| Mulberry leaves,as the Chinese medicine in the"immortal grass",because of its rich variety of nutrients is gradually being valued by the public,mulberry leaves as health care products to be developed business opportunities are gradually being excavated,development of mulberry leaf tea,mulberry leaf drink and mulberry leaf noodles and other green natural food.In order to make the mulberry leaves with short shelf-life can be used as food or medicine in non-fruit period,this paper studied the best technology of drying fresh mulberry leaves by hot air drying technology and closed heat-pump drying technology,Industrial production to provide a theoretical basis.In order to efficiently dry mulberry leaves on a large scale and to ensure good quality of mulberry leaves,in this paper,the best conditions for drying mulberry leaves in hot air dryer were investigated,study three factors of mulberry food drying such as temperature,wind speed and scalding time,with drying rate,the content of flavonoids and protein as the indexes.The result s of the single factor experiments showed that mulberry leaf was superior in quality at 1~3 min of scalding time,1~3 m/s of wind speed and 55~75?.Besides,the rate of a reaction varies directly as temperature and wind speed.Based on the single-factor experiment,orthogonal experiments of three factors and three factors of scald ing time,wind speed and temperature were carried out,and the content of flavonoids and protein components of mulberry leaves after drying were analyzed by direct analysis method.According to the experimental results,the temperature,wind speed and scalding time are three parallel factors of 55?,65?,75?;1 m/s,2m/s,3 m/s;1 min,2 min and 3 min.As results of orthogonal experiment,75?of temperature,3 m/s of wind speed,50g of loadcapacity were optimum technology parameter,the hot air dryer takes about 2h and comprehensive evaluation value of the index was 89.443.The factors affecting the drying of mulberry leaves,such as drying temperature,wind speed,scalding time,pretreatment positive pressure and the way of filtration water before drying,were studied by single factor experiment with the heat pump drying technique,the results show that one min of the scalding time,3000 N/m2 of positive pressure of pretreatment,the temperature is bigger and the wind speed is smaller,which is respectively the optimal process of single factor.In the single-factor selection of the influence of large scalding time,temperature and wind speed design orthogonal test,using the orthogonal comprehensive balance method analyzed the optimum process of drying fresh fresh mulberry leaves by closed heat-pump,the criteria for the determination were:the content of flavonoids in the dried mulberry leaves,the protein content,the size of rehydration ratio and the size of drying rate.The result of the orthogonal test showed that the optimal combination of parameters were:65?oftemperature,3 m/s of the wind speed,0.5 min of scaldingtime,5kg/m~2ofslice thickness and 3000 N/m~2ofpositive pressure of pretreatment,the average drying time was 6.0 h,detection the rehydration value of the dried mulberry leaves was3.54,flavonoid content was 0.56,and the drying rate was 13.49%.The comprehensive value of the indicators is 94.986.In the case of the same yield,compared to the heat pump drying,hot air drying there are shortcomings:1:not enough energy.2:O utput per unit time is small.3:poor quality. |
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