Study On The Key Processing Technology Of Spray Drying Yam Powder

Yam is rich in many nutrients and physiologically active ingredients and is of great value as a nourishing health food or commonly used medicinal material.However,fresh yam has high moisture content,is difficult to store,and is easy to deteriorate and lose nutrients.This directly affects its edible and medicinal value.Therefore,it is particularly important to apply drying technology to yam processing to prolong its storage time.In this study,fresh yam was used as experiment material to compare the characteristics of yam powder obtained by hot-air drying and spray drying two process conditions to determine an appropriate yam powder drying method,to study the appropriate addition amount of drying aids and suitable spray drying process conditions and quality stability of yam powder during storage when spray drying was used to prepare yam powder,which provided a theoretical basis and data support for spray drying yam powder.The main study contents and results are as follows:1.The selection of drying method of yam powder.(1)Study on preparation of yam powder by hot air drying: the effect of slice thickness and drying temperature on the drying characteristics of yam was studied,the rehydration rate of yam powder prepared at different drying temperatures was investigated.At the same time,the sensory evaluation was performed.It was determined that the suitable process condition for preparation of yam powder by hot air drying was: slice thickness 4mm,drying temperature 60?.(2)Preliminary study on preparation of yam powder by spray drying: the influence of soluble solids content of feed liquid and inlet temperature on the effect of spray drying was studied,the rehydration rate and moisture content of yam powder prepared at different inlet temperatures were investigated.It was initially determined that the suitable process condition for preparation of yam powder by spray drying was: soluble solids content of feed liquid 15%,inlet temperature 180?.(3)Comparison of the above two drying methods: from the three aspects of rehydration rate,taste and flavor,reconstituability and drying energy consumption to compare,the results showed that the quality of spray drying yam powder was better than the quality of hot-air drying yam powder.Therefore,spray drying is an appropriate drying method for preparing yam powder.2.The effect of the amount of drying aids added on the spray drying process of yam powder was studied.In order to improve the wall sticking phenomenon during the spray drying process of yam and increase the powder collection rate of yam powder,the effects of different addition amounts of maltodextrin,?-cyclodextrin and gum arabic on the powder collection rate and moisture content of yam powder were studied.It was determined that the appropriate addition amount of drying aids for the preparation of yam powder by spray drying was(based on the soluble solids content of feed liquid): maltodextrin 50%,?-cyclodextrin 10%,and gum arabic 1%.Under this condition,the powder collection rate of yam powder was 36.25%,and the moisture content was 5.49%.3.The study optimized the process conditions for preparation of yam powder by spray drying.In order to increase the powder collection rate of yam powder and obtain the yam powder which is easy to store,the effects of equipment inlet temperature,inlet air volume,soluble solids content of feed liquid,and feed temperature on the powder collection rate and moisture content of yam powder were studied.It was determined that the appropriate process condition for the preparation of yam powder by spray drying was: inlet temperature 180?,soluble solids content of feed liquid 16%,inlet air volume 0.5 m3 /min,and feed temperature 60?.Under this condition,the powder collection rate of yam powder was 38.69% and the moisture content was 5.31%.4.The quality stability of spray drying yam powder during storage was studied.In order to obtain the suitable storage period of spray drying yam powder,the moisture content,color parameters,polysaccharide content,protein content,and microbiological index of the vacuum-packed spray drying yam powder were measured periodically.The results showed that the physicochemical and microbiological indexes of yam powder had little change after 12 weeks of storage,indicating that the spray drying yam powder can maintain stable quality during storage.