臺灣市售盒裝豆腐硬度值分析

Hardness Analysis for Boxed Tofu on the Taiwanese Market

"臺灣65 歲以上人口逐漸上升，並於2018 年正式邁入高齡社會，高齡者無論是牙齒或牙口之功能皆可能有下降的影響，且可能進一步造成咀嚼吞嚥障礙而有營養不良的疑慮。豆腐在臺灣是深受民眾喜愛且易取得的食品，除了價格便宜、熱量低、不含膽固醇又富含植物性蛋白質營養價值高外，其硬度普遍較低，是非常建議高齡者的食品之一。本實驗對臺灣市售盒裝豆腐硬度進行分析，品牌包含大漢、中華、義美、頂好、雅方與西北共6 種，而種類有家常豆腐、嫩豆腐、超嫩豆腐、雞蛋豆腐、板豆腐、涼拌豆腐、火鍋豆腐與凍豆腐共8 類22 種，並依據豆腐水煮處理與否，分成經水煮處理的熟食豆腐或不處理的生食豆腐以進行硬度的探討，透過質構儀(texture analyzer, ILS-S 1000N) 進行硬度分析，將收集硬度數據採用t 檢定、單因子變異數分析進行統計分析。 結果顯示不同品牌的豆腐硬度不同，經水煮後硬度值也會有差異。家常和超嫩豆腐中，生食的豆腐中華牌比大漢牌硬，經水煮後大漢牌豆腐隨著水煮時間增加硬度逐漸變軟，但是中華牌的硬度沒有隨水煮時間有太大變化，兩牌硬度熟食時為中華牌較硬；火鍋豆腐中在生食或熟食組，皆是中華牌比大漢牌硬，經水煮後兩牌於2 分鐘達硬度值最低；在生食的嫩豆腐中，義美牌硬度大於大漢及頂好牌，水煮後發現大漢牌的豆腐比較硬，而義美與大漢牌於水煮2 分鐘時的硬度比較低，頂好牌則於水煮3 分鐘後硬度比較低；雞蛋豆腐於生食或是熟食皆是中華牌比大漢及義美牌硬，三者均是在煮3 分鐘時硬度達最低；在板豆腐的部分則是生食或熟食均是義美牌硬度值大於大漢牌及中華牌，義美牌於水煮3 分鐘、大漢牌於水煮2 分鐘、中華牌於水煮1 分鐘時豆腐硬度最低；涼拌豆腐的生食組中，為大漢( 基改) 豆腐硬度值高於大漢牌與中華牌，在熟食組則硬度都明顯下降；凍豆腐則雅芳牌與西北牌於水煮1 分鐘時硬度達最低值，中華與義美牌於水煮30 秒時硬度達最低值。凍豆腐的硬度於實驗結果中呈現為硬度最高的豆腐種類不同品牌，分析發現凍豆腐的硬度與凝固劑種類有關，其均添加了含鈣凝固劑；而在不同品牌豆腐有不同硬度分析中也發現，中華牌豆腐如家常豆腐、超嫩豆腐、涼拌豆腐、火鍋豆腐等硬度比較高的產品是傾向使用含鈣凝固劑如硫酸鈣或碳酸鈣，而他牌皆使用非含鈣凝固劑如葡萄糖酸-δ- 內酯與氯化鎂。 影響豆腐質地的因素眾多，如凝固劑的含量及種類、豆漿加熱時間、溫度和pH 值等，不同品牌與不同種類的豆腐硬度會不同，由實驗得知添加含鈣凝固劑的豆腐硬度會比較硬，但是水煮3 分鐘內即可以軟化，希冀此次實驗結果能作為高齡者的備餐依據。"

"Taiwan, with its constantly growing population aged 65 years or older, has officially become an aged society in 2018. Older adults experienced decline in both their tooth conditions and chewing function, which can progress into chewing and swallowing disorders and thus cause malnutrition. Tofu is an accessible food ingredient well enjoyed by the Taiwanese public, and it boasts various favorable qualities, namely being low in cost and calories, free of cholesterol, rich in plant proteins, and usually soft in texture. Therefore, it is a highly recommended food for older adults. In this study, an experiment was conducted to analyze the hardness of boxed tofu of six brands on the market: Dahan, Chung Hwa, I-Mei Foods, Wellcome, Yaa Fang, and SEE BEST Food. A total of 22 tofu products that encompassed 8 types were analyzed; the types of tofu were tofu for general cooking, silken tofu, soft silken tofu, egg tofu, firm tofu, tofu for salad, tofu for hot pot, and frozen tofu. In the hardness analysis, all tofu products were analyzed in both their cooked and raw states. The analysis was conducted using the texture analyzer ILS-S 1000N. The hardness data were then analyzed statistically using a t-test and analysis of variance. The results showed that the hardness of tofu differed across brands, and their hardness changed after being cooked in water. Regarding tofu for general cooking and soft silken tofu, the raw tofu of Chung Hwa was harder than that of Dahan; when cooked, as the time of cooking in water increased, the Dahan tofu softened, whereas the Chung Hwa tofu did not change much in hardness. The Chung Hwa tofu was harder than the Dahan tofu after cooking. In terms of the tofu for hot pot, the Chung Hwa tofu was harder than the Dahan one, cooked or raw. The hardness of the 2 tofu products reached the lowest level after 2 minutes of cooking in water. For raw silken tofu, the I-Mai tofu was harder than that of Dahan and Wellcome. When cooked, the Dahan silken tofu was the hardest; the lowest hardness was observed after cooking in water for 2 minutes for the I-Mei and Dahan tofu and after 3 minutes for the Wellcome tofu. Regarding egg tofu, the Chung Hwa tofu was harder, cooked or raw, than that of Dahan and I-Mei. The 3 tofu products all reached the lowest hardness after 3 minutes of cooking. The I-Mei firm tofu was harder, cooked or raw, than that of Dahan and Chung Hwa. The lowest tofu hardness was observed after 3 minutes of cooking for I-Mei, 2 minutes for Dahan, and 1 minute for Chung Hwa. With regards to tofu for salad, the genetically modified Dahan tofu was harder than the Chung Hwa tofu and non-geneticallymodified Dahan tofu; the hardness of the three tofu products all dropped considerably after cooking. For frozen tofu, the Yaa Fang tofu and SEE BEST tofu both reached the lowest hardness after 1 minute of cooking in water, whereas the lowest point of hardness for the Chung Hwa and I-Mei tofu was reached after 30 seconds of cooking. Frozen tofu exhibited the highest hardness of all types for all six brands in the experiment, and its hardness was associated with the type of coagulant used; the coagulants used in all frozen tofu products contain calcium. The hardness analysis also revealed that Chung Hwa’s tofu products, such as the tofu for general cooking, soft silken tofu, tofu for salad, and tofu for hot pot, tended to be harder than the others’ because it used calcium sulfate or calcium carbonate as the coagulant. By contrast, all the other brands used coagulants that do not contain calcium, such as glucono delta-lactone and magnesium chloride, in their tofu products. The texture of tofu is affected by various factors including the content and type of coagulant as well as the heating time for, heating temperature for, and pH level of the soymilk. The hardness of tofu differed across brands and types. As shown in the experiment, tofu with coagulant containing calcium had a harder texture but softened within 3 minutes of cooking in water. The results could provide insights into meal preparing for older adults. "