Just what the changes are that take place in the transformation of hard fruits into sparkling jellies does not appear to be fully settled by the chemists. Referring to the group of carbohydrates known as "pectin bodies," or " pectose," Dr. Robert Hutchi son says. " These are the substances which give to fruits their power of forming jellies when boiled, and little is known of their exact chemical nature, hut they appear to be converted into a special kind of sugar when digested (pentose), which is at least partly assimilable by the body." At present the general opinion seems to be that the pectose, insoluble in unripe fruits, under the influence of a ferment-like body called poctase, which is present in ripening fruits, or of acids and heat, becomes pectin, a soluble substance which stiffens the juices and produces the compound we know as jelly. As Miss Parloa says, "Pectin is at its best when the fruit is just ripe or a little before. If the juice ferments, or the cooking of the jelly is continued too long, the pectin undergoes a change, and loses its power of gelatinizing." By continued evaporation of certain fruit juices containing much pectin, jelly may be made without addition of sugar. Currant jelly may be made by combining the warm juice and warm sugar without further cooking, placing the glasses where sunlight will do the remainder.
The effect of a damp season may be seen in jellies. There appears to be less of the jellying property, more boiling is needed to evaporate moisture, and there will be more shrinkage of the jelly in the glass afterwards.
The apple may be used to illustrate the general process of jelly-making, since that contains a large proportion of the pectosic principle, and having a less distinctive flavor of its own may be combined with more expensive fruits, as the pine apple, to produce satisfactory results. A supply of jellies may be secured from different varieties of apples alone, the different kinds ranging from the pale color of the Porter to the deep red of some winter varieties, with flavors as unlike as the shades of color. The fruit is cleaned, quartered and cooked in water until soft, but no longer. The average proportion is one quart of water to two quarts of apples, but this varies with the juiciness of the apples. The cooked fruit must drain without pressure. One simple old-fashioned way to accomplish this is to spread a square of cheese-cloth over a large agate or earthen pan, pour the hot fruit into this, tie the opposite cor ners of the cloth together, and hang over a strong stick placed across two chairs so the juice will drip into the pan. Better than chairs and stick is a strong bird-cage book in the wall over the kitchen table; or the cheese-cloth may be laid over a hair sieve which is set in a pan. The frame of
the sieve will raise the fruit out of the juice. The cloth should always be moistened before the fruit is put in it.
Jelly-making is seldom as successful in damp weather as on a clear, bright day, for evaporation is slower. Sugar is peculiarly affected by the weather and, though in less degree, some of the same difficulties attend jelly-making as the manu facture of candy. On a clear, windy day evapora tion is rapid and less boiling is required. In mid summer, bacteria are so active on some of the hot, muggy days, that it is almost impossible to make everything sterile.
The juice must be measured and boiled rapidly in a shallow kettle. It is often more satisfactory to boil lots of one or two quarts than in larger quantities. The process is hastened by heating in the oven for ten minutes the nearly equal weight of sugar, while the juice is boiling on the top of the stove. When the sugar will hiss as it meets the liquid, it is put in, stirred till blended, and the whole boiled for about ten minutes more. Careful skimming at intervals is essential to secure a clear jelly, for if the froth once boils in, the jelly, even if strained afterwards, will never be quite clear. The time and the general appearance of the jelly tell us when to stop. If uncertain, single drops on a cold surface will show the consistency.
Strain the jelly quickly through a new wire strainer into a pitcher and pour from that into the final receptacle. Tumblers are generally preferred, giving a good form for the table, but tin covers are undesirable. When the jelly is cold and firm, melted paraffine may be poured over till one-fourth inch thick. One thinner layer may be allowed to cool, and then the remainder poured on will cover any cracks. Papers dipped in alcohol or brandy, laid directly on the jelly, will prevent mold, but a layer of absorbent cotton or batting is an addi tional safeguard, and strong paper may be pasted over all.
Jellies crystallize because of excess of sugar or too hard boiling. A temperature even 2° higher will make the color darker, and cause a loss of flavor in the jelly.
Fruit syrup.
Jellies that do not stiffen properly, and any sur plus syrup from preserves, should be bottled for future use as the foundation of many desserts, such as gelatine or custard puddings, ice creams, and the like. Often several odd lots of fruit juice may be combined for a summer beverage. Occa sionally it has been found more convenient to can the fruit juice and make jelly at another time.