NATURA MONTENEGRINA, Podgorica, 2011, 10(3):

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1 NATURA MONTENEGRINA, Podgorica, 2011, 10(3): PALM STEARIN IN THE SOAP-MAKING PROCESS Saâd MOULAY*, Ahmed CHALANE and Zahia OUAD-FEUL Laboratoire de Chimie-Physique Moléculaire et Macromoléculaire, Faculté des Sciences de l Ingénieur, Département de Chimie Industrielle, Université Saad Dahlab de Blida, Route de Soumâa, B. P. 270, Blida 09000, Algeria. * Corresponding author - polymchemlab@hotmail.com SYNOPSIS Key ords: Palm stearin, Soap, Spent lye. A laboratory scale soap-making process using the palm stearin in a varying percentage of the fat as undertaken. Analysis of the spent soap lye alloed the assessing of the amounts (t. %) of glycerol, sodium chloride, alkali, and ater. The results ere ithin the range of the industrial values. Soaps made ith different concentrations of palm stearin ere analyzed in terms of the titre, sodium chloride, total fatty matter, glycerol, and ater. The results shoed no significant differences from the standard values. INTRODUCTION Soap is considered the oldest hygienic substance and has been used since the Egyptian era (Tsujii, 1998). Because of the advent in the detergent industry, the soap is noadays used mostly as toiletry soap bar. Hoever, the third orld countries still use soap abundantly for the fabric cleansing. It is important to point out that the soap is also a component in the detergent formulation as a foam control agent (Fujimoto, 1985). A historical survey of the soap-making reveals that the natures of the fat and the alkaline substance employed in the saponification played basic roles in the final performance of the soaps. Yet, the cleansing properties of soap are more tightly bound to the nature of the used fatty matter than to the type of the alkaline substance. To meet the criteria of the soap detergency such as firm texture and foaming, the soap-making industries commonly manufacture their household soaps employing a mixture of 75-85% of hard fats such as the beef tallo or the palm oil and 15-25% of lauric fats such as the coconut oil or the palm kernel oil. The luxury toilet soaps require a relatively higher content of lauric fat, but a skin irritation may be caused hen exceeding a certain percentage of this matter (lauric acid). 335

2 Natura Montenegrina 10(3), 2011 In a continuation of our research on the valorisation of natural products in the soap and detergent making (Moulay et al., 2003; Moulay et al., 2005), e herein report some results on the use of stearin as one of the fatty constituents in a household soap. The consideration of the palm stearin as a ra material for soapmaking is of a great interest. Besides the palm olein, about 10% of solid stearin is obtained by fractionation of palm oil after crystallization. There are many uses of this stearin. For example, shaving soaps are prepared using a blend of 80% of stearin and 20 % of lauric acid as fatty matter and the alkaline system NaOH/KOH in the ratio of 1:3. Moreover, the palm stearin has been valorised as an ingredient in shortenings, table, bakery and pastry margarine (Norlida et al., 1996). A chemical interesterification of the palm stearin ith vegetable oils and fats resulted in hard fats that are employed in the soft margarines production (Petrauskaite et al., 1998; deman & deman, 1995). MATERIAL AND METHODS The chemicals and the various indicators used in this ork ere purchased from manufacturers Aldrich, Sigma, and Riedel dehaën. The palm stearin, the beef tallo and the coconut oil ere supplied by ENCG (Entreprise Nationale des Corps Gras, Algiers, Algeria). Deionized ater as used in the soap-making process. The different analyses of the fat and the palm stearin-based soaps ere made ith the equipment included the folloing: (i) phmeter LpH 230T; (ii) Refractometer, to determine the refractive index; (iii) Digital densimeter DM A48, to determine the density; (v) Tintometer Lovibond L14, to estimate the aspect of the fat; (vi) Electromagnetic agitator; (vii) Oven Memmert ( C). FAT ANALYSES EXPERIMENTAL ESTIMATION OF ACID VALUE, AV In a 250ml round-bottomed flask, ml of neutralized ethyl alcohol as added to 1g of fat. The alcoholic solution as titrated ith N ethanolic solution of KOH, in the presence of phenolphthalein as an indicator. The acidity expressed as the percentage of palmitic acid as estimated using Equation 1: Acidity = V x N 1000 x M x 100 [1] 336

