热泵干燥槟榔中试工艺参数优化

Technologic parameter optimization in pilot-scale process of heat pump drying of Areca catechu L.

为了探索新型节能、低碳排放的槟榔干燥技术,应用热泵干燥设备对槟榔进行干燥研究,获得槟榔热泵干燥中试工艺参数。单因素试验分析了煮沸时间对槟榔硬度的影响,干燥温度和装载量对槟榔水分的影响;采用正交试验,通过加权评分值计算方法评价干果品质,优化热泵干燥工艺参数;测定储藏30 d后的干果进行理化和微生物指标;比较热泵干燥、蒸汽干燥和传统干燥槟榔的成本及品质。结果表明,新鲜槟榔经过沸水煮沸15 min,前12 h内干燥温度为50℃、12 h后干燥温度为65℃、装料量为3.5 t、烘房空气相对湿度为25%时,槟榔含水率为16.8%,好果率为96.0%,均匀度为91%,单位质量干果耗电量为0.92(k W·h)/kg,所干燥的槟榔干果综合评分为90.1分,呈橄榄黄或褐色。25℃储藏30 d无霉腐现象,检测结果显示含水率为17.8%,未检测出汞和苯并芘,铅和砷质量分数分别为0.02和0.1 mg/kg,致病菌未检出,大肠菌群数<30 cfu/g,霉菌计数为30 cfu/g。经比较,热泵干燥槟榔比蒸汽干燥成本低11%,比传统土炉干燥成本低50%,零排放、无污染、操作智能化。研究结果为槟榔热泵干燥的标准化生产提供技术参考。

Areca catechu L. belongs to perennial aiphyllium of palmae. It has very high medicinal value and is regarded as the first one of 4 kinds of the south medicines in China. Areca catechu L. abounds in Hainan, 10% for fresh food, more than 90% dried for further processing, Areca catechu L. drying has become the important processing industry in Hainan, the annual output of dried betel nut is about 200 000 t, and the annual output value is more than 10 billion yuan. For the Areca catechu L. drying, there are hot air drying and vacuum freeze drying, which have not been applied in production because of the limitation of experimental conditions and equipments, and the traditional furnace drying, steam drying and heat pump drying are used in production. The traditional furnace drying is a kind of small workshop processing, and its characteristics of small scale, large labor intensity and serious pollution are difficult to adapt to the modern agriculture development, so it has been gradually eliminated. For the steam drying whose heat source is from the burning coal, the characteristic of large scale and high mechanical strength adapts to the intensive agricultural product processing development, however it is limited because of a lot of greenhouse gases emitted from burning coal. Only the energy-conservation and environment-protection drying method is suitable for the Areca catechu L. drying industry＇s sustainable and healthy development. The betel nut drying was studied using the heat pump drying equipment in this paper. The influences of boiling time on betel nut hardness, and drying temperature and loading capacity on moisture content of dried fruit were analyzed via the single factor experiment. The technology parameters of heat pump drying were optimized by the orthogonal experiment, and the quality of the dried betel nut was evaluated using the weighted score method. After 30-day storage, the physical, chemical and microbiological indicators of the dried fruits were detected, and moreover, the advantages and benefits were analyzed based on the comparison between the heat pump drying method and the steam drying and traditional drying methods. The optimum drying parameters were： boiling time of 15 min, initial drying time of 12 h at 50℃, following drying time of 84 h at 65℃, loading capacity of 3.5 t, 25% air relative humidity of dried room, and 16.8% water content of betel nut. The results showed as follows： the ratio of good dried fruit was 96%, the uniformity of dried fruit was 91%, the power consumption of dried fruit was 0.92（kW ·h）/kg, the comprehensive score of dried betel nut quality was 90.1, and the color of dried fruit was either olive yellow or brown. After 30-day storage at 25℃, the dried fruit did not mildew, and the physical and chemical indicators were in the controllable range. The cost of drying betel nut by heat pump was more economical, 11% lower than that of the steam drying and 50% lower than that of the traditional drying. The heat pump drying had the advantages of energy saving, low emissions, intelligent operation, low drying cost and good economic benefit. The research results provide the technical reference for the standardized processing of the betel fruit with the heat pump drying method.