ANÁLISES FÍSICO-QUÍMICAS DO ÓLEO DE SOJA UTILIZADO EM FRITURAS

Abstract

Oils and fats are man's main sources of energy, also called lipids. These foods must be consumed because they have essential fatty acids (linoleic acid and oleic acid) that the body does not produce. They can be consumed through animal or vegetable species that have this component and also in the use in preparations, mainly in frying processes. This process occurs when the food is immersed in oil heated to about 150ºC 180º C. When preparing food, oil has the function of imparting flavor and aroma, making it more attractive for consumption, but recently there has been an increase in studies regarding the consequences of excessive consumption of fried food, because during the frying process, the food acquires the properties that are present in oil. Therefore, the high temperatures cause alterations in the oil's composition, because they are highly oxidized and can bring nutritional implications, leading to pre-disposition to atherosclerosis and mutagenic action or even carcinogenic. With this, this study aims to analyze the changes that occur in oil from continuous frying of pastries for 6 hours. To do this, titulometric methods were used to investigate the physicochemical characteristics (acidity index, peroxide, and refraction) and also with sophisticated equipment, through gas chromatography coupled to the mass spectrum. The methodology used was from the book Physical-chemical methods for food analysis from the Adolfo Lutz Institute, 4th edition (2008). Seven samples were analyzed, the first without heating and every 1 hour for 6 consecutive hours. The results obtained in the chromatography showed that the oil did not undergo significant changes in its composition during the entire process. According to the percentage of concentration in the samples we have: linoleic acid, which is an essential fatty acid; elaidic acid, which is the trans fatty acid of oleic acid and the major competitor with linoleic acid in the body; palmitic acid, which has a hypercholesterolemic effect that can increase the blood cholesterol level; and stearic acid, which is a neutral fatty acid that can act to reduce LDL (low density lipoprotein), and thus prevent cardiovascular diseases. In the physicochemical analyzes the acidity index showed the greatest difference found, the lowest value found was 0.1612 mg NaOH/g and the highest value was 0.3969 mg NaOH/g before that we have that after 6 hours of frying, it still kept ANVISA specifications, which for refined oils is 0.6 mg KOH/g. We conclude, therefore, that there were hydrolytic breaks associated with randity, which quantifies the formation of free fatty acids. In the peroxide index, the lowest calculated value was 2.719 meq/Kg and the highest was 3.736 meq/Kg, these values are within the stipulated by ANVISA, which is 10 meq/Kg. The difference found in the values characterizes the process of oxidative rancidity, which is the autooxidation of acylglycerols with unsaturated fatty acids by atmospheric oxygen. In the refractive index, there was the smallest difference found, which was 0.0014 between the first and the last sample, this parameter indicates the increase in the degree of unsaturation of the bonds and the increase in the length of the hydrocarbon chain, as there was little change, we concluded that there was no change in the composition of the samples for unsaturated fatty acids. In view of the above, this work obtained good results on the transformations that occurred in the oil, all within the parameters showing that changes occur in 6 hours of frying, but the oil can still be reused, as it is within the specifications of ANVISA.