| Areca taro is a high-quality vegetable has high starch content which restricted the development of deep processing products. In order to improve the processing technology, this paper studied the extrusion process of the areca taro powder. The physic-chemical characteristics of the areca taro and extrusive areca taro were compared. Based on these, explored a product of areca taro instant powder which has good stability and solubility. The main results and conclusions were as follows:(1) Areca taro was chosen as the raw material and extruded by Twin-Screw Extruder. The influence of different screw speed, feed speed, materiel moisture content and barrel middle temperature on the radial expansion ratio, the gelatinization degree, density, WAI and WSI of areca taro whole meal were studied. The results showed that the optimal parameters of each single factor:The screw speed was 400r/min, feed speed was 200r/min, materiel moisture content was 14% and barrel middle temperature was 140℃.(2) Base on the single factor experiment, response surface methodology was used to optimize the process parameters. Using Design Expert 8.0.6 software to build a mathematical model, then studying the best single factor of areca taro whole meal extrusion process and the various factors interaction effect on radial expansion ratio and gelatinization degree. The results showed that the optimum process parameters: screw.speed was 398r/min, feed rate was 227.2r/min, material moisture content was 13.98%, barrel middle temperature was 138.87℃. Under optimal conditions, the radial expansion ratio was 4.47% and the degree of gelatinization was 85.94%.(3) The change of physic-chemical characteristics between the areca taro and the areca taro extruded by optimum process parameters were studied. The results showed that:Water, starch, crude fat, protein and crude fibre content of the areca taro had declined after extrusion. The extrusive areca taro’s gelatinization degree and WSI were increased. WAI, transmittance and powder liquidity were decreased. The areca taro starch paste had the higher solubility, better retrogradation and bad freeze-thaw stability and expansion degree. Areca taro starch paste and extrusive areca taro starch paste were both pseudoplastic fluid. After extrusion, the viscidity and consistence were lower than the original, thixotropy was not obvious, the degree of in-shear structural recovery was increase. The decrease of extrusive areca taro starch paste’s gel property showed the fluid behavior development. Extrusive areca taro powder appeared a new absorption peak in 817.80cm-1. It showed that generated a new group. The absorption peak was not obvious in 2250-2500cm-1 showed the areca taro starch react with sodium trimetaphosphate is more easily after extrusion. Scanning electronic micrographs showed that extrusion make starch from the elliptical shape to mutual adhesion and irregular blocky structure.(4) On the basis of the above, according to the NY/T 1884-2010 Green food-Fruit and vegetable powder, the comprehensive evaluation method of vague mathematics and f function method, we explored a areca taro instant powder. The results showed the effect degree of stability on areca taro instant powder is sodium alginate>pectin>β-cyclic dextrin>carrageenan>arabic gum>sodium carboxymethyl cellulose. The effect degree of sensory quality on areca taro instant powder is citric acid>white granulated sugar>honey. The preferable addition of flavoring is:white granulated sugar 14%-18%, honey 1%-3%, citric acid 0.3%～0.5%. The optimal proportion of flavoring is:white granulated sugar 16%, honey 1%, citric acid 0.3%. The study of extrusion areca taro instant powder showed the best disperal of instant powder was made by rotary pelleting machine with 2.0mm sieve diameter. Then providing theoretical basis and scientific guidance for industrial production. |
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