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Lipids not only serve as lubricant during extrution, but also
participate in various physico-chemical reactions, thus
affect- ing the quality of extrudate. In this research, the
interactions between lipids and other components in rice
during extrusion, and the effects of these interactions on the
quality attributes of rice extrudates were investigated.
Results showed that barrel temperature, muisture content of
feed, and screw speed were the major factors which affected
the binding of lipids with other rice components. In general,
more vigorous conditions would result in more interactions. At
barrel temperature 150 degree C, 200rpm of screw speed, and
23％ of feed moisture content, the rice lipids were primarily
interacted with proteins. At barrel temperature 200 degree C,
200rpm of screw speed, 13％ of feed moisture content,
possibly due to protein denaturation and starch
gelatinization, less interaction was observed between lipid
and protein, but the interaction between lipid and starch
increased significantly. Becausbe of bulky size and lack of
functional groups, the triglyceride formed weak bond ing with
othercomponents in rice, such as Van Der Waals force and dipole
dipersion force. The interactions between free fatty acids and
phospholipids, on the other hand, were stronger,their bonding
included hydrogen bonding, hydrophobic interaction, and
electro- static interaction. The bonding between lipids
and other rice components were physical in nature. Since the
interaction between exogenous lipids and protein was more
vigorous than that between endogenous lipids and proteins
during extrusion, the breaking force of the milled rice
extrudate containing added rice oil was greater than that of
brown rice extrudate. In general, the interactions be- tween
lipids and other rice components did not affect the quality of
rice extrudate. However, lipid binding increased the stability
of rice oil in extrudates during storage.
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