| The effect of different conditions about hot air drying(HAD), short and medium-wave infrared drying(SMIRD) and hot air-explosion puffing drying(HA-EPD) were investigated for strawberry drying. Compared with freeze-drying(FD) strawberry powder, the quality changes of above three kinds of drying methods for strawberry powder were studied, and optimum strawberry powder were obtained. According to fine crushing time to control the different particle size of strawberry powder, and the based quality (include physical and chemistry quality, nutrition quality and antioxidant activity quality) and the behavior processing quality (include flowability quality and shear quality). A comprehensive and systematic evaluation system were established of strawberry powder, to provide theoretical basis for industry production. Major conclusions were listed below:1. The HAD and SMIRD of strawberry process occurred mainly in the falling rate period. The effective moisture diffusion coefficient of HAD and SMIRD strawberry respectively ranged from 5.419×l0-10～9.407×10-10 m2/s and 0.607x10-9 m2/s～2.126×10-9 m2/s. The activation energy was 39.54 KJ/mol and 39.54 KJ/mol, which was determined from Arrhenius equation. Drying temperature had a more significant impact on the drying rate than drying power. Optimum technology conditions of HAD for strawberry are 70℃ and 360 min. The SMIRD conditions are 70 ℃ and 1125 W power for 190 min. The HA-EPD conditions are 60% of pre-drying moisture content, vacuum drying temperature are 70℃(60 min)-60℃ (40 min), total drying time are 255 min. Strawberry drying products had high efficiency and short drying time and good quality under the above drying conditions.2. The drying methods have different affections on strawberry powder quality. Due to the low temperature vacuum drying, the physical and chemistry quality and nutrition quality and antioxidant activity quality of FD strawberry powder are better. But the behavior processing quality is bad, and has low flowability quality againsting transmission. The best color and highest anthocyanin retention of the pelargonidin-3-glucoside chloride and cyaniding-3-glucoside chloride was obtained at the HA-EPD strawberry powder, and had better behavior processing quality. HAD strawberry power also showed significant advantage on the soluble solids and titratable acidity property. The products were found to present the best total phenol and flavone property and the highest antioxidant capacity for SMIRD strawberry powder. HA-EPD strawberry powder has best quality through correlation analysis and principal component analysis and clustering analysis and analytic hierarchy process comprehensive evaluation.3. The effects of crushing time on particle size of strawberry powder were investigated. The particle size of Fine crushing 5 min～25 min of strawberry powder are ranged from 68.10 μ to 38.61 μm, and reached the powder fine crushing technology. The effects of different particle size on the quality of strawberry powders were investigated. The smaller particle size, the better particle size physical and chemistry quality, such as the soluble solids and titratable acidity and solubility property. But the colour is worse. So the don’t deal with crushing 0 min of strawberry powders has best color. Similarly, Fragrant component strength is strong with bigger particle size. The esters of strawberry powder is the main aroma components. Fine crushing time from 5 min to 25 min, the content change of ester material is gradually reduced. The content VC, fructose, glucose and sucrose is increased gradually with the reduction of strawberry powder particle size. But the content of total phenol and flavonoids trends in contrast. More interestingly, the antioxidant capacity is increased gradually with the reduction of strawberry powder particle size. The anthocyanin retention(Pg-3-Glu and Cy-3-Glu) increased first but decreased later with the the reduction of strawberry powder particle size.The total flowbility energy is increased gradually with the reduction of strawberry powder particle size, the corresponding SI values and FRI values is increased gradually. At the model of aerated flowbility test, the trend of AE and AR is obviously different. The AR is increased gradually with the reduction of strawberry powder particle size, but AE is decreased. The order of compressibility from high to low is 5 min>10 min>25 min>15 min>0 min,5 min values is highest,0 min values is lowest. The permeability of the smaller the particle size of strawberry powder is worse, and is bad for packing. The strawberry powder for fine crushing 0 min has the largest shear property. But the shear property of fine crushing 5 min-25 min are lower. Review described above, strawberry powder belongs to non-sticky powder, and lump phenomena is not easy to happen. The aeration is increased and the shear is decreased gradually with the reduction of particle size. But the permeability is increased and not conducive to partial shipments. During processing, in terms of the environment of processing and the use of pulverizing to measure, improving the state of strawberry powder. |
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