Comparison of the oxidative stability of linseed (Linum usitatissimum L.) oil by pressure differential scanning calorimetry and Rancimat measurements.

The aim of this study was to compare the oxidative stability of linseed oil using the pressure differential scanning calorimetry (PDSC) and Rancimat methods, and to determine the kinetic parameters of linseed oil oxidation. Five cold pressed linseed oils were oxidized at different temperatures under PDSC (90-140 °C) and Rancimat (70-140 °C) test conditions. The oxidative stability of the linseed oils was calculated based on induction times (PDSCτmax, Rancimat τon), the Arrhenius equation and activated complex theory, frequency factors (Z), the reaction rate coefficient (k) for all temperatures, activation energies (Ea), Q10 numbers, activation enthalpies (∆H++), and activation entropies (∆S++). The PDSC method was more convenient for the determination of the induction time of linseed oils than the Rancimat method. During oxidation measurement by Rancimat method, the linseed oil polymerized, which affected the measurements. The reaction rate coefficient increased with rising temperature during measurement by both methods. The activation energy values of linseed oil oxidation using the PDSC and Rancimat methods ranged from 93.14 to 94.53 and 74.03 to 77.76 kJ mol-1, respectively. The Q10 , ∆H++, and ∆S++ values for the analyzed linseed oils were between 2.11-2.13, 90.54-91.30 kJ mol-1, -33.20 to -30.90 J mol K-1 calculated by PDSC measurements, and 2.23-2.32, 71.03-74.76, -59.42 to -49.08 J mol K-1 by Rancimat measurements, respectively.

Reversed phase HPLC with UHPLC benefits for the determination of tocochromanols in the seeds of edible fruits in the Rosaceae family.

Rosaceae family includes several edible fruit species processed in vast quantities and generates large amounts of seeds valuable in tocopherols. In the present study, the composition of tocochromanols in the seeds of 141 samples was determined by reversed phase high-performance liquid chromatography (RPLC) with diode array detector (DAD), fluorescence detector (FLD) and confirmed by mass detector (MS). The thirteen species belonging to the Rosaceae family were classified by multivariate statistical analysis, hierarchical cluster analysis (HCA) and principal component analysis (PCA) into two groups based on tocochromanols content. Group 'A' includes pears (Pyrus communis), sweet cherry (Prunus avium), sour cherry (Prunus cerasus), apricots (Prunus armeniaca), hexaploid plums (Prunus domestica), diploid plums (Prunus cerasifera), raspberry (Rubus idaeus), and rose hip (Rosa rugosa); while group 'B' quince (Cydonia oblonga), Japanese quince (Chaenomeles japonica), strawberry (Fragaria × ananassa), dessert apples (Malus domestica), and crab apples (Malus spp.). Two rapid (6-7 min) and low pressure (7.2-8.1 MPa) separation methods were developed and validated using two core-shell columns (i) C18 and (ii) F5. The F5 achieved a separation of ß and γ isomers while the C18 column did not.

Dry-aged beef quality with the addition of Mucor flavus - Sensory, chemosensory and fatty acid analysis.

Dry-aged beef is a premium product known for its unique taste and aroma. These characteristics are thought to partially depend on the composition of the microorganisms present on the meat surface during ageing. Recently several attempts to standardise this process were made. This study aimed to assess the effect of a fungal biostarter application on the profile of volatile compounds, fatty acid composition and sensory quality of dry-aged beef. The Longissimus muscle used in the experiment originated from 20 crossbred (10 heifers and 10 steers) animals from the crossing of Holstein-Friesian cows with beef breed bulls. A fungal biostarter composed of Mucor flavus strain KKP2092p was used for meat inoculation. Half of the material was aged without the use of a biostarter (Control samples). The dry-ageing of the meat was performed at a temperature of 1.5 °C with approximately 80-90 % relative humidity for 28 days. The use of Mucor flavus KKP2092p improved meat quality attributes (aroma liking, flavour and overall liking) as a result of the formation of specific volatile compounds. The profile of volatile compounds in the meat aged with Mucor flavus and control variants was differentiated. This study also indicated that Mucor flavus biostarter had an impact on the specific fatty acid composition. An insignificant effect of Mucor flavus on lipid oxidation expressed as mg/kg of malonaldehyde was also observed.

