EMULSIFIERS SUITABLE FOR WATER-IN-OIL (W/O) EMULSION SYSTEMS PRODUCED USING CORN COB, WHEAT BRAN, SUNFLOWER RECEPTACLE, AND FATTY ACIDS, AND THEIR PRODUCTION METHOD

TECHNICAL FIELD

The invention relates to emulgators and their production method, which are compatible with emulsion systems having various water-in-oil ratios, using products with high cellulose content obtained from plant residues containing relatively short fibers, and fatty acids, and have different properties.

BACKGROUND OF THE INVENTION

Cellulose, one of the most common polymers in nature, can be used directly in the paper industry or in the production of biodegradable packaging with different properties through esterification with fatty acids. Thus, cellulose resources can be transformed into high-added-value products. However, food industry wastes containing relatively short cellulose fibers are not suitable for use neither in the paper industry nor in the production of biodegradable packaging. Therefore, they cannot be converted into high-added-value products. On the other hand, many products in the food industry are produced using emulgators, and the use of natural emulgators is not possible in the production of some emulsion products. Therefore, more additives and artificial emulgators are used. Moreover, more additives and/or synthetic emulgators are used in some water-in-oil emulsion systems to ensure appropriate physical properties in the final product. The food industry’s relatively short-fibered food residues, high in cellulose content, are used in animal feeding or as fuel. Therefore, these high-cellulose-content products are considered low-value by-products.

BRIEF DESCRIPTION OF THE INVENTION

Emulgators are substances needed to enable the mixing of two or more liquids, like water and oil, that do not mix with each other, and are present as a food component in the production of some foods. They also positively affect viscosity, texture, and sensory properties by preventing physical defects that may occur in foods depending on their shelf life. This function of emulgators stems from the fact that one end of the molecule has an affinity for water (hydrophilic) and the other end has a greater affinity for oil (lipophilic). Emulgators that ensure emulsion stability are referred to as surfactants or emulsion agents.

Emulgators are divided into two as natural (proteins, phospholipids, bile acids, glycolipids, saponins, etc.) and artificial (Stearyl-2-lactylate, Datem, Citrem, monoglycerides and diglycerides and their acetic and lactic acid esters, sucrose fatty acid esters, sorbitan fatty acid esters, etc.) emulgators. The most well-known and used emulgators in the food industry are monoglycerides and/or diglycerides and lecithin. As understood from the given examples, emulgators are generally artificial or natural products obtained by esterifying a component with hydrophilic properties and a lipophilic component.

Mono- and diglycerides, which are some of the most widely used emulgators in the food industry, are produced through methods such as hydrolysis of triglycerides, glycerolysis of triglycerides, direct esterification of glycerol and fatty acids, and transesterification of glycerol and methyl esters of fatty acids, depending on the purpose and place of use. Another important emulgator, lecithin, is mostly obtained from sunflower and soybeans through acetone application or low-temperature ultrafiltration. In the production process, when organic solvents are used, there is a residue of acetone, a chemical solvent, in the lecithin.

The ratios of lipophilic and hydrophilic groups that emulgators have affect their areas of use. Emulgators suitable for the water-in-oil emulsion type need to have a larger hydrophilic part, while emulgators suitable for the oil-in-water emulsion type need to have a larger lipophilic part.

Under our invention, emulgators suitable for water-in-oil (w/o) emulsion systems have been produced using corn cob, wheat bran, and sunflower receptacle residues, which contain relatively short fibers, thereby obtaining high-value end products from these high-cellulose content residues. Raw materials with high cellulose content are generally used in the paper or packaging industry. However, in order to be used in these areas, the cellulose fibers they contain need to have long chains. Indeed, since wheat bran, corn cobs, and sunflower receptacle contain short cellulose fibers, they are not used in the paper and packaging industry. Therefore, these residues have been evaluated within the scope of our invention.

With the method subject to the invention, the production of different emulgators for emulsion systems with different water-in-oil ratios can be made with the use of different raw materials and production conditions. Additionally, the emulgators obtained depending on the raw material and method conditions used in production have different rheological and physical effects in water-in-oil (w/o) emulsion systems. Therefore, there is an advantage of providing different rheological and physical properties of the emulsion system. On the other hand, it is also suitable for use for very different raw materials.

