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AN INTRODUCTION TO PECTIN Pectin describes a family of polysaccharides, which give structure and strength to certain tissues in many land plants. In this form the pectins are often insoluble because of the high molecular weight, and due to the interaction with cellulosic material in and between the cell walls. It is only as the molecular weight decreases and the bonds break, - is seen by the tissue softening or fruit ripening-, that the pectin becomes soluble. Like all natural materials, the individual molecules of pectin are not identical but are of similar composition. For convenience the following discussions take account of this by considering the overall or average characteristics of the pectin. The major constituent of pectin is galacturonic acid, which is simply a sugar, galactose, which carries an acid group. Several hundred of these units are linked together to form a long chain molecule of poly galacturonic acid. A proportion of these individual galacturonic acid units are methoxylated and although it is not necessary to understand the chemistry of this, it is essential to understand that the amount of the methoxyl groups present strongly influences the performance of the pectin. This value is so important that it has been given a definition “Degree of methoxylation” (DM) is defined as the average number of methoxyl groups per 100 acid units, i.e., a simple ratio of methoxylated units per 100 units. An example of a pectin of 70% DM is where 7 out of every 10 units carry methoxyl group. By convention, pectins are split into two groups. If the DM is greater than 50%, the pectin is referred to as a High Methoxyl Pectin or HM for short. Thus the previous example of 70% DM was an HM pectin. Pectins of less than 50% are called Low methoxyl Pectins or LMs. Thus a pectin of 40% DM would be a LM pectin. There are two forms in which LM pectins can be made, the first is conventional LM and the second is amidated LM, the difference being the second

AN INTRODUCTION TO PECTIN

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Page 1: AN INTRODUCTION TO PECTIN

AN INTRODUCTION TO PECTIN 

Pectin describes a family of polysaccharides, which give structure and strength to certain tissues in many land plants.  In this form the pectins are often insoluble because of the high molecular weight, and due to the interaction with cellulosic material in and between the cell walls. It is only as the molecular weight decreases and the bonds break, - is seen by the tissue softening or fruit ripening-, that the pectin becomes soluble.

 

Like all natural materials, the individual molecules of pectin are not identical but are of similar composition.  For convenience the following discussions take account of this by considering the overall or average characteristics of the pectin.

 

The major constituent of pectin is galacturonic acid, which is simply a sugar, galactose, which carries an acid group. Several hundred of these units are linked together to form a long chain molecule of poly galacturonic acid. A proportion of these individual galacturonic acid units are methoxylated and although it is not necessary to understand the chemistry of this, it is essential to understand that the amount of the methoxyl groups present strongly influences the performance of the pectin. This value is so important that it has been given a definition “Degree of methoxylation” (DM) is defined as the average number of methoxyl groups per 100 acid units, i.e., a simple ratio of methoxylated units per 100 units. An example of a pectin of 70% DM is where 7 out of every 10 units carry methoxyl group.

 

By convention, pectins are split into two groups. If the DM is greater than 50%, the pectin is referred to as a High Methoxyl Pectin or HM for short. Thus the previous example of 70% DM was an HM pectin. Pectins of less than 50% are called Low methoxyl Pectins or LMs. Thus a pectin of 40% DM would be a LM pectin. There are two forms in which LM pectins can be made, the first is conventional LM and the second is amidated LM, the difference being the second contains amide groups as well as methoxyl and acid groups. The “Degree of Amidation” or DA is also very important to the performance of a pectin and it has a similar definition to DM. DA is the average number of amidated units per 100 units. Thus we can define any pectin in terms of its percent DM for HM and convetional LMs, and percent DM and DA for amide LMs, and these values should help us identify the behaviour that we would    expect from the pectin.

 

Although the major unit of pectin is galacturonic acid, other sugars or groups may also be present depending on the source of the pectin. Neutral sugars, such as rhamnose, arabinose, galactose and xylose may occur as side chains or on the backbone of the pectin. They may be present at up to 25% in certain pectins, such as that extracted from apple, while citrus pectins normally contain only low levels of these. The presence of these sugars modify the behaviour and the performance of the pectin, as can be seen with comparison of

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apple and citrus pectins of the same DM. Typically apple pectins result in a more pasty, less smoothly gelled product. Apple pectin may also be contaminated by the presence of starch which unless specifically removed will also modify its performance. Again, this tends to cause pastiness or graininess and disrupts the gel structure.

 

Other groups may also affect the properties of pectin. For example, the acetyl groups present in pectins from sugar beet or sunflower disrupt the formation of the gel and as a result these pectins are not common and would not be suitable to replace citrus or apple pectins for gelation (unless modified to remove these groups).

 

Therefore, the major commercial sources of pectin are citrus peel and apple pomace, which are residues from the juice industry. The quantity and quality of the pectin in these raw materials depend on several factors. The type of fruit has a major influence on the final pectin quality, for example lime peel usually contains the highest obtainable quality and at the largest levels. This is followed by lemons, oranges, and other citrus fruits. Apple pomace contains lower levels of pectins than citrus fruit and due to the natural sugars and starch has slightly different properties.

 

Quality and quantity are also affected by any factor influencing the fruit or peel, such as growing conditions, stage of ripeness and picking, severity of peel drying etc. Unfortunately the fruit are chosen for juice production, which is close but not at the optimum for pectin production. The extraction procedures also affect the quality and quantity of pectin recovered and commercial extraction is in fact a compromise between the total amount of extracted pectin and its quality.

