辉光放电低温等离子体改性大豆分离蛋白可食膜工艺优化

为制备具有良好性能的可食膜,该文采用大豆分离蛋白(soy protein isolate,SPI)为成膜基材,利用辉光放电等离子体作用对可食膜进行改性,并研究等离子体处理时间、丙三醇质量浓度、pH值对可食膜水蒸气透过系数(water vapor permeability,WVP)、氧气透过率(oxygen permeability,OP)抗拉强度(tensile strength,TS)、断裂伸长率(elongation,E)的影响。利用响应面法对工艺参数进行优化,得到各因素对可食膜性能影响的大小依次为pH值丙三醇质量浓度等离子体处理时间。试验结果表明:丙三醇质量浓度为0.02 g/mL、等离子体处理时间为11.31 min、pH值为11,可食膜性能综合得分S为0.90。此时可食膜的断裂伸长率为273.77%、抗张强度为3.46 MPa、水蒸气透过系数为1.81×10~(-12) g/(cm·s·Pa)、氧气透过率为1.43×10~(-5) cm~3/(m~2·d·Pa)。通过原子力显微镜和接触角测量仪对可食膜表面进行观察,结果表明:经低温等离子体处理的可食膜表面物理结构发生改变,粗糙度增加,水接触角变小,有效提高大豆分离蛋白膜的机械性能和表面润湿性。

Process optimization of protein isolate edible films modified by glow discharge low temperature plasma treatment

Abstract: Soy protein isolate (SPI) is economic renewable material due to its degradability, high safety, special nutritious and healthcare function. It is ideal raw material to prepare edible films. Despite of a strong performance of air resistance and oil resistance, SPI is poor in terms of its mechanical strength and moisture resistance. In order to obtain a high quality SPI edible film in the experimental study, the optimal comprehensive score of edible film was used as the objective. And the total score of edible film depends on the elongation, tensile strength, water vapor permeability, oxygen permeability. Through consulting a large number of the edible film literatures, we found that the low temperature plasma can improve the quality of edible film. Therefore, the treatment of low temperature plasma can improve the mechanical properties, water vapor permeability and oxygen permeability coefficient of SPI film. And the comprehensive score of edible film was affected. In order to narrow the scope of the experiment, the single-factor experiment is conducted to study the influence of plasma treatment time, the pH value of membrane-forming materials and glycerol concentration. After considering the change of elongation, tensile strength, water vapor permeability and oxygen permeability, the range of data suitable for the next experiment is obtained. At this time, we will reduce the pH value to 9-11. At the same time, the amount of added glycerol concentration was determined as 0.015-0.025 g/mL. The experimental range of plasma time was 6-12 min. At this point, the experiment entered the critical moment. That is, we use principal component analysis and the comprehensive score of membership. Principal component analysis of experimental data is performed using SPSS software. Then the results obtained from the main component analysis are summarized. We can get the weight of each factor by combining the characteristic root, the variance contribution rate and the load matrix coefficient. Among them, the weight of elongation is 0.19, the weight of tensile strength is 0.22, the weight of water vapor permeability coefficient is about 0.29, and the weight of oxygen permeability rate is about 0.3. And we can get the comprehensive score of the edible film by the comprehensive score method. By using Design-Expert software to analyze and evaluate the comprehensive score of edible film, we can make a further analysis of the experimental data. Through the analysis of model, the influence degree of various factors on edible membrane is in the following order: pH value > glycerol concentration > plasma treatment time. Under the conditions of plasma processing time of 11.31 min, glycerin concentration of 0.02 g/mL and pH value of 11, the overall physical properties of edible films were the best with a score as high as 0.90, and the elongation, tensile strength, water vapor permeability and oxygen permeability of the edible films were 37.77%, 3.46 MPa, 1.81×10-12 g/(cm·s·Pa) and 1.43×10-5 cm3/(m2·d·Pa) respectively. The edible film was observed by atomic force microscopy and contact angles. The results showed that the edible film treated with low temperature plasma increased the roughness and decreased the contact angle. The plasma effect can effectively improve the mechanical properties and surface wettability of the SPI membrane. The results of this paper can provide the new reference for the development of edible films.