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

Abstract: 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.