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

The effect of the thermal treatment on chemical parameters of margarines enriched with phytosteryl fatty acid esters is evaluated. Sterols, fatty acids, polar and volatile compounds, dimers, trimers, tocopherols, 3‐MCPD and glycidyl esters are analyzed applying GPC‐RI, GC‐FID, GC‐MS, and HPLC. Additionally, a Rancimat test is performed to compare the oxidative stability of margarines. This study shows that margarines with and without added phytosteryl esters are both stable at a mild temperature of 60 °C over a period of at least 7 days. On the other side after 15 min of pan‐frying at 180 °C a degradation of unsaturated fatty acids (14–47%), phytosterols (31–49%), and vitamin‐E‐active compounds (71–100%) is found. The supplementation of margarines with phytosteryl fatty acid esters have no effect on their oxidative stability during pan‐frying characterized by Rancimat test and total polar compounds. Volatile, degradation products of fatty acids as well as phytosterols, are 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 is 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 is only very moderate. Practical Application : 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 °C. A significant amount of nutritionals as phytosterols, vitamin E active compounds, unsaturated fatty acids are degraded within 15 min and other undesired compounds as dimers, trimers, 3‐MCPD esters are 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. The research presents chemical changes in margarines with and without additional phytosteryl/phytostanyl fatty acid esters. In the graphical abstract compounds which naturally occur in those margarines are presented and compounds which are formed after thermo‐oxidative degradation during pan‐frying.