本研究探討臭豆腐油炸過程中油炸油品質的變化，並評估建議炸油品質的快速篩選指標。實驗以大豆沙 拉油在170 ± 10℃ 下油炸臭豆腐，每次油炸5分鐘，油炸頻率每小時六次，每天四小時，連續油炸5天。結果 顯示油炸臭豆腐油脂之總極性物質則由第一天的8.71%持續上升至第五天的27.89%酸價也有類似的變化趨勢， 顯示臭豆腐基質成分參與油脂氧化反應是油炸油脂質劣變的主要因素。油炸油的總極性物質與酸價呈正相關 R2 = 0.935，但是總極性物質達規定標準25%時，酸價僅達1.60 mg KOH/g oil左右，仍低於規定值的2.0 mg KOH/ g oil。進一步分析共軛雙烯價 (UV234 吸收值) 和色澤變化，包括L, a, b以及代表褐變程度的420 nm吸收值等， 結果顯示UV234 吸收值、b值和420 nm吸收值均隨著油炸天數的延長而有顯著增加，且均與總極性物質呈正相 關，R2分別為0.951、0.894和0.904，當總極性物質達25%時，UV234 吸收值、b值和420 nm吸收值分別約為1.0、 8.0和0.45左右，建議此三種光學檢測方法應可作為以大豆油油炸臭豆腐時，油炸油品質管理的快速初步篩選 指標。

The purpose of this study was to investigate the quality change in frying oil during frying of stinky soybean curd. The proper method for fast determination of the oil quality was also evaluated. The stinky soybean curd was fried in soybean oil at 170 ± 10oC for 5 min. The frying process was carried out six times per hour for four hours per day, and fried for five days, continuously. The results indicated that the total polar compounds of frying oil increased from 8.71% to 27.89% during five days frying. Changes of acid value showed similar trend as total polar compounds. This hinted that the matric of stinky soybean curd involved in lipid oxidation of frying oil, which led to accelerate the deterioration of the frying oil. The determination coefficient between total polar compounds and acid value was 0.935. However, the total polar compounds of frying oil reached to the action level, 25%, while the acid value was only about 1.60 mg KOH/g oil, which was still lower than action level, 2.0 mg KOH/g oil. Furthermore, the absorbance of UV234 nm, UV420 nm, and b value of L, a, b increased significantly during frying processing. Positive correlation between total polar compounds and these three indices was observed with determination coefficient of 0.951, 0.904, and 0.894, respectively. The absorbance of UV234 nm, UV420 nm, and b value were 1,0, 0.45, and 8.0, while the total polar compounds was 25%. Thus, it is suggested that these three spectrometric methods could be used, single or combined, as rapid screening method to evaluate the quality of frying oil, i.e. soybean oil, during fried stinky soybean curd processing.