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< prev - next > Food processing Preserves KnO 100301_Strawberry jam (Printable PDF)
Strawberry Flavoured Jam
Practical Action
Fruit selection and preparation
Select mature fruit that has no bruising or insect damage. Very ripe or over-ripe fruit has low
levels of pectin and is not suitable for jam making and should not be used. Fruit that is very
under-ripe is also not recommended as the taste and sweetness of the fruit are under-
developed. Wash the fruit well in clean water.
Remove the peel from the gourd and chop the flesh into small pieces. Add a small amount of
water. If the fruit pieces are left standing for a long time they will start to turn brown, therefore
the cut pieces should be covered in water while the rest of the gourd is prepared. Once a batch
of gourd is prepared, it is best to boil it to make a pulp rather than leave it standing around
where it is open to contamination by flies and dust.
Ingredient mixing
Use accurate scales to weigh out the ingredients and take care to weigh out the correct amount
for each batch of jam.
Fruit pulp
Boil the fruit pieces in the water for about 30 minutes until they are soft. Remove the pieces
from the water and mash them into a smooth pulp. Keep the pulp covered to prevent
contamination from flies.
Food colours and preservatives
Ash gourd does not have a colour or taste, therefore a food-grade red colour and strawberry
flavouring are added towards the end of the boiling period. It is important that the colouring
used is of food grade and is permitted for use in your country. Check with the local Bureau of
Standards to see which colours are allowed in your particular country and the permitted levels.
Only buy colours from reputable suppliers. Some colourings are tainted with illegal (toxic) dyes
and should not be used for food products. Most consumers prefer to eat preserves that are free
from artificial colourings therefore it is better if natural fruit colours can be used for example,
adding dark red fruits or berries can give a more attractive and natural colour to jams. As a
processor, you are likely to get a higher price for products that are more natural and free from
In most countries, it is illegal to add preservative (such as benzoic acid, sodium or potassium
benzoate or sulphur dioxide) to jams. Besides, if the correct recipe is used, good quality
assurance procedures are in place, the method is followed accurately and the jam is made
under hygienic conditions, it is not necessary to add preservatives to jams. The sugar acts as a
preservative. The only exception is in jam that is made from fruit pulp that has been stored
with chemical preservatives. In this case, a residue of preservative (either 100ppm sulphur
dioxide or 500ppm benzoic acid) is allowed in the jam.
Citric acid is not a preservative. It is added to the ash gourd pulp to adjust the pH so that the
pectin will form a good gel. Jams give a gel when there is the correct ratio of pectin to water and
the pH is between 2.5-3.45 pH. The optimum pH to give a good gel is pH 3.0.
Boiling to reach the final sugar concentration
The aim of boiling is to reduce the water content of the mixture and concentrate the fruit and
sugar in as short a time as possible. The final Total Soluble Solids (TSS) content of a jam (also
known as the “Degrees Brix” or “end-point of the jam”) should be 65 to 68% (the TSS is a
measure of the amount of material that is soluble in water. It is expressed as a percentage -a
product with 100% soluble solids, has no water and one with 0% soluble solids is all water).