3 Moulay et al.: PALM STEARIN IN SOAPMAKING PROCESS V is the volume of KOH consumed in ml; N is the normality of the solution of KOH, N; M is the molecular eight of palmitic acid, 256 g/mole; is the sample eight in grams, g. The acid value as determined as described by Norris (1965), Equation 2, or according to DIN , Equation 3. AV = AV = 2 x Acidity V x N x 56.1 [2] [3] EXPERIMENTAL ESTIMATION OF SAPONIFICATION VALUE, SV In a 250ml round-bottomed flask equipped ith a reflux condenser, 2g of fat and 25ml of 0.5 N ethanolic solution of KOH ere charged. The mixture as stirred under reflux for 1h. The excess of KOH as back titrated ith 0.5 N aqueous solution of H 2 SO 4 in the presence of 4% solution of phenolphthalein as indicator. The estimation of SV as provided by Equation 4: SV = (V0 - V) x N x M [4] V 0 is the volume in ml of the H 2 SO 4 solution, for the blank test, 22 ml; V is the volume in ml of the H 2 SO 4 solution, for the fat; N is the normality of the H 2 SO 4 solution, 0.5; M is the molecular eight of KOH, 56.1 g/mole; is the sample eight in grams, g. EXPERIMENTAL ESTIMATION OF IODINE VALUE, IV Initially, the Wijs reagent as prepared by dissolving 12g of iodine monobromide (IBr) in 1L of glacial acetic acid in an amber flask. A 0.6g of fat as accurately eighed and charged into a 250ml flame-dried amber flask. After addition of 10ml of chloroform, the system as cooled by immersing it in an ice-bath in order to add 25ml of the Wijs reagent. The system as alloed to stand for 3h at room temperature. A 25ml of a 100 g/l aqueous solution of potassium iodide as then introduced and the mixture as stirred for 2h. Finally, 70ml of distilled ater as added to the mixture. The titration of this mixture ith 0.1 N solution of sodium thiosulfate, Na 2 S 2 O 3, in the presence of starch as performed to estimate the excess of iodine. Equation 5 alloed the estimation of IV: [5] IV = (V 0 - V) x N x M V 0 is the volume in ml of the Na 2 S 2 O 3 solution, for the blank test, 22ml; V is the volume in ml of the Na 2 S 2 O 3 solution, for the fat; N is the normality of the Na 2 S 2 O 3 solution, 0.1; M is the molecular eight of palmitic acid, 256 g/mole; is the sample eight in grams, g. 337

4 Natura Montenegrina 10(3), 2011 EXPERIMENTAL ESTIMATION OF UNSAPONIFIABLE MATTER, UM In a 250ml round-bottomed flask fitted ith a reflux condenser, a mixture of 5g of fat and 50ml of 1 N ethanolic solution of KOH as refluxed for 1h. After cooling the mixture to room temperature, 50ml of distilled ater ere added. The hole mixture as then poured into a separatory funnel and the flask as rinsed ith 50ml of petroleum ether. After vigorously shaking the funnel, the mixture as alloed to stand for a phase separation. The petroleum ether layer containing the unsaponifiable matter as ithdran. The soapy layer as rinsed tice ith 50ml of petroleum ether. The extracts ere gathered, ashed tice ith 50ml of ethanol, and dried over anhydrous Na 2 SO 4 for 24h. Finally, the petroleum ether as evaporated to dryness and the residue as eighed. The UM as estimated using the Equation 6: UM = 0 x is the sample eight, g; is the residue eight in grams. [6] EXPERIMENTAL ESTIMATION OF THE TITRE An amount of 70g of fat as mixed ith 70 ml of ethanol and 40 ml of NaOH (39 Bé) and the mixture as heated until saponification. The soap obtained as dissolved in hot ater and 50 ml of 20% aqueous solution H 2 SO 4 as added to give the corresponding fatty acids. The mixture as then heated until an oily layer formed. The system as afterards transferred into a separatory funnel in order to extract the organic layer hich as ashed ith arm distilled ater. The system as alloed to decant for 2h, then the organic layer as filtered off. The filtrate as introduced into a test tube fitted ith an adequate thermometer and the temperature as gradually loered don; the temperature at hich the first crystal appeared corresponds to the titre of the fat. PREPARATION OF SOAP Eleven soap formulations (F i ) ere prepared as presented in Table 1. A general procedure for their preparation is outlined belo and consists of four steps: saponification, boiling, ashing, and fitting. 1. SAPONIFICATION In an appropriate beaker, 200g of fat consisting of 10% of coconut oil and 90% of palm stearin/beef tallo are mixed ith an amount of aqueous solution of NaOH (35% concentration). The necessary eight of NaOH, W NaOH (g/kg of fat), as calculated from the saponification value of the mixture, SV mix, by computing Equations 7 and

