Jam Manufacture - Its Theory and Practice

By William C. Jago

This vintage book contains a complete guide to jam manufacture, and includes information on different manufacturing operations, packing, chemical examination, machinery, materials, and much more. This comprehensive guide contains a wealth of interesting and useful information on the subject of jam manufacturing. It will greatly appeal to those with an interest in the development of jam, and the jam industry more generally. The chapters of this book include: 'Introductory', 'Raw Materials', 'Apparatus and Plant', 'Manufacturing Operations', 'Bottled Fruits', 'Packing and General Handling of Jams', 'Chemical and Biological Examination of Raw Materials and Finished Substances', etcetera. We are republishing this vintage book now in an affordable, modern edition - complete with a specially commissioned new introduction on preserving and canning food.

• Language: English
• Publisher: Read Books Ltd.
• Release date: Nov 15, 2011
• ISBN: 9781447492320

Book preview

JAM MANUFACTURE:

Its Theory and Practice

CHAPTER I.

INTRODUCTORY.

FROM time immemorial, fruit has been regarded not merely as an article of food, but also as a luxury.

In composition, fresh fruit contains, approximately, the following ingredients, the quantities varying according to the nature and degree of ripeness of the fruit:—

The amount of protein and fat is too small to be of any practical importance, but the carbohydrates are the principal food substances present. The greater part of these consists of sugar, the particular variety being that known as lævulose or fruit sugar, of which from one half to two-thirds of the carbohydrates may consist. Some fruits, as for example apples, apricots, and pineapples, contain also cane sugar. The remainder of the carbohydrates consists of pectin or vegetable gum; it is this body which causes the concentrated juice of fruits to acquire its well-known jelly-like consistency.

Another group of bodies which have an important bearing on the flavour of fruit is that of the various acids, among which are tartaric acid in grapes, citric acid in lemons, and malic acid in apples. These acids are generally present as acid salts of potassium. As the fruit ripens, the acid somewhat diminishes, and is also more or less masked by the increasing quantity of sugar being produced. The characteristic flavours of fruits are largely due to the presence of minute quantities of certain ethereal substances, which, in certain cases, have been identified, while, in others, they have eluded chemical investigation. Thus, the flavour of jargonelle pears is due to amyl acetate, and that of pineapples to ethyl butyrate.

The season during which each ripe fruit can be obtained is in most cases of only short duration, and ripe fruit is exceedingly perishable, not only from the unstable nature of its constituents, but also because it forms a ready medium for the growth of bacteria and moulds. Hence some method of fruit preservation is a matter of importance. The most convenient process, and also that most generally adopted, consists of boiling the fruit with sugar, the resultant product being known as preserves or jam. The act of boiling sterilises the fruit, and its concentration with sugar transforms the juice into a mass of considerable body, while the sugar itself acts as a preservative agent.

An old dictionary definition of jam is a confectionery preparation of fruit or other vegetable products preserved with sugar. One of the earliest references to this means of treating fruit is that of Surflet, who in 1600 stated that There is but very seldome any preserues made of the flowers and leaves of herbes; I vnderstand by this preserues taken properly, the presenting of things whole and not stampt and beaten into one bodie. It will be noticed that Surflet draws, a distinction between the preservation of whole fruits and those beaten or stamped into one uniform substance. Preserves proper were at that time regarded as consisting of the fruit in the whole condition, although evidently it was also a practice to make a pulped variety of preserved fruit. It is this latter which apparently received the name of jam, which name is said to be derived from an old verb to jamb, meaning crush or pulp. Although this distinction originally existed between preserves and jam, the trend of modern practice has been towards preserving the fruit as entire as possible in the present form of manufactured article. Jam is therefore no longer necessarily a pulped form of preserved fruit.

The subject matter of jam manufacture may be conveniently dealt with under the following headings:—

Raw Materials.

Apparatus and Plant.

Manufacturing Operations.

Bottled Fruits.

Packing and general handling of finished Jams.

Chemical and biological examination of raw materials and finished substances.

Other preserved fruit products, and allied manufactures.

CHAPTER II.

RAW MATERIALS.

The raw materials used by the jam manufacturer comprise the following: 1, fruits; 2, sugars; 3, pectinous or jelly producing bodies; 4, citric and tartaric acids; 5, preservatives.

I. FRUITS.

Probably the most convenient order in which to take these is that of the seasons in which the ripe fruit comes into the market, which arrangement has therefore been adopted.

RHUBARB.

Although this is rather a vegetable than a fruit, and is seldom or never put up as a whole fruit jam by the jam manufacturer, yet there is a fair quantity made in home circles. Forced rhubarb can be obtained in February, and the outdoor growth is fairly plentiful in April and May. For the sake of its pectinous properties, concentrated rhubarb juice has been known as an ingredient of the jams of certain fruits which do not jelly well. Rhubarb is largely grown in England.

GOOSEBERRIES.

The season for this fruit commences about the beginning of May, and lasts until the middle or third week of June. For jam making, the fruit is used in its unripe or green state, and any sound variety of the fruit may be used without discrimination. If ripe, the fruit is too tender, and therefore medium size berries which have a thoroughly developed flavour, without passing over to ripeness, are preferable. Further, the over ripe fruit makes a runny or pulpy jam, unless very carefully made. Gooseberries make an exceedingly good jam when judged by its physical state, as the fruit is highly pectinous, and thus sets well into a stiff jelly. From these properties, gooseberries are useful as a stiffening agent in other kinds of jam. The fruit itself may be mixed in with these others when both are at the same time in season, or the gooseberry juice may be expressed, filtered, concentrated, and employed as occasion arises. The heads are removed before the fruit is made into jam. The gooseberries used in England are of home growth. Gooseberries and also most other fruits are frequently boiled down into a pulp while fresh, and thus preserved for use in jams during the off season.

STRAWBERRIES.

The strawberry jam manufacturing season lasts from about the end of May until the middle of July. The first crops come generally from France, where as a result of the warmer climate, the fruit ripens earlier than in this country. Later supplies are obtained from the southern and midland counties, the ripening period being later as the latitude becomes higher. The fruit is used in a fairly ripe condition, but not so far gone as to be soft and mushy. In fact, the flesh of the fruit should be firm and not watery. Small fruit is preferably selected for jam making, as it remains to a much greater degree whole in the jam than do the larger berries. Strawberries are comparatively free from pectin, and therefore, when used alone, do not make so stiff a jam as do many other fruits.

CHERRIES.

These come into season shortly after strawberries first reach the manufacturer. Cherries vary in hue from the very pale white heart to the so-called black cherries. White hearts are usually too expensive