Study On Controlled Freezing-Point Storagetechnology Of Bamboo Shoots

Bamboo shoots are rich in nutritional value with high protein,low fat and high dietary fiber,often referred to as natural and health food.Although China is rich in bamboo resources,bamboo shoots in postharvest are still living and constantly carrying out various life activities,such as water loss and lignifications.These changes will cause the bamboo shoots to lose their value and limit the development of bamboo shoots processing industry.In addition,traditional bamboo shoots preservation methods such as smoked sulfur,preservatives,not only cause serious loss of nutrients,but also leave chemical substances.On the contrary fruits and vegetables can keep the original flavor and fresh and keep friendly to the human body and the environment through the controlled freezing-point storageThis paper,which used Dendrocalamuslatiflorus bamboo shoots as main raw material,studied on freezing point temperature of bamboo shoots and the effects of different freezing point regulators and soaking time.And the test also compared the effects of different storage temperatures on respiration intensity,soluble Protein content,vitamin C content,lignin and cellulose content and enzyme activity.On this basis,the effects of konjac glucomannan(KGM)coating on the freshness of bamboo shoots with controlled freezing-point storage were studied.It would provide some theoretical basis and technical references for preservation techniques of bamboo shoots.The main results were as follows:1.The freezing point of bamboo shoots at different parts was determined and the influence of different freezing point regulator on bamboo shoots was measured in this paper.The results showed that: The freezing point of bottom of bamboo shoots was-0.8? and other parts were-0.7?.Sodium chloride was a best freezing point regulator,when bamboo shoots was processed with 3%sodium chloride 30 min,the freezing point of bamboo shoots was decreased from-0.7? to-1.1?.There was a good negative correlation between the freezing point of bamboo shoots and the content of soluble solids,and the linear regression equation was y = 0.195x-18.84,R2 = 0.989;There wasa positive correlation between the freezing point and the water content of the bamboo shoots,and the linear regression equation was y =-0.333 x + 1.117,R2 = 0.987.2.This study was about the influence on bamboo shoots quality during the controlled freezing-point storage.The results showed that,weight loss,cellulose and lignin content of bamboo shoots continued to rise,but water content,vitamin C content and soluble protein content continued to decline during the storage.The arrival time of the peak of respiration of the bamboo shoots reached on the 10 th day in the cold storage group.But it will be postponed for 5 days in controlled freezing-point storage and the maximum peak value was significantly lower than cold storage group.The activities of PPO enzyme and PAL enzyme showed the three-step change “up-down-up”.POD enzyme activities showed "mountain type" change trends.Obviously,the activities of three enzymes stored under controlled freezing-point were always lower than those of cold storage.And the arrival of the highest peak of the PAL enzyme and POD enzyme will be postponed 5 days.After storage for 15 days,the cold storage groups of bamboo shoots were not edible.But the controlled freezing-point storage can extend shelf life to20 days.Therefore,the results of this study indicate that the controlled freezing-point storage can significantly inhibit the respiration and lignification and delay the aging of bamboo shoots.3.This study was about the effect on bamboo shoots by cold acclimation treatment during the controlled freezing-point storage.The results showed that,compared without any treatment before the controlled freezing-point storage,the experiment of cold acclimation can reduce respiration and weight loss,inhibit the synthesis of cellulose and lignin of bamboo shoots.Although the changes of the three enzyme activities are the same,the activities of cold acclimation treatment groups were always lower than without any treatment groups.On the 25 day of storage,the cellulose and lignin contents of bamboo shoots treated with cold acclimation were 84.46%and 80.10% of the untreated group.There was no significant difference in vitamin C and soluble protein content between the two treatment groups.Therefore,the results of this study indicate that cold acclimation treatment before the controlled freezing-point storage can maintain the better quality of bamboo shoots.Through this method,the bamboo shoots have better sensory qualities,only a slight loss of water and maintain fragrant and edible.4.This study was about the effect of KGM coating treatments on bamboo shoots during the controlled freezing-point storage.The results showed that,KGM coatingtreatments on bamboo shoots can extend shelf life to 25 days.Water content,vitamin C and soluble protein content were high through the coating treatment after storage for 25 days.Obviously compared to single controlled freezing-point storage,KGM coating can make up for the disadvantages of poor nutrition contents and improve storage qualities of bamboo shoots.Therefore the results of this study indicate that 0.6% KGM coating can inhibit respiratory rate,reduce weight loss,delay the accumulation of cellulose and lignin and obtain the highest score of sensory evaluation of bamboo shoots.In summary,KGM coating a good way to keep fresh quality of bamboo shoots during the controlled freezing-point storage.