5 Moulay et al.: PALM STEARIN IN SOAPMAKING PROCESS SV mix = (SV co x W co + SV PS x W PS + SV BT x W BT ) ( %) [7] W NaOH = SV mix x 40 / 56.1 [8] Where the subscripts SV CO, SV PS, and SV BT are the saponification values of coconut oil, palm stearin, and beef tallo, respectively; W CO, W PS, and W BT, their corresponding eight percentages, and 0.3% is the excess of NaOH used. The mixture as stirred under nitrogen atmosphere hile heated at 65 C until a homogeneous phase as observed. The saponification as controlled by the use of phenolphthalein as indicator. The reaction as over hen red colour appeared and lasted for 10 min. Afterards, the salting-out process as carried out by adding an appropriate quantity of 40% NaCl solution to the mixture. While the spent lye as drained off and recuperated, the top soapy layer as orked up in the folloing steps. Table 1: Physico-chemical characteristics of the used fats. Parameters Palm stearin Coconut oil Beef tallo SV (mg/g) M* AV (mg/g) EV (mg/g) IV (mg/100g) H 2 O (%)** UM (%) d (30 C) (24 C) (51 C) η D T ( C) Aspect*** 0.8R/3Y 2.5R/10Y 1.4R /10Y/0.6B * M is the mean molecular eight calculated as (56.1/SV) ** Moisture as estimated as a eight loss of a fat sample at 105±2 C. ** The letters R, Y, and B stand for the red, yello, and blue colour, respectively 2. BOILING A small amount of 35% NaOH solution as added to the soapy paste obtained in the saponification step, and the system as vigorously agitated under nitrogen atmosphere and heated at 65 C for an additional time of 4h. 3. WASHING Sequential ashings of the boiling product ith ater alloed adjusting both the percentages of NaOH and NaCl to their ranges. 339

6 Natura Montenegrina 10(3), FITTING A volume of ater as carefully added to the soapy paste in sequential portions to induce dissolution. A foaming as observed, and a small amount of ethyl alcohol as added to suppress it. The system as alloed to stand for four days at room temperature, the period ithin hich the soap as formed at the top layer. ANALYSES OF THE SPENT LYE FREE CAUSTIC ALKALI To an aliquot of 10 ml of the spent lye, 50 ml of distilled ater and fe drops of phenolphthalein solution ere added. The neutralization as performed ith 0.1 N H 2 SO 4. The free caustic alkali (% NaOH) as estimated by Equation 9. Alkali (%) = (0.4 V) / [9] V is the volume of 0.1 N H 2 SO 4 solution, in ml, necessary for the neutralization, and is the sample eight in grams. FREE SODIUM CHLORIDE Mother liquor as prepared by diluting 2 ml of spent lye ith 250ml of deionized ater in a flask. To an aliquot of 10 ml ere added 50ml and fe drops of 10% potassium chromate solution as indicator, and the solution obtained as titrated ith 0.1 N silver nitrate solution to the endpoint. The percentage of NaCl present in the spent lye is calculated using Equation 10. NaCl (%) = V 5.85 [10] V is the volume of the 0.1 N silver nitrate solution at the endpoint. GLYCEROL CONTENT A volume of 2ml of spent lye as diluted ith 50ml of distilled ater in the presence of fe drops of bromocresol blue. The solution as then neutralized ith 0.1N H 2 SO 4 folloed by addition of sodium hydroxide solution until the yelloish colour turned purple. Potassium periodate (1.4g) as then introduced into the solution, and the hole system as heated at 40 C and stirred until complete dissolution. Propylene glycol (3ml) as injected into the solution hich as neutralized ith 0.1N sodium hydroxide solution. The percentage of glycerol present in the spent lye as computed from Equation 11. Glycerol (%) = (0.92 V) / [11] V is the volume in ml of the 0.1N NaOH solution necessary for the neutralization; is the sample eight in grams. 340

