不同豆腐種類的質地與微結構之比較

Texture and Microstructure of Different Types of Tofu

劉曉卉(Hsiao-Hui Liu) ； 黃耀主(Yao-Chu Huang) ； 郭孟怡(Meng-I Kuo)

《輔仁民生學誌》 18卷1期 (2012/06) Pp. 145-158

https://doi.org/10.29440/FJJHE.201206.0008

摘要

豆腐在亞洲是一種重要的食材，台灣市場上有許多種類的豆腐。這些豆腐有相似的加工過程，但是依照凝結劑種類、使用濃度或排出的乳清含量不同而製成多種不同質地的豆腐。然而不曾有研究比較豆腐的加工因子與其質地和微結構的關係，或探討微結構與質地特性的相關性。本研究的目的為測量台灣市售豆腐之化學組成分、微結構與質地特性，並比較其經不同前處理和不同顯微鏡觀察之微結構的差異。從市場購得五種豆腐，使用兩種掃描式電子顯微鏡（SEM，ESEM）與物性儀分別分析豆腐之微結構與質地特性。SEM樣品前處理分為兩種，豆腐使用2.5 %的戊二醛與1 %的鋨酸固定，與未經固定處裡的豆腐樣品；ESEM樣品前處理為冷凍乾燥且不進行鍍金。結果顯示，加工方式是主要造成豆腐化學組成分及質地特性不同的最大因素。嫩豆腐的微結構最鬆散並呈現蜂巢狀，板豆腐比家常豆腐和油豆腐有更為緊實的結構，豆干的顯微影像則最密實，因此嫩豆腐和豆干分別有最低和最高的硬度。未固定及利用ESEM觀察的豆腐樣品之顯微影像較有立體感。以上結果顯示質地特性與微結構有緊密的關聯，而加工造成的豆腐微結構變異可藉由掃描式電子顯微鏡觀察。了解微結構與質地特性的相關係有助於創造新穎的加工方法，提升豆腐的質地以滿足顧客的需求。

關鍵字

豆腐 ； 質地 ； 微結構

並列摘要

Tofu is a food product indigenous to Asia. Many types of tofu have appeared in the Taiwan's market. These tofu are made in a similar procedure except for variations in the type and concentration of coagulants and the amount of whey being pressed out. However, research on the relationship between these processing variables and the texture or microstructure of tofu, or the correlation between microstructure and texture properties was not found. The objectives of this study were to determine the chemical composition, microstructure and texture property of Taiwan's commercial tofu and to compare the microstructure of tofu observed with different types of microscope and pre-treated with different methods. Five types of commercial tofu, soft tofu, tofu-with-vegetable, plank tofu, fried tofu, and dried tofu were purchased in the market. The microstructure and texture property of tofu were measured by two types of scanning electron microscope (SEM, ESEM) and texture analyzer, respectively. The pretreatment of SEM sample was divided into two portions, one part was fixed with 2.5% glutaraldehyde and then 1% osmium tetroxide, and the other part was unfixed. The ESEM sample was pretreated with freeze-drying but without gold-coating. The differences in the chemical composition and texture properties of tofus were mainly due to the processing method. Soft tofu possessed faveolate and loosest structure. Plank tofu had more compact microstructure than tofu-with-vegetable and fried tofu. Dried tofu possessed the densest structure. Therefore, the hardness of soft tofu was the lowest and that of dried tofu was the highest. The microstructure of unfixed and ESEM observed tofu sample showed more stereoscopic. The above results revealed that the texture property of tofu correlated well with microstructure and the effect of processing variables on tofu microstructure could be observed by SEM. Understanding the relationship between the microstructure and the texture property of tofu would allow us to create novel method on improving the texture of tofu and fulfill the customer's need.

並列關鍵字

Tofu ； texture ； microstructure