Buttermilk Powder: why 144 g per cup is wrong
King Arthur Baking Ingredient Weight Chart publishes 144 g (5.1 oz) per US cup of buttermilk powder. This site rejects that figure and publishes 120 g (4.2 oz) instead, from USDA SR Legacy "Milk, buttermilk, dried" (FDC 171274) (density 0.5072 g/mL, matching the composition of the substance). The reason:
0.609 g/mL contradicts King Arthur's own Dried Buttermilk Powder package, which gives 1/4 cup at 30 g, 120 g per cup. USDA SR Legacy (1 cup = 120 g), NOW Foods (1/4 cup = 30 g) and Bob's Red Mill (2 tbsp = 15 g) give the same density as the package. From USDA's composition the solid powder is about 1.43 g/mL, so a spooned cup at 120 g is about a third powder; 144 g is the same cup packed a fifth tighter, a scooped or tapped cup rather than a spooned one.
The arithmetic
| Source | 1 cup | Density | Status |
|---|---|---|---|
| King Arthur Baking Ingredient Weight Chart | 144 g5.1 oz | 0.6087 g/mL | Rejected on physics |
| USDA SR Legacy "Milk, buttermilk, dried" (FDC 171274) | 120 g4.2 oz | 0.5072 g/mL | Published here |
The published figure and its sources
The full sourcing for buttermilk powder, including every accepted and rejected figure, the state or filling method behind each, and the physics or standards reasoning applied, is on the ingredient page.
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