Monitoring Oxidative Degradation of  Thermally Stressed Palm Olein Shortening  by Spectroscopic and Chromatographic Techniques

Muhammad Hamid Raza,Adnan Mujahid,Tajamal Hussain,Ahsan Sharif,Azeem Intisar,Saba Nazir,Ejaz Ahmed

doi:10.4236/ojapps.2018.812048

Abstract

Deep frying with repeated use of same edible oil leads to the formation of lipid oxidation products. The presence of these oxidized products formed during frying at elevated temperature is hazardous for human health and therefore, requires prompt analysis for ensuring its fitness/quality. In this study, oxidative degradation of thermally stressed edible oils canola, sunflower and palm olein shortening was studied at 180&#176C ± 5&#176C up to 48 hours. Palm olein shortening remained stable during this period as the increase in its acid value was significantly less than canola and sunflower seed oils. The shortening samples were further studied by attenuated total reflectance Fourier transformation infrared (ATR-FTIR) and gas chromatography mass spectrometry (GC-MS) to evaluate the formation of various oxidation products due to thermal stress. ATR-FTIR indicates the formation of free fatty acids (FFAs), aldehyde groups and change in degree of unsaturation while GC-MS gives important information about profile of FFAs. The combination of these analytical techniques is useful for rapid and highly sensitive analysis of oxidized edible oil thus, ensuring its quality and fitness for safe use.

Highlights

The shortening samples were further studied by attenuated total reflectance Fourier transformation infrared (ATR-FTIR) and gas chromatography mass spectrometry (GC-MS) to evaluate the formation of various oxidation products due to thermal stress
In this graph it can be seen that acid values for canola and sunflower oil increases considerably as the heating time increases indicating that thermal stress results significant oxidation of edible oils
While palm olein shortening remains stable for quite long time and the increase in acid value is much less as compare to canola and sunflower oil samples

Summary

Introduction

Vegetable seed oils are important part of daily human diet [1] [2] as they give characteristics texture and flavor to food but they contain essential. These oils are polyunsaturated fatty acids which are susceptible to oxidation [4] [5] [6] and start to decompose the moment after they are collected from seeds and this process is accelerated by environmental factors including atmospheric oxidation, humidity and temperature. When oxygen molecules interact with polyunsaturated oils at high temperatures, it is mainly absorbed at double bond linkages and starts the degradation process This results in the formation of various breakdown products including hydroperoxides and a range of carbonyl compounds e.g. aldehydes, ketones, free fatty acids (FFAs) and other compounds [7]. The use of ATR-FTIR and GC-MS is suitable for analyzing breakdown products in thermally stressed palm olein shortening and accessing its quality in quick time without extensive sample preparation steps. These chemicals include potassium hydroxide (KOH), phenolphthalein (C20H14O4), isopropyl alcohol (C3H8O) and oxalic acid (C2H2O4)

Thermal Treatment of Edible Oil Samples

Acid Value Determination

GC-MS Analysis

Results and Discussion

Conclusion