This section is from the book "Food - What It Is And Does", by Edith Greer. Also available from Amazon: Food: What it is and Does.
The waste in food is not always evident even when real.
None - spinach, tomatoes skinned, peas and beans dried. 7-15% - beans (7%); onions (10%); cabbage, cucumbers, lettuce (15%). 20-30% - potatoes (also sweet), parsnips, beets, carrots, celery (20%); turnips (30%). 45-60% - green peas (45%); squash (50%); sweet corn (60%).
When it is remembered that water as well as refuse enters largely into the composition of vegetables as procured, it is realized that bulk is a significant characteristic of vegetable food.
Where the nutritive substances are in foods and how they are physically arranged affect their availability. Potatoes have an outer and inner skin. Both are richer in protein and salts than the flesh of the potato. Potatoes when peeled raw not only remove more nutrients than when peeled cooked, but in cooking permit the nutrients to be also dissolved out, as potato protein is in soluble form. Potato cooking-water, if the process is begun with cold water, contains 4/5 of the protein. But if plunged in boiling water, even peeled potatoes lose less than 1/10; unpeeled, only 1/100.
9/10 water; solids mainly starch. (Breading increases value).
9/10 water. Eaten raw retains nutrients. Cooked loses half.
Over 9/10 water. Used only for palatability. No food-value.
Over 9/10 water; sugar over 1/2 solids (sugar and protein soluble. Use juice therefore); some malic acid. Remove tomatoes from tin whenever not sealed air-tight.
Over 9/10 water. Valued for chlorophyll (green coloring matter). Contains iron.
Valued for oils giving flavor. Stimulating to digestion.
Solids 1/10, mainly sugar, that with oils and acids gives the flavor.
 
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