 

When peel is received at the factory, samples are taken for analysis of the extractable pectin, and the conditions for extraction optimized. The peel is washed in water to remove extraneous matter before the pectin is extracted in hot acidic water. The extraction is carried out by  transporting the peel through a series of tanks, where the pH, temperature and time are controlled as determined previously. The pectin solution is then recovered from the peel residue by filtration, it is clarified and then concentrated. The liquid concentrate may then be hydrolysed at this stage if required to produce pectins of different DMs and thus different performances. The pectin is recovered from solution by precipitation. The precipitate is collected and washed in aqueous alcohol to remove impurities and then the pH is adjusted by the addition of sodium carbonate, to control the solution pH of the pectin. The washed pectin precipitate is then again recovered prior to drying, grinding and testing. The powdered pectin of known DM and performance is then blended as required and re-tested to confirm behaviour before dispatch to the customer.

 

Pectins are usually blended with sugars to a specified gel strength or gel grade. However, where required, other ingredients can also be included, or the pectin may be standardized by

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some other parameter such as viscosity or protein powder. Amide pectins are prepared in a different way and are manufactured by the treatment of the recovered pectin in alcohol with aqueous ammonia. Once prepared the amide pectins are similarly dried, ground, tested, blended and then re-tested.

 

In principle, there are two types of pectin, HM and LM, which because of the different DMs (and DAs, where appropriate) have quite different properties.

 

HMs are pectins with DM greater than 50%, but in practice the DM varies from about 75 to 55%. LM pectins have a DM of less than 50% and the actual values are in the order of 30 to 50% for conventional LM and 20 to 40% for amidated pectins. However, it is important to remember that these values are averages and that a pectin of 50% DM may be made up of an equal mixture of two pectins having DMs of 25 and 75% respectively. As the DM is known the performance of the gel of this pectin “50% DM” may not perform exactly as expected! Further to this, although the cut-off for HM and LM pectins is 50%, the change in behaviour is gradual as the DM changes, and the characteristics do not suddenly alter at 49.9% to an LM pectin performance. Thus a pectin of 50% DM will exhibit a certain behaviour which due to that DM and will reflect some HM and some LM characteristics. When producing pectin, we do not normally mix pectins over radically different DMs, although during our blending operation we do blend together pectins of similar, but not exactly identical DMs.

 

HIGH METHOXYL PECTINS

 

High methoxyl pectins are defined as having a DM of greater than 50% and the exact value of the DM affects the performance of the pectin. HM pectins have several quite distinct functions in the food industry, the most important property being gelation. However, these pectins have other advantageous properties such as physiological, viscous, stabilizing and protein protecting properties.

 

Pectin is a water soluble fibre which may be used in food to provide viscosity in the stomach and deliberately slow down the absorption of nutrients. It is also used in wound and similar dressing to absorb weeping to keep the wound dry.

 

Due to the viscosity of HM pectins, they find use in ready-to-drink and dilutable beverages, providing mouth feel and body, especially in low juice and low calorie products.

In acid milk systems, HM pectins protect the product from loss of texture due to the acidification or heat treatment. In this application the pectin reacts with the sensitive proteins limiting or preventing adverse reactions.

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The most important property of HM pectin is gelation and these pectins gel when the condition sufficiently reduce the water activity (normally by the addition of sugars) and when the pH is sufficiently acidic. Normally an HM pectin will gel when the soluble solid content is greater than 55% and the pH is in the range of 2.0 to 3.8. Generally the higher DM of an HM pectin, the easier the gel forms. This is seen in the difference in the rate of set of pectins of different DM and it leads to the nomenclature of HM pectins. A pectin of very high DM, for example 72%, exhibits gelation at a very high temperature and thus sets very quickly. For this reason it is known as rapid set pectin. On the other hand a pectin of lower DM, for example 60%, will gel at a lower temperature and take longer to set, and is therefore, known as a slow set pectin. Pectin of intermediate DM will show intermediate properties and is known as a medium rapid set. Although many factors in a recipe may also influence the final setting temperature of a product, it is important to define the setting characteristics of a pectin under standard conditions to allow the correct use of a pectin in a recipe. For example, if whole fruit pieces are present in a jam, it will be necessary to use a rapid set so that the gel will form before the fruit pieces float to the top.  A slow set pectin will not gel sufficiently quickly to stop the fruit from floating.

 

Therefore, when using HM pectins for gelation there are two main parameters, which should be defined:

1.   Strength. The strength of HM pectins is usually standardized by the USA SAG grade,  which defines the power of that pectin to gel under very tightly controlled conditions of pH, soluble solids content etc. Normally, HM pectins are blended with sugar to result in a SAG grade of 150 ± 5. Thus our customers can rely on the quality of the pectin and can develop a standard recipe with a set addition rate.

 

2.   Setting rate. The time the gel takes to develop, or the temperature at which the gel starts are both measures of the rate of set.  In some countries the setting temperature is used to define the pectin under a standard laboratory test method and is used to measure this to ensure the pectin is correctly quantified and thus described. (note: the results by this test do not indicate the performance in product, but rather in test method). However, in other countries the setting time may be used to indicate the behaviour of the pectin. (This technique is also a laboratory based test which gives comparative, not actual figures.)

Typical values of HM pectins are:-

 

Type of Pectin                       Setting Temperature                    Setting Time

Rapid Set                                80-95ºC                                         Less than 90 seconds

Medium Rapid Set                   75-79ºC                                         110-135 Seconds

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Slow Set                                  Less than 60ºC                              Greater than MRS

 

Having now defined the gel strength and setting rate or behaviour, the HM pectin is ready for use in a specific application. For example, slow set pectin would be chosen when producing a jelly where there is no fruit to suspend, and where the air bubbles should rise to the surface before the gel sets, resulting in a clear bubble free jelly.