LIST OF FIGURES

Figure 1a. The effect of fatty acid chlorite salt quantities on the degree of esterification

Figure 1 b. The effect of the variety of fatty acid chlorite salts on the degree of esterification

Figure 2. The effect of esterification degree on emulsion formation in water-in-oil emulsion systems created with caproic acid-high cellulose content nanofiber esters Figure 3. The effect of esterification degree on emulsion formation in water-in-oil emulsion systems created with lauric acid-high cellulose content nanofiber esters Figure 4. The effect of esterification degree on emulsion formation in water-in-oil emulsion systems created with oleic acid-high cellulose content nanofiber esters Figure 5. The effect of esterification degree on emulsion formation in water-in-oil emulsion systems created with stearic acid-high cellulose content nanofiber esters

DETAILED DESCRIPTION OF THE INVENTION

Within the scope of the invention, high cellulose content nanofibers were initially obtained using at least one of wheat bran, corn cob, and sunflower receptacle. The purpose of this is that the fibers found in plant sources are present in clusters, and therefore a significant portion of the hydrophilic (-OH) groups is enclosed. By separating these fiber clusters from each other, the hydrophilic groups (-OH) in the obtained high cellulose content nanofibers have been exposed. Subsequently, some of these -OH groups were esterified with lipophilic components (fatty acids with different chain lengths) to produce products with both lipophilic and hydrophilic groups.

For the extraction of high cellulose content nanofibers, a colloid mill and micro- fluidizer device were used after the delignification process. For this purpose, plant sources (wheat bran, corn cob, and sunflower receptacle) were subjected to the necessary fragmentation processes and then placed into alkaline (having a pH value of 10-14) pure water containing NaOH at a temperature of 80°C. After being left for 48 hours to ensure the separation of the lignin present in the structure, it was washed with pure water until the dark color of the water was removed (until the pH value is 7). The obtained fibers were subjected to a size reduction process in the colloid mill. For this purpose, the fibers were passed three times through a colloid mill with a rotation speed of 10000-12000 rpm, reducing their sizes to levels that will form a colloidal solution. In the final stage, the fibers, whose size was reduced with the colloid mill, were passed through micro-channels in a high-pressure micro-fluidizer device at 12000-15000 psi pressure, obtaining high cellulose content nanofibers. These fibers were frozen at (-)70°C, then freeze-dried under vacuum at (-)90°C, and stored at (-)70°C.

Within the scope of the invention, cellulose-rich nanofibers produced have undergone optimization studies for the esterification process after being mixed with chlorite salts of caproic acid, lauric acid, stearic acid, and oleic acid. The purpose of using these fatty acids is that cellulose fibers do not function as emulsifiers due to only containing hydrophilic groups (-OH). However, they can be used as viscosity enhancers in addition to emulsifiers in emulsion systems. Some of the -OH groups of the cellulose fibers are esterified with fatty acids to add lipophilic groups to the structure. In this way, the final products, which have both hydrophilic and lipophilic groups, can be used for emulsion systems. However, as previously mentioned, not only the size of the cellulose fibers but also the chain length of the added fatty acids is important for the formation of the emulsion. Indeed, as the chain length of the fatty acids increases, lipophilic properties also increase. On the other hand, since cellulose monomers contain three -OH groups, the degree of esterification, meaning the level at which the fatty acid binds to the cellulose, can be at most three. If the degree of esterification is three, the hydrophilic groups of the cellulose will be completely bound by the fatty acids, and there will be no hydrophilic groups. Therefore, it cannot act as an emulsifier. Thus, if fatty acids suitable for the emulsion type are bound to the cellulose at a level suitable for the emulsion type, it will have both hydrophilic and lipophilic groups.

During the optimization studies, 3 moles of Dimethylaminopyridine (DMAP) per 1 mole of cellulose and the chlorite salts of the aforementioned fatty acids (caproyl chloride, lauryl chloride, stearoyl chloride, and oleyl chloride) were utilized in various molar ratios (3-15 moles). Within the methodology framework, cellulose samples obtained from wheat bran, corn cobs, and sunflower receptacle (0.5 g) were initially dissolved in 20 mL of 6.7% LiCI-containing DMAc (Dimethylacetamide) at 50°C for one day. Subsequently, 3 moles of Dimethylaminopyridine (DMAP) as a catalyst per 1 mole of cellulose - due to the cellulose monomers containing 3 -OH groups - (in a ratio of 1 :3), and different fatty acid chlorite salts (caproyl chloride, lauryl chloride, stearoyl chloride, and oleyl chloride) in different molar ratios (3-15 moles) were added to the samples, and the reaction was facilitated for determined periods at a stirring speed of 75 rpm in a water bath set to 80°C to enable reaction occurrence. Upon reaction completion, 15 mL of methanol was added to the medium to cease the reaction and remove residues; after coarse filtering, it was washed with 15 mL of 70% ethanol. In the samples post-washing, solvent extraction utilizing a fat solvent like hexane was conducted via a Behr E6 device, operating with the Randall method, to ensure no fatty acid residue remained. Subsequently, a vacuum oven was employed to evaporate residual hexane (at 70° for 24 hours).

