Abstract
The objective of this research was to investigate the effect of heating temperature on the quality parameters of avocado and peanut oils subjected to heating. Vegetable oils were heated at varying temperatures (110, 140, 170, 200 and 230�C for 30 min) to follow quality alterations. Levels of peroxide value, iodine value, thiobarbituric acid reactive substances, total polar compounds, refractive index, free acidity, and fatty acids composition were determined to measure the extent of lipid oxidation. Peroxide value was significantly (p [ 0.001) influenced by heating temperature in the case of peanut oil. Iodine value decreased significantly (p [ 0.01) in both oils with the increase in heating temperature due to the decrease of the unsaturation degree. Avocado oil showed the smallest increase in thiobarbituric acid reactive substances and total polar compounds during heat treatment. The fatty acids profile of peanut oil was rich in polyunsaturated fatty acids with a level of 42%, followed by monounsaturated fatty acids with about 36%. The heat treatment of oils has produced changes in unsaturated fatty acids, these have undergone isomerization from cis to trans form. The increases of heating temperature up to 230�C significantly deteriorated the quality of peanut oil, but to a lesser extent the one of avocado oil.
Highlights
Vegetable oils have energy benefits and are necessary for the normal functioning of the body, lipids being the structural constituents of the body's cells
Values for Peroxide value (PV), iodine value (IV), Thiobarbituric acid reactive substances (TBARS), total polar compounds (TPC), refractive index (RI), and acid value (AV) are shown in Table 1 and Table 2
This study showed that oil from pressed and microwave-dried avocado pulp presented the lowest PV and AV, the highest oxidative and hydrolytic stability compared to the oil extracted with ethanol
Summary
Vegetable oils have energy benefits and are necessary for the normal functioning of the body, lipids being the structural constituents of the body's cells. Consumed in a moderate amount, these are an essential and healthy component of our daily diet [1]. Due to the widespread use of frying oils, the effect of high temperatures on these is of great concern both for their quality and nutritive value. Oils are subjected to numerous chemical reactions. These affect the flavour of the fried product and the quality of the frying oil. The taste, flavour, lifetime, and consumer acceptance of fried product are related to the frying oil quality [25]
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