The acids contained in fruits often have much to do with their digestibility. In health apples and strawberries can usually be eaten with impunity but in some gastric disorders the malic acid in them and other fruits makes them unwholesome. More than one acid is contained in some fruits, though one usually predominates. Apples, blackberries and strawberries contain malic acid; currants and grapes tartaric acid; and oranges, lemons, grape fruit, and gooseberries, citric acid. Of these the citrous fruits are the best tolerated by all persons.

Sugar And Acid Content Of Common Fruits

1 "Foods and Their Adulterations." Wiley, 1911.

Olives

Two food products of considerable importance are made from olives - namely, olive oil, or salad oil, and pickled olives. A third product, little known in America, is the dried olive, much eaten in Greece and some neighboring countries. All olive oil and pickled olives were formerly imported, most generally from southern Europe. In recent years California has developed olive growing.

The ripe olive fruit is not unlike an oval damson plum in form and size. In color it ranges from various shades of purple to almost black. It has a sour and persistent bitter flavor. Both pulp and pit contain oil. The amount of oil in the pulp in different samples ranges from 13 to about 88 per cent.; that in the pit, from 0.36 to 1.52 per cent.

Whether used for oil making or pickling, the olive should be carefully gathered. The ripe fruit is used for oil making and for pickling; the exact stage when it is best suited for this purpose must be learned by experience. The green fruit is also used for pickling and should be gathered when full grown and just before it begins to color and soften. The pickled olives usually found in the American market are made from the green fruit. The pickled ripe olives are also met with and may be recognized by their dark color.

The best oil is made by crushing the carefully picked fresh olives. To facilitate the extraction of the oil, the olives are often partially dried before crushing. Old-fashioned stone mills are commonly used to crush the fruit, although bronze crushers are sometimes employed. The ground mass is pressed to extract the liquid portion, which contains watery plant juices in addition to the oil and more or less pulpy matter. Various devices are used to separate the oil and to purify it. It is said that the best oil is obtained by allowing the pulp, etc., to settle, and decanting the clear oil. It generally takes about one month for oil to settle the first time. It is usually decanted three times. The oil thus obtained is almost as bright as can be produced by the most effective filtration, and it has, besides, the distinctive olive flavor and lacks the greasiness that is characteristic of all filtered oils. Great cleanliness must be observed in oil making and every precaution taken to avoid rancidity.

Essentially the same process is followed in making pickles, whether from ripe or green olives. The unpleasant acid and bitter flavor is removed by soaking the fruit in a solution of potash lye for a short time or by longer soaking in water. The lye also softens the skin, so that the undesirable substances may be more readily extracted by water. Olives treated with lye must be soaked in clear water, which is frequently changed, to remove the potash. They are then placed in a weak brine for a short time and afterward in stronger brines. The details of each step of the process vary considerably, and much depends upon skill and experience. An abundant supply of pure water is of the first importance, and great care must be exercised to prevent the growth of molds, etc. As in the manufacture of oil, cleanliness is a prime requisite.

The uses of olive oil and olives as articles of diet are familiar. The former is used chiefly for salad dressing and for frying; the latter as a relish for seasoning sauces, etc., and for garnishing various foods. The oil, like all fats, has a high fuel value, and on this its value as a food depends.

Composition Of Pickled Ripe And Green Olives

Composition Of Fruits

Green olives are simply a relish and to be used in very limited quantities in the same way as pickled walnuts or cucumbers. A meal of bread and ripe olives is not only palatable, but nutritious and sustaining, and the amount eaten is to be limited only by the same considerations as that of any other good, wholesome food. In southern Europe and other regions the ripe olive is used as a staple article of diet.

The following table will show the composition of most fruits. From one-half to three-fourths of the carbohydrates in them is sugar. In this table, taken from Hutchison, the cellulose is sometimes included with the other carbohydrates and sometimes estimated separately.