Impact of Added Phytosteryl/Phytostanyl Fatty Acid Esters on Chemical Parameters of Margarines upon Heating and Pan-frying

Abstract

The effect of the thermal treatment on chemical parameters of margarines enriched with phytosteryl fatty acid esters was evaluated. Sterols, fatty acids, polar and volatile compounds, dimers, trimers, tocopherols, 3-MCPD and glycidyl esters were analysed applying GPC-RI, GC-FID, GC-MS and HPLC. Additionally, a Rancimat test was performed to compare the oxidative stability of margarines. This study showed that margarines with and without added phytosteryl esters are both stable at a mild temperature of 60 ºC over a period of at least seven days. On the other side after 15 minutes of pan-frying at 180 ºC a degradation of unsaturated fatty acids (14-47%), phytosterols (31-49%) and vitamin-E-active compounds (71-100%) was found. The supplementation of margarines with phytosteryl fatty acid esters had no effect on their oxidative stability during pan-frying characterised by Rancimat test and total polar compounds. Volatile, degradation products of fatty acids as well as phytosterols, were found after pan-frying. The composition of volatiles after pan-frying significantly differed depends on the presence of additional PSE in margarines. For the first time, it was shown that pan-frying with margarines over a period of 15 min results in a remarkable formation of 3-MCPD esters while the increase of glycidyl esters was only very moderate.

Practical applications: Based on this study results additional phytosteryl esters do not have antioxidative properties on margarines upon pan-frying. What is more, they are not stable during pan-frying at 180 ºC. A significant amount of nutritionals as phytosterols, vitamin E active compounds, unsaturated fatty acids were degraded within 15 minutes and other undesired compounds as dimers, trimers, 3-MCPD esters were formed. According to the research, heating at a high temperature over longer time should not be applied to this kind of product to avoid oxidation of valuable constituents and formation of degradation products. Volatile compounds which were found are characteristic for fatty acids and phytosterols degradation and can be used as indicators of margarines oxidation.

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