Study On Quality Improve Of Extruded Instant Rice

The dehydration extruded instant rice has been prepared by extrusion granulatingtechnology．The raw material selection range of extruded instant rice was been establishedby exploring pasting properties of different varieties rice．Acomposite quality improver ofanti-aging appropriated to rice food (include extruded instant rice) has been determined byscreening multiple types quality improver with anti-aging effect．And the improvementsituation of the extruded rice added composite quality improver was been explored bycomparing of textural properties，rehydration properties，sensory properties，pastingproperties and micro structures．At last，the optimal edible methods of instant rice steamcook and rehydration cook were been discussed by sensory evaluation and rice palatabilitymeasurement．Measuring essential components and pasting properties of nine kinds rice，thendiscussing the correlation between them．The difference of pasting properties is due to theamylose content．And the aging phenomenon still is due to the difference of amylasecontent．Compounding rice flour with different amylase content then measuring theirpasting properties．Considering pasting properties and production technique of extrudedinstant rice，then determine the suitable amylose content to make extruded instant rice is13%-16%．In order to simulate the cooked rice food(include extruded instant rice)，the rice cakewas been made by adding the emulsifiers，hydrocolloids，modified starch to the riceflour．The results of different quality improver anti-aging which were tested by singlefactor experiments with the texture analyzer are as follow：wheat gluten＞hydroxypropylwaxy rice starch＞guar gum＞monoglycerides＞sodium alginate＞xanthan gum＞sucrosefatty acid ester． Considering the single factor experiment results，additives categories andsense，the compound additive was formed by monoglycerides，guar gum，hydroxypropylwaxy rice starch．The compound quality improver to delay the aging of rice food was beendetermined by response surface experiments as below： monoglycerides1%、 guargum1.06%、hydroxypropyl waxy rice starch4%．The extruded instant rice has been prepared by using twin-screw extruder and addingthe compound quality improver to rice flour with amylose content14．51%．Comparing thedifference of textural properties， rehydration properties，and sensory properties betweenthe extruded rice adding quality improver and the extruded rice without quality improver，then discussing the improved situation of extruded instant rice adding quality improver．The study shows that the adding of compound quality improver can significantlydelay aging of extruded instant rice and improve the sensory properties of extruded instantrice rehydration cooked．The sensory score of extruded rice adding quality improver andwithout quality improver were separately55points and80points．The scanning electronmicroscope showed that the interior structure of extruded rice without adding qualityimprover is tigh，and the surface is glaze without obvious gap．The interior structure ofextruded rice adding quality improvers is linear chain．This structure can delay the gatherof starch molecules and restrain the aging of starch．The better edible methods of compound extruded instant rice which include steamcook and rehydration cook were measured by sensory evaluation and rice palatabilitymeasurement．The experiments show that when steam cooking，rice to water ratio1:1.0-1:1.2，steam10-12min with boiled water，at this time the instant rice taste good；when rehydration cook，soak120min with20℃water，soak90min with50℃w ater，soak60min with70℃w ater，soak30min with20℃water，then the instant rice is edible．Incomparison，rice to water ratio1:1.2-1:1.5soak30min，then can get the better taste instantrice．However，the instant rice soke120min with20℃w ater still can eat，this also explainthat the extruded instant rice is convention to eat at certain environment conditions．...