Tel: 01723 373662

1-3 Sandside, Scarborough YO11 1PE

Tel: 01723 373662

1-3 Sandside, Scarborough YO11 1PE

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Ice Cream Ingredients

Milk and Milk Products

Milk and milk products form an important part of the ice cream mix. Fresh milk is composed of fat (about 3.5%), protein, lactose (milk sugar) and minerals. These last three constituents are known as serum solids or milk solids non-fat and make up about 9.0% of fresh milk. The balance is almost entirely water.
Milk can be handled in several forms and the following table summarises the average consumptions of the various milk products that can be used. These figures are given as a guide only, and may vary from sample to sample.

Milk Product

% Fat

% Milk Solids

% Water

Fresh Milk

3.5

9.0

87.5

Full cream milk powder

26.0

71.0

3.0

Skim milk powder

1.0

95.0

4.0

Condensed skim milk (24% MSNF)

0.5

24.0

75.5

Condensed skim milk (33% MSNF)

0.5

33.0

66.5

Cream (48% fat)

48

4.5

45.5

The inclusion of milk solids non-fat in an ice cream mix has the effect of improving the texture and body, allowing a higher overrun to be obtained without the formation of a flaky or fluffy texture. Too high a proportion of milk-solids-non-fat will tend to produce a sandiness in the texture on storage due the formation of lactose crystals; lactose is a sugar present in milk which is less soluble than sucrose. There is also a danger that overheating the milk will result in a cooked flavour in the final product.

It is important that best quality milk products are obtained for best flavour results and that the materials are carefully stored. Ideal conditions vary according to the type of milk product in use, and it is suggested that the supplier is consulted if further information is required.

“YOU ONLY GET OUT WHAT YOU PUT IN”

Fats

In dairy ice cream, butter or milk fat is the fat that must be used, but in standard ice cream, other fats can be used as well and these are discussed in more detail below. Fats are used in ice cream to increase the richness of flavour, to give smooth texture to the product and to help impart body. They also increase the food value of the product.

The quality of the fat used is very important. If the melting point is too high, or it melts over a wide temperature range, the ice cream made from it will have a waxy or greasy taste. For this reason, it is desirable to use a fat which melts quickly and which melts below body temperature (37°C). At the same time, the flavour of the fat is important and in general it should be bland. Otherwise, the flavour of the fat itself may detract from the delicate flavour of the finished ice cream. Where margarines are used, the unsalted varieties are employed and it is customary for the fat manufacturer to incorporate colour and butter flavour into the product.

Finally it is essential that the fat does not develop or pick up off-flavours or rancid flavours in storage. For this reason, it is necessary for the ice cream fat to be properly refined from suitable oils, and for the fats to be stored under good conditions. Fats should be stored as cool as possible in a dry, well-ventilated area.

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Sugars

The use of sweeteners in ice cream increases product acceptability, making it sweeter and enhancing the flavour. They increase the viscosity and total solids of the mix and therefore improve both body and texture. Excess sugar makes the product soggy and depresses the freezing point; the ice cream then requires a lower freezing point and a lower hardening temperature. Insufficient sugar results in an ice cream with weak and coarse texture. Sugars are among the cheapest source of solids and are used at levels between 10-16% of the total mix, depending on the fat content, the process used and the type of product required. Some authorities state that poor ice cream is obtained when less than 12% sugar is used.

The commonest sugar used is sucrose. Dextrose hydrate is less sweet than sucrose and 1¼lb of dextrose is equivalent in sweetening power to 1lb of sucrose. Its presence tends to retard the crystallization of sucrose and can therefore be used to improve texture.

However, it has a greater depressing effect on freezing point than sucrose and it is preferable to restrict its use to 25% of the total sugars. Lactose is also less sweet than sucrose and is present in milk, the serum solids of milk contain about 50% lactose. When present in significant concentrations, lactose may tend to separate out as crystals large enough to impart a sandiness to the ice cream. Its use should therefore be limited to less than one twelfth of the total amount of free water, including the lactose present in the serum solids.

Corn solids are also available and contain varying amounts of sugar and total solids, depending on the type of syrup. They are obtained by the hydrolysis of starch and contain dextrins which tend to raise the freezing point of the mix. They should not be used at high levels in excess of 25% of the total sugar content and tend to give a heavier, firmer body to the ice cream.
Invert sugar is sweeter than Sucrose and lowers the freezing point; it should not be used above 30% of the total sugars. Other sweeteners can be used but care should be taken as many of them, honey for example, have very characteristic flavours which may not be acceptable.

Emulsifers

These are substances which help the stable emulsions between two immiscible liquids such as oil and water.

They concentrate at the boundaries between the two liquids and act by reducing the surface tension of the system; in ice cream they improve dispersion of the liquids and of the air; these effects result in smaller ice crystals and the formation of a smoother final texture. They also improve whipping ability and give a drier ice cream. In excess they slow the melt-down.

