Jam, jellies & marmalade
Practical Action
JAMS, JELLIES AND MARMALADE
Introduction
Jams, jellies and marmalade can be made from a variety of fruits and some vegetables such as carrot and pumpkin. They are sometimes referred to collectively as preserves. The products are typically luxury items that are purchased by consumers in affluent urban areas. As with all food products, it is essential to carry out a market and technical feasibility study before starting to make preserves, to assess the level of demand for the products in your area. Please remember that jam making requires a large amount of sugar and making a high quality product requires some technical knowledge, the correct equipment and good packaging materials. A surplus of (over-ripe) fruit is not a good reason for starting a business making preserves. The preservation principles of jam, jelly and marmalade production are quite complex, but in essence involve the correct combination of acidity, sugar level and pectin content. All three must be correct to obtain a satisfactory product. One important feature of preserves is the high acidity which prevents the growth of food poisoning bacteria and also helps maintain the colour and flavour of most fruits. However, some moulds and yeasts are able to grow at levels of high acidity and these can spoil the food. They are prevented from spoiling jams by ensuring that the sugar content of the preserve is at least 68%. If for any reason the sugar content is lower than this (eg if water condenses on the lid of the jar and falls onto the jam during cooling or if the jam is not boiled for long enough to reduce the moisture content) the sugar content will be diluted and moulds will start to grow on the surface of the product.
Figure 1: Testing for the end point of jam. A food processing training course in Bangladesh. ©Sue Azam Ali/Practical Action
This technical brief describes the principles and process of jam making. Generic formulae are given which the more technical processors can use to create their own recipes. In addition, some tried and tested recipes for various fruits are included.
Types of Products
Jams are solid gels made from fruit pulp or juice, sugar and added pectin. They can be made from single fruits or a combination of fruits. The fruit content should be at least 40%. In mixed fruit jams the first-named fruit should be at least 50% of the total fruit added (based on UK legislation). The total sugar content of jam should not be less than 68%.
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Jam, jellies & marmalade
Practical Action
Jellies are crystal clear jams, produced using filtered fruit juice instead of fruit pulp. Marmalades are produced mainly from clear citrus juices and have fine shreds of peel suspended in the gel. Commonly used fruits include lime, orange, grapefruit, lemon and orange. Ginger may also be used alone or in combination with these citrus fruits. The fruit content should not be less than 20% citrus fruit and the sugar content is similar to jams.
Quality control and assurance
The main areas of quality control that are needed to produce uniformly high quality products are as follows: fruit preparation, accurate weighing and mixing of ingredients, hygienic preparation of fruits and fruit juices, correct acidity, moisture content and final total soluble solids content.
Fruit preparation
Fruit should be sorted and cleaned thoroughly. Only mature fruit, without mould, excessive bruising or insect damage should be used. All stems, leaves and skins should be removed and discarded. 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.
Ingredient mixing
Accurate scales are needed to weigh out the ingredients and care is needed to make sure that the correct weights are used each time. In particular, pectin powder should be thoroughly mixed with sugar to prevent lumps forming and resulting in a weak gel.
Production/preparation
Fruit pulp/juice It is possible to peel and pulp the fruit and press and filter the juice by hand, but the amount of fruit that can be processed this way in one working day is very low (eg 10-20 half kilogram jars per day). Also, the procedure is both laborious and time consuming and is more prone to contamination as the juice is left lying around for long periods before it is processed. If this is the level of production required, then it is fine to do the whole process manually. However, for a slightly higher and more efficient level of production it is better to use small manual or powered equipment to pulp the fruit and/or express the juice. Juice or pulp contains enzymes and in many fruits these cause rapid browning of the exposed fruit juice or flesh if they are not destroyed or inhibited from acting. The easiest way to control browning is to heat the juice in small batches as it is produced, rather than producing a large amount and storing it for several hours before use. The procedure described under 'batch preparation' and 'boiling' has been found to work very well. Sugar If possible, refined, granular, white sugar should be used, but even this sometimes contains small amounts of material (eg black specks) which reduce the value of a preserve. To make a higher quality clearer jam, the sugar should be dissolved in water to make a strong syrup and then filtered through muslin cloth or a fine mesh before it is added to the fruit pulp. It is most important that the filters and pans are thoroughly cleaned each day to prevent insects and microorganisms from contaminating the equipment. The strength of the sugar syrup can be easily calculated as follows: % sugar = weight sugar x 100 weight sugar + weight water So for example a 50% sugar solution (50°Brix) could be made by dissolving 500g sugar in 500ml water. Pectin All fruits contain pectin in the skins and to a lesser extent in the pulp. However, the amount of pectin varies with the type of fruit and the stage of maturity. Apples, citrus peels and passion fruit all contain a high concentration of pectin while strawberries and melon contain less. In
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Jam, jellies & marmalade
Practical Action
