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PINEAPPLE JAM
Sri Lanka has two varieties of pineapple, Kewpine and Mauritius. Kewpine is the cooking
pineapple, the fruits are larger and they give a better yield of juice. However, the flavour is
not as good as the Mauritius variety which being sweeter is usually eaten fresh. We found
that the Mauritius variety made a better jam (a better set, flavour and colour). The pulp from
pineapple varies (core included) from pH 3.4-4.1. This means that, to give a jam with a good
set the recipe has to be adjusted each time new pulp is used. The yield from whole fruit to
usable fruit pulp from Mauritius is approximately 30% and for Kewpine
35%.
Pineapple
contains little or no pectin so pectin must be added when making jam. Pineapples contain
the enzyme bromelain, which is a proteolytic enzyme (breaks down proteins). This can
cause problems for operators hands which are in contact with the juice for long periods
during cutting operations, gloves should therefore be worn and washed each day. To make
200 x 1Ib jars of pineapple jam requires approximately 62kg of sugar and 158kg of fresh
pineapple.
Recipe
Sugar
49%
Fruit pulp
38%
(starting recipe
Pectin (grade unknown)
1 %
before boiling)
Water
12%
Citric acid
Added as required
In most countries, preservative is not allowed to be added to the jam. Only a residue of
preservative is allowed in jam which has been made from fruit pulp which has been stored
with chemical preservatives, (l00ppm sulphur dioxide or 500ppm benzoic acid). Citric acid is
not a preservative, it is added to adjust the pH. Jams give a gel when there is the correct
ratio of pectin to water and the pH is between 2.5-3.45.
The optimum pH to give a good gel
is pH 3.0.
Method
Remove stalks and tops from fruits, cut off the outer cortex and pick out the eyes. Cut the
fruit into pieces, discarding any fruit which is bad.
Make the pieces into fruit pulp by liquidising, or passing through a Kenwood colander/sieve
(large aperture). Liquidising the pieces gives a fruit pulp with a chunky texture but contains
a lot of pith and hard pieces . Using the colander/sieve will give a fruit pulp of a smooth
consistency, which is good for making pineapple jelly. The residue which does not pass
through the colander/sieve can be put into a muslin cloth and the juice squeezed out to get
the maximum extraction of fruit pulp. The yield of fruit pulp from whole fruit is 30%
(colander/sieve),
35%
(liquidiser).
Adjust the pH of the fruit pulp by adding citric acid until it is pH 3.0. This can be measured
with a pH meter, or less accurately with pH paper, (using Whatmans pH paper
1-5
pH range,
the colour of the juice effects the result, so that a reading 2.5 pH is in fact 3.0 pH). Mix the
pectin with a small portion of the sugar. The dry mixing of the pectin is important because
pectin powder is very difficult to dissolve in water because it clumps together. If it is still a
problem to dissolve, grind the sugar to a fine powder and then mix it with the pectin.
Mix the water, fruit pulp, and the remaining sugar in a stainless steel saucepan and start to
boil. When nearing the end point the dry mix of pectin and sugar is added. (The pectin
should not be heated for longer than necessary because it will be broken down and then the
jam will not set).