ABSTRACT: Soaps made from blends of distilled palm stearin (PS) and palm (PK) kernel fatty acids were evaluated for total fatty matter, sodium chloride content, moisture content, hard- ness, Hunter whiteness, foamability, iodine value, titer value, and acid value. Data showed that these soaps had properties similar to palm-based soaps made from distilled palm oil and palm kernel fatty acids. The soaps showed good whiteness (greater than 80%) and foamability. Total fatty matter ranged from 10–18%, sodium chloride content was 0.5%, and free caustic was 0.1% except for blend 8 containing 10 PS:90 PK, which had a free caustic of 0.03%. Initial penetration value, a reflection of soap hardness, ranged from 32–126 mm, with an average value of 54 mm. This value is within the range of the best blends of palm-based soaps (50–63 mm). There was no ob- vious trend observed. Penetration value, however was found to stabilize after a month of storage with an average value of 19.4 mm. Soap with this hardness value is relatively hard and there- fore should be blended with a small amount of soft oils.
JSD 1,329–334 (1998).
KEY WORDS: Foamability, hardness, palm-based soap, palm kernel oil, palm stearin, total fatty matter, whiteness.
Soap making is a well-established technology that has pro- gressed tremendously through the years with production of high-quality soap (1). In the process of this develop- ment, new raw materials were evaluated and technology modified to accommodate these materials (2,3). In the soap-making industry, raw material choice depends on three important factors, such as properties of the oils or fats, availability and cost competitiveness of raw materi- als. The traditional raw material for soap making is a com- bination of tallow and coconut oils. However, with expan- sion of the palm oil industry, new raw materials (4,5) such as palm and palm kernel (PK) oil can replace tallow and coconut oils, respectively. Soaps made from fatty acids of palm oil and PK oil are widely available in today’s market especially in Malaysia. Another suitable fat, a product from palm oil, is palm stearin (PS). PS is an inexpensive raw ma- terial and could also be used for making soap economi-
cally. PS is sold at a discount compared to palm oil, and its price falls into the range of inedible tallow (6).
Palm oil is a semi-solid oil derived from the mesocarp of the palm fruit (Elaeis guineensis), and PS constitutes the solid fraction. There are three different grades of stearin:
hard, medium hard, and soft. The fatty acid composition of stearin is 0.1–0.6% lauric acid, 1.1–1.9% myristic acid, 47.2–73.8% palmitic acid, 0.05–0.2% palmitoleic acid, 4.4–5.6% stearic acid, 15.6–37.0% oleic acid, 3.2–9.8%
linoleic acid, 0.1–0.6% linolenic acid, and 0.1–0.6%
arachidic acid (5). Iodine values range from 21.6–49.4%.
Slip melting point is between 44.5–56.2°C, and saponifica- tion value is between 193–206 mg KOH/g oil (5). Titer of PS ranges from 46–54°C with an average of 50°C (6). Dis- tilled PS fatty acid is derived from the splitting process of PS. Generally, soaps made from blends of oil with this range of titer are slightly harder. Soaps of this hardness level need to be blended with a small amount of soft oil such as palm oil, PK olein, tallow and olive oil, to produce a toilet soap of equivalent softness. Alternatively, soap of this hardness can be used in a situation of high humidity such as during Turkish or steam bath, as hard soap has low solubility and will last longer. The objective of this paper is to evaluate the properties of soaps made from various blends of distilled PS and PK fatty acids.
EXPERIMENTAL PROCEDURES
Parameters for fatty acids.Distilled PS and PK fatty acids, ob- tained from Unichema Malaysia (Bukit Rajah, Selangor, Malaysia), are expressed in weight percentage (w/w). All blends were evaluated using the following AOCS Official Methods: acid value (Da 14-48) (7) and titer (Da 13-48) (7).
Iodine value was measured according to Siew (8).
Preparation of soap samples. PS and PK fatty acid blends (4 kg) (Table 1) were melted in an amalgamator fitted with hot water jacket. Half the amount (refer to Table 1) of total sodium hydroxide (R&M Chemicals, Essex, United King- dom) was added slowly at the rate of 200 mL of 50%
(wt/vol) sodium hydroxide solution per 15–20 min. The remaining sodium hydroxide was added as a mixture with ethylenediaminetetraacetic acid (EDTA) (analytical grade;
J.T. Baker, Phillipsburg, NJ) and sodium chloride (Riedel
*To whom correspondence should be addressed at Chemistry and Technology Division, Palm Oil Research Institute of Malaysia, 6 Per- siaran Institusi, Bandar Baru Bangi, Kajang, Selangor, Malaysia.
