Impact Of Selected Chemical Charactersitics Of Cold-Pressed Oils
One of the most essential parameters used to measure oil quality is oxidative stability, which determines the oil’s resistance to oxidation. Unsaturated fatty acids oxidise during storage or heat treatment, causing their quality to deteriorate. Oils high in polyunsaturated fatty acids, particularly linolenic acid, are particularly susceptible to oxidation. Oils obtained by cold pressed technology in addition to triacylglycerides also contained lipid-accompanying compounds. As a result, its stability is determined not only by the composition of fatty acids, but also by the presence of antioxidants, primary and secondary oxidation products, metals, and other pollutants that may speed up or slow down the oxidation process.
Fig.1. Chemistry and Functionality of Cold Pressed Oils (ScienceDirect.com)
Thermal techniques can also be used to determine the oxidative stability of oil. Pressure differential scanning calorimetry (PDSC) is a good method for assessing the oxidative stability of vegetable oils in an accelerated mode; results are acquired faster due to the high temperature and pressure used. The fact that oil oxidation is an exothermic process is used in the PDSC approach. A reference sample is compared to the heat emitted during the oxidation of an oil sample. The difference in generated heat is graphed over time, from which the determined start time and maximal oxidation duration can be calculated. Both metrics are used to describe the oxidation of oil, although they relate to different stages of the oxidation process.
The products formed in the oxidation process have an ad-verse effect on the human body; therefore, proper assessment of the oxidative stability is a decisive step in the safety assessment of oil. The methods for determining the oxidative stability of oils are numerous.