2009_Book_FoodChemistry

852 18 Fruits and Fruit Products
marmalade is then poured into appropriate containers.
18.2.6.2 Jams
Jams are produced similarly to marmalades but
usually from one kind of fruit. They are thickened
by boiling and constant stirring of the whole
or sliced fresh or fresh stored raw material, or of
fruit pulp. Ordinary jams are also made from fruit
slurry. Boiling under a vacuum at 65–80 ◦ Coffers
the advantage of preserving the aroma and
color. The disadvantages are the absence of sucrose
inversion and the low caramelization. These
reactions produce the characteristic taste of jams
boiled in an open kettle (T: 105 ◦ C). Table 18.38
provides compositional data for some commercial
jams. The optimal pH of 3.0 required for
gelling is adjusted by the addition of lactic, citric
or tartaric acid, if necessary.
18.2.6.3 Jellies
Jellies are gelatinous, spreadable preparations
made from the juice or aqueous extract of fresh
fruits by boiling down with sugar. The addition of
fruit pectin (0.5% as calcium pectate) and tartaric
acid or lactic acid (0.5%) is normal. In general,
the water content is 42%, and the sugar content
between 50% and 70%. The juice is boiled down
in open kettles or in vacuum kettles with sugar
(about half the weight of the fruit), pectin, if
necessary, and the substances mentioned above.
Table 18.38. Composition of various jams (average values
in %)
Jam from Moisture Total Total Ash Dietary
sugar acid a fiber
Strawberries 35.0 58.7 0.89 0.23 0.80
Apricots 36.9 51.3 1.14 0.28 0.60
Cherries 36.6 57.3 1.26 0.28 0.50
Blackberries 34.2 58.0 0.37 0.24 1.20
Raspberries 35.9 54.6 1.03 0.23 1.20
Bilberries 35.1 55.8 0.60 0.22 0.37 b
Plums/prunes 31.1 59.1 0.42 0.24 0.43 b
a Sum of malic and citric acid.
b Pectin as calcium pectate.
The scum is carefully skimmed off and the
mixture is boiled further until a moisture content
of about 42% is reached.
18.2.7 Plum Sauce (Damson Cheese)
Plum/prune sauce is produced by thickening
through boiling of fresh fruit pulps or fruit
slurries. The use of dried plums is also common.
Normally, the product has no added sugar,
but sweetened products or products with other
ingredients added are also produced. The soluble
solids have to be at least 60% by weight.
18.2.8 Fruit Juices
Fruit juices are usually obtained directly from
fruit by mechanical means, and also from juice
concentrates (cf. 18.2.10) by dilution with water.
The solid matter content is generally 5–20%. The
juices are consumed as such or are used as intermediary
products, e. g., for the production of
syrups, jellies, lemonades, fruit juice liqueurs or
fruit candies. Fruit juice production is regulated
in most countries.
Juices from acidic fruits are usually sweetened
by adding sucrose, glucose or fructose. Juices
used for further processing usually contain chemical
preservatives to inhibit fermentation. Some
juices from berries and stone fruits, because of
their high acid content, are not suitable for direct
consumption. Addition of sugar and subsequent
dilution with water provides fruit nectars
or sweet musts (cf. 18.2.9). Since 1990, the per
capita consumption of fruit juice and fruit nectar
in Germany has been fairly constant at 40 l. In the
case of fruit juices, the products presented in Table
18.39 are predominant.
Table 18.39. Per capita consumption of fruit juices in
Germany (2004)
Product
Apple juice 12.8
Orange juice 8.9
Multivitamin juice 3.8
Grape juice 1.3
Amount (l)