Study On The Technology And Effects Of Vacuum Osmotic Dehydration Process On The Quality Of Canned Yam

Yams(Dioscorea opposite Thunb)is the traditional Chinese medicine and food resources which is rich in nutrition and has many health functions.The development of the yamindustry is severely hindered due to the fixed harvest period and the shorter storage period of yam.The canned processing,an important way of processing and utilizing yam,will not only enable its nutritional value to be preserved but also make it convenient to carry and eat.However,due to the high starch content,brittle texture,susceptible to browning stains and other factors,the canned yam is prone to quality problems,such as turbid soup,discoloration and more.Appropriate pretreatment of yamraw materials play a decisive role in ensuring the quality of the canned Chinese yam.Vacuum osmosis dehydration can improve the dehydration rate,shorten the dehydration time,and retain the nutrients of the material effectively.In this study,the requirements of the vacuum osmotic dehydration process were studied,the process parameters were optimized,and the effects of it on the quality of canned yam were explored with the Tiegun yam as the raw material.The feasibility of pretreating samples of canned yam with the vacuum osmotic dehydration process was demonstrated by comparing it with the conventional blanching treatment.The results are as follows:(1)Through single factor and response surface experiments,the fructose syrup was determined as the permeate for osmotic dehydration of yam.The optimal process conditions for vacuum osmotic dehydration of yam were 1.5 cm slice thickness,solid-liquid ratio 1:10permeate concentration 46%,treated at 45?for 5 h.(2)Compared with untreated,hot blanching treatment could cause the hardness of yam to decline and the loss of nutrients,while infiltration treatment could better maintain the hardness and nutrients of yam.Scanning electron microscopy showed that the hot blanching treatment had great damage to the tissue structure of yam,starch granules were gelatinized,and the outer layer of the infiltrated yam starch granules was wrapped by sugar solution,so the pores became smaller and the structure became more compact.(3)Three kinds of pretreatment methods(blanching,osmotic treatment at constant pressure and vacuum osmotic treatment)had different effects on the texture of the cannedyam,among which the vacuum osmotic dehydration treatment performs better in maintaining the integrity of the structure of the canned yam.The contents of flavone,polyphenol and soluble solids would decline at the beginning of storage until they were balanced after a period of time.Canned food processing would lead to the great loss of allantoin content in the yam.The three pretreatment methods,however,had no significant impact on the allantoin content in the canned yam.It could be concluded by the sensory evaluation of the canned yam pretreated by the three kinds of methods that the one pretreated with vacuum osmotic dehydration for 4h had the best sensory quality.