The degree of esterification for each produced sample was determined using the volumetric method. For this purpose, the manufactured esters, following saponification with 0.25M NaOH alcoholic solution at 70°C for 16 hours, were titrated with 0.01 N hydrochloric acid, determining the degree of esterification.

For the covalent attachment of fatty acids to cellulose nanofibers, a requisite duration is necessitated, contingent upon a defined quantity of fatty acid and its respective concentration. As deduced from the conducted research, and as visually elucidated in Figure 1a and Figure 1 b, it was ascertained that an elevation in the amount of fatty acid chlorite salts resulted in the conjugation of an enhanced quantity of fatty acids, while an increment in the chain length of fatty acid chlorite salts resulted in the conjugation of a diminished quantity of fatty acids.

Considering that the glucose units constituting cellulose encompass three reactive hydroxyl (OH) groups, the esterification degree can achieve a maximum of 3. Therefore, deriving from the optimization results, a total of 48 products (3x4x4) possessing four different esterification degrees (approximately 0.5, 1.25, 2, and 2.75±0.05) have been synthesized anew with four distinct fatty acids from three disparate sources (Table 1 ).

Table 1. Actual and predicted esterification degrees of products produced according to parameters obtained from optimization results

No Time Fiber Source Fatty acids Mol of Predicted Actual

(min) fatty esterification esterification acids degrees degrees

1 60 Sunflower Caproic acid 3.0 0.49 0.51 ±0.01 receptacle

2 240 Sunflower Caproic acid 4.0 1.25 1.25±0.01 receptacle

3 250 Sunflower Caproic acid 7.0 1.99 2.04±0.02 receptacle

4 275 Sunflower Caproic acid 11.0 2.76 2.74±0.02 receptacle

5 60 Wheat bran Caproic acid 3.0 0.50 0.52±0.01

6 240 Wheat bran Caproic acid 4.0 1.26 1.24±0.01

7 250 Wheat bran Caproic acid 7.0 2.00 1.98±0.02

8 275 Wheat bran Caproic acid 11.0 2.77 2.74±0.02

9 60 Corn cob Caproic acid 3.0 0.51 0.53±0.01

10 240 Corn cob Caproic acid 4.0 1.24 1.27±0.01

11 250 Corn cob Caproic acid 7.0 1 .98 2.02±0.02

12 275 Corn cob Caproic acid 11.0 2.75 2.77±0.03

13 60 Sunflower Lauric acid 3.1 0.50 0.47±0.01 receptacle 240 Sunflower Lauric acid 4.2 1.25 1.27±0.01 receptacle