7 Moulay et al.: PALM STEARIN IN SOAPMAKING PROCESS ANALYSES OF THE SOAP FORMULATIONS, F I TOTAL FATTY MATTER The total fatty matter (TFM) as estimated using Equation 12 (100- X) % TFM = [12] 1.08 Where 100 is the percentage by eight of the soap and X is the percentage of ater. X as estimated as follos: An evaporating dish containing 10g of soap as placed in the oven at the temperature of 105 C until a constant eight. The percentage of ater present in the soap as calculated using Equation 13. Water (%) = W1 - W2 x 100 W1 - W0 [13] W 0 is the eight of the evaporating dish; W 1 is the eight of the soap sample/dish before drying; W 2 is the eight of the soap sample/dish after drying. FREE CAUSTIC ALKALI In a 250 ml round-bottomed flask equipped ith a reflux condenser, 10g of soap and 100 ml of neutralized ethanol (80% v:v) ere charged. The system as heated in a sand bath until a homogeneous phase as observed. The mixture as cooled to room temperature and titrated ith 0.1 N ethanolic solution of H 2 SO 4 in the presence of phenolphthalein. The alkali as estimated as % of Na 2 O using Equation 14. Na2O (%) = 0.04 x V x N x 100 x and are the molecular eight of NaOH in g and mg, respectively; V is the volume of the solution of 0.1 N H 2 SO 4 in ml; is the eight of sample in grams; 31 is the equivalent mass of Na 2 O. [14] FREE SODIUM CHLORIDE An amount of 10 g of soap as dissolved in 50 ml of hot ater. A fe millilitres of 20% H 2 SO 4 and fe drops of the methyl orange solution ere added to the soap solution hich as heated until the colour turned rose. After cooling to room temperature, the solution as filtered off and transferred into a 250 ml flask; ater as then added to make 250 ml solution. An aliquot of 100 ml as ithdran and poured into a 250 ml Erlenmeyer flask, and the H 2 SO 4 excess as neutralized ith concentrated sodium hydroxide solution. The neutralized solution as titrated ith 0.1 N silver nitrate solution in the presence of fe drops of 10% potassium chromate solution as indicator; at the endpoint, the colour changed to red brick. The percentage of sodium chloride present in the soap as estimated by Equation 15. NaCl (%) = V x 5.85 [15] 341

