Changes in Physical and Chemical Properties of Thermally and Oxidatively Degraded Sunflower Oil and Palm Fat

Deep-fat frying is an important process used worldwide for the preparation of foods. Due to oxidation, hydrolysis, decomposition and oligomerization, numerous polar compounds are formed. These compounds change the physical, nutritional and sensory properties of the oil or fat. The standard methods of the German Society for Fat Science for the assessment of the quality of frying fats are time consuming and cost intensive. Therefore, alternative cost-effective and sensitive rapid methods, which ideally allow the quantitative determination of the quality of frying fats “in-line” in the deep-frying pan are needed. Sunflower oil and palm fat were thermally and oxidatively degraded in a beaker at atmospheric pressure under intensive stirring for 76 h at 175 °C. To evaluate the development of the physical properties during heat treatment, the viscosity and dielectric constant of these oils were measured. The temperature in a deep-frying pan can vary within a wide range (160–190 °C), and the viscosity and dielectric constant show a strong temperature dependence. Therefore, it was necessary to measure the temperature dependence of the viscosity and dielectric constant of the different degraded oils. Additionally, their chemical properties were characterized by high-performance gel permeation chromatography and Fourier-transform infrared spectroscopy (FTIR). The determination of the dielectric constant, which is directly correlated with the concentration of polar compounds, seems to be the best method for the assessment of the quality of used frying oils.

TECHNOLOGY OF CULINARY (FRYING) FATS

The increased popularity of deep-fried foods has put health and safety concerns on the agenda. Factors that affect the quality and safety of culinary (frying) fats include the fatty acid profile, as well as cooking modes and time, especially when renewal rates are low. The industry is currently facing a top-of-mind technology challenge: to reduce the “oil content” of fried foods by developing a frying fat that would meet up-to-date food production standards. In other words, there is a need for a frying fat, which should last as long as possible without oxidizing and changing colour. Furthermore, its uptake by foods, fried in it, must be 40–50 % less than that of conventional fats. To this end, the authors put forward an innovative technology for producing culinary (frying) fats through esterification of fatty acids with high molecular weight alcohols. The research work that has been carried out so far prove the possibility of producing specialty fats by such modification to the applicable regulatory requirements: the melting range is between 29.6 and 34.65 °С, the acid value is up to 0.4 mg КОН/g. The viscosity of modified fats is lower than that of oils, which is due to the fat structure, and this circumstance will have a positive effect on the fat content in a finished product. The researchers has identified a numerical relationship (expressed as a regression model) of the yield of the desired fraction of a modified fat versus the ratio of reagents, reaction time, and process temperature, as well as calculated rational process parameters. The aim of the research is to develop the technology of obtaining culinary (frying) fats by esterification of fatty acids with high molecular weight alcohols

Imports and Use of Palm Oil as a Way to Increase Safety of Food Fats

The authors compare the biological value and safety of hydrogenated fat containing trans-isomers of oleic acid and palm oil-based fat. The chapter assesses the potential of replacing hydrogenated fats by palm oil in the production of special fat products. Hematological and histological studies are carried out in a form of biological experiment on animals (white rats). The study reveals the explicit negative effect of trans-isomers even with a relatively low concentration of trans-isomers in a diet. Pathological changes are not observed in animals when palm-based fat is introduced into their ration. The findings suggest that palm oil along with its fractions may be considered as an alternative to hydrogenated fats in the production of margarine, cooking, baking, and deep-frying fats. The use of palm oil in the production of special fats of increased hardness (spreads. confectionery, waffles and fillings, and chocolate coating) requires the application of modern methods for modifying triglyceride composition of fats – biocatalytic interesterification and fractionation.