Monodiglycerides and distilled monodiglycerides are in common use in ice cream but are not necessarily the most suitable. Sorbitan esters have also been used, and often blends of several types are employed.

Dairy products and eggs contain natural emulsifying agents, but these have only theoretical importance; pasteurisation may largely denature the naturally occurring emulsifying agent. Some stabilisers also have a certain emulsifying effect. Many suppliers offer combined emulsifier/stabiliser systems for ice cream. Whichever type is used, it should be selected carefully to avoid problems associated with flavour or melting point effects. In general, glyceryl monostearate can be used at a level of 0.5-0.6% of the total mix.

Stabilisers

These are effective in ice cream either because they form gels with water or because they can combine with water as part of hydration. Either way, they function because of their high water holding capacity, preventing the formation of large crystals particularly under adverse or fluctuating storage conditions. Because of this they produce a smoother, more stable texture and body and assist in maintaining the shape on melting. They have no apparent effect on the freezing point of mix. In excess, they are likely to give much too much body and resistance to melting and a poor sensation on the palate.

Many substances are available and some suppliers offer combinations of products for improved effect. Points to bear in mind when choosing a stabiliser include cost, ease of dispersion and resistance to heat. Some substances tend to lose stabilising power when excess heat, such as that met in high temperature methods of pasteurisation, is applied. Common stabilisers include gelatine (used at the rate of about 0.5% of the total mix), sodium alginate (0.25%), carageenan or Irish Moss (0.15%) cellulose ethers such as sodium carboxymethyl cellulose (0.15%) agar (0.5%) and pectin (0.15%). Generally, stabilisers can be added by mixing them with about five times their weight of sugar or by suspending the material in cold water before adding to the hot mix.

The Harbour Bar Scarborough Vintage Ice Cream Van

Recipe Balance

What is Recipe Balance and how does it affect the ice cream we make? 

Ice cream is composed of several ingredients and each of these has a role to play. Fat mainly imparts a richness without which the product would be too thin. Sugar gives the sweetness, improves flavour and texture but between them, fat and sugar do not give much body and other solids must be used. In general, these are obtained from milk solids or, to a lesser extent, from fillers. Emulsifying agents are used to stabilise the oil in the water emulsion and to improve the air incorporation and disperation and stabilisers are used to prevent the formation of large water crystals. The recipe has to be formulated in such a way that there is neither excess water which will freeze into large ice crystals or insufficient water which may result in lactose crystallisation, (sandiness).

Air is also an important ingredient and is incorporated at the freezer; the air content of ice cream is defined by the overrun of the product; overrun is the increase in the volume of ice cream obtained over that of the mix, expressed as a percentage of the amount of mix taken.
It is important to obtain the correct overrun as well as the correct balance between the various ingredients, and the type of equipment used in the freezing process has some bearing on the final recipe and on the overrun.

Dairy Mixes

In dairy ice cream, the fat used is cream or butter and at least 8% fat should be used. Skim milk powder, not lactose, should be used for balancing the solid content as a dairy mix is generally heavier in solids, the use of filler is probably not necessary. It is absolutely essential to use the correct emulsifier in a dairy mix; in general slightly more should be used, or that based on a harder fat should be used. The emulsifier supplier should be consulted for further information, if required.

Interior of Scarborough's Famous Harbour Bar

The Processing of Ice Cream

So we have the ingredients, we have decided on our balance how do we bring it all together to produce the end product that we all enjoy?

Blending the Mix

Fresh milk is taken to 100°F and the milk powder added and dissolved. Where full cream milk powders are used, some fat separation may occur but this is corrected during later stages of mixing. The sugar and lactose (if used) are then added and dissolved. Stabilisers can be added at this point by first mixing them with about four or five times their weight of sugar, or by adding them in a suspension with cold water when the mix temperature has reached 160°F, and after the fat.

The mix is completed by adding emulsifier, fat, and butter or cream (if used) and by this time a homogenous mix is obtained at a temperature of 72°C.

Pasteurising the Mix

The mix is pasteurised by heating to render it substantially free from pathogenic bacteria.Pasteurisation is also said to ensure that all the mix is brought into the solution, that the production of a more uniform product results, and that the water binding effect of the milk proteins is increased. Pasteurisation is achieved either by holding the mix at 150°F (66°C) for at least 30 minutes, at 160°F (72°C) for at least 10 minutes, at 176°F (80°C) for one second or by any method which satisfies the Ice Cream (Heat Treatment, etc) regulations, 1959.

In batch pasteurisation, the mix is agitated while heated and the vessel is kept covered during the process. It is also possible to effect pasteurisation continuously, often incorporating a device which automatically re-circulates the mix if pasteurising conditions have not been met. Cooked flavours can result if the temperature exceeds 176°F for more than 20 seconds.