 

Although the choice of pectin will depend on the performance of that pectin in principle, it can be modified by other ingredients present in the recipe, the most important of these parameters are pH, soluble solid content, type of soluble solids and cooling rate, and they can be used independently or together to manipulate the performance of the chosen pectin. For example, a slow set pectin can be made to set faster if the pH is reduced or the soluble solid content is raised. As a result of the influence of these parameters it is essential that these should be set and held within the specification during production.  Thus although the performance of a pectin can be defined in a controlled standard method, the behaviour in product will be modified by other factors. These will be dealt with in each application section.

 

LOW METHOXYL PECTINS

 

LM pectins, whether conventional or amide, gel or thicken by interactions with calcium over a broad range of soluble solids contents, (or greater than 5% to about 85%), and over a broad pH spectrum from 2.6 to about 7. As a result low methoxyl pectins can be used in a very much wider range of foods so long as there is sufficient calcium for the required interaction. the calcium may be added specially but fruit and milk may have sufficient calcium naturally present to cause the interaction. As the DM of HM pectins affects the rate of set, the DM and DA of LM pectin also influence the setting characteristics. This is because of the effect of these on the calcium requirements for optimum performance.

For any LM pectin, the gel strength and setting rate will depend on the calcium level. There is an optimum value of calcium, at which the gel is clear, elastic, strong, free from syneresis. At lower levels of calcium, i.e., if the calcium content is reduced or limited, the gel will not be strong but it will remain clear and bright. At very low levels a gel may not form at all, but there may be an increase in the viscosity observed. However, if too much calcium is present, for example from the fruit, or too much is added, the pectin calcium interactions become excessive and the gel network becomes too tightly pulled together, and like squeezing a sponge, the aqueous phase gets squeezed out as syneresis.  In addition, the gel becomes cloudy and brittle and may become very grainy or sandy. If excessively high levels of calcium are present a coherent gel may not occur at all but rather a soup of jelly lumps in a sloppy liquid is formed. The DM (and DA) influences the actual value of calcium at which optimum gelation occurs and a range of LM pectins are available to ensure that required behaviour can be achieved. Generally as the DM is increased, the amount of calcium necessary to achieve optimum gelation is also increased. Thus a pectin of 30% DM will require less calcium than a pectin of 45 DM, the pectin of 30 DM being more calcium sensitive.

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There is no international standard test for the gel strength or setting performance of LM pectins because they depend so heavily on the calcium content. However, a standard technique is used by Citrico to ensure that each pectin is correctly assessed for reactivity.

 

LM pectins are therefore selected according to the required performance in product in the same way as HM pectins are selected, the other ingredients and processing parameters in a product can influence the performance of that pectin. The most important of these parameters are pH, soluble solid content, type of soluble solids, available calcium as determined by the total calcium and the calcium sequestering ability and the method of production. In addition to the influence of the ingredients the method of preparation of the product widens an already broad range of possible products. For example, the behaviour to heat can easily be modified to provide heat stable or reversible products. In addition, the textures can also be altered by the method of production, forming anything from a gel or foam to a sheer thinning viscous product.

LMs are therefore very much more versatile than high methoxyl pectins and are showing large sales growth as even more uses become clear.

 

 

Jams and Preserves 

Early civilisations have preserved their seasonal fruits by either boiling on their own or together with some form of sugar. This not only destroys the naturally occurring enzymes but also the water activity will be reduced to prevent the growth of spoilage organisms such as yeasts and moulds.

 

A the same time as effecting preservation, the heating in a solution will serve to extract the pectin in the fruit and when this combines with the naturally occurring sugar the pectin will thicken or gel the fruit system.

Whilst this process form s the basis of all present day large scale jam production, technology also plays a considerable role. Not only are commercially produced pectins use to compensate for any deficiency from the fruit, but specially prepared types (low methoxyl pectins) are widely used to set systems where the sugar content is too low for normal pectins to be effective.

 

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To appreciate the role and application of pectins in such products, it is useful to understand a few terms which are used to describe and characterise them.

 

HIGH METHOXYL (HM) AND LOW METHOXYL (LM) PECTINS

 

Whilst HM pectins are capable of forming sugar gels only at a high soluble solids level (greater than about 55%), LM pectins can also form low solids gels. These require the presence of a controlled level of certain di- or polyvalent cat-ions, of which calcium is the only one used in the food industry. Naturally occurring pectins are almost always of the HM variety, with LM pectins normally being made from these by treatment under acidic conditions.

 

AMIDATED PECTINS

 

These are produced by the controlled treatment of HM pectin and ammonia. In most situations they behave in a similar way to LM pectins, although they do show certain differences which sometimes make their application preferred.

 

GRADE

 

The grade of a pectin is a measure of the ability of that pectin to form a gel under standard laboratory conditions. For HM pectins, the USA-SAG or IFT method is most frequently used, standardisation being achieved by dilution with sugar to 150 or 200 grade (150X SAG or 200X SAG).

 

LM pectins are used under a much wider range of conditions and so there is less uniformity in the methods of grading which are applied.

 

SETTING TEMPERATURE AND SETTING TIME

 

HM pectins can be classified either by setting temperature or by setting time. The first of these is defined as the temperature at which setting occurs and the second as the time

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between the pouring of a hot jelly mix and the occurrence of setting. These are measured under precise laboratory conditions and must not be confused with production setting rates. Neither parameter is normally specified for any LM pectin.