general, the amount of pectin in fruit decreases as the fruit matures. Fruits that are high in pectin can be mixed with those that are lower, for example, strawberry and apple, to make a mixed fruit jam. Although it is possible to make a Making your own pectin solution good preserve using the pectin already in the fruit, a higher Slice the skins of passion fruit, lime, lemon, orange quality product can be made by or grapefruit and boil in water for 20-30 minutes. adding commercial pectin powder Filter the solution before adding to the fruit pulp. or solution. This will produce a The amount of solution to be added depends on the standardised gel each time and type of fruit and a number of other factors, and must there will be less risk of a batch be found by trial and error. failing to set. However, commercial pectin may not be available in all areas or may be too expensive for small scale processors. If this is so, a pectin extract can be made at home from fruits that are naturally rich in pectin. There are several different types of pectin available, but for preserves, a slow setting type is needed so that the gel forms in the jar during cooling. However, in larger containers (eg 5-10kg jars of jam) or for preserves in which peels or pieces of fruit are suspended in the gel, a faster setting pectin in needed. In both types, the concentration of pectin varies from 0.2 -0.7% depending on the type of fruit being used. Pectin is usually supplied as '150 grade' (or 150 SAG) which indicates the ratio of the weight of sugar to weight of pectin that will produce a standard strength of gel when the preserve is boiled to 65% soluble solids. 5 SAG is normally enough to produce a good gel. How to calculate the amount of pectin to add Assume the commercial pectin is 150 SAG. This means that if you use 100g of this pectin per 100g jam you would get a pectin strength of 150SAG. This is too strong for jam, which only needs a strength of 5SAG. Therefore the commercial pectin needs to be diluted to 5 SAG, (ie it is diluted 30 times). Therefore 3.3g (100/30) pectin would be used for every 100g of material. Acid Acids are added to fruit juice to bring the pH within the range 3.0-3.3 which is necessary for jam making (pH is a measure of acidity – the lower pH means greater acidity). As the acidity varies in different types of fruit and also in different samples of the same fruit, it may be necessary to check for the correct acidity if different fruits are used. Limes are very acidic and have a pH lower than 3.3. Sodium bicarbonate may need to be added to the fruit juice to reduce the acidity. The only acids that are allowed to be added to jam are citric acid, tartaric acid and malic acid. In practice citric acid (which is found in lemon juice) is usually used and this is widely available from chemists or pharmacies. If citric acid is not available, lemon juice is often used instead. Food colours and preservatives During boiling, fruit pulps and juices usually darken in colour. Some fruits only change a small amount and produce a colour which is still acceptable for jam making. Other fruits darken too much and produce a dark brown preserve which is not very attractive to consumers. Processors may consider adding some artificial colour to these products to improve their appearance. 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. Most consumers prefer to eat preserves that are free from artificial colourings. As a processor, you are likely to get a higher price for products that are more natural and free from colours. If you do need to add colour to your preserve, it is important to check with the local Bureau of Standards to see which colours are allowed in your particular country and the permitted levels.
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Jam, jellies & marmalade
Practical Action
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 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 fruit juice 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. 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 you might consider using a refractometer to ensure consistency between different batches of the jam. When making jam for home consumption, you can use other methods to determine the end point: 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.
Determination of the end point of a jam
a) Use a refractometer This is the most accurate method. Measuring the sugar content with a refractometer 1. Take a small portion of jam from the pan. Let it cool to 20°C. (Remember to take the pan off the heat) 2. Place one or two drops of the jam onto the prism and carefully close the prism. Make sure the sample spreads evenly over the surface of the prism. 3. Hold the refractometer near a source of light and look through the end piece. 4. The line between the dark and light fields will be seen through the viewer. Read the corresponding number on the scale, which is the percentage of sugar in the sample. 5. Open the prism and remove the sample with a piece of tissue paper or wet cotton wool.
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Jam, jellies & marmalade
Practical Action
b) Use a sugar thermometer This method is slightly less accurate, but is very useful at the small-scale. A solution of 68% sugar boils at 105°C at sea level. When the boiling jam reaches this temperature, it is at its end point. After boiling for a few minutes, stir the jam and remove the pan from the heat. Dip the thermometer into hot water and then into the jam. If the thermometer reads 104 -105°C, the jam is ready. If it is lower than this, return to the heat and continue to boil. Test t he temperature frequently as the jam soon reaches its end point. Note: At higher altitudes the boiling point decreases and should be adjusted. The end point is about 4.5-5°C above the boiling point of water at any altitude (see table 1 for estimates of the boiling point of water at different altitudes). A sugar thermometer costs about US$10. Altitude above sea level Boiling point of End boiling point of water (°C) jam (°C) Ft m 0 0 100 105 1000 305 99 104 2000 610 97.9 102.9 3000 915 96.9 101.9 4000 1220 95.8 100.8 5000 1525 94.8 99.8 6000 1830 93.7 98.7 Table 1. Boiling point of water and end point of jam at different altitudes c) Use the drop test This is the cheapest option, but is the least accurate of the methods. It is good enough for use at the home level, for jam that will be used within a fairly short time. It is not recommended for jams that are meant for sale as there is no guarantee of consistency from one batch of jam to another. After two minutes of rapid boiling, remove the pan from heat. Dip a clean wooden spoon into the jam and hold it over the pan for 1 to 2 seconds. If the jam runs back freely, repeat the test every two minutes until the jam looks like a heavy syrup. When a small lump of jam forms on the back of the spoon and breaks away from the rest, the setting point has been reached. Alternatively, you can drop the jam into a glass of cold water: Take a small drop of the boiled jam on a spoon. Cool it slightly and drop into a glass of cold water. If the drop falls in a single piece until it reaches the bottom of the glass the end point has been reached. If it disperses in the water it requires boiling for longer. d) Use the skin wrinkle test This method is also cheap and about as accurate as the drop test. You need a cold plate or saucer. After two minutes of rapid boiling, remove the pan from heat. Dip a clean wooden spoon into the jam and drip a small amount of jam onto the cold plate surface. Let it cool and then push the lump of jam with your finger. If the surface of the lump of jam wrinkles when you push it, it is cooked.
You can always cook for a little longer, but you cannot go back if you heat for too long. It is better to take the jam off the heat too early and then re-heat if it is too soft. Test the jam at frequent intervals so you do not miss the end point.
Remember to remove the pan of boiling jam from the heat source while you are doing these tests as the jam will continue to cook and may become over-cooked.
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