| Four kinds of edible vegetable oil including peanut oil, soybean oil, blended oil and palm oil were used to fry three kinds of food stuffs including tofu, chicken fillet wrapped in flour and fried dough sticks. The effects of frying time on the polar compounds content and carbonyl value of frying oil to fix the early warning time of frying oil, and the effects of different frying oil and food stuffs on the polar compounds content of frying oil were studied. The results showed that polar compounds content and carbonyl value were positively correlated with frying time (rpolar compounds=0.809, rcarbonyl value=0.859,P=0.000). The mean value of polar compounds content increased from 11.85% to 20.96% after frying for 6-11 h, and the maximum value was 34.10%, which could be used as the early warning time for the quality of frying oil. The polar compounds content in the frying oil after frying for 12 h from low to high were as follows:21.1% for peanut oil, 24.1% for palm oil, 26.8% for blended oil, 27.8% for soybean oil, and 17.7% for tofu frying oil, 25.0% for chicken fillet wrapped in flour frying oil, 32.2% for fried dough sticks frying oil. After frying for 18 h, the increase of polar compounds content in different frying oil and different fried food oils from low to high were as follows: palm oil/blended oil, soybean oil, peanut oil, and tofu frying oil, chicken fillet wrapped in flour frying oil, fried dough sticks frying oil. |
