Oil stability index correlated with sensory determination of oxidative stability in light-exposed soybean oil

Validity of the oil stability index (OSI) as an accelerated test of oxidative stability has been questioned because of its high holding temperature, 110 degreesC, which may cause reactions that would not occur at lower temperatures. The purpose of this study was to characterize the usefulness of OSI as an accelerated oxidative stability test for oil of varying metal catalyst content by correlating OSI with the sensory induction period of light-exposed soybean oil. Five 400-9 aliquots of soybean oil were placed in Erlenmeyer flasks and treated with increasing levels of a metal pro-oxidant Cu2+ 2-ethylhexanoate. Pro-oxidant concentration ranged from 0 to 3.13 x 10(-5) M. Five-gram aliquots were taken from duplicate flasks and immediately tested using the Oxidative Stability Instrument. Heating block temperature was 110 degreesC. Sample flasks were then exposed to 800 footcandles of light and held at ambient temperature for 3 wk. One-gram aliquots were regularly withdrawn and Evaluated for rancidity by 10 trained panelists to determine the sensory induction period of each sample. Aliquots were also taken to determine OSI of light-exposed oil samples. Sensory induction periods were correlated with OSI, resulting in a squared partial correlation coefficient (r(2)) of 0.920. The r(2) for OSI of light-exposed oil samples ranged from 0.897 to 0.979. OSI appears to be an acceptable accelerated method for measuring the oxidative stability of light-exposed soybean oil that varies in metal catalyst content.