Milk fat (butterfat): SAP value and fatty acids
Milk fat (butterfat) has a saponification value of 227.5 mg KOH/g. One gram needs 0.162 g of sodium hydroxide (NaOH) for bar soap or 0.228 g of potassium hydroxide (KOH) for liquid soap to turn fully into soap, before any superfat.
Key numbers
- SAP, NaOH
- 0.162181 g per g oil
- SAP, KOH
- 0.2275 g per g oil
- Saponification value
- 227.5 mg KOH/g
- Iodine value
- 35.5
- INS
- 192
- INCI name
- Milk Lipids
Example: 100 g of Milk fat (butterfat) with no superfat needs 16.2 g of 100% NaOH, or 22.8 g of 100% KOH. A 5% superfat uses 5% less.
In soap
Its main fatty acids in our cited profile are palmitic (27.7%) and oleic (26.5%). The eight fatty acids used in soap-quality scores make up 84.5% of the profile.
On its own it scores 54 for hardness, 14 for cleansing and 30 for conditioning, with a saturated : unsaturated split of 54 : 30.
Cow's milk fat contains short-chain acids (butyric etc.), so its SAP is higher than tallow's. Ghee is near-pure milk fat.
Fatty-acid profile
| Fatty acid | % of fatty acids | Counts toward |
|---|---|---|
| lauric | 3% | hardness, cleansing, bubbly lather |
| myristic | 10.6% | hardness, cleansing, bubbly lather |
| palmitic | 27.7% | hardness, creamy lather |
| stearic | 12.8% | hardness, creamy lather |
| ricinoleic | 0% | conditioning, bubbly and creamy lather |
| oleic | 26.5% | conditioning |
| linoleic | 2.4% | conditioning |
| linolenic | 1.5% | conditioning |
Basis: USDA FDC SR Legacy 173412 "Butter oil, anhydrous", individual fatty acids divided by total fatty acids.
Soap-quality scores (this oil alone)
| Hardness | 54 |
|---|---|
| Cleansing | 14 |
| Conditioning | 30 |
| Bubbly lather | 14 |
| Creamy lather | 41 |
| Iodine | 36 |
| INS | 192 |
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: 227.5 mg KOH/g (JSQI 2021 range midpoint), from Japanese Standards of Quasi-drug Ingredients 2021 (医薬部外品原料規格2021), PSEHB notification 0325-1 of 25 March 2021, Ministry of Health, Labour and Welfare (Japan). Printed value: 210～245 mg KOH/g.
Published values we checked:
- 210～245 mg KOH/g — Ministry of Health, Labour and Welfare (Japan)
- NaOH 0.1599 / KOH 0.2252 g alkali per g oil — Certified Lye
Fatty acids and iodine: USDA FoodData Central, SR Legacy: Butter oil, anhydrous (FDC ID 173412), U.S. Department of Agriculture, Agricultural Research Service. Also checked: Food & Nutrition Research (peer-reviewed, open access) (Table 1, weighted mean 2001 (Swedish dairy milk)); Ministry of Health, Labour and Welfare (Japan) (Monograph 乳脂 Milk Fat (iodine value)).
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 .