Experimental Study On Carrot Fine Pulverizing Technology And Related Parameters

Carrot contains a lot of kinds of nutrient composition and has higher nutritional, health and medical value. Ultra-fine pulverization technology is one of the most advanced food processing technologies developed since decade. Ultra-fine pulverization for carrot has no strict request for size and shape and has no residues to pollute environment. Ultra-fine pulverization of carrot can full utilize diet fiber and nutritional constituents in carrot.Based on reviewing current status and research progress of fine pulverization, influence of different dehydration and pretreatment method on carrot fine pulverization was experimentally investigated. Experiment of quadratic regression orthogonal design with four factors was carried out in order to study the impact of planetary ball mill pulverization on carrot pulverizing in which the effect of smashing speed of ball mill, smashing time, smashing charge ratio of medium, smashing material filling ratio on smashing efficiency and unit powder energy consumption was studied, and mathematical models describing relations of experiment criteria and factors were established, experiment parameters were optimized. Grain size distribution, surface area ratio and mean particle size of pulverized carrot from high speed rotation pulverizing equipment and planetary ball mill were analyzed through micro-particle measuring instrument, meanwhile relationship of smashing time with carrot powder granularity and surface area ratio was developed; carrot powder was analyzed for determination of bulk density, water and oil solubility, and nutritional components. Main research conclusions were as following.(1) Theoretical analysis of ultra-fine pulverization procedure with planetary mill indicated that the biggest centrifugal force of the mill ball was directly proportional to the ratio of rotation speed between mill rotation and ball cylinder revolution, ball mass and mill rotation speed. Milling ball moving speed is directly proportional to mill rotation speed and inversely proportional to material mass and charge ratio of material and ball. Average free path of ball movement was directly proportional to ball radius, ball density and cylinder volume and inversely proportional to material mass and charge ratio. Collision frequency of ball was directly proportional to rotation speed of the mill and inversely proportional to ball density and cylinder volume. The influence of material mass on ball collision frequency was not significant.(2) Experiments of influencing factors for carrot fine powder processing (>80 mesh screen) showed that factors of influencing carrot smashing were dehydrating method > pretreatment way > carrot shape; the dehydrating methods for carrot smashing were freeze drying > microwave drying > vacuum drying > hot air drying. Carrot with freezing and thawing was easy to smashing than that of curing. Influence of carrot shape on smashing was not significant. The experiment result showed that carrot with freeze drying and freezing and thawing could be pulverized easily.(3) Experiments of ball milling parameters for carrot micro-powder processing (>160 mesh screen) indicated that the factors order for influencing ball milling were smashed material filling rate > smash time >ball mill rotation speed > smash medium filling rate; the factors of influencing unit powder energy consumption were smash time > smash material filling rate > ball mill rotation speed > smash medium filling rate. The optimal technological parameters for carrot pulverizing with planetary ball mill were determined through multi-objective no-linear optimization method and the optimum technological parameters were verified with fresh carrot→5 mm~3 block→freeze drying→fine smashing→passing 80 mesh screen→pulverizing with ball mill; parameters for ball mill were rotate speed 230 r/min, smash time 60 min, medium filling rate 24% and material filling rate 17%, with which the efficiency of carrot micro-smashing was higher and unit energy consumption was lower.(4) Experiment for influence of different carrot drying and pulverizing methods on granularity of carrot powder showed that mean particle diameter of carrot powder was smaller and surface ratio was larger with freeze drying than that with hot air drying; and effects of smash medium with steel ball was the same than that with agate ball. The best pulverizing results were obtained with 60min smashing time no matter what dehydrating method and ball medium were used. Mass average grain size and surface ratio of carrot ultra-fine powder changed unevenly when smashing time lasted from 90min to 240min. Experiment results showed that smashing efficiency for carrot ultra-fine powder processed by freeze drying with planetary ball mill was higher with steel ball medium for 60min, powder mass mean grain size was 17.2μm, mass surface ratio was 0.41 m~2/g. The best pulverizing effects were achieved for carrot ultra-fine pulverizing with high rotation speed smashing device for 12min with freeze drying and 15min with hot air drying, if smashing time increased than that there will be counter-grinding phenomenon. The optimal carrot pulverizing technology with high rotation speed smashing device was freeze drying, smashing for 12min, the powder mass mean grain size was 11.8μm and mass surface ratio was 0.49 m~2/g.(5) Analysis of physical and chemical properties of ultra-fine carrot powder showed that carrot micro powder gained by hot air drying and microwave drying had large bulk density than that by freeze drying. Water solubility of carrot micro powder gained by microwave drying was higher than that gained by freeze drying; and water solubility of carrot fine powder was higher for raw carrot than cooked carrot. The aminophenol content of raw powder was more than that of cooked carrot powder, freezing and thawing powder. The aminophenol content was the highest when raw carrot was treated with freeze-drying and grain size small than 240 mesh screen. The vitamin C content of carrot micro powder processed by freezing and thawing was higher than that of raw and cooked carrot powder. The vitamin C content of carrot micro powder processed by freeze drying was the highest following microwave and vacuum drying. The highest vitamin C content for carrot ultra-fine powder was achieved with freezing and thawing carrot processed by freeze-drying for 80 to 120 mesh screen. Carrot element content decreased with decrement of granularity, carrot element content was the highest for freeze-drying and freezing and thawing processing procedure with grain size 80 to 120 mesh screen.