Characteristics of oleogel prepared from red palm oil using hybrid oleogelator

. The combination of oleogelators had potential to exploit synergistic effects that contributed to functionality of oleogel. Red palm oil provided high carotenoids which add nutrition to oleogel. This research is aimed to provide high carotenoids oleogel using oleogelators combinations. Stability, oil binding capacity, hardness, thermal profile and total carotenoid were observed to learn oleogelator effect. This study was designed using a factorial completely randomized design consisting of three factors, are concentrations of ethyl cellulose (Ec), monoglycerol stearate (Ms) and beeswax (Bw). Ethyl cellulose concentrations are 1%; 2% and 4%, monoglycerol stearate concentrations are 4% and 6% and beeswax concentrations are 2% and 4%. Data were analyzed by analysis of variance (p=0,05). Results showed that low oleogel concentrations produced unstable oleogels and it was obtained stability at a certain ++concentration limit. Each oleogel concentration had significant effect on oil-holding capacity, hardness, and total carotene, but had no significant effect on melting point. Oleogelator interaction had significant effect on total carotene, but did not significantly affect on hardness and oil-holding capacity. Oleogelator formulations Ec 1% -Ms 4% -Bw 2% , Ec 1% -Ms6 % -Bw 2% and Ec 2% -Ms 4% -Bw 2% had hardness values that were close to margarine, but these formulations are not stable. Melting point is temperature range of 38.15-43.17 o C and is close to melting point of margarine sample of 40.44 o C. Some oleogel formulations had characteristics that are close to margarine samples such as melting point and hardness, but improving oleogel stability was essential to studying further.


Introduction
Fat is essential for human diet because one of the nutritional components that have a role as source of energy, solvent of vitamins and bioactive compounds [1].In addition, application of fat in food is known to increase acceptance of product.Fats are used in food for modifying structure, improving textures, providing viscous and mouthfeel sensation and bringing lipophilic and creamy taste [2,3].Fats like margarine, butter and shortening are commonly used in cakes, breads, ice cream, cookies and candy.Functional properties as melting point and high viscosity are the reasons of fats are chosen as ingredients.Fat has high content of saturated fatty acids so it has a high melting point and viscosity [2].
In recent decades consumers are aware and concerned on bad effects of consuming high saturated fatty acids and trans fatty acids.Consume high amounts of saturated fatty acids caused increase the risk of diabetes, obesity and cardiovascular disease.Trans fatty acids increase levels of LDL (low-density lipoprotein) which triggers coronary heart disease.In addition, trans fatty acids also reduce levels of HDL (high-density lipoprotein) so that trans fatty acids is twice bad effect of saturated fatty acids [4].
The study suggested that product low in saturated fat and trans-free can be produced by adding oleogel as a substitute fat [5][6][7].Oleogel is an oil fraction that has undergone structuring with the addition of an oleogelator and it formed a physique like solid fat [5,6].Red palm oil has the potential as an oleogel ingredient. it is made from fractionated palm oil through a molecular distillation process which retains 80% of palm carotenoids.Carotenoids are known to have an effect on cancer prevention and act as precursors of vitamin A. Furthermore, red palm oil also contains about 40% oleic acid which is known to lower cholesterol and blood pressure.Vitamin E which has high antioxidant activity is also present in large amounts of red palm oil [8,9].Based on research, monoglycerides is better in oleogelation ability than other triacylglyceride derivatives such as diglycerides and stearic fatty acids [10][11][12], ethyl cellulose is polymer that capable structuring vegetable oil into gel directly [13,14] and oleogel from a mixture of almond oil and beeswax is known to be able to replace shortening in the manufacture of cookies [15].
The combination of oleogelators has the potential to exploit the synergistic effect that sagiri contributes to the functionality of oleogels.It will enable wider application of oleogels as well as a solution to the regulation of thresholds for the use of oleogelators as food additives.This research aims to prepare red palm oil oleogel using combination of oleogelators namely monoglyceride, ethyl cellulose and beeswax.Hardness, stability, melting point and total carotenoids were observed to see the effect of oleogelator.

