Research On Drying Technology Of Basswood Tongjiang Tremella Fuciformis And Characteristics Of Polysaccharide From Tremella Fuciformis

China is one of the major producing and exporting countries of Tremella fuciformis.There are two main different cultivation patterns of Tremella fuciformis,namely-wooden cultivation and substitute cultivation,with the main producing areas of Sichuan Tongjiang and Fujian Gutian,respectively.Due to high moisture content（> 80%）in Fresh Tremella fuciformis,in the storage period there is microbial corruption,and is easy to suffer spoilage.The production of substitute cultivated Tremella fuciformis（STF）accounted for over 90% of the total production in China.Currently,much of the attention has been focused on the drying technology for STF while little is on basswood Tongjiang Tremella fuciformis（BTF）.The appearance of BTF is smaller and more irregular,the moisture content is higher than STF.Therefore,the drying technology of BTF is urgent need for research.In addition,there are many researches concerning about the characteristics polysaccharides of substitute cultivated Tremella.No reports highlights differences between the BTF and STF.It was necessary to explore the quality difference between two kinds of Tremella,to provide scientific basis for the development of Tremella industry.To choose a suitable dehydration technology of BTF for better storage and transport,Six different drying methods involving hot-air constant/variable temperature drying,microwave drying,freeze drying,microwave-hot-air drying and freeze-hot-air drying were applied to Tremella fuciformis dehydrated products（TFDP）.Coefficient of variation weight methods was used to assess TFDP quality with factors including sensory quality（full marks 10 points）,Rehydration rate,shrink rate,browning degree and unit energy consumption.The quality and the biological activity of TFDP was investigated.For the purpose of scientific assessment of the characteristics of Tremella,this paper compared and analyzed the main nutrients（content of the ash,crude protein,crude polysaccharides,fat,Ca,K,Na,Fe,Mg,Zn）,the sensory quality（chromatic aberration and texture）and Fourier transform infrared spectroscopy（FTIP）of Tremella fuciformis.Meanwhile,we studied the physico-chemical characteristics of polysaccharides respectively with alkaline extraction,acid extraction and aqueous extraction.The indices of polysaccharides including the content of uronic acid and sulfate anion,the range of molecules,the monosaccharide compositions,viscosity,solubility and the FTIP were measured and analyzed by descriptive statistics and correlation analysis.Principal component analysis was employed to build a composite score mathematical model,and then the composite scores were analyzed by K-means cluster and linear discriminant analysis.Results of the specific research were as follows:1.Drying Method of BTF: The highest comprehensive scored method was hot-air drying with gradient temperature from 50 ℃ to 40 ℃,the sensory quality,rehydration rate,shrink rate,browning degree,and unit energy consumption of products were 8.52,9.04,27.87 %,0.313 and 34.5 KJ/g,respectively.The content of polysaccharide and polyphenol were 9.81±0.29% and 0.51±0.03%,respectively.The IC50 value of DPPH（1,1-diphenyl-2-picrylhydrazyl）radical,Hydroxyl radical,superoxide anion were 18.32±0.15 mg/mL,1.91±0.10 mg/mL,4.35±0.15 mg/mL,respectively.Reducing power（A700）was 0.521±0.003.Overall,the most optimal drying method was hot-air gradient temperature drying whose product qualities were similar to that of freeze-hot-air drying,while the cost is lower and easier to operate,the savings ratio of invalid energy consumption was 20%.It is a kind of method that can be intensively studied and worthy of popularization.2.In vitro antioxidant capacity of Tremella: different drying methods have significant influences on in vitro antioxidant capacity of Tremella and the contents of polysaccharides and polyphenols（p < 0.05）.When the drying temperature was higher,the time for drying was longer,and the antioxidant capacity of Tremella would be poorer,and the contents of polysaccharides and polyphenols in Tremella would be lower.Meanwhile,research found that in the Tremella,the scavenging abilities of DPPH radical and the reducing power were relatively poor,and the scavenging abilities of Hydroxyl and superoxide anion radicals were strong.Correlation analysis showed that,the content of polysaccharides in Tremella was significantly related（p < 0.05）to four antioxidant indexes（the scavenging abilities of DPPH,Hydroxyl and superoxide anion radicals and reducing power）,and the content of polyphenols was significantly related（p < 0.05）to three antioxidant indexes（the scavenging abilities of Hydroxyl and superoxide anion radicals and reducing power）.Before and after drying,the content of polysaccharides was correlated significantly with that of polyphenols,and every antioxidant index was related to each other（p < 0.05）.3.Comparison of physicochemical property between BTF and STF: there were obvious differences in the main nutrients（content of ash,crude protein,fat,Ca、K、Na、Fe、Zn）and sensory quality of Tremella fuciforms,while no significant differences in polysaccharide content and Fourier infrared spectrogram were detected between BTF and STF.4.Characteristics of polysaccharides from BTF and STF: the polysaccharides of Tremella were mostly acidic heteropolysaccharides with mannose as the main chain,xylose and glucuronic acid as the branched chain.The polysaccharides extraction conditions had significant influence on the physico-chemical characteristics of the Tremella.Under the same extraction conditions,there is no significant difference in physico-chemical characteristics of the polysaccharides between BTF and STF,and the antioxidant capacity of the Tremella polysaccharides was in the following order: alkaline extraction and acid extraction>aqueous extraction.After the description of differences on polysaccharides through the methods of principal component analysis,K-means cluster and linear discriminant analysis,it can be seen that,under the condition that the cultivation method of polysaccharide was known,only 50% of BTF and STF could be classified correctly,that is,the difference in the physico-chemical characteristics of polysaccharides between BTF and STF is not obvious.100% of the Tremella polysaccharides obtained by different extractions could be classified correctly,which suggested that the difference in the physico-chemical characteristics of the polysaccharides through different extractions be obvious.The main discriminant region of FTIP is 400⁹50cm^-1,through which polysaccharides of BTF by alkaline extraction can be quickly distinguished from polysaccharides of STF by alkaline extraction.In general,although there were obvious differences in sensory quality and contents of nutrition between BTF and STF,there was basically no significant differences in the major functional components——the characteristics of polysaccharides.