加工工艺对挂面干燥及产品特性的影响

Effects of Processing Technology on the Drying Characteristics and Quality Properties of Chinese Dried Noodles

为明确加工工艺对挂面干燥和产品特性的影响,提高挂面干燥工艺效能,以小麦精粉为原料,采用自主开发的食品水分分析试验平台,设计3因素不等水平(加水量30%,35%;真空度0.00,0.06 MPa;干燥温度32,40,48℃)全排列挂面干燥试验。在相对湿度75%条件下定时(300 min)干燥,测定挂面干燥及产品特性。结果表明,和面加水量对挂面干燥和产品特性有极显著影响,其次是干燥温度;真空度仅对产品的抗弯强度有显著影响;因素互作对产品特性有较大影响;抗弯强度是与多因素关联的产品质量特性,可考虑作为挂面产品质量评价的主要性状之一。提高加水量,可以显著提高挂面的弯曲距离和弯曲功;提高干燥温度时,挂面弯曲距离先增大后减小。

Mixing and drying are the key processes during the production of Chinese dried noodles（CDN）, which have great influences on the noodle property and product cost. Most studies on the drying process of CDN were about the effects of drying parameters（temperature, relative humidity and wind speed） on the drying and product characteristics. However, mixing stage also has a strong influence on the drying and product characteristics. Water addition is an important parameter in dough mixing. Vacuum mixing is a new technology which can improve the eating quality of noodles, has been used for the production of CDN. Drying temperature, relative humidity and wind speed are the main parameters in the drying process. However, the relative humidity is controlled by changing the drying temperature during drying. Relative humidity and wind speed are hard to control by themselves during industrial manufacturing under the current condition. Thus water addition, vacuum degree, and drying temperature are selected as the critical factors in CDN manufacturing. In order to investigate the effects of those processing parameters on drying characteristics and quality properties of the CDN, experiments were conducted with water addition set to be 30% and 35%, vacuum degree of 0.00 MPa and 0.06 MPa, and drying temperatures of 32, 40 ℃ and 48 ℃. Drying characteristics include final moisture content, drying rate, drying rate of the former 40 minutes, and quality properties included color（CIE L＊, a＊and b＊） and texture properties of dried noodles（bending strength, bending distance and bending work） were measured. The relative humidity of the drying condition was 75% and drying time was 300 minutes. The results showed that water addition was the most important factor affecting the drying process and quality properties, which affects all the processing characteristics and quality traits. Increased water addition was significantly related with increased final moisture content, drying rate and b＊value. But L＊value and a＊value were decreased when water addition was increased. Increased water addition resulted in increased bending distance and bending work, implying that the formation of gluten network is better when the water addition is higher. Drying temperature was another important factor affecting the drying process and quality properties. Increased drying temperature was significantly related with decreased final moisture content, increased drying rate.Bending strength was increased when the drying temperature was increased at water addition 30%, 0.00 MPa. But bending strength was decreased initially and then increased when the drying temperature was increased at water addition 35%,0.06 MPa. How will the drying temperature affect bending strength under different conditions needs further investigation.The bending distance was increased initially and then decreased when the drying temperature was increased at water addition of 35%, no matter which degree the vacuum was. Vacuum degree only showed a significant effect on the bending strength, and it did not affect the final moisture content, drying rate, drying rate of the former 40 minutes when vacuum degree was increased. The vacuum degree affected the bending strength of dried noodles though factor interaction as vacuum can increase water binding capacity of starch and gluten network, which may cause an increase in the activation energy（energy necessary to start water migration）, and thus influenced the CDN drying process. Bending strength is related to all of the processing parameters, which could be used as a major index to evaluate the quality of CDN. Bending strength can be improved by increasing the water addition and drying temperature in a certain range. In conclusion, water addition and drying temperature are the critical parameters for CDN production.