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Studies on Water Mobility of Rice Starch/Galactomannan Systems Using Nuclear Magnetic Resonance
|關鍵字:||water mobility;水分子移動性;spin-spin relaxation time;T2;自旋-自旋弛緩時間||出版社:||食品科學系||摘要:||
本實驗主要利用核磁共振儀來測定米澱粉-半乳糖甘露聚醣混合系統中水分子的移動性及分布，並探討水分移動性與米澱粉糊物性間之關係。採用台農秈19號(TNuS19)、台農67號(TNu67)與台中糯70號(TCW70)三種米澱粉及關華豆膠(GG)與刺槐豆膠(LBG)兩種膠質為試驗材料，以Carr-Purcell-Meiboom-Gill (CPMG)分析法探討不同濃度(10-30%, w/w)米澱粉糊中水分子移動性。結果顯示，當澱粉濃度高於20 % 時，單純TNuS19及TNu67澱粉糊之自旋-自旋弛緩時間(spin-spin relaxation time; T2)係由兩個成份 (T2a及T2b) 所組成，TCW70則只由一個成分(T2b)組成。TNuS19之T2a值顯著高於TNu67，且隨著澱粉濃度提升而有較顯著的變化，而TNu67之T2a值則變化不大。三種樣品之T2b值皆隨澱粉濃度升高而降低 (p<0.05)，顯示水分子移動性隨濃度升高而降低，且 TCW70之T2b明顯高於TNuS19及TNu67。推測T2a及T2b分別來自於樣品中似固相(solid-like)及似液相(liquid-like)水分子之訊號。
During the investigation, rice starches of the known molecular structures from three of the most popular Taiwan varieties (TNuS19, indica; TNu67, japonica and TCW70, waxy) and two galactomannans (guar gum and locust bean gum) were used as samples to investigate the mobility and the distribution of water in starch/galactomannan systems using pulsed nuclear magnetic resonance (NMR). Carr-Purcell-Meiboom-Gill (CPMG) pulse sequence was used to elucidate the changes of the water mobility of starch pastes or starch/galactomannan mixtures at different concentrations (10-30%) and the spin-spin relaxation time (T2) was used to be an indicator of water mobility. The results indicated that the TNuS19 and TNu67 consisted two components (T2a and T2b) when starch concentration was more than 20%, but this situation was not observed for TCW70. TNuS19 had higher T2a than TNu67 and changed obviously with the increase of the starch concentration. TCW70 had higher T2b than TNuS19 and TNu67 for all samples. It suggested that T2a and T2b were corresponded to “solid-like” and “liquid-like” water molecular in starch pastes, respectively.
T2b of all samples were decreased as the increment of the storage time (p<0.05). However, the values of T2b of three samples were varied with the amylose content. It was suggested that retrogradation behavior in storage decreased the water mobility of starch pastes.
Dynamic rheometer and texture analyzer measured the physical properties of starch pastes. The result showed that the storage modulus (G'') and the loss modulus (G'''') of TNuS19 were highest among the three samples and followed by TNu67 and TCW70. But the tangent delta (tanδ) showed reverse situations.
Texture analyzer analysis indicated that TNuS19 had higher hardness, stickiness and adhesiveness than TNu67 and TCW70 and changed significantly with the increase of the starch concentration. The value of T2b was highly correlated with physical properties of starch pastes, especially with dynamic rheological parameters.
The value of T2 was increased as the increment of blending ratio of TCW70/TNuS19 starch composite systems (p<0.05). It was suggested that amylose may be play a major role of the water mobility of starch pastes. Generally, the addition of galactomannans caused the decrease the value of T2 of the starch composites especially for higher gum addition systems. It was suggested that adding galactomannans would decrease water mobility in starch/galactomannan systems.
|Appears in Collections:||食品暨應用生物科技學系|
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