Monika Fedko

The research aimed to evaluate the effect of high monounsaturated cold-pressed oil addition on the inhibition of refined rapeseed oil degradation during heating at frying temperature. Cold-pressed rapeseed, coriander seed, and apricot kernel oils were added in amounts of 5 and 25%. Refined rapeseed oil without additives and refined rapeseed oil supplemented with tert-butylhydroquinone (TBHQ) were negative and positive control samples, respectively. Blends were heated in a thin layer at 170 and 200 °C. Considering the increase in total polar compounds (TPCs) and oxidized triacylglycerol monomer (oxTAG) content, natural additives demonstrated protective properties and were more effective than the TBHQ additive, especially at 200 °C. The lowest increases in TPC and oxTAG were found in AO5% at 170 °C (10.17% and 1.40 mg/g oil, respectively) and in AO25% at 200 °C (5.71% and 47.53 mg/g oil, respectively). The presence of triacylglycerol (TAG) dimers was found only in samples heated at 200 °C, and the lowest was in the sample with 25% coriander oil. It can be concluded that the addition of cold-pressed oils limited the TAG oxidation process. The addition of 25% coriander oil was effective in inhibiting the TAG polymerization process, and it may be a powerful alternative to synthetic antioxidants in improving stabilization of frying oils.

Cold-pressed oils are rich sources of bioactive substances, which may protect triacylglycerols from degradation during frying. Nevertheless, these substances may decompose under high temperature. This work considers the content of bioactive substances in blends and their changes during high-temperature heating. Blends of refined rapeseed oil with 5% or 25% in one of three cold-pressed oils (rapeseed, coriander and apricot) were heated at 170 or 200 °C in a thin layer on a pan. All non-heated blends and cold-pressed oils were tested for fatty acid profile, content and composition of phytosterols, tocochromanols, chlorophyll and radical scavenging activity (RSA) analyzed by 2,2-diphenyl-1-picrylhydrazyl (DPPH), and 2,2′-azino-bis(3-ethylbenzothiazoline-6-sulphonic acid) (ABTS) assays. Moreover, the stability of phytosterols, tocochromanols, DPPH and ABTS values was determined in heated blends. All tocochromanols were lost during the heating process, in particular, at 200 °C. However, there were some differences between homologues. α-Tocopherol and δ-tocopherol were the most thermolabile and the most stable, respectively. Phytosterols were characterized by very high stability at both temperatures. We observed relationships between ABTS and DPPH values and contents of total tocochromanols and α-tocopherol. The obtained results may be useful in designing a new type of fried food with improved health properties and it may be the basis for further research on this topic.

The aim of the study was to determine the stability and heat resistance of extra premium olive oil. The study material consisted of six extra virgin olive oils (EVOO) obtained from Spain. Four samples were single-strain olive oils: Arbequina, Picual, Manzanilla, and Cornicabra. Two samples were a coupage of Arbequina and Picual varieties: Armonia (70% Arbequina and 30% Picual) and Sensation (70% Picual and 30% Arbequina). Olive oil samples were heated at 170 °C and 200 °C in a pan (thin layer model). In all samples, changes in indexes of lipid nutritional quality (PUFA/SFA, index of atherogenicity, index of thrombogenicity, and hypocholesterolemic/hypercholesterolemic ratio), changes in tocopherol, total polar compounds content, and triacylglycerol polymers were determined. Heating olive oil in a thin layer led to its degradation and depended on the temperature and the type of olive oil. Increasing the temperature from 170 to 200 °C resulted in significantly higher degradation of olive oil. At 200 °C, deterioration of lipid nutritional indices, total tocopherol degradation, and formation of triacylglycerol polymers were observed. A twofold increase in the polar fraction was also observed compared to samples heated at 170 °C. The most stable olive oils were Cornicabra and Picual.

Polar compounds and polymers are regarded as the most reliable indicators of oil degradation during heating, and it is desirable to find methods to reduce these undesirable changes. The aim of this study was (1) to determine the effect of enrichment with black cumin cold-pressed oil (CP) or essential oil obtained from black cumin cold-pressed oil in an equivalent amount (ES) on limiting the polar compounds and polymers content in blends based on refined rapeseed oil during high-temperature heating in a thin layer; (2) to determine tocochromanol losses and their effect on the change content of the polar compounds and polymers. Four fortified oils were made from refined rapeseed oil and one of the four additives (10% CP, 20% CP, 0.1% ES, and 0.2% ES). All fortified oils and refined rapeseed oil as a control sample were heated at 170 and 200 °C on the pan in a thin layer and evaluated regarding loss of individual tocochromanol homologs by HPLC-FL, polar compounds content, oxidized triacylglycerols (TAG), and polymers content by HPSEC-ELSD. Additionally, the fatty acid profile in nonheated oil was investigated. Tocochromanol analysis showed loss in all the samples. At 170 °C polymers were not detected; no difference was noted for polar compounds and oxidized TAG content; only the 20% CP sample showed a higher level. At 200 °C the 10% CP sample exhibited a significant protective effect with the lowest content of polar compounds, oxidized TAG, and dimers.