 

RAPID SET AND SLOW SET PECTINS

 

These terms are only used to describe HM pectins. Those exhibiting the highest Setting Temperature (and shortest setting time) are known as Rapid Set, whilst on progressive acid treatment of these, the Setting Temperature will drop and the Setting Time increase until Slow Set is reached.

 

PRODUCTION METHODS

 

Most preserves can be made in either of two general types of equipment although there are many variations which can be applied within each.

 

OPEN PAN (ATMOSPHERIC) BOILING

 

This is the traditional method of production where water is driven off by boiling ingredients in a heater pan. Heating is normally indirect by steam and the process is batch rather than continuous.

 

VACUUM BOILING

 

By processing ingredients under vacuum, a lower boiling temperature is achieved. This reduces degradation of the pectin (both added and naturally occurring from the fruit) and also gives better retention of both colour and flavour of the fruit.

 

Indirect steam heating is most frequently used with the following systems being commonly found:

Pot or Kettle                                   Batch

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Plate Evaporator                            Continuous

Scarped Surface Evaporator          Continuous

 

Of these, the continuous systems are restricted to processes where large fruit pieces are absent.

 

PRODUCT TYPES

 

Although certain novel systems are difficult to classify, most products can be placed in one of four main groups:

Conventional/traditional

Bakery/industrial

Low/reduced sugar

No added sugar

 

Conventional/traditional

 

These are essentially self preserving products of greater than 55% refractometer solids (soluble solids – s/s). They have appreciable fruit content and are normally sold direct to the final consumer in containers up to about 500g (up to about 5kg for catering and food service use).

 

Quantity of pectin

 

As the pectin added is only needed to supplement that from the fruit itself, the quantity required will largely depend upon the variety, amount and quality of the fruit used. On the basis of experience the following table gives an indication of levels required for jam of 65-68% s/s using whole, sieved or pulped fruit (g 150X SAG pectin per 100kg of finished product).

 

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Cherry                         Apricot                         Apple

Peach                          Blackberry                    Damson

Pear                             Blackcurrant                 Gooseberry

Pineapple                     Loganberry                  Greengage

Raspberry                    Guava                          Strawberry                  

Plum                            Quince                         Redcurrant

 

Fruit

Content

%

Marmalade

30 360-450 270-330 180-240

40 260-330 190-250 100-170

50 180-230 120-170 60-110

60 110-160 70-110 30-70

 

Weight of finished preserve

 

For jellies made with fruit juice, addition rates 25-50% higher than the above will be needed for fresh juice and even more for depectinised juice. Other factors affecting addition rate include: strength of set required, final soluble solids, pH, length of boil, size of containers being filled.

 

Type of pectin

 

Rapid or Medium Rapid Set pectins are normally used in conventional/traditional products except when:

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i)          Filling large containers.

ii)         Filling at lower than normal temperature.

iii)         Making jelly rather than jam.

iv)        The soluble solids content is greater than about 72%.

v)         The natural fruit pectin is very fast setting.

vi)        Sugars other than sucrose are used which may appreciably raise the setting

            temperature.  

                 

In all these situations Slow Set pectin should normally be used for open pan boiling. For vacuum boiling systems the choice of pectin will also depend upon the actual production technique used.

 

Citrico Pectins available for use in conventional/traditional preserves are as follows:

 

Rapid Set

Medium

Rapid Set Slow Set

Type 7010 Type 7020 Type 7030

Type 7016   Type 7046

 

Pectins should always be added to a preserve as a solution and not as a dry powder. Methods and techniques for preparing such solutions are given in the Citrico bulletin “Storage and Dissolving”.

 

Processing Conditions:

 

i)          pH

 

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Inadequate pH control results in more substandard preserves than does any other parameter. To achieve optimum performance and consistency the pH must be correct both in the finished product and at all stages of production process. Whilst there are many signs indicating an incorrect pH the commonest are pregelation, syneresis and floating of fruit. With acid being normally added at or near the end of the boil, the optimum product pH required is a function of pectin type, soluble solids and of the precise sugars used. For a product made solely with sucrose the following should give acceptable results (measured at 20ºC on a 50% solution of the preserves):

 

S/S - % pH  

75-8572-75

3.2-3.53.1-3.4

} Slow Set

68-75

64-68

60-64

55-60

3.0-3.3

2.9-3.1

2.8-3.0

2.6-2.8

} Rapid, Medium Rapid or Slow Set

 

ii)         Soluble Solids

 

Apart from possible legal and direct cost penalty implications, poor control of soluble solids can result in inconsistent texture and strength of set. Whilst the soluble solids content of the preserve during production can be measured either directly by refractometer, or directly from its boiling point, the first of these is strongly to be preferred.

 

When operating at other than normal soluble solids content of 65-68%, the pectin addition rate will need to be adjusted thus:   

                       

S/S - % Change in pectin addition

70 -5%

65-68 -

60 +10 to +15%

55 +25 to +40%

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These figures should only be taken as approximate.

 

iii)        Filling temperature

 

Control is essential over the temperature at which filling takes place. For containers of up to about 1kg, 82-88ºC should be regarded as acceptable even for jellies, where setting may occur until about 60ºC. Above this, whilst at lower temperatures there are increased risks of pregelation and microbiological spoilage.

 

Within the range for acceptable gelation, a lower pH will produce a higher setting temperature, and a higher pH a lower setting temperature.

