Soybean oil: SAP value and fatty acids
Soybean oil has a saponification value of 192 mg KOH/g. One gram needs 0.137 g of sodium hydroxide (NaOH) for bar soap or 0.192 g of potassium hydroxide (KOH) for liquid soap to turn fully into soap, before any superfat.
Key numbers
- SAP, NaOH
- 0.136873 g per g oil
- SAP, KOH
- 0.192 g per g oil
- Saponification value
- 192 mg KOH/g
- Iodine value
- 131.5
- INS
- 61
- INCI name
- Glycine Soja Oil
Example: 100 g of Soybean oil with no superfat needs 13.7 g of 100% NaOH, or 19.2 g of 100% KOH. A 5% superfat uses 5% less.
In soap
Its main fatty acids in our cited profile are linoleic (53.5%) and oleic (23.5%). The eight fatty acids used in soap-quality scores make up 99.5% of the profile.
On its own it scores 15 for hardness, 0 for cleansing and 85 for conditioning, with a saturated : unsaturated split of 15 : 85.
Fatty-acid profile
| Fatty acid | % of fatty acids | Counts toward |
|---|---|---|
| lauric | 0.1% | hardness, cleansing, bubbly lather |
| myristic | 0.1% | hardness, cleansing, bubbly lather |
| palmitic | 10.8% | hardness, creamy lather |
| stearic | 3.7% | hardness, creamy lather |
| ricinoleic | 0% | conditioning, bubbly and creamy lather |
| oleic | 23.5% | conditioning |
| linoleic | 53.5% | conditioning |
| linolenic | 7.8% | conditioning |
Basis: Codex CXS 210 Table 1 (soya bean oil) midpoints; Codex range midpoints; 'ND' = 0, 'ND–x' or '<x' = x/2.
Soap-quality scores (this oil alone)
| Hardness | 15 |
|---|---|
| Cleansing | 0 |
| Conditioning | 85 |
| Bubbly lather | 0 |
| Creamy lather | 15 |
| Iodine | 132 |
| INS | 61 |
Each score adds up certain fatty acids, the way Soap Ledger scores a whole recipe. They are for comparing recipes; they don't predict how a bar will feel, and they say nothing about safety or skin.
Sources
SAP value: 192 mg KOH/g (Codex CXS 210 range midpoint), from Codex Alimentarius CXS 210-1999, Standard for Named Vegetable Oils (Table 2: chemical and physical characteristics), FAO/WHO Codex Alimentarius Commission. Printed value: 189–195 mg KOH/g.
Published values we checked:
- 189–195 mg KOH/g — FAO/WHO Codex Alimentarius Commission
- 188–195 mg KOH/g — Ministry of Health, Labour and Welfare (Japan)
- 180–200 mg KOH/g — From Nature With Love (soap/cosmetic supplier)
- NaOH 0.1359 / KOH 0.1914 g alkali per g oil — Certified Lye
Fatty acids and iodine: Codex Alimentarius CXS 210-1999, Standard for Named Vegetable Oils (Table 2: chemical and physical characteristics), FAO/WHO Codex Alimentarius Commission. Also checked: USDA Agricultural Research Service (SR Legacy release 2018-04 (bulk CSV food_nutrient.csv); fatty acids in g/100 g food).
NaOH and KOH values are converted from mg KOH/g with the molar masses 39.997 and 56.106 and rounded to 6 decimals, exactly as in the Soap Ledger app. Real oils vary by origin, grade and lot: check your supplier's certificate of analysis. Verify every weight before you make this, and follow lye safety. Not a safety or compliance certification.
Last updated .