When you place a whole banana with its peel, a mango with its stone, or a handful of in-shell pistachios on a kitchen scale, you are weighing both the food you will eat and the inedible parts you will throw away.
Because reference nutrition databases report nutrients per 100 grams of edible portion only, knowing when to weigh before or after peeling prevents 15% to 50% logging errors.
Edible portion (EP) vs as-purchased (AP) weight in USDA data
In culinary purchasing and food composition science, as-purchased (AP) weight is the gross weight of the food as it comes from the market—including peels, rinds, cores, pits, stones, pods, shells and tough outer leaves. Edible portion (EP) weight is the net weight of the part actually eaten after that inedible "refuse" is removed.
In USDA FoodData Central (Foundation Foods and SR Legacy), nutrient values per 100 grams always apply to 100 grams of the edible portion unless the entry title explicitly states otherwise, and records include metadata noting what refuse was removed before laboratory analysis.
- Thick-peeled and rind fruits (bananas, oranges, pomegranates, melons, pineapple): Weigh the peeled flesh or seeded arils, not the whole unpeeled fruit.
- Stone fruits and avocados (mangoes, peaches, plums, dates, avocados): Weigh the pitted, peeled flesh—or subtract the weight of the pit and skin after eating.
- Hard-rind vegetables and trimmings (winter squash, pumpkin, cauliflower cores, woody herb stems): Weigh the trimmed, peeled pieces that actually go into the pot.
- In-shell nuts and pods (pistachios, walnuts, almonds in shell, fresh peas in pod): Always weigh the shelled kernels or peas unless a package label specifically gives an "in-shell" weight.
When the skin is edible: apples, potatoes, cucumbers and carrots
Not all skins are inedible refuse. For produce commonly eaten either way—such as apples, pears, potatoes, sweet potatoes, cucumbers and zucchini—USDA reference databases often list separate entries for "with skin" and "without skin" (peeled).
Choosing the matching entry matters for both weight and composition: peeling a potato or apple before cooking removes the weight of the peel and slightly reduces insoluble dietary fiber and skin-associated phytonutrients per 100 grams.
The two-weighing subtraction method for messy or cooked-in-skin foods
You do not need to peel a baked sweet potato, scoop a ripe avocado or pit a bowl of cherries before eating just to get an accurate edible portion weight.
Use the simple before-and-after subtraction method on your plate:
- Weigh the whole item on your plate before eating (hypothetical example: a whole mango or avocado half weighing 220 g with skin and pit).
- Eat the edible flesh as usual, leaving the inedible skin, peel, pit, rind or shells on the plate.
- Place the plate with the leftover refuse back on the scale (hypothetical example: 70 g of skin and pit remaining) and subtract from the starting weight (220 g − 70 g = 150 g edible portion eaten).
Sources & Classical References
- USDA FoodData Central: Data Type Documentation — Explains how USDA reference records report nutrient values per 100 grams of edible portion along with refuse descriptions.
- FDA: Serving Size on the Nutrition Facts Label — Describes how household measures and metric gram weights are declared for edible servings on food labels.