 

As the setting temperature of a high methoxyl pectin is dependent upon the rate of cooling, very rapid cooling may be used to allow a lower product filling temperature e.g., when filling larger containers.

 

iv)        Use of sugars other than sucrose

 

For reasons of cost and of product taste and texture, the partial or complete replacement of sucrose by other sugars is now widely established, the most commonly used being high fructose corn syrup (HFCS – containing about 45% fructose) and 42 and 63 DE glucose (corn) syrups. Whilst the general effect of glucose (corn) syrups is to (i) weaken the set, (ii) raise the optimum pH for gelation (iii) increase the setting temperature, changes resulting from the use of these and of HFCS can be quite pronounced and no simple guidelines can be defined. Further details relating to these and other sugars are available on request.

 

Note When high levels of glucose (corn) syrups and HFCS are included it is normal to use a Slow Set rather than a Rapid Set pectin.

 

TYPICAL RECIPE

 

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          Ingredients

 

          Fruit                                                                400g

A       Sugar                                                              300g

          Water                                                              60g

B       Sugar                                                              310g

C       Pectin Type 105 or 601 4% w/w soln             60g

D       Citric Acid H2O 50% w/v soln                         6ml

 

Final Batch Weight             1kg

pH (50% solution)              3.0-3.2

Soluble Solids                    65-66%

 

Method

 

Heat ingredients A and bring to boil. After 1-2 minutes add sugar B and return to boil. Boil for further 1-2 minutes and mix in pectin solution C. Stirring well, boil down to required soluble solids and remove from heat. Mix in acid solution D, cool to about 85ºC with stirring, fill into jars and seal at once.

 

Notes

1.         Alter level of pectin to achieve required set.

2.         Alter acid addition to maintain final pH of 3.0-3.2.

3.         Acid should always be added at the end of the boil.

 

 

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BAKERY/INDUSTRIAL

 

There are four main types, all of which are normally filled into large containers.  Note – certain specialised uses of LM pectin are not included here although details are available on request.

 

i)          Product of 65-70% s/s for spreading or depositing onto pastry before baking and which will withstand oven temperatures without excessive melting or boiling out. Type 115 Medium Rapid Set or Type 611 Bakery Pectin should be used in the same way as for conventional preserves except that a higher pectin level (0.6-0.8% depending on fruit or juice content) and a higher pH (3.2-3.3) are essential, combined with a lower filling temperature of about 70ºC. The use of glucose (corn) syrup will also tend to improve the level of heat resistance.

 

ii)         Product of 68-75% s/s for depositing onto pastry or cake after baking and will not soak into the base. Slow Set pectin such as Type 121, 621 or 622 should be used together with a proportion of glucose (corn) syrup. Production conditions are similar to those described for conventional preserves in large containers.

 

iii)        Product of 50-70% s/s to be deposited hot onto already baked base and which sets on cooling to give a gelled, cuttable jam or jelly. Such systems which include bakery glazes, make use of the heat reversibility and dilutability of gels based on buffered amidated LM pectins such at type 1300B. Whilst normally containing only low levels of fruit or juice, specific recommendations are available depending upon the exact requirements of use.

 

iv)        Very stiff jam or jelly of 75-85% s/s for use as a biscuit filling after baking. Slow Set pectin should be used together with an operating pH of 3.2-3.5. Due to high solids level more glucose (corn) syrup is used than with other bakery jams or jellies, certain special syrups being used ot over 50% of the total sugars.

 

 

LOW/REDUCED SUGAR

 

For jams and jellies of less than about 55% s/s, it is essential to use an LM pectin since HM types will not operate in this range. Whilst national regulations for these products vary considerably there are certain basic principles which are common to all systems.

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TYPE OF PECTIN

 

Due to their greater tolerance of variations in operating conditions, amidated LM pectins are generally preferred to conventional types. Within each group, more calcium reactive types should be used (i) at the lower end of the soluble solids range, (ii) when higher pH values are specified, (iii) when a higher setting temperature is required, (iv) at lower fruit content, (v) when levels of available calcium are low and no more can be added, (vi) when more brittle and less elastic set is required. Conversely, less reactive pectins should be used when these conditions are reversed.

 

  LM Pectin Types

  More Reactive LessAmidated        900 1000 2000 3000 4000

Conventional 170 172            173              174  

 

QUANTITY OF PECTIN

 

The natural pectin is present in the fruit is high methoxyl and will contribute little or nothing to the set of a low/reduced sugar jam. As a result neither the variety nor the amount of fruit used will have much effect on the quantity of LM pectin needed. Although the exact amount will depend upon the ingredients and on the nature of product required, an addition of 0.7-1.0% is normal for amidated pectins and slightly higher for conventional types. In all situations the LM pectin is best added as a predissolved solution.

 

PROCESSING CONDITIONS:

 

i)          Calcium

 

Whilst it is essential to operate with the correct ratio of pectin to calcium, it must be noted that this is the available rather than the total calcium in the system. As this cannot be measured analytically, the carrying out of preliminary trials is essential. In some systems, particularly those with a high fruit content, there will be sufficient available calcium whilst in

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others a separate addition will be needed. This is best carried out at  high temperatures during the boil using solutions of a soluble calcium salt, such as the lactate or chloride.

 

ii)         pH

 

A wider pH range is possible than with HM based products although, away from the optimum range, other parameters such as pectin and calcium addition rates will need more precise control. Whilst most products are made within range 3.0-4.0, no overall recommendations can be given. Specific details are available on request.

