30A-34 |
Oils, margarines, and butters: Study using differential scanning calorimetry and thermogravimetrical analysis |
C. CRUZ-HERNANDEZ, R. M. Cruz-Hernandez, and F. Mijangos-Santiago. Universidad Nacional Autonoma de Mexico-FES Zaragoza, Batalla del 5 de Mayo S/N, Esq. Fuerte de Loreto, Col. Ejercito de Oriente, Delegacion Iztapalapa, Mexico, 09230, Mexico In the oils and fats industry a major use of physical property measurement is for quality control. Another area where physical property data are used is in the innovation and development of new products. Using Differential Scanning Calorimetry (DSC) and Thermogravimetrical analysis (TG) it is possible to identify typical behavior for materials, depending on their composition. During long storage, atmospheric oxygen is absorbed by the oils, and changes occur through slow oxidation. Weight change by oxygen absorption is measured by TG to help determine optimum storage conditons, and appropriate antioxidants. The objective of this study was to develop an analytical technique to characterize oils, margarines and butters using DSC and TG. Analysis was conducted by heating the sample from 50-300°C at the rate of 10°C/min under nitrogen or oxygen with a flow rate at 50mL/min. By DSC, decomposition and evaporation were evaluated under nitrogen atmosphere; oxidation was evaluated under oxygen atmosphere. The enthalpies in each thermogram were determined and used as a quantitative variable to make the analysis. Also, the weight loss, by TG due to decomposition or evaporation, was determined and used in this study. Analytical conditions and possible differences among oils - sunflower, maize, canola and mixed oils- as well as for different butters and margarines in the market were obtained. In this study some observed behaviors were considered as characteristic for the materials of this work. The following relationship for molecular weight was obtained; oils less than margarines less than butters. These results have demonstrated the effectiveness of the DSC and TG techniques for characterization of oils, margarines and butters. A correlation between the thermal behavior and the material composition was found. From these results, DSC and TG are proposed as alternative techniques in quality control. The results also serve as a reference for future use in DSC studies of similar materials.
Session 30A, Food Chemistry: Lipids
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