| Chinese yam(Dioscorea opposita Thunb)is not only good for nourishing and healthy opposita material,but it is a common material and has the value of both medicinal and edible opposites.The unique advantage of yam is that it is rich in mucilage,which is a kind of polysaccharide and protein polymerization,with a variety of biological activities.Because it is not easy to store,it is processed into yam slices,powder medicine.In the current industry,the production mode is usually drying and extruding and then grinding,and a large amount of mucilage is washed away by water in the production process.Spray drying is a kind of hot drying technology which can retain nutrients to the maximum extent.However,due to the high viscosity of yam slurry in production,spray drying is easy to cause clogging of equipment nozzle and serious wall hanging phenomenon,which seriously affects the powder collection rate and quality of products.Dynamic high pressure microfluidization(DHPM),as a new type of ultrafine grinding equipment,can achieve high efficiency crushing of materials.The fineness of crushing is much higher than that of ordinary grinding methods,and can improve the dissolution rate of effective substances and reduce the viscosity of the system.Therefore,in this paper,an Industry-Scale Microfluidizer System(ISMS)based on the principle of Dynamic high pressure microfluidization technology was used to prepare yam grout and spray drying to prepare super-fine yam powder,to study the influence of ISMS pressure on the physical properties of yam grout,ISMS viscosity reduction mechanism,preparation and characterization of ultra-fine yam powder,and to develop an instant yam powder through formula optimization.The main research results are as follows:1.Effects of ISMS pressure on physical properties of Yam seriflux: Yam seriflux was prepared by ISMS at different pressures(0,60,90 and 120 MPa)with the ratio of material to water of 1:2.Rheological properties showed that ISMS treatment reduced the apparent viscosity and increased the fluidity of yam slurry system.The particle size results showed that ISMS treatment could reduce the particle size of yams slurry.Particle size D[4,3] decreased from 76.23 μm at 0 MPa to20.90 μm after 120 MPa treatment.The particle size distribution changed from bimodal to unimodal to bimodal,and the peak position moved to the left.It was observed by microscope that ISMS can destroy the integrity of yam serous cells,break the cells into fragments of different degrees,and release the cell contents.ISMS treatment had no significant effect on the Zeta potential value of yam seriflux,which was between-(10.61-11.33)m V.The sediment weight ratio of yam seriflux decreased significantly after ISMS treatment,from 0 MPa 27.13% to 120 MPa 12.78%.ISMS processing can reduce the light transmittance finger pattern area and instability index of sample,and improve the stability of slurry.In addition,spray drying after ISMS,the slurry hanging condition is improved,the nozzle is no longer blocked,can realize continuous drying production.In summary,ISMS treatment reduces the apparent viscosity of yam grout,reduces the particle size by destroying the tissue structure of yam grout,improves the physical stability of yam grout,and yam grout can be spray dried,which provides a new treatment method for actual production.2.ISMS Viscosity reducing mechanism: Extracting Chinese yam mucilage under different ISMS pressure to study.The rheological properties showed that the apparent viscosity of yams treated by ISMS decreased from 0.10 Pa·s under 0 MPa treatment to 0.0351 Pa·s under 120 MPa treatment,and the fluidity increased.The particle size results showed that ISMS treatment could reduce the particle size of Chinese herb slime.Particle size D[4,3] decreased from 79.33 μm under 0 MPa treatment to 22.27 μm under 120 MPa treatment.The particle size distribution presented a unimodal distribution and the peak moved to the left with the increase of treatment pressure.Environmental scanning electron microscopy(SEM)observed that the apparent morphology changed from the original wafer structure to fine fragments or fine filaments and there were obvious holes in the sample.The results of IR spectra showed that all absorption peaks of mucilage did not change significantly,ISMS processing had no effect on the basic structure of mucilage.The above results indicated that ISMS could cause degradation of Chinese yam mucilage,and the degradation degree was aggravated with the increase of ISMS processing pressure.Further extraction of mucilage polysaccharides under different ISMS processing for study,the rheological properties of mucilage polysaccharides,laser diffraction particle size analysis,microstructure,molecular weight results showed that ISMS caused the degradation of mucilage polysaccharides.The results of reducing sugar and infrared spectroscopy showed that ISMS had no effect on the basic structure of mucilage polysaccharide,and the degradation of polysaccharide was mainly due to the break of glycosidic bond.In conclusion,under ISMS treatment,the breakage of glycosidic bond causes the degradation of mucilage polysaccharide,resulting in the loss of viscosity of mucilage polymers depolymerization and the decrease of viscosity of yam serous system.3.Preparation and characterization of super-fine yam powder: after ISMS treatment,the viscosity of yam slurry system is reduced,which makes the spray drying can be carried out smoothly.The results show that the yam powder yield increases with the increase of ISMS treatment pressure,and when the treatment pressure increases from 0 MPa to 120 MPa,the yam powder yield increases about 2times.The treatment of ISMS under different pressure has no significant effect on the color,moisture content and moisture activity of powder.The particle size analysis results of laser diffraction showed that ISMS treatment reduced the particle size of yam powder,and D[4,3] decreased with the increase of pressure,from 33.50 μm in 0MPa treatment to 28.45 μm in 120 MPa treatment.The micromorphology of ISMS changes,and the particles change from uniform and dry to uniform and spheroid small particles.With the increase of ISMS processing pressure,the friction in the powder decreased,Angle of repose decreased from 0 MPa 51.2° to 120 MPa 43°,bulk density,vibration density increased,the fluidity of the powder was improved.ISMS treatment pressure increased from 0 to 120 MPa,and damaged starch content increased from 0.43% to 3.7%.The hydration property of the powder is increased significantly,the gelatinization viscosity is decreased significantly,and the recovery rate is slowed down.In addition,the digestibility of yam powder was improved,and the fast digestible starch increased from 53.45% to 59.12%.At the same time,ISMS treatment can improve the dissolution rate of phenols,polysaccharides and other active substances.The dissolution rate of polysaccharides increased from 3% under 0MPa treatment to 5.3% under 120 MPa treatment,and improve the antioxidant activity of polysaccharides.The results showed that ISMS treatment can improve the yield and fluidity of powder,improve the digestibility,can get the effective ingredient dissolution rate,bioactivity higher yam powder.4.Based on the previous studies,ISMS 120 MPa processed slurry was selected as raw material,and maltodextrin and lecithin were selected as quick solvents to optimize the instant solubility.With the increase of maltodextrin supplemental level,the dispersion,packing density and Angle of reactivity of yam powder were improved.The sensory evaluation was the highest when maltodextrin supplemental level was1% and 1.5%(there was no significant difference between the two groups).Based on all the results,the maltodextrin supplemental level was 1.5% for the next instant optimization.With the increase of lecithin supplemental level,the bulk density and Angle of rerest of yam powder had no significant change,but the dispersivity increased with the increase of the supplemental level,and the highest sensory evaluation was 0.15%.To sum up,1.5% maltodextrin and 0.15% lecithin were selected for instant solution optimization to prepare yam powder with better color and sensory experience.The conclusion of this paper can provide theoretical basis for the wet grinding-spray drying of Chinese yam powder and its product development. |
PDF Full Text Request