E-mail: [email protected]
and Palm Kernel Fatty Acids
Ainie Kuntom* and Hamirin Kifli
Chemistry and Technology Division, Palm Oil Research Institute of Malaysia, Selangor, Malaysia
de Haen, Salze, Germany). Sodium chloride solution was added to reduce viscosity and EDTA to chelate any metal contaminants. The neat soap was then processed into 100- g soap bars after drying (9).
Determination of the properties of soap bars. Free caustic or free acid content was determined using AOCS Official Method Da 4a-48 (7); moisture content using a moisture balance; total fatty matter (TFM) using Kenyan Standard Method (10); foamability (method developed in PORIM) (11); Hunter whiteness using Color and Color Difference Meter (9); sodium chloride content using AOCS Official Method Da 9-48 (7), and hardness using a PNR6 penetrom- eter (SUR, Berlin, Germany) with a reading of 1/10-mm penetration depth.
RESULTS AND DISCUSSION
Quality of the fatty acid.Table 2 shows the acid value, titer value, and iodine value for distilled PS/PK fatty acid blends. Titer for commercial palm-based soap from dis- tilled fatty acids is normally in the range of 39–44°C (11).
Thus, blends 4, 5, and 6 fall within or close to this range.
Therefore, soap from these blends is of good quality.
The fatty acid content (FAC) of distilled PS fatty acid shows the presence 0.2% lauric acid (C12), 1.0% myristic acid (C14), 60.8% palmitic acid (C16), 4.9% stearic acid (C18), 26.3% oleic acid (C18:1), 5.4% linoleic acid (C18:2), 0.3% do- decanoic acid (C20), and 1.0% of others. Distilled PK fatty acid contained 2% caprylic acid (C8), 3% caproic acid (C10),
51% lauric acid, 18% myristic acid, 10% palmitic acid, 2%
stearic acid, 13% oleic acid, and 1.0% others.
Figure 1 shows the relationship between FAC and titer, iodine, and acid values. Acid value increased with increas- ing amount of C12–C14fatty acids and decreased with de- creasing amount of C16–C18fatty acids. Titer and iodine values decrease with increasing amount of C12–C14fatty acids and increase with increasing amount of C16–C18fatty acids in the blends.
Properties of soap samples.Table 3 lists soap properties found in this experiment. Moisture content ranged from 9.7–17.5%. Blends 6, 7, and 11 had very high moisture con- tent compared to other samples. The range of free caustic for all blends was 0.03–0.12%. Sodium chloride content was 0.5% for all blends.
Figure 2 shows the initial degree of whiteness at 20°C, after 1 wk and 1 mon storage. At all times the samples maintained a greater than 80% degree of whiteness except for blend 7 which had a whiteness of 79% after 1-mon stor- age. The whiteness limit for a good, pure white soap is 80%
(9). Comparatively, soap with high content of distilled PS fatty acid showed good whiteness as in blend 1 (100% dis- tilled PS fatty acids) that was 91% initially, 89% after 1 wk, and 88% after 1 mon. Another blend, 100% PK fatty acid, also showed a good degree of whiteness. This is attributed to the light color of the starting raw materials which are 0.3R and 0.1R for PS and PK, respectively. The saponifica- tion color values of PS and PK are 1.2R and 0.6R, respec- tively.
330 A. KUNTOM AND H. KIFLI
TABLE 1
Composition (% w/w) of Soap Blends from Distilled PS and PK Fatty Acidsa
Distilled fatty acid blends
1 2 3 4 5 6 7 8 9 10 11
100 PS 90 PS 80 PS 70 PS 60 PS 50 PS 40 PS 30 PS 20 PS 10 PS 0 PS
Raw material 0 PK 10 PK 20 PK 30 PK 40 PS 50 PK 60 PK 70 PK 80 PK 90 PK 100 PK
Distilled PS FA (g) 4000 3600 3200 2800 2400 2000 1600 1200 800 400 0
Distilled PK FA (g) 0 400 800 1200 1600 2000 2400 2800 3200 3600 4000
Sodium hydroxide (g) 609.90 615.53 625.57 641.43 654.72 668.41 680.93 693.11 707.68 719.37 733.15
Sodium chloride (g) 20 20 20 20 20 20 20 20 20 20 20
Distilled water (g) 123.00 1251.14 1251.14 1282.86 1309.44 1336.82 1361.86 1386.22 1415.36 1438.74 1466.30
Titanium dioxide (g) 5.0 5.0 5.0 5.0 5.0 5.0 5.0 5.0 5.0 5.0 5.0
EDTA (g) 4.0 4.0 4.0 4.0 4.0 4.0 4.0 4.0 4.0 4.0 4.0
aPS, distilled palm stearin fatty acid; FA, fatty acid; PK, distilled palm kernel fatty acid; EDTA, ethylenediaminetetraacetic acid.
