Comparison of the oxidative stability of soybean and sunflower oils enriched with herbal plant extracts.

The present study was conducted to determine and compare the oxidative stability of soybean and sunflower oils using differential scanning calorimetry (DSC). These edible oils were enriched with marjoram (Origanum majorana L.), thyme (Thymus vulgaris L.), and oregano (Origanum vulgare L.) extracts at three different concentrations and synthetic antioxidant (BHA). The fatty acid composition of studied oils was determined by gas chromatography mass spectrometry to evaluate the content of unsaturated fatty acids that are sensitive to oxidation process. Oil samples were heated in the DSC at different heating rates (4.0, 7.5, 10.0, 12.5, and 15.0 °C min-1) and oxidation kinetic parameters (activation energy, pre-exponential factor, and oxidation rate constant) were calculated. The results showed that the oxidative stability of sunflower oil samples enriched with oregano extracts and soybean oil supplemented with thyme extracts was improved compared to samples without the addition of herbal plant extracts and the synthetic antioxidant.

Furan in roasted, ground and brewed coffee

Coffee is the most popular hot beverage in the world. The annual coffee production in 2010, 2014 and 2016 was 8.1, 9.0 and 9.3 million tons respectively. There are more than 100 coffee species, but only two of them: Arabica (Coffea arabica) and Robusta (Coffea canephora) have gained commercial importance. During roasting of green coffee beans not only desirable compounds are formed, that exert positive influence on the taste and flavour of coffee, but also small quantities of undesirable ones. Furan (C4H4O) is one of the latter. Furan is a volatile compound (boiling temp. of 31.4 oC) formed during thermal processing of food. The toxicity of furan has been well documented and it is classified as "possible human carcinogen" (Group 2B) by the International Agency for Research on Cancer. Various pathways have been reported for furan formation during food processing. It can be formed from carbohydrates, amino acids by their thermal degradation or thermal re-arrangement and by oxidation of ascorbic acid and polyunsaturated acids and carotenoids. High concentrations of furan have been reported in coffee, baked and roasted food and in food subjected to preserving in cans and jars. Furan levels in brewed coffee are typically near or below 120 µg/L, but it can approach thousands µg/kg in roasted whole beans or ground coffee. The highest concentration of furan in roasted coffee reaches the level of 7000 µg/kg. Taking into account that coffee is the most popular hot drink, it becomes the main contributor to furan exposure from dietary sources for adults. In this article the published scientific papers concerned with the presence of furan in roasted non-brewed and brewed coffee have been reviewed. The formation mechanisms and occurrence of furan in coffee and the harmful influence of furan on the consumer health have been discussed.

Fatty acids and sterols composition, and antioxidant activity of oils extracted from plant seeds.

This study determined and compared the contents of bioactive components in plant seed oils extracted with n-hexane (Soxhlet method) and chloroform/methanol (Folch method) from coriander, caraway, anise, nutmeg and white mustard seeds. Oleic acid dominated among unsaturated fatty acids in nutmeg and anise seed oils while petroselinic acid was present in coriander and caraway oils. Concerning sterols, ß-sitosterol was the main component in seed oils extracted with both methods. The content of total phenolics in nutmeg, white mustard and coriander seed oils extracted with chloroform/methanol was higher than in their counterparts prepared with n-hexane. The seed oil samples extracted according to the Folch method exhibited a higher ability to scavenge DPPH radicals compared to the oil samples prepared with the Soxhlet method. DPPH values of the methanolic extracts derived from oils produced with the Folch method were also higher than in the oils extracted with n-hexane.

Performance of structured lipids incorporating selected phenolic and ascorbic acids.

Conditions applied during frying require antioxidant which is stable at these conditions and provides protection for frying oil and fried food. Novel structured lipids containing nutraceuticals and antioxidants were formed by enzymatic transesterification, exploring canola oil and naturally occurring antioxidants such as ascorbic and selected phenolic acids as substrates. Lipozyme RM IM lipase from Rhizomucor miehei was used as biocatalyst. Frying performance and oxidative stability of the final transesterification products were evaluated. The novel lipids showed significantly improved frying performance compared to canola oil. Oxidative stability assessment of the structured lipids showed significant improvement in resistance to oxidative deterioration compared to original canola oil. Interestingly, the presence of ascorbic acid in an acylglycerol structure protected α-tocopherol against thermal degradation, which was not observed for the phenolic acids. Developed structured lipids containing nutraceuticals and antioxidants may directly affect nutritional properties of lipids also offering nutraceutical ingredients for food formulation.

Enzymatic interesterification of a lard and rapeseed oil equal-weight blend.

A mixture of lard and rapeseed oil (1:1, wt/wt) was interesterified using immobilized lipases from Rhizomucor miehei (Lipozyme RM IM) and Candida antarctica (Novozym 435) as catalysts. Enzymatic interesterifications were carried out at 60°C for 8 h with Lipozyme RM IM or at 80°C for 4 h with Novozym 435. The biocatalyst doses were kept constant (8 wt-%). The starting blend was quantitatively separated by column chromatography into pure triacylglycerol fraction (98.5%), and a nontriacylglycerol fraction containing free fatty acids (0.3%) and of mono- and diacylglycerols (1.2%). It was found that after interesterification the contents of free fatty acids and of mono- and diacylglycerols increased to 3.5% and 6.3% or to 1.5% and 4.5% when Lipozyme RM IM and Novozym 435 were used, respectively.The slip melting temperatures and solid fat contents of the triacylglycerol fractions separated from interesterified samples were lower compared with the nonesterified blend. The sn-2 and sn-1,3 distribution of fatty acids in the triacylglycerol fractions before and after interesterification were determined. The compositions of fatty acids at sn-2 were near statistical (33.3%) when Novozym 435 was used. When Lipozyme RM IM was used, the fatty acid compositions at the sn-2 position remained practically unchanged, compared with the starting blend. The changes in molecular structures of fat components due to interesterification have greatly influenced on the melting profiles of products as illustrated by the DSC melting scans. The interesterified fats and isolated triacylglycerols had reduced oxidative stabilities, as assessed by Dynamic DSC and Isothermal PDSC measurements. The Arrhenius kinetic parameters for fats oxidation based on DSC and PDSC measurements were calculated.