Strawberry flavoured jam can be made from ash gourd with the addition of artificial strawberry flavouring and red food colouring. It should not be confused with strawberry jam which is made from real strawberries.
Ash gourd is a cheap fruit which can be stored for up to a year without deterioration. It is fairly tasteless and so can be used as the base for several different products. Flavourings and food colourings are added to give a range of products. The yield of usable fruit material from the whole fruit is approximately 75%. Ash gourd has enough natural pectin present to make a good jam without the addition of artificial pectin. It is extremely important that the label on the jar states that this product is strawberry flavoured rather than strawberry jam. See the technical brief on labelling for more information on the legalities of labelling foods.
(starting recipe before boiling)
Fruit pulp: 44%
Citric acid: 0.53%
Strawberry flavouring: 0.12%
Red food-grade colouring: 0.032%
The main areas of quality control that are needed to produce uniformly high quality products are as follows: fruit selection and preparation, accurate weighing and mixing of ingredients, hygienic preparation of fruits, correct acidity, moisture content and final total soluble solids content.
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.
Use accurate scales to weigh out the ingredients and take care to weigh out the correct amount for each batch of jam.
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 colours.
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).
The correct sugar content is critical for proper gel formation and for preservation of the jam or jelly. If the final TSS of jam is lower than 65-68% the shelf life will be reduced. The jam will have a runny consistency and bacteria and moulds will be able to grow in the product. If the TSS is higher than 68%, the jam will be very stiff and the sugar might start to form crystals in the jam.
The end-point of boiling is measured in different ways. The most accurate method is to use a refractometer to measure the total sugar concentration. Remove the pan from the heat during testing as the jam will continue to cook and may become over-cooked. It is always possible to cook the jam a little bit more, but once it is over-cooked (and too thick) it cannot be reversed.
Cool the sample before it is measured by smearing it on a cold dry plate or saucepan lid. All implements used to take the sample must be dry otherwise the reading will be reduced. It is important to stir the jam at all times during heating, otherwise it may burn at the bottom of the saucepan, causing off flavours and discoloration.
This method is not really suitable for home-use as a refractometer costs about US$ 150. It is only when making jam for sale that a refractometer is necessary, to ensure consistency between different batches of the jam. When making jam for home consumption, other methods can be used to determine the end point: these include the drop test, the skin wrinkle test, or the use of a jam thermometer to test the temperature (68% sugar corresponds to a jam temperature of 105°C).
When the jam starts to thicken, it is important to test for the end point at frequent intervals. Remember to remove the pan from the heat source while you test or it will continue to thicken and may burn.
Filling into jars, cooling and labelling
Wash and sterilise the glass jars and lids by placing in a pan of water and boiling for 10 minutes. Remove the jars from the water with a pair of tongs and stand upside down to drain. Do not dry with a towel as this could contaminate the jars.
If glass jars are not available, use plastic jars. These cannot be sterilised with boiling water as they will melt. They should be thoroughly cleaned in warm soapy water and rinsed with a weak solution of sodium metabisulphite. Sterilising tablets (made of sodium metabisulphite) can be bought for this purpose.
Allow the jam to cool slightly (to about 80°C for glass jars and 60°C for plastic jars) and then pour it into clean, sterilised jars. The jars should still be warm to prevent them from cracking when the hot jam is poured in. If the jam is cooled too much it will be difficult to pour. Place the clean lids on top and fasten. Invert the jars to form a seal. The filled jars can be placed in water to cool down the jam so that it does not keep cooking in the jar. The water should not be too cold or the glass may crack. Also, the water level must be kept below the lid of the jar. The gel starts to form as the temperature of the jam reduces (about 55°C) and continues until it is cold. The jars should not be moved or shaken while they are cooling or the gel will not form and the jam will not set.
Jam that is hygienically prepared, boiled until it reaches the correct final total soluble solids (68%) and which is packaged in sterilised glass jars can be stored for up to a year so long as it is kept in a cool place away from direct sunlight. Jam that is packaged in plastic containers has a shorter shelf life – up to 4 months.
Glass jars, Omnia lids and labels, Stainless steel cutting knife and spoon, Omnia capper, Wooden spoon for stirring, Cooking facilities, gas ring, electric ring, etc, Refractometer, Stainless steel, saucepan, Cutting board, Thermometer in protective jacket, Scales, Liquidiser or mashing tool
Cutting and slicing equipment
A range of manual and powered cutting and slicing machinery is available.
It is important to have accurate weighing machines. Quite often more than one machine is required – a large one to weigh the fruit and a small one for weighing out the dry ingredients such as pectin and spices.
Juice extractors and pulpers
A variety of juice extractors and pulpers is available from a wide range of suppliers. They are available in different capacities and either manual or powered (either electric or diesel).
Boiling pans should be made of aluminium, enamelled metal or stainless steel. For larger quantities it is necessary to buy equipment which does not cause burning or sticking of the product to the bottom of the pan. Stainless steel steam jacketed kettles, which are double walled pans are suitable for boiling large quantities of jam and are available in a range of sizes (from 5 to 500litres).
The refractometer is used to measure the sugar content.