连续式中红外-热风组合干燥设备的研制与试验

Development and test of continuous combined mid-infrared with hot air drying equipment

为解决现有肉干干燥设备效率低、品质差等问题,研制了一种适合肉干连续化生产的中红外-热风组合(combined mid-infrared with hot air,CMIHA)干燥设备,该设备包括进料段、加热段和出料冷却段3个单元,其中每个加热段均由输送系统、加热系统、对流循环系统和控制系统等组成。通过红外加热波长的定向设计及辐射强度的有效控制,加大红外辐射能的利用率,提高脱水效率。同时通过对连续式CMIHA干燥设备的加热系统、对流系统、冷却系统等主要工艺参数的优化计算,研制出用于肉干连续式脱水的CMIHA干燥设备,并进行生产试验,比较分析该干燥设备与传统热风干燥设备对牛肉干脱水效率及品质的影响。结果表明,在相同条件下(加热功率105 k W,加热温度70℃,热风风速1 m/s,冷却风速3 m/s,加热距离8 cm),与传统热风干燥设备相比,连续式CMIHA干燥设备能够加快牛肉干肌肉蛋白的变性,降低干燥活化能,减少脱水所需的能量,降低干燥耗时,提高生产效率,其活化能和干燥耗时分别降低了10.33%和57.14%,生产效率提高了2倍;同时,连续式CMIHA干燥设备能够减轻牛肉干表面结痂现象,减缓(P<0.05)肌红蛋白的氧化,提高氧合肌红蛋白的含量,降低高铁肌红蛋白的含量,使牛肉干具有较好的"咬感"及色泽,其咀嚼性、剪切力、收缩率、红度a*值、色度C*值、色调H*值均显著优于(P<0.05)热风干燥设备,赋予了牛肉干较好的感官品质,实现了肉干的高效率、高品质脱水干燥。该研究为风干肉连续式干燥设备的研制提供了参考。

Drying efficiency was always considered to be the most important factor by factories, however, low thermal conductivity and case hardening of the material slowed the moisture migration in hot air drying, and resulted in more time and energy consumption. So to solve the existing problems of present drying equipment, a continuous drying equipment of combined mid-infrared and hot air（CMIHA） was developed in this paper. This drying equipment included feed section, heating sections and cooling section, of which each heating section was made up of four parts, i.e. conveying system, heating system, convective circulation system and control system. As we all know, since infrared energy is converted into heat only when material absorbs the radiation, it was essential to select a heat source emitting radiation with the range in which the material to be processed had maximum absorption. So, the radiation wavelength of infrared was selected by the infrared spectra of meats, and the radiation intensity could be controlled by changing the amount of working lamps to make good use of the radiation energy. At the same time, this equipment was developed by calculating the main technological parameters of convection system, cooling system and heating system, and then the production verification test was also done to compare the difference between CMIHA drying and hot air drying on beef jerky. Results showed that, in the same conditions（heating power 105 kW, heating temperature 70℃, wind velocity 1 m/s, cooling wind velocity 3 m/s, heating distance 8 cm）, compared with hot air drying, the continuous CMIHA drying equipment could speed up muscle protein denaturation, reduce activation energy, reduce the energy that jerky needed to accelerate moisture migration, and improve drying efficiency. The time consumption that the beef samples in the first row on the conveyor dehydrated from raw to weight reduction by 50% for CMIHA drying equipment was 120 min, and the production efficiency was 120 kg/h, if the working time of equipment was more than 10 h every day. However, the time consumption and production efficiency of hot air drying equipment were 280 min and 40 kg/h, respectively. Besides, compared with hot air drying equipment, CMIHA drying equipment could reduce the case hardening of jerky, significantly decrease（P〈0.05） the value of shear force and shrinkage rate, and increase（P〈0.05） the values of chewiness of jerky, and the chewiness, shear force and shrinkage rate were 44.79 N, 143.59 N and 45.48%, respectively, but those of hot air drying were 35.87 N, 182.69 N and 55.0%, respectively. As we all know, different kinds of myoglobin can make meat have different colors, of which myoglobin is kermesinus, oxymyoglobin is bright red and metmyoglobin is taupe brown. Compared with hot air drying equipment, CMIHA drying equipment could increase the content of oxymyoglobin, and reduce the content of metmyoglobin, which made jerky have better color. The values of a^＊（redness value）, C^＊（chroma value） and H＊（hue value） of jerky dried with CMIHA were significantly higher（P〈0.05） than hot air. Besides, the sensory evaluation of jerky dried with CMIHA drying had higher scores than hot air drying. This study can provide valuable information for designing and developing this new continues combined mid-infrared and hot air drying equipment that can be used for solving the problems that low drying efficiency and poor quality of jerky.