TABLE 2
Quality of Blends of Distilled PS and PK Fatty Acidsa
Blends of distilled fatty acids
1 2 3 4 5 6 7 8 9 10 11
100 PS 90 PS 80 PS 70 PS 60 PS 50 PS 40 PS 30 PS 20 PS 10 PS 0 PS
Raw material 0 PK 10 PK 20 PK 30 PK 40 PK 50 PK 60 PK 70 PK 80 PK 90 PK 100 PK
Acid value 211 216 219 225 230 234 239 243 248 252 257
Titer °C 52 50 48 46 43 40 36 31 28 26 25
Iodine value 33 29 27 22 24 21 18 17 16 15 11
aSee Table 1 for abbreviations.
FIG. 1. Relationship between fatty acid content (FAC) of distilled palm stearin (PS):palm kernel (PK) fatty acid blends with (A) titer, (B) iodine, and (C) acid values: ●, C12–C14; ◆, C16–C18.
TFM was greater than 80% (Fig. 3),being higher than the required specification in some countries. Even after 1-mon storage, the TFM remained greater than 80% except for blend 6 (50PS:50PK fatty acid). All blends started with a high TFM except for 100% PK fatty acid which, however, increased to 81% after 1-mon storage. This could be partly due to loss of moisture which in turn is reflected in an in- crease of TFM.
Figure 4 shows the trend of initial foamability, and foamability after 5 min. There is no great variation in the foamability between blends. The volume of initial foam was good, and the average volume of foam was 525.5 mL with a standard deviation of 17.096 and coefficient of vari- ation of 3.3%. After 5 min the volume decreased to an av- erage volume of 355.9 mL (standard deviation 19.598, coef- ficient of variation 5.5%) and remained unchanged there- after. Average volume reduction was 170.9 mL (standard deviation 7.006, coefficient of variation 4.1%).
There is no obvious trend in the initial penetration value, which is a reflection of soap hardness (Fig. 5). As seen in the figure, blends 1, 2, 6, 7, and 11 had high initial penetration values, indicating that the soaps were quite
soft. Blends 6 and 7 had moisture contents of 14.2 and 17.5, respectively. This factor could contribute to soap softness.
However after 1-wk storage at 20°C, the soaps stabilized slightly, as seen in Figure 7. At 1-mon storage, the soap sta- bilized and the penetration value was 15.3–24.4 mm with an average of 19.4 mm (standard deviation 3.241, coeffi-
332 A. KUNTOM AND H. KIFLI
FIG. 2. Degree of soap whiteness from various PS:PK blends: left-hatched bars, initial; dotted bars, after 1 wk; and horizontal line bars, after 1 mon. See Figure 1 for abbreviations.
TABLE 3
Properties of Soap Derived from Blends of PS and PK Fatty Acids
Soap blends
1 2 3 4 5 6 7 8 9 10 11
100 PS 90 PS 80 PS 70 PS 60 PS 50 PS 40 PS 30 PS 20 PS 10 PS 0 PS
Raw material 0 PK 10 PK 20 PK 30 PK 40 PK 50 PK 60 PK 70 PK 80 PK 90 PK 100 PK
Hunter whiteness (%) 91 86 82.1 86 85 87 81 85 86 87 88
Penetration value 1/10 mm 91 63 56 57 37 86 126 32 36 47 69
Free caustic/acid* (%) 0.1 0.10 0.10 0.10 0.10 0.10 0.10 0.10 0.10 0.03 0.10
Total fatty matter (%) 83 84 83 82 82 79 80 82 81 81 79
Sodium chloride (%) 0.5 0.5 0.5 0.5 0.5 0.5 0.5 0.5 0.5 0.5 0.5
Foamability (mL) 520/340* 520/340* 510/345* 500/325* 525/355* 540/375* 530/365* 520/355* 555/385* 510/345* 550/385*
Moisture content (%) 13 13 12 12 10 14 18 10 12 13 15
TABLE 4
Properties of Some Commercial Toilet-Soap Samplesa
Malaysia Europe Japan
palm-based tallow-based tallow-based
Parameter FAa FAa FAa
Iodine value 39–44 28.3–38.5 30.5–53.6
Total fatty matter (%) 83–86 83–85 83–85
Free caustic content (%) <0.1 <0.1 <0.1
Sodium chloride (%) <1 <1 <1
Titer (°C) 39–43 30–38 37–38
Moisture (%) 6–9 6–8 8–11
Penetration values 26–38 19–29 14–19
Hunter whiteness 81–86 85 89.2
Foamability 460/295B 530/360B 345/220B
aSource: Reference 11. FA, Fatty acid.
bVolume of foam after 5 min.
