| Extrusion technology is widely used in textured vegetable protein food production.Gluten is a kind of vegetable proteins derived from wheat with a variety of sources and can be used to significantly improve the texture and fibrosis of the extrusion textured food. The current studies about wheat gluten focused on low-moisture extrusion with wheat flour as raw material. However, the literature reports about high-moisture extrusion with wheat gluten powder as raw materials are less, and the gluten extrusion textured processing technology are lack of systematic research.In this paper, the single factor experiment and multiple factor experiment were used to study the influence of extrusion operation parameters on system parameters and target parameters in gluten extrusion process. The factor analysis method was applied to comprehensive evaluation and the extrusion parameters were optimized. And the changes of product structure in high and low moisture extrusion process are studied individually. Additionally, different wheat varieties HMW-GS composition on gluten flour by high-moisture extrusion effect has also been investigated. The main results indicated as follow:(1) The single factor experiment of gluten at high and low moisture content showed that material moisture and barrel temperature have siginificant effects on system parameters during low-moisture extrusion. Material moisture, barrel temperature, screw speed and feed speed effect on the target parameters (product property). The suitable range of each operation parameter is intially screened. The range of operation parameters is20%～24%material moisture, barrel temperature about190℃, screw speed at160r/min ～220r/min, feed speed at77.58g/min-81.85g/min. Material moisture, barrel temperature and feed speed have siginificant effects on system parameters during high-moisture extrusion. Material moisture, barrel temperature, screw speed and feed speed effect on the target parameters (product property). The suitable range of each operation parameter is intially screened. The range of operation parameters is50%～54%material moisture, barrel temperature160℃～170℃, screw speed at160r/min, feed speed at18.90g/min.The compare of extrusion property with high and low moisture showed the torque and press with high-moisture extrusion are lower than that of low-moisture extrusion. Specific mechanical energy of high-moisture extrusion is lower than that of low-moisture. The water holding capacities which at different material moisture and screw speed with high-moisture extrusion are higher than that of low-moisture extrusion.(2) The multiple factor experiment of gluten showed that different system parameters of extrusion machine showed a significant positive correlation (P<0.01), system parameters and many characteristics of product exhibited significantly related (P<0.05), and the different product characteristics showed a complex correlation; different product quality characteristics are in line with different regression models. Three common factors have been used to the characterization of extruded products. According to the factor score of sample, a comprehensive evaluation score of sample was carried out, and then a regression equation of the score was constructed. The effect of operation parameters to the product quality for low-moisture gluten extrusion was follow by barrel temperature> material moisture> screw speed> feed speed. The effect of operation parameters to the product quality for high-moisture gluten extrusion was follow by material moisture>feed speed>barrel temperature> screw speed. A frequency analysics was used to optimize the extrusion process. The optimization of operation parameters at low-moisture were:material moisture21.10%～21.83%, barrel temperature191.39℃～193.94℃, screw speed177.12r/min-188.19r/min, feed speed67.47g/min-70.63g/min. The optimization of operation parameters at high-moisture were:material moisture52.70%-53.49%, barrel temperature159.08℃～162.02℃, screw speed154.39r/min-165.61r/min, feed speed21.66g/min～23.32g/min。(3) The product structure of gluten with high and low moisture extrusion showed a similar variation. After extrusion, total protein SDS-PAGE (SDS-polyacrylamide gel electrophoresis) bands showed a lighter color, gliadin content was decreased, and the number of low molecular weight spectrum decreased in A-PAGE (acid polyacrylamide gel electrophoresis). The solubility of product in buffer solution (PB)(extraction of natural protein) and PB+SDS (break the hydrogen bonding and hydrophobic interaction) were reduced. With the increase of barrel temperature, glutenin content decreased and the color of SDS-PAGE bands showed lighter, and it’s solubility in PB, PB+2-ME (breaking the two disulfide bonds) and PB+SDS was increased. With the increasing of moisture content, the solubility of extrusion products in PB+2-ME tends to decrease. When the barrel temperature achieves the need of complete organization state, protein fractions content in gluten with high and low moisture extrusion tend to a similar tendency.(4) The difference of protein structure between high and low moisture extrusion texturization existed There would be a new band in total protein SDS-PAGE band of low-moisture extrusion product. The solubility in gliadin content and the number of low molecular weight spectrum in glutenin SDS-PAGE in high moisture products was declined, and the number of low molecular weight spectrum in glutenin SDS-PAGE are reduced, but it’s solubility in the PB+2-ME solubility are increased. With the moisture content increase, for the low-moisture extrusion, the bands of total protein SDS-PAGE are lighter color, the gliadin content first decreased and then increased, a band color in a region are shallowing, the solubility in PB, PB+SDS and PB+SDS are first decreased and then increased, and the solubility in PB+SDS+2-ME increased. For the high-moisture extrusion, the gliadin content in products decreased gradually, the color of a band in co region is pale, but a band in y region is deepening. Glutenin content increased and SDS-PAGE bands of color deepening, the solubility in PB, PB+2-ME and PB+SDS solution solubility decreased, while the solubility in PB+SDS+2-ME solution slightly elevated. As the increase of temperature in barrel, during the low-moisture extrusion, the color of total protein SDS-PAGE band was shallowing, and the gliadin content reduced first and then elevated. One of the bands in alpha zone gradually become darker, the color of two high molecular weight bands at the upper ω area deepened. During the high-moisture extrusion, the gliadin content increased, the color of a band in ω region of A-PAGE deepening, and its solubility in PB, PB+SDS, PB+2-ME solubility increased.(5) Gluten extrusion texturization with different HMW-GS composition properties showed that composition of raw materials affect the property of extruded gluten. The gluten extrusion system parameters between different subunit types and subunits have not significant difference. Different subunits of site types of extrusion products have significant effects on the color, and different subunit combinations type have significantly influence on product property.1,7+9,5+10combined extrusion product quality is better for the high moisture wheat gluten extrusion texturization. |
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