聚麩胺酸與儲存對豆腐理化特性的影響

Effects of Poly-γ-Glutamic Acid and Storage on the Physicochemical Properties of Tofu

李烱源(Chiung-Yuan Lee) ； 郭孟怡(Meng-I Kuo)

《輔仁民生學誌》 20卷1期 (2014/06) Pp. 51-69

摘要

本研究以分子、結構和巨觀等三個層次探討於16天儲存期間盒裝豆腐的水分子狀態、流變特性以及微結構等理化特性之變化，並探討添加不同分子量（高、中、低）及濃度（0.10%、0.15%及0.20%）聚麩胺酸的影響。藉由離心作用方式可將盒裝豆腐內水分子狀態區分為expressible water及entrapped water。儲存期間控制組豆腐內的expressible water含量減少而entrapped water含量增加。豆腐之水分子狀態亦根據核磁共振儀之spin-spin relaxation time（T2）分析區分成低移動性（T21~19 ms）及高移動性（T22~90 ms）與相對應的質子強度A1和A2。儲存期間控制組豆腐內的T21及A1呈現增加趨勢，而A2則呈現下降趨勢。儲存期間豆腐內entrapped water含量以及低移動性水分子含量（A1）增加表示其保水性提高。添加γ-PGA會增加豆腐內entrapped water含量以及低移動性水分子含量。儲存期間γ-PGA豆腐內水分子狀態之變化趨勢與控制組相同，而以添加0.2% HMW γ-PGA豆腐的保水性最佳，於儲存期間最安定。添加γ-PGA會降低豆腐的G'及G＂值，儲存期間豆腐的G'及G＂值有增加的趨勢。控制組豆腐內呈現蜂窩狀且孔洞較均一的結構，γ-PGA豆腐則呈現孔洞較不均一且不連續的結構。儲存期間控制組豆腐和γ-PGA豆腐均改變成為較小孔洞且緊密的結構。因此，豆腐內蛋白質分子以及水分子於儲存期間重新排列，進而增加豆腐的保水性和黏彈性，而添加γ-PGA能有效改善豆腐於儲存期間之變化。

關鍵字

豆腐 ； 聚麩胺酸 ； 儲存 ； 水分子移動性 ； 流變特性

並列摘要

The changes in the physicochemical properties, including the state of water, rheological property, and microstructure, of packed tofu during 16-d storage were investigated under molecular, structural and macroscopic levels; and the effects of γ-PGA addition with different molecular weight (high, medium, low) and concentration (0.10%, 0.15%, 0.20%) on the physicochemical properties of tofu during storage were also studied. Water in tofu was divided into expressible water and entrapped water using centrifugation. The amount of expressible water in control tofu decreased but that of entrapped water increased during 16-d storage. The state of water in tofu was also classified into two fractions based on the spin-spin relaxation time (T2) measured by nuclear magnetic resonance. T21 (19 ms) and T22 (90 ms) represented low and high water mobility in tofu, respectively, and their corresponding proton intensities were A1 and A2. The values of T21 and A1 increased but that of A2 decreased in control tofu during storage. Increase in the amount of entrapped water and low mobility water indicated an increase in water-holding capacity of tofu. The addition of γ-PGA resulted in increase in the amount of entrapped water and low mobility water in tofu. Change in the state of water in γ-PGA tofu during storage was similar to control. Tofu prepared with 0.2% high MW γ-PGA had best water-holding capacity and storage stability. The G' and G＂ of tofu decreased with γ-PGA addition and that of tofu increased with storage. The control tofu showed the uniform and honeycomb-like structure, and γ-PGA tofu showed the discontinuous structure with larger pores. The microstructure of both tofus became compact with small pores during storage. The above results revealed that the redistribution of protein and the state of water in tofu during storage would lead to an increase in its water-holding capacity and viscoelasticity. The addition of γ-PGA could improve the changes of tofu during storage.

並列關鍵字

tofu ； poly-γ-glutamic acid ； storage ； water mobility ； rheological property