Eureka! Institutional Repository

Frying is one of the oldest and most common cooking methods and is used both for home use and for food industry, catering and food services. The main purpose of frying is to make food more appealing to consumers. This improves their organoleptic characteristics and gives them crisp texture, pleasant flavor and attractive colour. The hot oil during frying is used as a heat transfer medium, while a series of chemical reactions (hydrolysis, oxidation, polymerization, isomerisation) take place which contribute to the degradation of the oil quality. The oils that they were used for the study experiments are olive oil, palm oil and sunflower oil and they got analyzed for their characteristics and chemical composition. These oils have a vegetable origin and they had been got fried with various foods (potato, pumpkin, minced meat), fried without food but also and fresh. The measurement of their toxicity is based on a bacterial test on Vibrio fischeri sea bacterium, measuring its luminescence inhibition, characteristic of this bacterium. In the first stage, the oil samples are getting prepared to isolate their polar components with a rotary evaporator under vacuum. The addition of DMSO solution and seawater, results in the final solution which is added to V. fischeri and then the toxicity test is carried out by using the Microtox model 500 device. The results are presented in three food-based aggregated tables and in diagrams showing the percentage of luminescence inhibition of bacteria relative to the number of fryings of each oil. Repeated fryers increase toxic compounds. The concentration of polar ingredients in consecutive fryings of all oils with the three different foods but without food, has shown to increase. Greater "resistance" to fry, stability in toxicity, appears to have olive oil, sunflower oil, palm oil in turn. The biggest stability of olive oil during frying, is caused of the mono-unsaturated fatty acids from which it is composed. In conclusion, the Microtox test is a rapid method of assessing toxicity but needs further evaluation.