Fruits and Vegetables

The Chemistry Of Food and Nutrition
by A. W. Duncan, F.C.S.

(Page 6 of 11)

Fruits are generally looked upon as luxuries, rather than as food capable of supplying a meal or a substantial part of one. They are usually eaten only when the appetite has been appeased by what is considered more substantial fare. Fresh fruits contain a larger proportion of water than nearly all other raw foods, and consequently the proportion of nourishment is small; but we must not despise them on this account. Milk contains as much or more water. Certain foods which in the raw state contain very little water, such as the pulses and cereals when cooked absorb a very large quantity; this is the case in making porridge. Cabbage, cauliflower, Spanish onions and turnips, after cooking contain even 97 per cent. of water. Roast beef contains on an average 48 per cent., and cooked round steak with fat removed 63 per cent. of water. It is customary at meal times to drink water, tea, coffee, beer, wine. When a meal contains any considerable quantity of fresh fruits there need be no desire to drink.

Notwithstanding that fruits contain so much water, a dietary consisting of fruits with nuts, to which may be added bread and vegetables, will contain less water than the total quantity usually consumed by a person taking the more customary highly cooked and seasoned foods. An advantage is that the water in fruits is in a wholesome condition, free from the pollution often met with in the water used for drinking purposes. Raw fruits favor mastication, with its consequent advantages, whilst cooked and soft food discourages it. Plums and what are termed stone fruits, if eaten in more than very small quantities, are apt to disagree. Persons with good digestions can take fruit with bread, biscuits and with uncooked foods without any inconvenience. Fruit is more likely to disagree when taken in conjunction with elaborately cooked foods.

Many cannot take fruit, especially if it be acid, at the same time as cereal or starchy substances, and the difficulty is said to be greater at the morning's meal. If the indigestion produced is due to the acid of the fruit preventing the saliva acting on the starch, scientific principles would direct that the fruit be eaten quite towards the end of the meal. The same consideration condemns the use of mint sauce, cucumber and vinegar, or pickles, with potatoes and bread, or even mint sauce with green peas. Bananas are an exception, as not interfering with the digestion of starch. Bananas are generally eaten in an unripe condition, white and somewhat mealy; they should be kept until the starch has been converted into sugar, when they are both more pleasant and wholesome. Nuts and fruit go well together. For a portable meal, stoned raisins or other dried fruit and walnut kernels or other nuts are excellent.

What has been called a defect in most fruits, is the fact that the Protein is small in proportion to the other constituents. This has been too much dwelt upon, owing to the prevailing exaggerated idea of the quantity of Protein required. The tomato contains a large proportion, though the water is very high. Bananas, grapes and strawberries contain to each part of Protein from 10 to 12 parts of other solid nutritive constituents (any oil being calculated into starch equivalents); this is termed the nutritive ratio. Although this may seem a small proportion of Protein, there are reasons for believing that it is sufficient. Taking the average of 29 analyses of American apples, a nutritive ratio of 33 was obtained. If it were suggested that life should be sustained on apples alone, this small quantity of Protein would be an insurmountable difficulty. As the addition of nuts or other nutritious food sufficiently increases the Protein, no objection can with justice be made against the use of fruit. A study of our teeth, digestive organs and general structure, and of comparative anatomy, points to fruits, nuts and succulent vegetables as our original diet.

The potash and other salts of the organic acids in fruits tend to keep the blood properly alkaline. Where there is a tendency to the deposition of uric acid in the body, they hinder its formation. Citric, tartaric, malice and other organic acids exist in fruits in combination with potash and other bases, as well as in the free state. The free acids in fruits, when eaten, combine with the alkalis in the intestinal tract, and are absorbed by the body and pass into the blood, not as acids, but as neutral salts. Here they are converted into potassium carbonate or some other carbonate. Fruit acids never make the blood acid but the reverse. Fruit salts and acids are antiscorbutic. Fruits have often proved of the greatest benefit in illness. What is known as the grape cure has been productive of much good. Lemons and oranges have also been of great benefit. Strawberries have been craved for and have proved of the greatest advantage in some extreme cases of illness when more concentrated food could not be endured.

Fruit is coming into greater use, especially owing to its better distribution and lessened cost. Fruit is not as cheap as it should be, as it can be produced in great abundance at little cost, and with comparatively little labor. The price paid by the public greatly exceeds the real cost of production. A very large proportion, often the greater part of the cost to the consumer, goes in railway and other rates and in middle-men's profits. It is commonly cheaper to bring fruit from over the sea, including land carriage on either side, than it is to transport English produce from one part of our country to another. English homegrown fruit would be cheaper were it not for the difficulty of buying suitable land at a reasonable price, and the cost of transit. For the production of prime fruit there is a lack of sufficient intelligence, of scientific culture and co-operation.

Vegetables - using the name in its popular sense - contain valuable saline constituents or salts. By the usual method of cooking a large proportion of the salts is lost. It is better to steam than to boil them. The fibrous portion of vegetables is not all digested, but it is useful in stimulating the peristaltic action of the bowels and lessening any tendency to constipation. Vegetables are more especially useful to non-vegetarians to correct the defects of their other food.

The potato belongs to a poisonous order - the Solanace. There is a little alkaloid in the skin, but this is lost in the cooking. The eyes and sprouting portions contain the most and should be cut out.

Fungi - There are about a hundred edible species in this country, but many of the fungi are poisonous, some intensely so. It can scarcely be expected that these lowly organized plants, differing so much in their manner of growth from the green or chlorophyll bearing plants, can be nourishing. It is only the fructifying part, which appears above the ground, that is generally eaten. It is of very rapid growth. Of 9 edible fungi of 4 species, obtained in the Belgrade market, the average amount of water was 89.3 per cent., leaving only 10.7 per cent. of solid matter; the average of fat was 0.55 per cent. The food value of fungi has been greatly over-rated. In most of the analyses given in text-books and elsewhere, the total nitrogen has been multiplied by 6.25 and the result expressed as Protein. The amount of nitrogen in a form useless for the purpose of nutrition is about a third of the whole. Of the remainder or Protein nitrogen, it is said much is not assimilated, sometimes quite half, owing to the somewhat indigestible character of the fungi. An analysis of the common mushroom gave Proteins 2.2 per cent., amides (useless nitrogenous compounds) 1.3 per cent., and water 93.7 per cent. The fungi are of inferior nutritive value to many fresh vegetables and are much more expensive. Their chief value is as a flavoring.

Manchester the Vegetarian Society, 1905.