 

iii)        Soluble solids

 

As with conventional preserves, control is important. Due to the lower sugar concentrations a boiling point technique cannot be applied and use of a refractometer is essential.

 

iv)        Filling temperature

 

To prevent separation of the fruit, containers must be filled only just above the setting temperature of the system. With all LM pectins the actual setting temperature is a function of the system in which it is used and not an absolute property of the pectin itself. Unlike that of an HM the setting temperature of an LM pectin based system is independent of the rate of cooling, i.e., it is only the temperature and not temperature/time dependent.

 

Note Systems based on amidated pectin can often melt and reset on repeated heating and cooling, without significant loss in strength. This property is often referred to as heat or thermo-reversibility.

 

v)         Use of preservative

 

Since this type of product is not inherently self preserving once the container has been opened, addition of a suitable permitted preservative may be advisable.

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TYPICAL RECIPE

 

            Ingredients

 

            Strawberries    450g

A          Sugar   405g

            Water   100ml

B          Amidated pectin type 2000      7g

            Water   200ml

C          Calcium lactate 5H2O 3% w/v soln       0-10ml

D          Citric acid H2O 50% w/v soln   7ml

 

Final batch weight              1kg

pH                                      3.1-3.3

Soluble solids                    45%

 

METHOD

 

Heat ingredients A together until sugar has dissolved. Add amidated pectin B, previously dissolved in water at 55-70ºC using a suitable high speed mixer, and heat to boiling. Add C followed by D and reduce to required soluble solids. Cool with stirring to 80ºC, fill into jars and seal at once.

 

Notes

 

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1.         Set can be varied between soft and firm by altering calcium lactate within quoted range.

2.         Alter acid addition to maintain final pH of 3.1-3.3.

3.         Preservative, if used, should be added at the very end of the process.

 

NO ADDED SUGAR

 

Products are now made in which the sugar has been replaced by concentrated fruit juice (normally apple or grape). These are mostly of below 55% s/s and require an LM pectin to achieve sufficient set. Due to the high level of fruit acids present from the concentrate, much of the natural calcium present will be sequestered and therefore not available for gelation. To overcome this one you can either use a pectin which is more calcium reactive or include extra calcium in the form of a soluble salt such as lactate or chloride. In all other respects these products are similar to low/reduced sugar jams and jellies.

 

TYPICAL RECIPE

 

            Ingredients

 

A          Concentrated Apple Juice (70% s/s)    570g

            Strawberries    450g

B          Amidated Pectin Types 2200   5.5g

            Water   200ml

C          Sodium Benzoate 20% w/v soln           2.5ml

 

Final Batch Weight             1kg

pH                                      approx. 3.0

Soluble Sodium                  45%

 

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METHOD        

 

Heat ingredients A and add amidated pectin B, previously dissolved in water using a suitable high speed mixer. Bring to boil and reduce to required Soluble Solids. Add sodium benzoate and cool to 65ºC. Fill into jars and seal at once.

 

Notes

 

1.         As this is a “no added sugar” product, the amidated pectin is one in which contains no standardising sugar (Type 2200 is the unstandardised version of Type 2000).

2.         If set is too weak, either use a more calcium sensitive amidated pectin (Type 1200) or add a quantity of suitable calcium salt (lactate or chloride – as solution).

3.         Preservative is necessary in recipe due to the low setting/filling temperature of the system. Mixture of conventional and amidated LM pectins will have a higher setting temperature and reduce the need for added preservative.

4.         The concentrated fruit juice used should be kept consistent on order to minimise changes in sequestering power which would otherwise make formulation changes necessary.

 

 

TRADITIONAL JAMS

FAULTS AND FAILURES 

In order to maintain sufficiently high quality standards when producing traditional jams and preserves, the possession and regular application of three particular measuring instruments is strongly recommended. These are:-

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i)        An accurate thermometer up to at least 120ºC (248ºF)

ii)       A refractometer calibrated directly in percent sugar solids and   covering at least the range 55-70%.

iii)      A pH meter capable of being read to the nearest 0.1 pH unit or better. For this type of product, values are normally measured on a 50% solution (by weight).

 

Various problems which can occur in the manufacture of jams and their remedies are discussed below:-

 

Possible cause                                                 Analysis/comments

 

A  WEAK OR SLACK SET

 

1.    Use of pectin which has been                    Check stock rotation. Refer

       stored too long                                           to pectin manufacturer if in     doubt

2.    Use of pectin which has been                    Store cool or dry. Refer to

       stored under bad conditions                      pectin manufacturer if in doubt

3.    Powder pectin not fully                              Solution should be smooth

       dissolved before use                                 with no grittiness. Difficult      to detect visually in the finished product unless  severe. Unlikely to cause setting problems unless  very severe.  Check operating procedures

4.    Use of stale pectin solution                        Solution is best used on day of          preparation.     Pectin enzymes can act very quickly.

5.    Thermal degradation of pectin                   If prepared hot, pectin solution should

       solution                                                      either be used immediately, or cooled to 40ºC or below as soon as possible.

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6.    Low soluble solids content. Check final product with refractometer.  Results from insufficient boiling (note: compositional and labelling regulations).

7.    (Open Pan Boiling only)                             Check recipe formulation for the amount        Excessive boiling time  of water to be removed by boiling.  May

       leading to breakdown                                 also result in excessive sugar

       of pectin.                                                    inversion when a high proportion of sucrose is used.

