食用油脂加熱後酸價、過氧化價及電阻之變化

THE VARIATIONS OF ACID VALUE, PEROXIDE VALUE, AND RESISTANCE IN

為瞭解臺灣地區大宗食用油脂之氧化作用，探討不同加熱時間對加熱或油炸油中酸價、過氧化價及電阻之變化關係，尋求其特性，以供食品業者及食品衛生檢驗人員之參考。本試驗將未添加抗氧化劑之大豆沙拉油、花生油及豬油等三種食用油脂，以不同加熱時間（0、15、30、45、60、75、90分鐘）分別調製成有否油炸食物之不同檢體進行試驗。酸價及過氧化價之試驗，依據中國國家標準食用油脂檢驗法（CNS 3639）；電阻之測定則採用高單位電阻測定器進行測定。這三種食用油脂在同一溫度、相同加熱時間下，經測試結果顯示：日油炸食物之油比僅加熱之油，其油中酸價、過氧化價及電阻之變化較快。口經加熱後酸價及過氧化價之增加以豬油最快，尤其是油炸食物之豬油。有三種油脂經加熱至200°C，（但花生油續加熱十五分鐘）所測定之電阻為最大；三者若再繼續加熱則電阻隨加熱時間之延長而減小。（亦即導電度隨之增加）由試驗結果可知，大豆沙拉油及花生油在短時間加熱較適於油炸食物，至於加熱時間與油脂品質之關係，則有待進一步之探討。 In order to know the oxidation in edible oil, that was commonly used in Taiwan area, we try to find the relationship of the variations of acid value, peroxide value, & resistance in edible oil after heating or frying in different time.We take soybean oil, peanut oil, & lard, that are not added with antioxidants, to make the experiment. The above samples were heated & fried respectively in different time. (0, 15, 30, 45, 60, 75, 90 min.). According to the CNS 3639, the acid value & peroxide value of the samples were examined. By use of the Mega Ohmmeter, the resistance was examined.In the same temperature & time, we have observed: (1) The variations of acid value, peroxide value,& resistance in oil after frying is faster than heating. (2) After heating, the incresment of acid value& peroxide value of lard is faster than the others, especially by frying. (3) The three kinds of oil were heated at 200°C, (but the peanut oil was heated continually after 15 min.) we get the largest resistance. Then, the longer time we heated, the less resistance we observed. (ie. the conductivity is increased when we increase the heating time.) The experiment showed that, soybean oil & peanut oil is suitable to fry food in short heating time. But the experiment of relationship between the heating time & the quality of oil need to be explored.