提高紫花苜蓿热风干燥品质的工艺参数优化

Technological parameters optimization for improving quality of heated-air dried alfalfa

紫花苜蓿的热风干燥是牧草收获后贮藏、深加工的必要预处理方式,为了研究紫花苜蓿干燥过程中各因素对干燥的影响及变化规律,为实际生产工艺提供参考,解决目前紫花苜蓿干燥加工中存在的营养成分损失大、含水率不稳定等问题,利用GZ-1型干燥试验装置,对紫花苜蓿的热风干燥特性和工艺进行了研究。以新鲜的紫花苜蓿为原料,紫花苜蓿的干品品质(粗蛋白含量、酸性洗涤纤维含量、中性洗涤纤维含量)为指标,在对其有影响的4个因素(热风温度、热风速度、茎秆压扁与切断长度情况、助干剂种类与浓度)进行单因素试验的基础上;采用4因素3水平正交试验进行了优化。通过对试验数据进行极差与方差分析,找出了优化工艺参数组合并得出结论:热风温度是影响苜蓿干品粗蛋白质含量的最主要因素,茎秆压扁与切断长度情况是影响苜蓿干品中酸性洗涤纤维和中性洗涤纤维含量的最主要因素,热风干燥优化后的工艺参数组合为热风温度70℃、热风速度2.5m/s、茎秆切断长度10 cm且压扁、碳酸钾浓度3%。在此工艺参数条件下,能有效提高干燥效率,并降低干草中营养成分的损失。研究为确定紫花苜蓿热风干燥工艺参数,提高紫花苜蓿热风干燥品质提供参考。

Alfalfa is a perennial herb and it is from the Near East and East Asia. Alfalfa is rich in nutrients and trace elements such as proteins, iron and manganese that is necessary to growing of life. Alfalfa is also the high quality livestock forage. Because alfalfa contains more carbohydrates and less colloidal substances, it is difficult in ensiling. Alfalfa must be dried promptly after hay harvest. With the rapid development of animal husbandry, grass planting area is increasing rapidly. So production and modulation of hay is an important link of hay industrialization in China. Accordingly, alfalfa drying is the necessary pretreatment way of storage and processing after hay harvest. With the characteristics of green color, leaf-rich, soft texture, fragrance and palatability, alfalfa is an essential livestock forage in winter and spring for livestock. Alfalfa is also the main raw material for the forage processing enterprises. Scientific processing methods can effectively reduce the nutritive value loss of hay. It is important to the actual production with the research of drying characteristic and drying technology. In order to study the influence and variable law with different factors in alfalfa drying, solve the problems of low quality of hay alfalfa after drying and provide reference for the actual drying process, alfalfa drying characteristic and technology were investigated using GZ-1 drying test device. Hot air temperature, hot air velocity, culms length, culms physical pretreatment methods, drying aid species and drying aid concentration were discussed with fresh alfalfa based on dried quality which included crude protein content, acid detergent fiber content and neutral detergent fiber content. Then the four factors were optimized through orthogonal experiment. Through experimental analysis, the order of priority which influenced the content of nutrition components in alfalfa is obtained. Finally, significant factors and optimal combination were determined by using analysis of range and variance to experimental data. Hot air temperature, hot air velocity, culms length, culms physical pretreatment methods, drying aid species and drying aid concentration is the main factors which influence hot air drying characteristic. And the main factors which influence crude protein percentage composition and the percentage composition of washing fiber content are hot air temperature and physical pretreatment method respectively. The best drying combination is A2, B2, C1 and D1 that means hot air temperature 70℃, hot air velocity 2.5 m/s, physical pretreatment methods 10 cm crushed and potash concentration 3%. Dry efficiency is increased and nutritional ingredient is preserved under the optimized technological parameters. The research provides theoretical reference to determine technological parameters of alfalfa hot drying and improve the hot drying quality of alfalfa. It is important to the development of alfalfa industry.