8.    Incorrect pH:

 

(a)   During boil                                                 Too low pH can lead to increased breakdown of pectin and in extreme cases                                                to pregelation in the boil.

(b)   In the final product                                     Within the pH range of satisfactory gelation (which is determined both by pectin type used and composition of sugars present) a lowering of pH will produce a faster and slightly stronger set. Below this range pregelation (possibly even in boil) and syneresis may occur, whilst  even slightly above it little or no set will be obtained.  Optimum pH values for gelation are higher for fast setting pectins than for slow setting.

9.    Filling at too low a temperature                  Partial setting before or during filling, may result in a lumpy, grainy or broken set together with possible syneresis.  Check by observation whilst filling.  A slower setting pectin may be  required.

10.  Movement of filled containers                    May result in a broken set and syneresis.

       before setting is completed                       

11.  Filling at too high a temperature.                Slow cooling at centre of container can (large container only)                                                                  lead to thermal degradation of the pectin                                together with possible caramelisation and high levels of sugar inversion. Can also                              occur if a number of smaller containers are                                  packed together whilst still too hot (“stack                                                                                burn”).

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12. Insufficient pectin added                            Should be considered only when other

                                                                         factors are checked.  May be due to either a deficiency or the low grade of the natural pectin extracted from the fruit during cooking.  Cannot be determined by direct analysis of the fruit itself. Actual pectin requirements can best be determined by preparation of trial production batch.

 

B TOO FIRM SET

 

1.    Too much added pectin                             In extreme cases may lead to premature setting.  Correct addition cannot be determined by direct analysis of the fruit itself.   Preparation of trial batch is  recommended.

2.  Too much natural fruit pectin.                      In systems containing high level of good quality fruit, the fruit itself can provide too much pectin even without any being added. Should be detected in trial batch.  Problem is rare and the best remedy will depend upon exact circumstances.

3.    High soluble solids content.                       Results from over boiling.  Check final product with refractometer.

4.    Incorrect pH in final product. Within the pH range for gelation, a raising of pH will result in a slower and slightly weaker set.

 

C  SYNERSIS                                     

 

1.    Use of pectin which has been                    Check store rotation. Refer to           

       stored for too long                                     pectin manufacturer if in doubt.

2.    Use of pectin which has been                    Store cool and dry. Refer to

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       stored under bad conditions.                     manufacturer if in doubt.

3.    Powder pectin not fully                              Solution should be smooth, with no

       dissolved before use.                                grittiness.  Difficult to detect visually in                                   finished product unless severe.  Unlikely to                                          cause syneresis unless very severe.                                  Check operating procedures.

4.    Use of stale pectin solution.                       Solution is best used on day of          preparation.     Pectin enzymes can act very quickly.

5.    Thermal breakdown of                               If prepared hot, pectin solution should

       pectin solution.                                           be used immediately, or cooled to 40ºC or below as soon as possible.

6.    Insufficient added pectin                            Weak setting can be associated with syneresis.  Maybe due to either a deficiency or the low grade of the natural pectin extracted from fruit during cooking.  Should be detected in trail batch.

7.    Low soluble solids content.                        Check final product with refractometer.                                  Results from insufficient boiling.

8.    Excessive boiling time                                Check recipe formulation for the amount

       leading to breakdown of                             of water to be removed by boiling.

       pectin (Open Pan Boiling only)                  

9.    Incorrect pH in final product

 

       (a)  too low                                                 If pH is below range satisfactory gelation, pregelation can result in syneresis even                                                    without significant loss in strength of set.

       (b)  too high                                               If pH is above range for satisfactory gelation, weak setting can be associated                                                with syneresis.

10.  Filling at too low a temperature                  Partial setting before or during filling can result in syneresis together with lumpy grainy or broken set.  Check by observation whilst filling.  A slower setting  pectin may be required.

11. Movement of filling containers                   May also result in broken set.

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       before setting is complete

12. Difference in solids content                       Fruit pieces having the lower solids

       between fruit and the                                 content will slowly exude moisture to try

       surrounding gel                                          and reach equilibrium with the gel. Check, using refractometer, soluble solids content of fruit and surrounding gel.  Normally will only result from faulty technique, and should be detected in a trial batch.

13.  High calcium levels                                     Unlikely to occur except with poor quality fruit when using slow setting pectin. Check hardness of water and calcium content of ingredients.

      

D FRUIT SEPARATION (FLOATING OR SINKING)

 

1.    Use of pectin which is too                          Should be detected in trial batch.

       slow setting                                                Considered use of faster setting pectin.

2.    Weak set due to low                                   Check possible causes of weak       

       a setting temperature                                 set as per section A.

3.    Filling at too high a temperature                 Check filling conditions. Unless containers are heat treated after filling and sealing, excessive lowering of filling temperatures can lead to microbiological problems.

4.    Use of fruit with high content                     Unlikely to be found except with

       of slow setting pectin                                 poor quality fruit or sulphited fruit which has been stored for too long.  Consider use                                           of faster setting pectin.

5.    Incorrect pH                                               Fruit pieces having lower solids content may tend to float.  Normally will only result                                                  from faulty technique in not allowing                                   penetration sugar into the fruit. Unlikely to produce separation by itself but will                                magnify the effect due to any of the other                                    causes listed.

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6.    Differences in solids content                     Fruit pieces having the lower solids

       between fruit and surrounding                   content may tend to float. Normally

       gel.                                                             will only result from faulty technique in not allowing penetration of sugar into the                                                                fruit.  Unlikely to produce separation by                                                                                    itself but will magnify the effect due to                                   any of the other causes listed.

