Effects of low-temperature impact milling treatment on the properties of Tremella fuciformis and its polysaccharides

【Objective】To investigate the effects of low-temperature impact milling on the properties of Tremella fuciformis powders and T. fuciformis polysaccharides（TFP），with a view to providing theoretical basis for the deep processing of T. fuciformis powders and the extraction of active ingredients.【Method】Different classifier frequencies（10，20，30 and 40 Hz）of the low-temperature impact mill were used to crush the dried T. fuciformis，and TFP were obtained by water extraction and alcohol precipitation method. The basic nutrients，physical properties of different T. fuciformis powders and the basic physicochemical properties，rheological properties and structure of TFP were determined to investigate the effects of classifier frequency on T. fuciformis powders and TFP.【Result】As the frequency of the classifier increased，the moisture content（10.41%-12.18%）of T. fuciformis powders gradually decreased，while there was no significant difference in protein and ash contents（P>0.05）；the color of T. fuciformis powders gradually changed from yellow to white， which showed an increase in the L^* value，and decrease in the a^* and b^* values. The average particle size D₅₀（47.7-389.0 μm）was significantly reduced（P<0.05），the water holding capacity（2.90-3.63 g/g）and oil holding capacity（2.67-3.36 g/g） were increased，and the powder fluidity was reduced. Compared with the polysaccharide properties extracted from T. fuciformis powders without low-temperature impact milling treatment，the polysaccharide yields（5.23%-13.88%）obtained using the treated T. fuciformis powders，the content of neutral sugars（63.71%-74.12%）and glucuronic acid（24.17%-28.60%）were increased，while the protein content（0.29-0.65 g/g）was reduced. In addition，the lowest molecular weight of the polysaccharides was 15400 kD at a classifier frequency of 30 Hz；all the different TFP had mannose as the main monosaccharide，and the rest consisted of ribose，rhamnose，glucuronic acid，galacturonic acid，glucose，galactose，xylose，and fucose. The absolute values of polysaccharides Zeta potential increased gradually with the increase of frequencies of classifier. The results of rheological characterization showed that the different TFP solutions were all nonNewtonian fluids ，and the viscosity of the solutions was the highest when the classifier frequency was 20 Hz. Infrared spectroscopy and X-ray diffraction showed that the polysaccharides extracted from T. fuciformis powder with different classifier frequencies did not produce new functional groups and were amorphous.【Conclusion】Low-temperature impact milling can improve the color of T. fuciformis powder，change the particle size of T. fuciformis powder as well as the fluidity，improve the yield of polysaccharide，also affect the rheological properties of TFP，but will not change the monosaccharide composition and basic structure of the polysaccharides.