| Though Chinese rice output is the largest of the world, the processing of rice is still primary, more than80%rice of the amount is consumed as cooked rice directly; in the field of ready to eat food, the consumption of food made from rice is much less than the ones made from wheaten flour. People, who used to have rice for daily meals, are inclined to have bread, cake, pastry or others as breakfast now, which leads to the relative consumption of rice decreases. So it is of great significance to develop more rice-products based on its physiochemical properties and processing quality,In this research,71paddy varieties which widely cultivated nationwide were collected, after shelling and grinding to the second-class standard rice,the amylose content, protein content, taste value, gelatinization properties and other physiochemical properties of rice were detected; all the paddy varieties were processed into dehydrated instant rice by the technology of soaking and cooking once and hot-air drying, and their iodine blue value, enzymatic values, content of reducing sugar and textural properties after rehydration were tested too. Correlations and regression analysis were employed, combining with sensory qualities to find out the superior paddy with good processing quality, and then improving their technology. The principal research results are as follows:(1) Among the total71paddy varieties, the qualities of dehydrated instant rice made from18paddy varieties such as TYou272, Youyou128, TYou1128, ZhongYou9918, Bo You shuang qing, BoIIYou15, ZhanYou226, XianNong-2, ZhanYou2009, TYou100, Qiu Guang, ZhanYou809, ShenXian-2, LiaoXing-1, Jingxian89, Gui Chao, Hua Liang you-7and ChangBai-9(comes from Fu shun) are fairly good, for example, white color, clear, grain integrity, pretty looks and nice mouthfeel after rehydration, offer the products good commercial value and market prospect.(2) The results of correlation analysis between physiochemical properties and sensory qualities of dehydrated instant rice are as follows:the paddy with amylose content16%-22%, protein content8%-11%, taste value45-60(or65-70) and rice adhesive strength50mm-70mm(or80mm-95mm) for indica rice(or for japonica rice) have good processing performance, the appearance and mouthfeel of dehydrated instant rice made from which are at best class.Dehydrated instant rice of moisture content from6%-8%and iodine blue value no less than0.280taste good. reducing sugar of products made from indica rice are around20mg/g and for japonica rice, are about30mg/g, most of the enzymatic values are more than80%for both kinds.(3) The peak viscosity of different rice differs greatly: MeiChi-8from Yun Nan province has the largest peak viscosity (3.98Pa·s) is32times lager than YLiangYou-1’s peak viscosity (0.12Pa·s). Japonica’s viscosities (except for Xin Nian-3) are about2.5Pa·s while indica rice varies widely.Correlation between pasting temperature and sensory qualities of dehydrated instant rice is not significant, and correlation between the breakdown value and dehydrated instant rice’s shape is significantly negative; besides this, other gelatinization properties such as peak viscosity, trough viscosity, setback value, peak time and final viscosity has (highly) significant positive correlations with sensory qualities of dehydrated instant rice.The research shows that dehydrated instant rice made from paddy varieties with breakdown viscosity between0.8Pa·s-1.6Pa·s, peak time more than5.7min and setback viscosity gets close to zero has good qualities.(4) Hardness, springiness, gumminess, cohesiveness and resilience of textural analysis positively correlate with sensory qualities of dehydrated instant rice highly significantly, so they can reflect the qualities well. It were showed that the samples of which hardness value among2000-3500, cohesiveness above0.75and resilience above1.20have superior sensory qualities.(5) The regression analysis results showed that regression equation between physiochemical properties determined by the research and sensory qualities of dehydrated instant rice has highly significance (sig.=0.000a), so it is of great feasibility to use indexes such as taste value, amylose content, protein content and peak time to describe qualities of dehydrated instant rice.(6) The moisture content of rice can reach42%after soaking for72min at temperature of25℃±2℃, and it rises little even soaked more time.As for japonica rice,1.1times water (weight ratio) was added in, steamed for20 min, preserved for7min, then separated by stirring and dried by hot air (80℃), dehydrated instant rice(japonica rice as material) made by such techniques has more complete shape, less crack and fragment, higher yield, as well as good appearance and taste after rehydration. This techniques is also suitable for indica rice with setback value close to zero; while for indica rice,1.3times water (weight ratio) was added in, steamed for20min, preserved for10min, then separated with cool water and dried by hot air (80℃), dehydrated instant rice made by such techniques has entire shape, less crack and fragment, higher yield, as well as glossy, softer mouthfeel and nice chewiness after rehydration. |
