| Budget Amount *help |
¥3,800,000 (Direct Cost: ¥3,500,000、Indirect Cost: ¥300,000)
Fiscal Year 2007: ¥1,300,000 (Direct Cost: ¥1,000,000、Indirect Cost: ¥300,000)
Fiscal Year 2006: ¥1,000,000 (Direct Cost: ¥1,000,000)
Fiscal Year 2005: ¥1,500,000 (Direct Cost: ¥1,500,000)
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| Research Abstract |
The glass transition has attracted great interest from food scientists in recent years, because many phenomena related to food manufacturing and preservation could be systematically explained with a concept of glass transition : for example, food materials maintain their physical and chemical stability better in a glassy state than in a rubbery state. The glass transition temperature T_g for many foods has been determined by thermal analysis such as differential scanning calorimetry (DSC). The thermal analysis, however, does not provide information on molecular mobility. In this study, the difference in molecular mobility between glassy and rubbery materials was analyzed by a pulse NMR that can detect the mobility of the components in the system by analyzing the relaxation behavior of the protons, the and the effect of water on the molecular mobility being examined. In addition, the influence of glass transition on two important quality change of food powders, caking and color change w
… More
as investigated.
The glass transition temperature T_g for foods was determined by DSC. The values of T, for the foods examined decreased with increasing moisture content, due to plasticizing effect of water. As for wheat gluten, the critical point of color change AE can be taken as to correspond to the glass to rubber transition point. The DSC data of for gluten also support that gluten is in glassy state above the critical point of color change.
Water sorption isotherms of foods examined were sigmoidal similar to many food materials ; the amount of sorbed water increased drastically above glass to rubber transition point. The water sorption rate takes a maximum value near water activity 0.5-0.6.
FID (Free Induction Decay) of NMR was satisfactory described by a combination of two or three components, Gaussian, exponential, and Gaussian lineshapes. M_2 showed one or two transition temperatures. At low moisture content, the percentage immobile component was dominant, but it decreased as moisture content increased. At high moisture content, the protons directly attached to the carbon chains of molecules seemed to be immobile, those in the hydroxyl group to be relatively mobile, and those in water to be more mobile.
Powders stored at a temperature above T_g were caked after cooling to room temperature. Less
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