Design and fabrication of structured oil (oleogel) and emulsion (emulgel) from acorn fruit oil

Abstract

Abstract Introduction: Fats and oils are an essential part of the diet. One of the most important functions of fat is creating texture and structure in food products. In order to develop the functional properties of oils, the use of hydrogenation technology, interesterification and fractionation process has been of interest in the past years, so that solid fats made in this way are widely used as margarine, breakfast spreads, products Bakery, chocolate products, etc. are used. Following the increase in people's awareness of the dangers of consuming high-fat food products, there has been a significant increase in the demand for low-fat food products. Oleogel structures (structured oils) are considered as new methods to produce low-fat products. Oleogelation is the trapping of liquid oils inside the three-dimensional network and thermal reversibility of oleogel, which provides solid-like properties in oils without changing their fatty acid composition. Plant waxes as oleogelators have been widely considered due to their abundance, high gelling ability and cheapness. Oak is one of the most important tree species in the country, which is the main species in forests. Zagros is scattered and the fat content in different species is 2-30%. Objective:The purpose of this study is to investigate the method of extracting oil from acorn fruit, preparing oleogel from it with optimal amounts of carnauba wax oleogelator, preparing emulgel and chocolate spread from oleogel and investigating their physicochemical and rheological properties. Material and methods: acorn fruit oil was extracted using the cold press oil extraction method and tests were performed to determine the profile of fatty acids, the amount of sterols, the amount of peroxide, smoke point, iodine value and refractive index. Carnauba wax was added to acorn oil and pure soybean oil at a ratio of 6% by weight and mixed and heated with a heater equipped with a magnetic stirrer until the carnauba powder was completely dissolved. With the complete dissolution of the powder and obtaining a clear solution, the heating was stopped and then it was cooled down to a temperature of about 20 degrees Celsius with a low cooling rate. Then it was kept in the refrigerator for 24 hours at 4°C. After this period of time, rheological tests were performed using a rheometer device and possible interactions between compounds using Fourier transform infrared (FTIR) spectroscopy, as well as to check and observe the morphology and size of crystals from a polarized light microscope. and X-ray diffraction was used, then the thermal stability of the oleogel was determined using the differential scanning thermal analysis test method. Next, water/oleogel emulgels were prepared in ratios of 10:90, 30:70, 50:50, 70:30, and 90:10 and were subjected to appearance stability and morphology tests. Finally, chocolate spreads with different fat ratios were prepared from shortening, butter, acorn oil oleogel, rheological tests, determination of water activity, texture firmness and sensory evaluation were performed on them. Results: The amount of oil extracted from acorn fruit by cold pressing method was 14% by weight, the amount of saturated fatty acids in acorn oil was higher than that of pure soybean oil. β-sitosterol with 65.5 mg/kg was the most sterol of acorn oil. The peroxide index of acorn oil was associated with slight changes during storage, which confirms the oxidative stability of the oil due to its high saturated fatty acids. Among the prepared 6% by weight oleogels based on carnauba wax from soybean oil and oak, the oak oil oleogel had a higher elastic modulus and viscosity, so it is considered a stronger oleogel. Thermal behavior and X-ray diffraction pattern in oak oil oleogel indicate the formation of new crystal structures. CLSM images prepared from 50:50 emulgels (oleogel/water) confirmed the formation of Pickering emulsions/or crystal network formation by wax and lipid crystals around the oil droplets. Among the chocolate spreads prepared with different percentages of fats, the type of lipids and their content had a significant effect on firmness and physical stability. The action of wax particles in oleogel is related to butter fatty acids. In the evaluation of chocolate spread samples, the 50:50 (oleogel/butter) sample had similar overall acceptance as the sample prepared with 100% butter, despite the 50% oleogel. Conclusion: As a general conclusion, it is possible to produce stable food-grade oleogels using acorn fruit oil and carnauba wax. It seems that as a result of increasing the concentration of carnauba wax and preparing chocolate spreads, this combination has the ability to produce low-fat products, a healthy alternative to various types of semi-hydrogenated oils in all types of chocolate products. Key words: oak tree, oil extraction, emulgel, rheology, sensory evaluati