JAMS AND JELLIES. In the article FOOD PRESERVATION it is pointed out that concentrated sugar solutions inhibit the growth of organisms and so have a preservative action. The preparation of jams and jellies is based upon this fact. All fresh and succulent fruit contains a large percentage of water, amount ing to at least four-fifths of the whole, and a comparatively small proportion of sugar usually not exceeding 10 to 15%. Such fruit is naturally liable to decomposition unless the greater pro portion of the water is removed and the percentage of sugar much increased. Jams and jellies are preserves containing about two thirds their weight of sugar. All kinds of edible fruit can be made into jam but for the preparation of jellies only those fruits are suitable which contain a sufficient proportion of a chemical sub stance called pectin, on which the gelatinizing power of fruit depends. This substance is a carbohydrate of no feeding value but, being allied to the vegetable gums, after boiling has the property of solidifying to a gelatinous mass. It is present to some extent in all fresh fruit but to a larger extent in citrons fruits, red and black currants, gooseberries and apples, and certain other fruits which are capable of forming jellies. As some degree of gelatiniza tion is aimed at in jams pectin is sometimes added in the case of strawberries, raspberries, and other fruits which do not contain sufficient pectin to make them set. Iceland moss, gelatine and agar-agar have sometimes been added to give the necessary gelat inizing power, but such additions are not desirable.
The art of jam-making, once entirely domestic, is now a large branch of manufacture. The pulped or sliced fruit, sometimes with the addition of a little water, is mixed with about an equal weight of sugar and rapidly boiled down to the required consist ency. As the jellifying power of the pectin depends upon the acidity of the fruit, the consistency can often be improved by the addition of a small quantity (say one-half of 1 %) of tartaric or citric acid. Manufacturers sometimes add small quantities of aniline dyes to improve the colour. Considerable experience is required to stop the boiling at the right point; too short boiling leaves an excess of water, which results in fermentation, while over-boiling may cause crystallization of the sugar. The finishing point is usually judged by rule of thumb, although in some fac tories it is regulated by accurate thermometric measurement. The addition of chemical preservatives, such as salicylic acid, was at one time common, but it is not now permitted in most countries. Although a jam or jelly containing 6o or 7o% of sugar does not ferment or decompose it is still liable to the growth of mould on the surface, so in order to prevent this the pots into which the boiled jam is to be poured should be thoroughly cleaned and the jam or jelly sealed hermetically immediately, so that the spores of moulds may not fall upon the surface from the air.
Sometimes starch glucose and beet sugar are used to replace part of the cane sugar; the addition of glucose is not held to be an adulteration and is said to reduce the liability of the jam to crystallize and to aid gelatinization. A popular prejudice has it
that beet sugar is not suitable for jam making; this is quite erroneous; large quantities of beet sugar are used and the product is indistinguishable from that made from cane sugar. The gross adulteration of jam is now a thing of the past, but sometimes there is the addition of apple-pulp, or the pulp of certain vege tables to give gelatinizing power, particularly when fruit pulp which has been long stored or which has been preserved with sulphur dioxide is used, as such is apt to be very deficient in pectin. (H. E. C.) Jams and Jellies, Home•made.—Jellies. The gelatine must first be soaked about 20 minutes in water, and then melted with a small amount of water by stirring on top of a fire. Water should then be added in the proportion of about one pint to one ounce of gelatine, but certain fruits, such as the lemon, require more gela tine. The wine or other flavourings should be added while the mixture is hot ; if fruit juice is to be added instead of whole fruits, the fruit must be stewed until as much as possible of its body has gone into the juice. The mixture should be poured into a mould and left to cool.
To remove jelly from the mould, it is best to place the mould once in very hot water—not several times in lukewarm water. The jelly can then generally be removed with one sharp jerk.
In the United States jelly making from fruit is still a general home process, especially in rural communities and the smaller towns. The process is the same as for commercial jellies, cane or beet sugar being used. Paraffin is in common use for sealing. Of late years preparations of pectin have been marketed for use in the home, and these are being more and more employed.
For gelatine jellies, one pint of liquid requires about one table spoon of the usual granulated gelatine. This is soaked five min utes in double its own quantity of cold water, and dissolved in a little hot liquid before stirring into the mixture. The use of man ufactured gelatine jellies, already flavoured and needing only the addition of hot water, is wide and increasing.
Jam is made at home more generally than jelly, being easier, and if from marketed fruit, better.
Jams. Sugar should be provided in the proportion of anything from 2lb. to fib. for each pound of fruit, according to taste. The sugar should first be melted over the fire in a small quantity of water, and the fruit then added. The whole should be boiled in a preserving pan from 20 to 6o minutes, according to the hard ness of the fruit, being stirred regularly with a wooden spoon or stick, to prevent burning.
The jam must then immediately be placed in perfectly dry pots and sealed at once.