Effect of the Freeze-Dried Mullein Flower Extract (Verbascum nigrum L.) Addition on Oxidative Stability and Antioxidant Activity of Selected Cold-Pressed Oils.

The aim of the study was to analyze the influence of mullein flower extract addition on the oxidative stability and antioxidant activity of cold-pressed oils with a high content of unsaturated fatty acids. The conducted research has shown that the addition of mullein flower extract increases the oxidative stability of oils, but its addition depends on the type of oil and should be selected experimentally. In rapeseed and linseed oil, the best stability was found for samples with 60 mg of extract/kg of oil, while in chia seed oil and hemp oil, it was found with 20 and 15 mg of extract/kg of oil, respectively. The hemp oil exhibited the highest antioxidant properties, as evidenced by an increase in the induction time at 90 °C from 12.11 h to 14.05 h. Additionally, the extract demonstrated a protective factor of 1.16. Oils (rapeseed, chia seed, linseed, and hempseed) without and with the addition of mullein extract (2-200 mg of extract/kg of oil) were analyzed for oxidative stability, phenolic compounds content, and antioxidant activity using DPPH• and ABTS•+ radicals. After the addition of the extract, the oils had from 363.25 to 401.24 mg GAE/100 g for rapeseed oil and chia seed oil, respectively. The antioxidant activity of the oils after the addition of the extract ranged from 102.8 to 221.7 and from 324.9 to 888.8 µM Trolox/kg for the DPPH and ABTS methods, respectively. The kinetics parameters were calculated based on the oils' oxidative stability results. The extract increased the activation energy (Ea) and decreased the constant oxidation rate (k).

Oxidative Stability and Antioxidant Activity of Selected Cold-Pressed Oils and Oils Mixtures.

The aim of the study was to analyse the chemical composition and oxidation stability of selected cold-pressed oils and oil mixtures. The oils were tested for their initial quality, fatty acid composition, total phenolic compounds, DPPH, and ABTS free radical scavenging activity. The Rancimat method was used to assess oxidative stability. The obtained results were subjected to principal component analysis (PCA) to determine the influence of selected chemical properties on the oxidative stability of the oil. It has been found that different factors of oil quality influence the stability of cold-pressed oils. The highest correlation coefficient was noted between the induction time, peroxide value, and TOTOX indicator (r = 0.89). Fatty acid composition, including the percentage of SFA, MUFA, PUFA, and the ability to scavenge ABTS captions radicals, did not significantly affect the oxidative stability of the oils. Black cumin seed oil was the most resistant to the oxidation processes in the Rancimat apparatus, mainly due to the high content of phenolic compounds (384.66 mg GAE/100 g). On the other hand, linseed oil and its mixtures were the least stable. Their fatty acid composition was dominated by a polyunsaturated α-linolenic fatty acid, significantly reducing the antioxidant resistance.

Effect of Deep Frying of Potatoes and Tofu on Thermo-Oxidative Changes of Cold Pressed Rapeseed Oil, Cold Pressed High Oleic Rapeseed Oil and Palm Olein.

One of the commonly used food preparation methods is frying. Fried food is admired by consumers due to its unique taste and texture. Deep frying is a process of dipping food in oil at high temperature, usually 170-190 °C, and it requires a relatively short time. The aim of this study was to analyze the thermo-oxidative changes occurring during the deep frying of products such as potatoes and tofu in cold pressed rapeseed oils and palm olein. Cold pressed rapeseed oil from hulled seeds (RO), cold pressed high oleic rapeseed oil from hulled seeds (HORO), and palm olein (PO) (for purposes of comparison) were used. Characterization of fresh oils (after purchase) and oils after 6, 12, and 18 h of deep frying process of a starch product (potatoes) and a protein product (tofu) was performed. The quality of oils was analyzed by determining peroxide value, acid value, p-anisidine value, content of carotenoid and chlorophyll pigments, polar compounds, smoke point, color (CIE L*a*b*), fatty acids content and profile, calculation of lipid nutritional quality indicators, and oxidative stability index (Rancimat). Cold pressed high oleic rapeseed oil was more stable during deep frying compared to cold pressed rapeseed oil, but much less stable than palm olein. In addition, more thermo-oxidative changes occurred in the tested oils when deep frying the starch product (potatoes) compared to the deep frying of the protein product (tofu).