 

E  INCLUSION OF FOAM AND/OR BUBBLES

 

1.    Excessive rapid setting produced by:

       (a)  Use of too fast setting pectin.              use a slow setting pectin.

       (b)  Use of too much pectin.                      Set will be too firm.

       (c) Filling at too low a temperature             Check by observation whilst filling.

            leading to premature setting.

       (d)  Too low pH.                                         Check pH

       (e)  High solids content due                       Check using refractometer.

              to overboiling.                                              

 

Any of the above may prevent the release of any air bubbles or foam trapped in the product. These are not the only possible causes as faulty technique, particularly during filling can often be responsible.

 

F  CRYSTALLISATION

 

1.  Too much inversion resulting                       Check reduced sugar content. May

     in the formation of dextrose                         take some time to be initiated but

     crystals.                                                        is likely to become more pronounced with length of storage.  Possible causes are: (a)                                            too low pH, (b) excessive boiling time, (c)                        too long standing before filling and cooling,

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(d) too much invert sugar added, (e) (large                                                                              container only), filling at too high a                                         temperature also produces a poor set and                                                   darkening at centre of the container. Over inversion is also likely to produce a                                                 somewhat cooked or syrupy flavour.

 

2.  Formation of dextrose crystals                     Check recipe formulation.

     due to use of added dextrose

     monohydrate

 

3.  Too little inversion resulting                         Check reducing sugar content.  Is

     in the formation of sucrose                          likely to become more pronounced crystals. with length of storage.  Due to (a) too high pH, (b) too short a boiling time, (c) addition of too little inverted sugar or glucose syrup normally only found under vacuum boiling conditions, but may also occur with fruit of low  acidity under fast boiling, open pan conditions.

 

4. Grape jelly only                                            Check recipe formulation.

     Crystals of tartar (potassium

     hydrogen tartrate).                                                 

 

G  COLOUR DEFECTS

 

1.  Excessive boiling time                                  Check recipe formulation for the

     leading to caramelisation                              amount of water to be removed by boiling. May also lead to pectin breakdown or the                                               formation of too much invert sugar.

2.  (Large containers only)                                Check centre for high invert sugar

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     Incorrect filling technique                             content.  The centre may also show

     resulting in darkening at                               a weak set.

     centre of container.

3.  Poor quality fruit                                           Check fruit pulp visually. Many types of fruit show browning when over-ripe or                                                     bruised.

4.  Discoloured pulp.                                         May be masked by Sulphur dioxide. True colour is not apparent until the                                                                           preservative has been removed by boiling.                                                                               Strawberries are very susceptible to this.

5. Metallic contamination of                              Chemical analysis necessary.

    product either from the fruit                          Various metals including tin,

    or from the processing equipment                copper, zinc, if present in excessive quantities, may cause considerable haze or                                              discoloration.

6.  Cloudiness due to phosphates,                    Chemical analysis necessary. Most

     oxalates or other insoluble salts                   noticeable in jellies and jelly

     of calcium or magnesium.                             marmalade. Hard water may be partly

                                                                         responsible.

7.  Excessive buffer salts (either                       Check ingredients and recipe. May

     natural or added).                                         also delay or prevent setting.

 

H  TOUGH FRUIT

 

1. Cooking of certain fruits in                             Blackcurrants and the peel of all

     syrup without pre-boiling.                               citrus fruits will not absorb sugar

                                                                            unless pre-boiled in water without

                                                                            sugar for 10-15 minutes.

2.  Use of hard water for                                     Hard water will toughen skins and

     pre-boiling.                                                     peel rather than soften them.

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I  MICROBIOLOGICAL FAULTS

 

1.  (Non-hermetically sealed containers               Microbiological tests necessary, e.g.

     only) Storage under conditions of                  staining, culturing, under the

     too high relative humidity or                           microscopic examination, etc.  In

     temperature.                                                   general, non-hermetically sealed containers (ie, those with non-vacuum

                                                                            closures and most of those made from

                                                                            plastic) have a much shorter shelf life.

2. Low Solids Content due                                 Check soluble solids content with

     to insufficient boiling                                      refractometer. Danger level below                                       68% if not hermetically sealed.

                                                                            For hermetically sealed containers

                                                                            danger level below 65% soluble      

                                                                            solids particularly if contaminated

                                                                            before or during sealing.

3.  Contamination of container                             Microbiological test necessary.

     or closure before or during                             (a) certain moulds can grow even

     seal.                                                                though the solids content is greater

                                                                            than 68%. (b) Any condensation under the closure locally lowers the solids                                                                       content and permits the growth of any                                                                                         yeast or mould spores already present.                                (c) Too low a filling temperature may allow contamination to occur.

4.  (Hermetically sealed

     containers only):

     (a) absence of vacuum                                   (a)  faulty containers

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          under closure                                            (b)  faulty closure

                                                                            (c)  faulty techniques, e.g.  quantity of preserves on lip of container.

 

5.  (vacuum boiling only)                                      Microbiological tests necessary.

     Insufficient sterilisation.                                  Check processing temperatures.

 

J   OTHER FAULTS

 

1.       Flavour loss on storage.                            Frequently experienced with plastic containers (polystyrene polypropylene,                          etc) due to their porosity.

 

2.       Off-flavours.

 

          (a)   Contamination before or during sealing

          (b)  (plastic containers only) pick up of chemicals  in the preparation of the                              plastic-solvents, plasticisers, etc)

          (c)   Salty taste due to high concentration of buffer salts.