Jams, jellies and marmalades are increasing in importance in many countries, particularly in wealthy urban areas. The suitability for small-scale production offer entrepreneurs a promising business.
When made properly, jams and marmalades are safe products due to the high acid and sugar content.
It is essential that a survey is carried out to determine the potential market for the product before starting on production. A successful business depends on a good market for the product. Too often, small-scale processors decide to make jam because there is an abundant supply of raw material, with no evaluation of the demand for the product.
Jam – A solid gel made from the pulp of a single fruit or mixed fruits. The fruit content must be at least 40%. In mixed fruit jams the first-named fruit must be at least 50% of the total fruit. The total sugar content must be no less than 68%. In tropical climates, 70% sugar is preferable.
Jelly – A crystal clear jam, made from filtered fruit juice rather than fruit pulp.
Marmalade – Usually produced from citrus fruits and has fine shreds of peel suspended in the gel. The fruit content should not be less than 20% and the sugar content is similar to jam.
Preparation of the Fruit
Fruit should be washed in clean water, peeled and the stones removed. Fruit should be as fresh as possible and slightly under-ripe. Over-ripe and/or bruised fruit will not make good jam as it has low levels of pectin and/or acid.
The jam will not set. Accurate scales are needed to make sure that the correct amounts of ingredients are used each time. Two sets of scales are needed – one with a large capacity for sugar and fruit and a smaller set for pectin and citric acid.
Pectins are naturally present in fruits. Some fruits contain higer levels than others. The richest sources are citrus peels, passion fruit and apple. Strawberries and melon contain low levels. In general, the pectin level decreases as the fruit matures. Low-pectin fruits are often mixed with high pectin fruits to achieve the correct level. Pectin is needed to make the fruit set into a gel.
Although it is possible to get a good preserve using the pectin in the fruit, it is better to buy pectin powder or solution and add a known amount to the fruit juice or pulp. This will produce a standardised gel each time and there will be less risk of a batch failing to set.
Pectin can be bought, either as a light brown powder or a dark liquid concentrate. It is usually supplied as ‘150 grade’ (or 150 SAG) which indicates the ratio of the weight of sugar to pectin that will give a standard strength of gel when the preserve is boiled to 65% soluble solids. 5 SAG is normally enough to produce a good gel.
There are two main types of pectin, high methoxyl (HM) and low methoxyl (LM).
High methoxyl pectins form gels in high solid jams (above 55% solids) and in a pH range 2.0-3.5.
Low methoxyl pectins do not need sugar or acid to form a gel, instead they use calcium salts. LM pectins form a gel with a wide range of solids (10-80%) within a broad pH range of 2.5-6.5.
Pectins may be either slow or fast setting. For most preserves a slow setting type is needed so it can set in the jar. If pieces of fruit are suspended in the gel, or if large volumes of jam are being made, a fast setting pectin is needed. In both types, the concentration of pectin varies from 0.2-0.7% depending on the type of fruit being used.
To produce a clear juice for jelly, the juice should be filtered using a muslin cloth bag. The pH of the juice or pulp should be 3.0 to 3.3. It is measured using a pH meter and adjusted by adding citric acid or sodium bicarbonate (if the acidity is too high, for example with limes). Pectin is added to the pulp at this stage. Follow the instructions on the package.
There are two stages of heating. First, the fruit should be heated gently to soften the flesh and extract the pectin. This is followed by rapid boiling to evaporate the water until the final sugar content is reached. The end-point of boiling is measured using a refractometer (this measures the sugar concentration). A jam thermometer can also be used to assess the end point, but this is less accurate than using a refractometer.
The jars should be clean and sterilized. The ideal temperature for pouring is 82-85° C. Hotter than this and condensation will form under the lid. This will drop down and dilute the jam, allowing mould to grow. Colder than this and the jam will be difficult to pour. Containers should be filled to about 9/10ths of their volume.