8 Natura Montenegrina 10(3), 2011 V is the volume of 0.1 N silver nitrate solution in ml at the endpoint; is the soap sample in grams. TITRE The same procedure for the determination of the titres of fats as used for the titre of the palm stearin-based soap. The titre as estimated using Equation 16. T S = x 1 T PS + x 2 T BT + x 3 T CO [16] Where x 1, x 2, and x 3 are the eight fractions of the palm stearin, the beef tallo, and the coconut oil, respectively; T PS, T BT, and T CO are their respective titres. IODINE VALUE The iodine values, IV, ere computed form the additive Equation 17. IV S = x 1 IV PS + x 2 IV BT + x 3 IV CO [17] IV PS, IV BT, and IV CO are the iodine values of the palm stearin, the beef tallo, and the coconut oil, respectively. PARTITION COEFFICIENT, K G K G as computed via Equation 18 using the data of Tables 2 and 3. ([glycerol] + [ater]) soap K G = [18] ([glycerol] + [ater]) lye Where ([glycerol] + [ater]) soap and ([glycerol] + [ater]) lye are the sum of glycerol and ater contents (%) in soap and spent lye, respectively. WIGNER S CONSTANT, K S The constant K s as determined according to the empirical Wigner s equation (Equation 19). [NaCl] soap TFM = 1 - K S [19] [NaCl] 100 lye Where [NaCl] soap and [NaCl] lye are the percentages of salt (as NaCl) in the soap and the spent lye, respectively, and are dran from Tables 2 and 3. TFM is the total fatty matter (%) of the soap taken from Table 3. RESULTS AND DISCUSSION The physico-chemical properties of the fats used including moisture content, acid value (AV) and acidity, unsaponifiable matter (UM), saponification value (SV), 342

9 Moulay et al.: PALM STEARIN IN SOAPMAKING PROCESS ester value (EV), iodine value (IV), total fatty matter (TFM), free caustic alkali content, density, colour, and titre (T) ere experimentally determined. The results of the different analyses are summarized in Table 1. The fact that the palm stearin is composed of mainly palmitic acid (50-74%), therefore considered as hard oil, makes it a suitable substitute to the beef tallo. Thus, the saponification reaction as carried out using 10% of coconut oil and 90% of palm stearin/beef tallo; the amount of sodium hydroxide required for the saponification as estimated as reported (Moulay et al., 2005) using the SV s of the fats and their eight percentages. The results are actually in the range of the knon values (Woollatt, 1985; Davidsohn and Milidsky, 1987). After the saponification process, the spent soap lyes ere analyzed and the results are gathered in Table 2. The contents in NaCl, alkali (NaOH), glycerol, and ater ere found to vary ith stearin concentration but in a non systematic fashion. Yet, the estimated values are ithin the range of the standard ones (Woollatt, 1985; Davidsohn and Milidsky, 1987). Table 2: Composition of the spent soap lyes. Alkali (%) Run Stearin (%)* NaCl (%) Glycerol (%) Water (%)** (%Na 2 O)*** F (0.248) F (0.217) F (0.178) F (0.255) F (0.310) F (0.387) F (0.085) F (0.186) F (0.271) F (0.240) F (0.279) * % Palm stearin + % beef tallo = 100 ** Estimated as 100-(% NaCl + % alkali + % glycerol) *** % Na 2 O = % Alkali Table 3 compiles the analyses results of the soap produced at different palm stearin extents. It can be noticed that the titre of the soap, T S, increases ith an increasing palm stearin concentration. The best soap formulations ith respect to the recommended titre (38-42 C) are the runs 2-4 corresponding to 10-35% of palm stearin. The experimentally estimated titres presented in Table 3 are closer to the 343

10 Natura Montenegrina 10(3), 2011 theoretical ones. As shon in Table 3, the iodine values IV of the soap ould be loered as the palm stearin content increased in the fat blend. The salt content as found to be loer than unity and this finding is in a fair agreement ith the recommended salt concentration (<1%). Moreover, the total fatty matter, TFM, as found to be in the range of 64-70% hich is an acceptable value. The loer salt concentrations coupled ith the TFM values ould indicate that the actual saponification product is a neat soap and that the liquidation process, a critical saponification step, as successful. The free caustic alkali of the soap as about % suggesting an efficient ashing process during the manufacture, and this caustic amount ould not cause a hand irritation. Another parameter of the soap-making process is the partition coefficient, K G, hich is the glycerol repartition beteen the final soap (neat soap) and the spent lye. For a successful process, this factor as reported to be 0.4 (Woollatt, 1985). As can be seen in Table 4, the value for K G is ithin and hich is closer to the commonly found one. Table 3: Physico-chemical characteristics of the soap. Run IV (mg/100g) T S ( C) NaCl (%) Alkali (%) (% Na 2 O) TFM (%) Water (%) Glycerol* (%) F (0.085) F (0.070) F (0.030) F (0.070) F (0.093) F (0.046) F (0.062) F (0.077) F (0.038) F (0.054) F (0.054) *% Glycerol = 100 (% NaCl + % alkali + % ater + % TFM) It is orth mentioning that the present experimental results ere in line ith the Wigner s rule, also called the 66% rule. Indeed, the constant K S in the empirical equation of Wigner, Equation 19, as found in the range of as given in Table 4. These values are not far from the common one,

