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Analiza właściwości fizykochemicznych i charakterystyka spektrofotometryczna wybranych olejów roślinnych
Introduction. Vegetable oils are a known source of mono- and polyunsaturated fatty acids (MUFA and PUFA). The growing demand for vegetable oils, rich in unsaturated fatty acids, increases the use of new oil plants to obtain them. In this study, the physicochemical properties (density, pH, refractive index, dynamic viscosity, contact angle, surface tension, color) were examined, a spectroscopic analysis was carried out and antioxidant properties were determined. In order to determine the indicated parameters, simple and easily accessible analytical methods were used, which provide key information about the prop erties of oils and serve as indicators for assessing their quality. Six commercially available oils were se lected for the study: evening primrose seeds (Oenothera paradoxa), milk thistle seeds (Silybum maria num), pumpkin seeds (Cucurbita oleo), linseed (Linum usitaissimum L.), winter camelina seeds (Camelina silvestris) and black cumin seeds (Nigella sativa). Results and conclusions. The conducted research provided significant insights into the relationship between the determined parameters of vegetable oils. The positive correlation between density and refrac tive index also highlights the influence of fatty acid composition on these properties. The observed diversi ty of colors of the oils tested highlights the unique composition of dyes characteristic of each oil. It was found that the pH of vegetable oils is a key indicator reflecting the level of acidity in the oil. The correla tion between contact angle and surface tension revealed complex surface interactions.
Behavior at Air/Water Interface and Oxidative Stability of Vegetable Oils Analyzed Through Langmuir Monolayer Technique
This study aimed to evaluate the oxidative stability and surface properties of cold-pressed vegetable oils using the Langmuir monolayer technique. Six oils—milk thistle, evening primrose, flaxseed, camelina sativa, black cumin, and pumpkin seed—were analyzed to investigate their molecular organization and behavior at the air/water interface, particularly after undergoing oxidation. The results showed that oils rich in polyunsaturated fatty acids (PUFAs), such as flaxseed and evening primrose oils, formed monolayers with larger molecular areas and lower stability, which led to faster oxidative degradation, especially under thermal conditions. In contrast, pumpkin seed oil, with a higher content of saturated fatty acids (SFAs), formed more condensed and stable monolayers, enhancing its resistance to oxidation. Black cumin oil, with a balanced profile of SFAs and monounsaturated fatty acids (MUFAs), demonstrated similar stability. The Langmuir technique facilitated a detailed analysis of monolayer phase transitions: PUFA-rich oils transitioned more readily to less stable phases, while SFA-rich oils maintained durable, condensed structures. These findings underscore the utility of this method for assessing the oxidative stability of vegetable oils and highlight key parameters—such as surface pressure, molecular area, and elasticity modulus—that can support the optimization of oil storage and quality in the food industry and related sectors.