Oleogel preparation
Oleogelators were weighed according to the formulation.100 mL of red palm oil was preheated to 75 o C on hot plate magnetic stirrer.Each formulation of eleogelator were put into the oil and stirred at 200 rpm until the temperature reaches 160 o C for 5 minutes.The oleogel was then allowed to cool to 70 o C. The oleogel was then stored in the refrigerator at 5 o C for 24 hours [16].

Stability and oil-holding capacity
5 g of oleogel was put into a centrifuge tube and conditioned for one day in the refrigerator.Then, the tubes were centrifuged at 1300 rpm for 15 min at room temperature.Stable emulsions are indicated by the absence of oil coming out of the oleogel and marked (+).The percentage of oil that does not realeased is expressed as oil holding capacity [17].

Hardness
The analysis was carried out with an LFRA Brookfield texture analyzer equipped with a cylindrical probe with a diameter of 12.5 mm.The speed is set to 1 mm/s with a penetration depth of 10 mm and a trigger of 5 g.LFRA software is used to obtain hardness values.

Thermal profile
Samples were placed and sealed in aluminum pans and rapidly transferred to Differential Scanning Calorimetry (DSC).The sample was heated to 100 o C, equilibrated at that temperature for 5 min and cooled to 30 o C at a rate of 2 o C/min.TA Universal Analysis V4.7A software was used to obtain the melting point and crystallization temperatures.

Total carotenoid
1 g of oleogel sample was extracted with 100 mL of 80% acetone and stirred until the carotenoids were dissolved.The extract was then filtered using wathman 40 to obtain the filtrate.it was placed in a cuvette to measure the total carotenoid content using a spectrophotometer.Wavelengths spectrophotometer was set at 480 nm, 646 nm, and 663 nm.Total carotenoids were calculated by the following formula.

Data analysis
Data were analyzed using analysis of variance at the 5% level, and further tests with LSD at the 5% level.

Thermal profile
Observation of DSC data showed that the melting temperature range of oleogel is 38,15-43,17 o C (Table 4).This value is close to the melting temperature of the margarine sample that is used as a comparison, which is 40.44 o C. Furthermore, the crystallization temperature of the oleogel was found to have a lower value than its melting temperature.Oleogel formulated with more than one type of oleogelator had a lower crystallization temperature than the melting temperature [18].

Total carotenoids
Concentration of oleogelators and their interactions had significant effect on total carotenoid values.Increasing the concentration of ethyl cellulose oleogelator decreasing total carotene.This study found that increasing the concentration of ethyl cellulose had longer heating time to reach a temperature of 160 o C so that the degradation of carotenoid compounds by heating longer.Furthermore, increasing the concentration of monoglycerol stearate and beeswax was able to inhibit carotenoid degradation.Total carotenoids values was 125.71-263.92mg/L (figure 1).If comparation with red palm oil (RPO), oleogel had lower carotenoid than RPO.It was caused by caraotenoid degradation on heating processing [20].The content of carotenoid in oleogel is quite high as a source of carotene in food products.

Conclusion
Low concentration of oleogelator produces unstable oleogel and reaches stability at a certain concentration limit.The increase in oleogel hardness was obtained by increasing the concentration of the oleogelator.The oleogelator formulations of Ec1%-Ms4%-Bw2%, Ec1%-Ms6%-Bw2% and Ec2%-Ms4%-Bw2% had hardness values that are close to margarine, but these formulations are not stable.

Table 1 .
Stability of oleogel oleogel prepared red palm oil with hybrid oleogelator.

Table 2 .
Holding oil capacity of oleogel oleogel prepared red palm oil with hybrid oleogelator.

Table 3 .
Hardness of oleogel oleogel prepared red palm oil with hybrid oleogelator.

Table 4 .
Thermal profile of oleogel prepared red palm oil with hybrid oleogelator.
The melting point of oleogel is in the temperature range of 38.15-43.17o C and was close to the melting point of the margarine sample of 40.44 o C. Total carotenoid values was 125.71-263.92mg/L. it is quite high as a source of carotene in food products.There are oleogel formulations that had characteristics close to margarine reference, but were not stable.Improving stability was studied further.was sponsored by LPPM-PM of Teuku Umar University with UTU DIPA grants based on research contract number 022/UN59.7/PT.01.03/2021.