11 Moulay et al.: PALM STEARIN IN SOAPMAKING PROCESS Table 4: K S and K G from different soap-making runs. Run F 1 F 2 F 3 F 4 F 5 F 6 F 7 F 8 F 9 F 10 F 11 K S K G The palm stearin-based soap as a hite material ith a pleasant smell; usually, the neat soap is devoid of smell and the use of a fragrant is alays necessary for the toilet soap-making. Soap, made holly of beef tallo as the hard fat component, frequently tends to give off rancidity in the long run. Thus, a substitution extent of the tallo by the palm stearin may screen this draback. The cleaning performance tests ere assessed on a tomato paste-dirtied hite fabric according to a described process (Moulay et al., 2003; Moulay et al., 2005). The results ere acceptable as the degree of hiteness of the ashed fabric specimen as high. Besides, the ater solutions of the different soap samples gave copious foaming, indicating a high ashing performance. CONCLUSION In conclusion, the palm stearin is, in addition to its cost effectiveness, a good tallo substitute in the soap-making as revealed by the properties of the soap. Also, the soap-making process using the palm stearin as a part of hard fat shoed that the different parameters of the process ere ithin the norms. ACKNOWLEDGEMENTS The authors are indebted to the ENCG firm (Entreprise Nationale des Corps Gras, Algiers) for their supply of fats. We greatly thank the ENCG technicians for their helpful discussion. REFERENCES: Davidsohn, A. S., Milidsky, B.M., 1987: Synthetic Detergents, seventh ed., - John Wiley & Sons, Ne York, 315 pp. deman, J. & deman, L. 1995: Formulations of no-trans and Lo-trans Margarines and Shortenings. In: Oils-Fats-Lipids, Proceedings of the 21 st World Congress of the International Society for Fat Research (ISF). The Hague. - Publ. PJ Barnes & Associates, Bridgeater, pp Fujimoto, T., Ne Introduction to Surface Active Agents. - Sanyo Chemical Ind. Ltd., Kyoto, 605pp. Moulay, S., Bentaleb, H., Abdessemed, M., 2003: Algerian montmorillonite as a builder in a detergent poder. - Journal of Surfactants and Detergents, 6:

12 Natura Montenegrina 10(3), 2011 Moulay, S., Zenimi, A., Dib, M., 2005: Rosin/Acid oil-based Liquid Soap. - Journal of Surfactants and Detergents, 8: Norlida, H. M., Md Ali, A. R., Muhadkir, I., 1996: Blending of Palm Oil, Palm Stearin and Palm Kernel Oil in the Preparation of Table and Pastry Margarines. - International Journal of Food Sciences & Nutrition, 47: Norris, F. A., 1965: Fats and Fatty Acids. In: Kirk-Othmer Encyclopedia of Chemical Technology, second ed. - John Wiley & Sons, Ne York, Vol. 8, pp Petrauskaite, V., de Greyt, W., Kellens, M., Huyghbaent, A., 1998: Physical and Chemical Properties of trans-free Fats Produced by Chemical Interesterification of Vegetable Oil Blends. - Journal of the American Oil Chemists' Society, 75: Tsujii, K., 1998: Surface Activity: Principles, Phenomena and Applications. - Academic Press, San Diego, 245pp. Woollatt, E., 1985: The Manufacture of Soaps, Other Detergents and Glycerol, first ed. - John Wiley & Sons, Ne York, 474pp. Received: 8 February