SEM investigation of minor constituents of carbide materials prepared from shungite rocks

The “SiC-Al₂OC”-based composite prepared from Karelian shungite rocks has been studied by X-ray diffraction analysis and scanning electron microscopy. SEM investigation has been done to determine the mode and distribution of admixture constituents. It is found that the most common minor phase represents Al–Fe–Si–C-based alloys. Special attention has been given to describing the noble metals admixtures. It is revealed that the noble metals phases occur as separate microsized grains, most of which have been indicated as Au–Ag–Hg amalgam and rarely as Pt-rich compounds. The obtained data can be mainly used to advance technologies for manufacturing carbide-based composite materials from natural carbonaceous rocks.     

ANTIOXIDANT ACTIVITY OF ROSEMARY AND SAGE EXTRACTS IN RAPESEED OIL

Rosemary and sage leaves were extracted with hexane, acetone, ethyl acetate and ethanol. Yields of extracts and of carnosic acid contents were higher in solvents of medium polarity. Both carnosic acid and carnosol showed medium activity in deodorized rapeseed oil, about the same as that of butylated hydroxyanisole. Carnosic acid was moderately more active than carnosol, and the resulting oxidative stability of extracts was correlated with the content of carnosic acid, but not with the content of carnosol. The antioxidant activity was about the same in rapeseed oil as in sunflower oil, but substantially lower than that in lard. Antioxidant activities, expressed as protection factors, were higher under Schaal oven test conditions at 40 or 60C than when determined in Oxipres at 100C. The dependence of the concentration of antioxidants and the protection factor showed similar negative exponential relations in all tests.     

EFFECT OF ROSEMARY EXTRACTS ON THE STABILIZATION OF FRYING OIL DURING DEEP FAT FRYING

Rapeseed oil and a mixture of rapeseed oil with palmolein containing silicone oil were used for preparation of french fries. The intermittent frying was continued for 5 days in a household fryer with replenishment of used oil. The decomposition of polyunsaturated triacylglycerols, formation of polar substances, polymers, colored products and conjugated dienes, but also of several sensory attributes, correlated with frying time. Polymers, dienes and coloration were closely intercorrelated and correlated with sensory characteristics of oil and fries, particularly when multiple regression was applied for prediction. Rosemary extracts inhibited the formation of polar substances, polymers and decomposition of polyunsaturated triacylglycerols, especially in the case of rapeseed oil and improved the sensory attributes of french fries.