The growing awareness of consumers means that new products are sought after, which, apart from meeting the basic demand for macronutrients and energy, will have a positive impact on our health. This article is a report on the characteristics of the new oil blends with a nutritious ω6/ω3 fatty acid ratio (5:1), as well as the heat treatment effect on the nutritional value and stability of the oils. Prepared oil blends were heated at 170 and 200 °C. The fatty acid composition and the changes in tocochromanols content during heating were analyzed, as well as the formation process of polar compounds and triacylglycerol polymers. During heating the highest loss of tocochromanols was characteristic of α-tocopherol and α-tocotrienol. The total content of tocopherols after heating was reduced to 1–6% of the original content in the unheated oil blends. The exception was the blend of oil with wheat germ oil, in which a high content of all tocopherols was observed in unheated and heated samples. The content of the polar fraction during heating increased on average 1.9 and 3.1 times in the samples heated at 170 and 200 °C, respectively, compared to the unheated oils. The level of the polar fraction was related to the high content of tocopherols or the presence of tocopherols and tocotrienols in the heated sample. The polymerization of triacylglycerols led mainly to the formation of triacylglycerol dimers. Trimers were observed in a small number of heated samples, especially those heated at 200 °C. Regardless of the changes in heated oils, none of the prepared blends exceeded the limit of the polar fraction content, maintaining the programmed ratio of ω6 to ω3 acids. The principal component analysis (PCA) used to define the clusters showed a large variety of unheated and heated samples. An outlier in all clusters was a blend of oil with wheat germ oil. In these samples, the degradation of tocopherols molecules and the increase of triacylglycerol polymers and the polar fraction content were the slowest.

The growing human population renders challenges for the future supply of food products with high nutritional value. Here, we enhanced the functional and nutritional value of biscuits, a popular sweet snack, by replacing the wheat flour with 2%, 6%, or 10% (w/w) cricket powder. Consumer acceptance ratings for reference and 2% augmented cookies were comparable, whereas the higher levels of enhancement received inferior consumer scores. This relatively small change in biscuit recipe provided significant and nutritionally desirable enhancements in the biscuits, observed in a series of analyses. An increase in the protein content was observed, including essential amino acids, as well as minerals and fat. This conversion also affected the physical properties of the biscuits, including hardness, and water molecular dynamics measured by ¹H NMR. Cricket powder-augmented biscuits join the line of enhanced, functionally superior food products. This and similar food augmentation provide a viable scenario to meet the human food demands in the future.

Phytosterols are naturally occurring substances in foods of plant origin that have positive effects on the human body. Their consumption can reduce the level of low density lipoprotein (LDL) cholesterol. The presence of unsaturated bonds in their structure leads to their oxidation during production, storage, and thermal processes. The aim of the study was to determine how the degree of unsaturation of rapeseed oil affects the oxidation of phytosterols in oil during 48 h of heating. In all not-heated oils, the dominant groups of oxyphytosterols were 7α- and 7β-hydroxy sterols. During 48 h of heating, the rapid decrease of phytosterols’ levels and the increase of the content of oxyphytosterols were observed. The main dominant group in heated samples was hydroxy and epoxy sterols. Despite differences in fatty acid composition and content and composition of single phytosterols in unheated oils samples, the total content of oxyphytosterols after finishing of heating was on a similar level for each of the tested oils. This showed that the fatty acid composition of oil is not the only factor that affects the oxidation of phytosterols in foods during heating.

The aim of the study was to analyze the influence of the surface area to volume ratio of pressed and refined rapeseed oils on the changes in tocopherol content and polymerization of triacylglycerols during heating. In the study the pressed and refined rapeseed oil was heated at 170 °C, during 6, 12, and 18 h with three different surface area to volume (s/v) ratios (0.378, 0.189, and 0.126 cm⁻¹). During heating, a decrease in tocopherols and increases in dimers, trimers, and oligomers of triacylglycerols were observed. However, the changes were dependent on the surface area to volume ratio used, type of oil and time of heating. The biggest changes were observed in oil with the biggest s/v ratio (0.378 cm⁻¹), and the lowest when the s/v ratio was 0.126 cm⁻¹. The pressed oil was characterized by faster degradation of tocopherols and slower increase of triacylglycerol polymer levels compared to refined oil.