| Summary: | 碩士 === 國立臺灣大學 === 食品科技研究所 === 84 === In extrusion cooking , both heat and mechanical force affect
food properties. Die acts as a former of the product.It is a high
temperature short time process . Recently , extrusion has been
used in manufacture of the third-generation snack . In this
process , pellet was formed by extrusion , then was heated by
frying , baking or other method to become a puffed product .
The characteristics of the final product depends upon
formulation and process conditions .
In this study , the effect of extrusion temperature(70℃, 85
℃, 100℃)and screw speed(50rpm ,80rpm ,110rpm) on the
product characteristics were investigated . The degree of
gelatinization increased with extrusion temperature , but
decreased as the increase of screw speed . The degree of
degradation increased with both extrusion temperature and
screw speed . The oil content of fried potato chips were lower
than the commercial product. The products made from high
extrusion temperature and high screw speed has the lowest oil
content among the tested samples . Increasing both extrusion
temperature and screw speed resulted in low bulk density of
pellet and high expansion ratio. The degree of expansion of fried
potato chips depended on the extrusion and frying condition .
The addition of NaHCO3 resulted in the decrease in bulk density
of pellet . As the NaHCO3 concentration were 0.35％, the
expansion of pellet increased remarkably. The color of the final
product became darker due to the browning reaction . Texture
profile analysis showed that the microwave potato chips had
higher hardness and crispness than the frying product . Thus the
method of heating can generate unique product characteristics .
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