| As a new staple food in our country, potatoes are rich in nutrition, especially tryptophan and lysine which are scarce in traditional staple food. Rice noodles are one kind of the traditional staple food in southern China and are very popular with consumers. If extrusion technology has been introduced in potato noodle processing, it not only benefits to the innovation of rice noodle processing technology, but also is of great significance to the development of potato staple food products which are in line with Chinese diet culture. In this paper, potato-rice flour blends were applied to the processing of extruded noodle products, and effects of flour blends, extrusion processing technology and quality improvers on quality of extruded potato noodles were studied.Firstly, in the study of the influence of potato–rice flour blends on the quality of potato noodles, the basic physical-chemical properties, pasting property and rheological property of flour blends in different proportion were test, and the effects on quality of potato noodles were analyzed. Results demonstrated that the addition of rice flour in raw materials system limited the swelling capacity and solubility of flour blends: swelling power dropped from 11.74 g/g to 10.27g/g,solubility dropped from 17.15 g/100 g to 14.39 g/100 g; enhanced the gelatinization viscosity and rheological viscoelastic. When the content of rice flour reached 40%, the quality of potato noodle improved significantly: the broken rate dropped from 17.78% to 5.56%; the hardness and chewiness increased to 2258 g and 1625 g respectively. The correlation between properties of flour blends materials and quality of potato noodles showed that the swelling power of flour blends was very significantly negative correlated with hardness, springiness and chewiness of potato noodles(P<0.01), and very significantly positive correlated with cohesiveness, cooking loss and broken rate(P<0.01); whereas the peak viscosity, through viscosity and final viscosity of flour blends were very significantly positive correlated with hardness, springiness and chewiness of potato noodles(P<0.01), and very significantly negative correlated with cohesiveness, cooking loss and broken rate(P<0.01). According to comprehensive analysis the extruded potato noodles made from blending of potato flour with rice flour in the proportion of 6: 4 was close to commercial rice noodle samples, and the content of rice flour was relatively low.Secondly, in the determination of process parameters, the moisture content, screw speed, barrel pasting temperature and extrusion temperature were selected as factors, and their influences on the quality of potato noodles were investigated. On the basis of single factor experiments, the optimal processing conditions were determined through orthogonal experiment. The result indicated that the effect of four factors on the quality of potato noodles was as follows: moisture content > extrusion temperature > screw speed > pasting temperature. And the optimal conditions for processing of extruded potato noodles were: moisture content 38%, screw speed 95 r/min, barrel pasting temperature 105oC, barrel extrusion temperature 92.5oC. Under the optimal conditions, the sensory evaluation score of potato noodles was 77.50, and the cooking loss and broken rate were 11.56% and 4.44% respectively.At last, in the study of quality improvement, xanthan gum, sucrose ester and corn starch were selected as quality improvers and their influences on the quality of potato noodles were tested. On the basis of single factor experiments, the optimal ratio of composite improvers were determined through orthogonal experiment. Results showed that the formula of the composite improvers were xanthan gum 0.4 g/100 g, sucrose ester 0.3 g/100 g and corn starch 8 g/100 g, and the cooking and texture quality of potato noodles had been improved significantly, sensory evaluation score enhanced from 77.50 to 87.70. |
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