Key Lime Juice: why 227 g per cup is wrong
King Arthur Baking Ingredient Weight Chart publishes 227 g (8 oz) per US cup of Key lime juice. This site rejects that figure and publishes 246 g (8.7 oz) instead, from USDA SR Legacy "Lime juice, canned or bottled, unsweetened" (FDC 168157) (density 1.0398 g/mL, matching the composition of the substance). The reason:
0.960 g/mL is lighter than water, and lime juice cannot be: it is water carrying about 10% dissolved citric acid and sugars (Key lime juice measures 9-10 °Brix), which makes it about 4% heavier than water. USDA weighs a cup of bottled lime juice at 246 g and fresh lime juice at 242 g. A cup is 8 fluid ounces and 227 g is 8 weight ounces: the fluid ounce read as a weight ounce, the same mistake as King Arthur's 227 g cup of water.
The arithmetic
| Source | 1 cup | Density | Status |
|---|---|---|---|
| King Arthur Baking Ingredient Weight Chart | 227 g8 oz | 0.9595 g/mL | Rejected on physics |
| USDA SR Legacy "Lime juice, canned or bottled, unsweetened" (FDC 168157) | 246 g8.7 oz | 1.0398 g/mL | Published here |
The 227-gram pattern
The figure 227 is 8 × 28.35 — the conversion for weight ounces (avoirdupois). It is applied to volume in fluid ounces without going through the substance’s density. For a substance that happens to have a density of about 0.96 g/mL, the answer would be right; for water, milk, yogurt, cream, buttermilk, pumpkin purée, ricotta and evaporated milk, all of which are denser than water, it is wrong. The same number 227 appears on the King Arthur chart for every one of these ingredients, which is the signature of an arithmetic pattern rather than a measurement.
The full list of 227-gram rejections is on the corrections page.
The published figure and its sources
The full sourcing for Key lime juice, 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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