| The resource of sweet potato leaves is rich in China,but they were not sufficiently comprehensive utilization.A lot of sweet potato leaves were discarded or burned.To avoid wasting sweet potato leaves,we should open up new markets of sweet potato leaves.Firstly,the effects of temperature(0,5,10 ℃,room temperature)and PE films(0.05,0.03 mm,microporous)on the storage quality of sweet potato leaf were studied.Secondly,hot air drying,microwave drying,vacuum freeze drying and spray drying were used to prepare sweet potato leaves powder,and the effect of different drying methods on the physical characteristics,nutritional and aroma components of sweet potato powder was compared,in order to select an appropriate drying method to the prepare of sweet potato leaf powder.The main results are as follows:(1)Fresh Sweet potato leaves were packaged by three different fresh films(0.05 mm PE films,0.03 mm PE films,microporous plastic films),and stored at different temperature(0,5,10 and room temperature).The results showed that fresh sweet potato leaves under 10 ℃ ℃combined with 0.05 mm plastic packaged had the best preservation effect.It delayed degradation of chlorophyll and flavonoids,maintained a significantly lower relative conductivity and weight loss,kept good sensory quality,and extended the storage life of fresh sweet potato leaves.The nitrite content of sweet potato leaves rose at first and then went down under 5,10 and room temperature.while nitrite content of sweet potato leaves was ℃increased gradually under 0 ℃,because sweet potato leaves appeared chilling phenomenon 5 days after.(2)The effect of 4 kinds of drying methods on the quality of sweet potato leaf powder was compared,and the results showed that :1)the color of sweet potato leaf powder prepared by spray drying and vacuum freeze drying were much better;sweet potato leaf powder prepared by spray drying had a low hygroscopicity;the bulk density of sweet potato leaf powder prepared by hot air drying was the largest;median,particle size of sweet potato leaf powder prepared by vacuum freeze-drying and spray drying were smaller.2)total sugar and protein content of sweet potato leaf powder by spray drying were 218.71 mg/g and 27.85 mg/g,and they are significantly higher than that of the other three kinds of sweet potato leaf powder(P<0.05);the total phenol content and flavonoids content of sweet potato leaf powder by vacuum freeze-drying was the highest.3)The comprehensive scores of sweet potato leaf powder by hot air drying,microwave drying,vacuum freeze drying and spray drying were-0.7170,-0.2680,0.4759,0.5091 respectively.It can be seen that the quality of sweet potato leaf powder prepared by spray drying was the best,followed by vacuum freeze drying,while sweet potato leaf powder prepared by hot air drying was the worst.(3)Fresh sweet potato leaf and 4 kinds of sweet potato leaf powder were detected 82 kinds of aroma components,Which fresh sweet potato leaves,hot air drying sweet potato leaf powder,microwave drying sweet potato leaf powder,vacuum freeze drying sweet potato leaf powder,spray drying sweet potato leaf powder were 26,49,49,41,52,respectively.(4)By comparing the volatile compounds of fresh sweet potato leaves and sweet potato leaf powder,it was found that the main volatile compounds in fresh sweet potato leaves were olefins accounted for 80.75%,and the contents of l-Caryophyllene,(-)-alpha-Cubebene,(+)-Aromadendrene,beta-Chamigrene were higher;sweet potato leaf powder prepared by hot air and microwave drying had more aldehydes and ketones;Olefins of sweet potato leaf powder prepared by vacuum freeze-drying are about 64.37%,and its aroma substances are close to fresh sweet potato leaves;sweet potato leaf powder prepared by spray drying produces more alcohol substances,and 2-Isopropoxyethanol content is higher. |
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