration intensity, keep low weight loss rate and a better quality, the shelf life was prolonged as well. The polyphenol oxidase (PPO) activity of the heat treatment group was higher than that in the control group, maybe the heat treatment increase the polyphenol oxidase (PPO) activity. Effects of preservation were different in various temperatures, heat treatment with40℃for30minutes had a good effect as well as40℃for30minutes, the differences between them were not significant. Therefore,40℃for30minutes was the suitable heat treatment condition before the yam was processed.2. ClO2solution had significant germicidal efficacy in fresh-cut Chinese yam, and in certain scope, the sterilization action was enhanced when its concentration increased.60mg/L ClO2and100mg/L ClO2had better affect and the differences between them were not significant. The results also showed that, the increasing of weight loss rate and total phenolic content was inhibited as well as PPO activity, the browning was delayed, L value was kept in a high level, and finally the shelf life was prolonged. Considering the economic cost and security, we confirmed that60mg/L ClO2was the most appropriate sanitizers in the process of fresh-cut Chinese yam. 3. The fresh-cut Chinese yam was treated by calcium lactate, L-cysteine, potassium sorbet and sodium chloride under different concentrations which made six different kinds of combinations. The optimized concentration of browning inhibitor was screened out by the uniform design in this study, and the result was:0.11%calcium lactate+0.49%L-cysteine+0.08%potassium sorbate+0.07%sodium chloride.4. Nisin had certain germicidal efficacy in fresh-cut Chinese yam, and in certain scope, the sterilization action was enhanced when its concentration increased.0.02%Nisin and0.03%Nisin had better affect, the differences between them were not significant. The results also showed that, the weight loss rate and total phenolic content were reduced as well as PPO activity, the browning and L value falls were delayed, and finally the shelf life was prolonged. But taken together the differences between0.02%Nisin and0.03%Nisin were not significant, considering the high price of Nisin and food safety,0.02%Nisin can be used in the process of fresh-cut Chinese yam.5. Packing materials to the effects of the fresh cut Chinese yam quality were significant during the storage period. Compared with the control, the vacuum package and konjak package could effectively inhibit the decreasing of L value and the browning as well as extend the shelf life of fresh-cut Chinese yam. The respiration intensity of fresh-cut Chinese yam with vacuum-packed had been in sharp rising, later sent out a very strong alcohol flavor. Although the surface color had no big change, but the weight loss of the konjak-packed one was so serious that caused the surface shrink which made its commodity value greatly abate. Therefore, this study confirmed that the vacuum package was the most appropriate packing method of the fresh-cut Chinese yam.6. Storage at low temperature not only restrained the respiratory intensity and the weight loss effectively, but also inhibited the polyphenol oxidase (PPO) activity and the increasing of total phenolic content, delayed the browning and L value fall, and extended the shelf life of the fresh-cut Chinese yam. The fresh-cut Chinese yam which storied at10℃had the worst preservation effect, it showed a deep snuff color and lost the commodity value and edible value on the tenth day. Storied at4℃on the tenth day the fresh-cut Chinese yam had only slight discoloration. However the fresh-cut Chinese yam which was storied at0℃almost were kept in white and no brown during the storage period, had the best preservation effect.Considering the practical commodity period and energy-saving, we confirmed4℃was the most appropriate storage temperature of the fresh-cut Chinese yam in the actual production.7. The fresh-cut Chinese yam products were rich in starch,polysaccharide,protein, total soluble sugar, crude fiber, crude fat, total phenolic, vitamin C, vitamin B1, vitamin B2and vitamin E etc, they also contained abundant amino acids types and high amino acids, arginine which was the essential amino acids to infant had the hightest content. In addition, the fresh-cut Chinese yam products still contained quite abundant minerals and trace elements.Furthermore the contents of total bacteria amount, E. coli and pathogenic bacteria of the fresh-cut Chinese yam were all in the food health range through inspecting the microbiology indexes.8. The application of HACCP to process of fresh-cut Chinese yam was investigated in this study. There were five critical control points in the process of fresh-cut Chinese yam, including the acceptance of raw materials, peeling and cutting, sterilization and rinsing, weighing and packing, storage, transportation, distribution and sales.