Preparation Of Instant Fresh-leaf Powder Of Dendrobium Huoshanensis By Spray Drying

Dendrobium huoshanensis is one of the most precious herbs in Dendrobium.Dendrobium huoshanensis leaves are rich in polysaccharides and have high nutritional value,but their utilization is too low and most of them are abandoned,resulting in waste of resources.The fresh leaves of Dendrobium have high moisture content,which is not conducive to preservation and storage.In this paper,the polysaccharide extracted from leaves of Dendrobium huoshanensis was extracted and were analyzed by Near Infrared Spectrometry(NIR).This paper takes the fresh leaves of Dendrobium huoshanensis as raw materials,and uses spray drying technology as the means to determine the kinds and proportions of the additives.Through single factor and response surface tests,the indexes of instant powder under different technological conditions were compared to determine the optimum technological conditions for spray drying,and The volatile components of instant powder were analyzed by GC-MS.Based on the study of small lab scale teast,pilot-teast was carried out.The results are as follows:1.The crude polysaccharides extracted from Dendrobium leaves by water-soluble alcohol precipitation were analyzed by NIR.According to the infrared absorption peak,it can be judged that the crude polysaccharides from Dendrobium leaves are pyran-type mannoside acid heteropolysaccharides.2.The effects of maltodextrin,?-cyclodextrin and Arabic gum on sensory quality,moisture content,product yield and dissolution time of instant powder were studied.It was concluded that 30%maltodextrin could significantly improve the sensory quality of instant powder,with a score of 80.7,a moisture content of 3.54%,a yield of 23.1%and a dissolution time of 62 s.3.On the basis of single factor experiment,the response surface test was conducted on three factors including inlet air temperature,feed flow rate and inlet air flow rate.The sensory quality,water content and product yield of instant powder were used as the response index.The optimum parameters of spray drying were determined as inlet air temperature was 148?,feed flow was 26 mL/min and inlet air flow was 36 m3/h.The yield was 20.15%,the sensory value was 82.51,and the moisture content was 3.32%.4.By comparing the antioxidant ability of instant powder prepared at different inlet temperatures,it is concluded that the scavenging ability of instant powder to DPPH,ABTS+,hydroxyl radicals decreases gradually with the increase of inlet temperature in transverse comparison,and the antioxidant ability of instant powder prepared at each inlet temperature increases with the increase of concentration in longitudinal comparison.But they were all smaller than ascorbic acid control group.5.The volatile components of instant powder were analyzed by SPME and GC-MS.A total of 48 compounds were detected in the volatile components of instant powder.Among them,2-hexenal and linalool were the main volatile components.6.Based on the results of the small lab scale test,in the pilot-test,the sensory score of the instant powder was 85.49;the powder properties and moisture content were basically consistent with small lab scale test;the polysaccharide content was 221.83 mg/g,slightly higher than that of small lab scale test.The pilot-test shows that the production of instant powder has a certain stability and high feasibility.