| The carrots were dried by hot-air drying, microwave drying and hot pump drying. The drying characteristics and process optimization of three drying methods were studied. The influence of three drying methods on carrot was researched. The physicochemical properties and the nutritional content of dissolution of different particle size of carrot powder were compared. The changes of ordinary powder were compared with superfine grinding powder before and after smashing. Theory basis and guidance for the controllable and continuous processing of carrot was provided. The results are as follows:1.The drying characteristics of hot-air drying of carrot were studied, the process of hot-air drying of carrot could be divided into raising speed stage, constant speed stage, slowing down stage. The higher drying temperature, the poorer color, the lager loading capacity, the poorer color. The higher drying temperature, the lower content of ca rotene, the lager loading capacity, the lower content of carotene. The higher drying temperature, the shorter drying time, the lager loading capacity, the longer drying time. The Page equation could be the fittest model to describe and predict the hot-air drying of carrot, MR=exp(-ktn), the dynamical model of this experiment could describe the change rule of the content of water in the hot-air drying of carrot. The influence of changes of temperature and loading capacity on the color, the content of carotene and drying time were analyzed by the orthogonal experiment of L4(23),the influence of the major factor on the color, the content of carotene and drying time were: loading capacity>temperature, the best parameter combination was determined by the color, the content of carotene and drying time, the temperature was 50℃,the loading capacity was 300 g, as a result, the number of color was 26.72,the content of carotene was 0.28mg/g, the drying time was 6h.2.The drying characteristics of microwave drying of carrot were studied, the process of microwave drying of carrot could be divided into raising speed stage, constant speed stage, slowing down stage. The higher drying temperature, the poorer color, the lager loading capacity, the poorer color, the higher power, the poorer color. The higher drying temperature, the lower content of carotene, the lager loading capacity, the lower content of carotene, the higher power, the lower content of carotene. The higher drying temperature, the shorter drying time, the lager loading capacity, the longer drying time, the higher power, the shorter drying time. The Page equation could be the fittest model to describe and predict the microwave drying of carrot, MR=exp(-ktn), the dynamical model of this experiment could describe the change rule of the content of water in the microwave drying of carrot. The influence of changes of temperature, loading capacity and power on the color, the content of carotene and drying time were analyzed by the orthogonal experiment of L9(34),the influence of the major factor on the color, the content of carotene and drying time was: temperature>power>loading capacity, the best parameter combination was determined by the color, the content of carotene and drying time, the temperature was 50℃,the loading capacity was 600 g and the power was 1.7kw, as a result, the number of color was 29.79,the content of carotene was 0.52mg/g, the drying time was 120 min.3.The drying characteristics of hot pump drying of carrot were studied, the process of hot pump drying of carrot could be divided into raising speed stage, constant speed stage, slow down stage. The higher drying temperature, the poorer color, the lager loading capacity, the poorer color, the higher wind speed, the poorer color. The higher drying temperature, the lower content of carotene, the lager loading capacity, the lower content of carotene, the higher wind speed, the poorer color. The higher drying temperature, the shorter drying time, the lager loading capacity, the longer drying time, the higher wind speed, the shorter drying time. The Page equation could be the fittest model to describe and predict the microwave drying of carrot, MR=exp(-ktn), the dynamical model of this experiment could describe the change rule of the content of water in the hot pump drying of carrot. The influence of changes of temperature, loading capacity and wind speed on the color, the content of carotene and drying time were analyzed by the orthogonal experiment of L9(34),the influence of the major factor on the color and the content of carotene was: temperature >wind speed>loading capacity, the best parameter combination was determined by the color, the content of carotene and drying time, the temperature was 50℃,the loading capacity was 2000 g and the wind speed was 1m/s, as a result, the number of color was 32.53,the content of carotene was 0.6mg/g, the drying time was 8h.4.The influence of different drying methods on the quality of carrot was studied, In the experimental range, the results showed that in the aspects of the color, the rehydration capacity, the oil-holding capacity, the content of carotene, the content of total sugar, the content of amino nitrogen and the sensory evaluation, hot-pump drying >microwave drying >hot-air drying. In the aspects of average drying rate, unit energy consumption, hot-pump drying > microwave drying > hot-air drying. In the aspects of drying capacity and energy consumption, hot-pump drying > hot-air drying > microwave drying. The tiny holes on the surface of the hot-pump drying products were large, the shrink degree of the surface was minimum, the organization structure of microwave drying products shrank in a certain degree, the tiny holes on the surface were symmetrical, but the hot-air drying products shrank and collapsed the worst. In the aspect of antitype vitamin C, microwave drying > hot-pump drying > hot-air drying.5.The physicochemical properties and the nutritional content of dissolution of different particle size of carrot powder were studied, in the physicochemical aspect, the particle size of the powder was smaller, the powder was whiter, the red color had the tendency of turning darker at first and becoming lighter at last, the yellow was not significantly different, the rehydration capacity was higher at first and became lower at last, the rehydration capacity of particle size of 250-180 μm was the strongest(4.691), the oil holding capacity decreased slowly and was not significantly different. In the aspect of nutritional content of dissolution, as the particle size of carrot became smaller, the content of carotene and antitype vitamin C decrease significantly, the content of amino nitrogen was higher at first and became lower at last, the particle size of 120-109 μm was the highest(0.249%), but the content of total sugar was almost the same.6.The influence of different drying methods and superfine grinding to the characteristics of carrot powder were studied, after the ordinary powder was ultramicro-porphyrized, the tissue of carrot became tiny, the shape was slightly regular, the size of the powder decreased significantly. The number of L* and b* of color were larger, the number of a* was smaller, the powder turned brighter, the red turned lighter and the yellow turned darker. angle of repose, slip angle and the bulk density were significantly bigger. The dehydration and oil-holding capacity were significantly smaller, index of water solubility enlarged significantly, swelling index decreased. The content of protein, fat, total sugar increased significantly, the content of carotene and antitype vitamin C decreased significantly. |
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