Ratio PS:PK
cient of variation 16.7%). Samples with higher PK fatty acid content tend to be slightly harder than those with high PS fatty acid content. The penetration value of palm-based (blends of distilled palm oil fatty acids and distilled PK fatty acids) commercial soap ranges from 26–38 mm (as shown in Table 4), and for experimental samples from sim- ilar blends the range was 50–60 mm (11). The range of val- ues for these soap samples was low which indicates that they are harder compared to palm oil-based commercial soap and experimental samples even though most other properties were similar. The results indicate that distilled PS fatty acid content should be in the range of 50–60%. A blend of 40% PS, 40% soft oils or fats and 20% PK or co- conut oil produced a good quality palm-based soap (12).
ACKNOWLEDGMENTS
We thank the Director-General of PORIM for making it possible for us to carry out this study. Many thanks are also extended to Y.L. Lee, Ghazali A. Razak, and Mohammad A. Rahman for their efforts. We also extend our appreciation to UNICHEMA Malaysia for providing raw materials.
REFERENCES
1. Jungermann, E., Soap/Cosmetic/Chemical Specialties 63(60):22 (1988).
2. Gupta, S., Chemistry, Chemical and Physical Properties &
Raw Materials, in Soap Technology for the 1990’s, edited by L.
Spitz, American Oil Chemists’ Society, Champaign, 1990, pp. 48–93.
FIG. 3. Total fatty matter of soaps made from blends distilled PS:PK fatty acid: left-hatched bars, initial; dotted bars, after 1 wk; and horizontal line bars, after 1 mon. See Figure 1 for ab- breviations.
FIG. 4. Foamability of soap blends made from various blends of distilled PS:PK fatty acid: left- hatched bars, initial and dotted bars, after 5 min. See Figure 1 for abbreviations.
Ratio PS:PK
Foamability (mL)
3. Jungermann, E., Soap/Cosmetic/Chemical Specialties 60(3):30 (1985).
4. Iftikhar, A., Use of Palm Stearin in Soaps, PORIM Technology, No. 2, PORIM publication, Selangor, Malaysia, June 1986.
5. Tan, B.K., and F.C.H. Oh, Oleins and Stearins from Malaysian Palm Oil: Chemical and Physical Characteristics, PORIM Technology,No. 4, PORIM Publication, Selangor, Malaysia, May 1984.
6. Iftikhar, A., Significance of Palm Oil and Palm Stearin as Fatty Raw Materials for Soap, PORIM Occasional Paper,No. 13, PORIM Publication, Selangor, Malaysia, June 1984.
7. Official Methods and Recommended Practices of the American Oil Chemists’ Society,4th edn., edited by David Firestone, Ameri- can Oil Chemists’ Society, Champaign, 1989.
8. Siew, W.L., PORIM Test Methods,published by Palm Oil Re- search Institute of Malaysia, Kuala Lumpur, 1988, pp. 72–75.
9. Kuntom, A., H. Kifli, and K.H. Chen, Gas Chromatographic Analysis of Fragrances in Palm–Based White Soaps, J. Am. Oil Chem. Soc. 69:614–620 (1992).
10. Kenya Bureau of Standards, KS 03-45: 1977, UDC 6681.1:
543.05.
11. Kuntom, A., H. Kifli, and P.K. Lim, Characteristics of Soap Made from Distilled Fatty Acid of Palm Oil and Palm Kernel Oil, J. Am. Oil Chem. Soc. 73:105-107 (1996).
12. Kifli, H., and S. Krishnan, Palm Oil Products in Soap Making Including Measurement of Properties of the Soap Developed, in Proceedings of the 1987 International Oil Palm/Palm Oil Con- ference—Progress and Prospects, Conference II: Technology,Palm Oil Research Institute of Malaysia (PORIM), Selangor, 1988, pp. 304–315.
[Received September 16, 1997; accepted April 6, 1998]
Ainie Kuntom is currently the principal research officer and an- alytical group leader in the Chemistry and Technology Division of PORIM. She received her Ph.D. degree from the State Univer- sity of Ghent, Ghent, Belgium. Areas of research interest are quality of oils/fats, analytical method development, and palm- based soaps.
Hamirin Kifli is the Director of Techno-Economic and Tech- nical Advisory Service Division of Palm Oil Research Institute of Malaysia (PORIM). He has a Ph.D. from the St. Andrews University, Scotland, United Kingdom. Research interest is in the area of palm-based product development in food, soap, and oleochemicals.
334 A. KUNTOM AND H. KIFLI
FIG. 5. Penetrometer values for blends of PS:PK soap: left-hatched bars, initial; dotted bars, after 1 wk; and horizontal line bars, after 1 mon. See Figure 1 for abbreviations.
Ratio PS:PK
