Machanism Of Paddy Storage And Varieties On The Properties Of Cantonese Rice Noodles

Paddies stored for over one years are traditionally used for processing Cantonese rice noodles, which provide good textural properties of rice noodles, such as low breaking ratio and low soup sediments. However more paddies stored for less than 1 year have to be used in Cantonese rice noodles processing, because of changes of market circumstance and aflatoxin pollution problem. Unfortunately these noodles made by newly paddies have poor textural properties, such as high breaking ratio and high soup sediments, under same processing conditions. Furthermore, textural properties of Cantonese rice noodles are also affected by varieties of paddies. It seems that studies on the effect of paddies storage and varieties on the textural properties of Cantonese rice noodles are necessary.A two steps single extruding machine was made. And the effect of extruding conditions on textural properties of Cantonese rice noodles was studies. Results showed that water ratio significantly affected the bulk density, cooking weight and cooking loss of Cantonese rice noodles. And the best water ratio was around 45%. Aperture of extruding machine had no effect on gelatinization degree, but had effect on cooking time, cooking weight and cooking loss. Gelatinization degree increased with water ratio, and showed no significant relations with cooking time, cooking weight and cooking loss.Chemical, thermal and crystal properties of paddies were determined during 18 months storage. Textural properties of rice noodles made by these paddies were also determined. Results showed that rice noodles made by longer stored paddies had better textural properties, including stretching, cutting, bending and were low in adhesiveness, fragment ratio, breaking ratio, soup sediments et al. Amylose content had little changes during 18 months storage, while fat acid value increased with storing time. No significant relationships was found between amylose content and textural properties of rice noodles (P>0.05). Adhesiveness, bending ratio and fragment ratio of rice noodles were significantly affected by fat acid value of paddies(P<0.01). Thermal properties of paddies changed a lot during storage, which showed a significant relationship with stretching properties of rice noodles(P<0.05). Crystal properties of paddies showed popular relationships with textural properties of rice noodles. It was significantly related with 13 of 14 indexes of textural properties of rice noodles.Chemical, thermal and crystal properties of 145 samples of early long-grain paddies harvested in Guangdong province in 2008 were determined. And textural properties of rice gels made by 27 different varieties of paddies out of 145 ones were determined too. Results showed that amylose content, gelconsistency and taste score were indexes affecting textural properties of rice gels, while chalky percentage, chalky kernels percentage and kernel form were indexes showed no effects. Firmness of rice gels was extremely affected by amylose content of paddies (n=27, r=0.536,P<0.01), gelconsistency (n=27, r=-0.584,P<0.01) and taste score (n=27, r=-0.471,P<0.05). Hardness of rice gels showed no relationship with amylose content of paddies, but with taste score (n=27, r=-0.479,P<0.05). Furthermore, textural properties were affected thermal properties of early long-grain paddies.ΔH negatively affected chewiness (n=27, r=-0.392,P<0.05) and firmness (n=27, r=-0.638,P<0.01) of rice gels. No significant relationship was found between crystal degree of early long-grain paddies and textural properties of rice gels (P>0.05). The existence of V style rice starch crystals caused the decreasing of firmness of rice gels.