Study Of The Characters In RS Using NMR&MRI

Starch is an important food material, but due to the unstable nature and easily digest, it is limited in food use. So this paper study the physichemical,water mobility and diffraction in them,digestion in vitro,the effects on dough,the changes of baked food during the storage time and glass state transition on resistant starch which is made by autolating. The results show that as follows:1 The transparency,SEM picture, granulesize, x-diffraction crytical, viscosity, specific surface area, diamma of ganule, the property of retrogradation and so on all of these exist some differnce to some extent due to formation of resistant starch.2 The water mobility and diffraction by NMR shows the WHC and the water mobility both decreases during the resistant starch. From the relaxation character, the proton density A₂₁ is lower than native starch, it shows the water mobility is weak, but the proton density A₂₃ is higher, meanwhile shows the free water is more than native starch, the water outside the system,not the water in the granule,so the mobility is good. Therefore, the water mobility of the resistant starch is better than the starch's.3 From NMR characters, the ability of combining with water decreases because starch easily degrades into monosaccharose. But RS is on the contrary. From the relaxation of T22 and T23, it is evident that T22 of starch decreases more than RS, but T23 increases. It shows that anti-digestibility of RS, because monosaccharose digested by RS is less than starch.4 The formation process of dough is the combination peocess between water and macromolecule like the protein and carbonhydrate. The character of relaxation and texture is studied by adding the different kinds and quantity resistant starch, and the effects on dough. Meanwhile, resistant starch has more functional and physiological functions, so it is necessary to search that. The results show that the 5% is best choice for addition. From the MRI, we can see the water change and mobility during the proving time, and during the 1～2 h, the whole is uniform from the picture.5 This part studies the effects on the bakes food. Among the different kinds, the WHC and absorption of the sweet potato resistant is least. From the texture, the tendency change of the hardness is greater after adding it. By the relative analysis, it finds the hardness, storage time and T22 play an important role during the storage.6 NMR is the technology by analyse relaxation character of the active nuclear to measure the mobility of the molecule. The basis of the polymer glass state transition is the molecule mobility, when polymer change the state from the glass to the oak state, the frequency of group including proton increase, then the NMR can measure the change of the proton activity. In the baked food such as bread and biscuit, the glass transition temperature of bread is—15℃～—10℃, the biscuit is—40℃～—35℃. The biscuit contain about 30% shorting oil, but the bread is not. In the dough, even if the different quantity of resistant starch is added into it, the temperature is not changed, just slightly decrease, but if the products are placed below the temperature, the shelf life is prolonged.