250 Sunflower Lauric acid 7.3 2.00 2.03±0.02 receptacle

275 Sunflower Lauric acid 11.4 2.75 2.76±0.02 receptacle

60 Wheat bran Lauric acid 3.1 0.51 0.49±0.01

240 Wheat bran Lauric acid 4.2 1.25 1.27±0.01

250 Wheat bran Lauric acid 7.3 2.01 2.02±0.02

275 Wheat bran Lauric acid 11.4 2.75 2.73±0.02

60 Corn cob Lauric acid 3.1 0.52 0.48±0.01

240 Corn cob Lauric acid 4.2 1.25 1.23±0.02

250 Corn cob Lauric acid 7.3 1.99 2.02±0.02

275 Corn cob Lauric acid 11.4 2.76 2.74±0.03

60 Sunflower Oleic acid 3.2 0.50 0.51±0.01 receptacle

240 Sunflower Oleic acid 4.3 1.24 1.28±0.01 receptacle

250 Sunflower Oleic acid 7.5 1.98 1.99±0.02 receptacle

275 Sunflower Oleic acid 11.8 2.75 2.78±0.02 receptacle

60 Wheat bran Oleic acid 3.2 0.50 0.51±0.01

240 Wheat bran Oleic acid 4.3 1.24 1.22±0.01

250 Wheat bran Oleic acid 7.5 1.99 2.00±0.02

275 Wheat bran Oleic acid 11.8 2.75 2.78±0.03

60 Corn cob Oleic acid 3.2 0.51 0.49±0.01

240 Corn cob Oleic acid 4.3 1.24 1.22±0.01

250 Corn cob Oleic acid 7.5 2.00 2.03±0.02

275 Corn cob Oleic acid 11.8 2.76 2.74±0.02 7 60 Sunflower Stearic acid 3.4 0.52 0.48±0.01 receptacle 8 240 Sunflower Stearic acid 4.5 1.26 1.24±0.02 receptacle 9 250 Sunflower Stearic acid 8.0 2.01 1.99±0.02 receptacle 0 275 Sunflower Stearic acid 12.0 2.77 2.73±0.02 receptacle 1 60 Wheat bran Stearic acid 3.4 0.50 0.53±0.012 240 Wheat bran Stearic acid 4.5 1.24 1.28±0.013 250 Wheat bran Stearic acid 8.0 1.98 2.01 ±0.024 275 Wheat bran Stearic acid 12.0 2.75 2.71 ±0.025 60 Corn cob Stearic acid 3.4 0.52 0.52±0.016 240 Corn cob Stearic acid 4.5 1.25 1.23±0.017 250 Corn cob Stearic acid 8.0 1 .99 2.03±0.028 275 Corn cob Stearic acid 12.0 2.76 2.73±0.02

Products obtained within the scope of the invention have been employed to formulate water-in-oil emulsions, obtained through the homogenization of sunflower oil and pure water in weight ratios of 85%, 75%, and 65%, respectively. Nanofiber-fatty acid esters, esterified at different ratios and derived from various fatty acids, were initially mixed with sunflower oil at weight ratios of 0.5-1 % utilizing an Ultra-Turrax device (5000 rpm). Subsequent to this, whilst the addition of water was performed, the homogenization process was continued with the Ultra-Turrax device for a duration of 5 minutes.

At this juncture, a total of 48 nanofiber-fatty acid esters, comprising four distinct esterification degrees created from three disparate raw materials and four different fatty acids, were utilized at four different ratios within three varied oil-water mixtures. In this stage, a surface scanning method was employed, and as delineated in Table 2, the production number was reduced to 46. Table 2. Experimental design of water-in-oil emulsions

Under the purview of the present disclosure, the suitability of the synthesized emulsifiers was evaluated to determine their aptitude toward different types of emulsions by employing model emulsions. Those that maintained stability under ambient conditions for a period of one day were considered to have successfully formed an emulsion. For the purpose of conducting statistical analyses and generating three-dimensional figures of the obtained results within the context of this invention, samples in which emulsion formation occurred were assigned a value of “1”, while those where it did not were designated a “0”. As observable from Figures 2 and 3, cellulose-rich nanofiber-caproic and lauric acid esters, with an esterification degree ranging from 2.00 to 2.75, were compatible with water-in-oil emulsions containing 85-65% oil and 15-35% water. However, samples with an esterification degree below 2.00 were deemed unsuitable.

From Figures 4 and 5, cellulose-rich nanofiber-oleic acid and stearic acid esters with an esterification degree of 1.25 and 2.00 were found suitable for water-in-oil emulsions (comprising 85-65% oil and 15-35% water), whereas samples with an esterification degree below 1 .25 and above 2.00 were considered inappropriate.

The results suggest that for water-in-oil (w/o) emulsions, short-chain fatty acid- cellulose-rich nanofiber esters (e.g., caproic acid and lauric acid) should possess an esterification degree of 2.00 and above. Conversely, long-chain fatty acid-cellulose-rich nanofiber esters (e.g., oleic acid and stearic acid) should have an esterification degree between 1 .25 and 2.00. Following the determination of the suitability of each product for different types of emulsions based on emulsion formation, emulsions were reformed, and the rheological and physical characteristics of the final products were ascertained, contingent upon the emulsion type and utilized emulsifier. Subsequent analyses confirmed that the type of emulsifier employed exerted significant impacts on the physical and rheological properties of the emulsions. Thus, it was established that emulsions with identical water/oil ratios but distinct rheological/physical properties could be obtained using different emulsifiers as described within the scope of the present disclosure.