Effects Of Ultrafine Grinding Treatment On The Quality Of Coix Seed Powder And Its Gel

Coix seed is a dried mature seed of the medicinal and food homologous plant with high medicinal and edible value,belonging to the high starch content of foods.Because of coix seed has a hard and dense structure,high starch enthalpy,and high onset gelatinization temperature,it is difficult to gelatinize and steam for a long time,which lead to its difficulty in gelatinization,loss of nutrients,and decreased pharmacological activity.Which has become the key common problems in the development and utilization of coix seed resources.Therefore,this paper analyzed the changes of physical and chemical characteristics of coix seed powder by ultrafine grinding treatment,compared the effects of different additives on the improvement of the retrogradation characteristics of coix seed powder gel,and discussed the changes of the storage quality of the ultrafine coix seed powder gel.It provides theoretical and technical reference for quality improvement and application promotion of subsequent coix seed products.The main results are as follows:（1）Use laser particle size analyzer,scan electron microscopy（SEM）,color difference meter,differential scanning calorimetry（DSC）,rapid visco analyser（RVA）,X-ray diffraction（XRD）,fourier transform infrared spectrometer（FTIR）and texture profile analysis（TPA）were used to analyze the effects of mechanical mechanical ultrafine grinding on the physicochemical properties and structural characteristics of coix seed powder.The results show that with the increase of grinding time,the particle size of coix seed powder decreases,the specific surface area increased,the L^*value increased,the brightness increased,and the phenomenon of agglomeration became more obvious.When the particle size decreased to 19.08μm,the distribution gradually became uniform.To,Tc,and△H gradually decreased with the decrease of particle size（P<0.05）,and Tp increased first and then decreased.Among them,the Tc and△H of the ultrafine coix seed powder samples in group C-15 were the lowest at77.61℃and 0.26 J/g.After ultrafine grinding,the gelatinization characteristics parameters changed significantly（P<0.05）.The final viscosity of the W-60 control group was the highest（1271.33 cP）,and the C-15 group had the lowest setback（176.00 cP）.Ultrafine grinding did not change the crystal structure of coix seed powder,the crystallinity gradually decreased with the decrease of particle size（P<0.05）,and the functional group structure did not change.After ultrafine grinding,coix seed powder gel characteristic parameters changed significantly（P<0.05）.The hardness,springiness,and chewiness of W-60 group were the highest.After 7 days of refrigerated storage,the hardness of superfine coix seed powder gel decreased and the springiness increased.Partial least squares regression analysis showed that the mean particle size of coix seed was significantly correlated with its physical and chemical characteristics..In summary,ultrafine grinding can significantly reduce the particle size of the coix seed powder,affect the gelatinization and thermal characteristics of the ultrafine powder,and improve the thermal stability of starch paste and the anti-retrogradation property of gel.（2）The effects of 0.3%monoglyceride,0.3%carrageenan,10%glycerin,35%syrup on the retrogradation properties of coix seed powder gel under refrigeration（4℃）were analyzed by means of TPA,DSC and low field-nuclear magnetic resonance（LF-NMR）.The results showed that there were significant differences in thermodynamic parameters,TPA characteristics and water state changes of W-60 gel and C-15 gel in different additive groups were significantly different（P<0.05）.DSC analysis showed that the additive could significantly increase the To range of W-60gel and decrease the△H and RD values of the gel system.The To,△H and RD values of each group changed significantly with the increase of storage time（P<0.05）.The additives could also significantly increase the To and Tc range of C-15gel,and the To,Tc,△H and RD values of each group changed significantly with the increase of storage time（P<0.05）.After 14 days of storage,the△H and RD values of all the sample groups increased to the peak,and the differences between the groups were significant（P<0.05）,while the addition of 35%syrup had different effects on the thermodynamic parameters and retrogradation degree of W-60 gel and C-15 gel.TPA analysis showed that additives significantly affected the hardness,springiness,and chewiness of the gel（P<0.05）.The mixed additives could effectively reduce the change rate of gel hardness,springiness and chewiness of coix seed powder gel.The hardness of the two gel samples increased significantly with the increase of the refrigerating time（P<0.05）,but the relative growth rate decreased gradually.LF-NMR analysis showed that the signal amplitude of C-15 gel was higher than that of W-60gel.With the increase of the refrigerating time,the internal water in the gel moved from the tightly bound water to the non-flowing and free-moving water.The T₂relaxation time could be moved in the direction of slow relaxation by adding the mixed additives.In summary,the gel system made of ultrafine coix seed powder with average particle size of 33.04±0.51μm has better anti-retrogradation effect.Mixed additives（0.3%monoglyceride,0.3%carrageenan,10%glycerin,35%syrup）can effectively delay the retrogradation and rejuvenation of coix seed powder gel.（3）The quality changes of coix seed powder gel with different particle sizes during storage were analyzed under the conditions of accelerated retrogradation at4℃and accelerated oxidation at 40℃.The results showed that the total texture parameters of coix seed gel with different particle sizes changed significantly with time at 4℃（P<0.05）.Compared with the W-60 control group,there were significant differences between the groups of ultrafine coix seed powder gel groups（P<0.05）.The hardness,adhesiveness and chewiness of the gel stored for 30 days increased,while the resilience decreased.The gel occurred retrogradation with the extension of the storage time,while the retrogradation rate of the C-20 gel was slower and the tissue stability was better.In the process of accelerated oxidation at 40℃,the water volume fraction,TBA value,L^*value,a^*value,b^*value and△E value of coix seed powder gel with different particle sizes changed significantly（P<0.05）.With the increase of storage time,the water volume fraction of the W-60 control group decreased,and the TBA value and b^*value increased,which were significantly different from the ultrafine coix seed powder gel（P<0.05）.To sum up,C-20 gel has better storage resistance at 4℃,and W-60 gel has severe oxidation browning and poor tissue stability at 40℃.