Quality assessment of frying oils and fats from 63 restaurants in Athens, Greece

Samples of used frying oils and fats from 63 restaurants and fast-food outlets, from the inner and outer suburbs of Athens, were randomly collected during a 1-month period. Sampling was performed after deep-frying or pan-frying of several foods, of both vegetable and animal origin, in different frying oils or fats (sunflower oil, cottonseed oil, corn oil, palm oil, palm kernel oil, soybean oil, vegetable shortening oil, vegetable cooking oils and fats). Sunflower oil was the most widely used frying medium and deep-fried potatoes (French fries) were the most common fried food. Sixteen samples (approximately 25%) were found with polymerized triglycerides (PTG) over the 12% limit of rejection, while 11 of them (approximately 17%) with total polar materials (TPM) over the 25% limit of rejection. From the above ‘over-limit’ samples, only one was from the pan-frying process. The higher TPM and PTG mean values were found in low-unsaturated vegetable frying oils and cooking fats, with the highest values observed when food of animal origin was fried. Vitamin E content of the fried samples examined was lower than that of the respective fresh samples (28% mean loss), but in most cases in relatively high levels.