Homogenising the Mix

By this stage of the processing, the mix is basically an oil in water emulsion. Homogenisation reduces the size of the oil droplets to a much smaller diameter and renders the mix more stable towards separation and clumping. The homogenised mix is smoother and more uniform and generally has an improved whipping ability; the resultant ice cream has better melt-down. During this process, the milk protein and surface active agents are distributed onto the fat globule surfaces.

Homogenisation is best effected at the pasteurising temperature and consists of passing the mix through a very small opening under high velocity and high pressure. There is a tendency for the fat particles to clump as the mix passes away from the homogenising valve, particularly if the mix is cold (less than 120°F) or more acid than usual, or based on butter.

If this clumping becomes marked, the mix becomes more viscous and slower to whip and freeze, and for this reason two stage homogenisation is sometimes used. In this, the mix is passed through a valve at relatively high pressure (about 2500psi) and then through a second valve at a lower pressure (about 500psi) to break up any clumps which are formed. The actual pressures used depend on a number of factors, including the composition of the mix. Mixes with higher fat content are homogenised at lower pressures. The viscosity of the mix can be reduced by lower homogenising pressures, higher temperature at homogenisation and by the use of a second valve.

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Homogenising the Mix

By this stage of the processing, the mix is basically an oil in water emulsion. Homogenisation reduces the size of the oil droplets to a much smaller diameter and renders the mix more stable towards separation and clumping. The homogenised mix is smoother and more uniform and generally has an improved whipping ability; the resultant ice cream has better melt-down. During this process, the milk protein and surface active agents are distributed onto the fat globule surfaces.

Homogenisation is best effected at the pasteurising temperature and consists of passing the mix through a very small opening under high velocity and high pressure. There is a tendency for the fat particles to clump as the mix passes away from the homogenising valve, particularly if the mix is cold (less than 120°F) or more acid than usual, or based on butter.

If this clumping becomes marked, the mix becomes more viscous and slower to whip and freeze, and for this reason two stage homogenisation is sometimes used. In this, the mix is passed through a valve at relatively high pressure (about 2500psi) and then through a second valve at a lower pressure (about 500psi) to break up any clumps which are formed. The actual pressures used depend on a number of factors, including the composition of the mix. Mixes with higher fat content are homogenised at lower pressures. The viscosity of the mix can be reduced by lower homogenising pressures, higher temperature at homogenisation and by the use of a second valve.

Cooling the Mix

Pasteurisation does not completely sterilise the milk but merely reduces the number of bacteria present to a low level. At this stage the mix will be harmless unless the bacteria are allowed to multiply and to avoid this multiplication, it is essential that the mix is cooled as soon as possible.

The regulations insist that the mix is cooled to 45°F or lower within 1½ hours of pasteurisation. At this stage, the mix should be thin enough to flow over or through the tubes of the cooler.

Ageing the Mix

After cooling, the mix is held with mild agitation in ageing vats at a temperature below 45°F for a period of time. This period varies but is generally at least 4 hours and up to 12 days. If the mix is frozen immediately after homogenisation and cooling, it tends to be thin and the resulting ice cream may have a low overrun.

Many changes occur during ageing but during this period, the fat globules solidify, some stabilisers combine with the water and swell and the protein structure may be modified. As a result of these factors, the viscosity of the mix increases and this results in improved whipping properties and good body to finish the ice cream. With modern stabilisers this occurs very rapidly, but time is required for the fat to crystallise.

Freezing the Mix

In the freezing process, air is incorporated and a proportion of the water is frozen. The resulting product is a three-phase system of air, liquid and solid. As the temperature of the mix is reduced, the water begins to freeze into ice. These ice crystals are composed of practically pure water and the rate of freezing should be rapid enough for these crystals to be as small as possible so the ice cream will be 'icy' in texture. As the water begins to freeze, the sugars and other soluble ingredients become more concentrated and therefore further crystallization will proceed at a slower rate. During the formation of ice, heat has to be removed from the mix. This is known as the latent heat of fusion and is not measured by a thermometer.

Consequently, the temperature of the mix does not appear to alter to any great extent during the formation of ice crystals, although the temperature will be seen to drop at a slow rate; this is because the freezing point of the water is reduced as the soluble materials become more concentrated in the water. In general about 30-60% of the water in the mix is frozen, the amount depending upon the formulation and type of freezer used.

Several types of freezer are in use, but in general these can be classified as follows:

• Vertical freezers
• Horizontal (batch) freezers
• Continuous freezers

Vertical freezers of a simple type are rather slow in operation and the scraper blades are immersed in the mix. Freezing is relatively slow and air is whipped in with difficulty and not in an easily controlled manner. The overrun obtainable is usually in the order of 40-50% and it is preferable not to use this type of machine with mixes of high total solids. Generally, the mix should contain no more than 7% fat and the total solids should be in the order of 30%. Direct expansion vertical freezers, where the freezing area is directly surrounded by the refrigerant coils, are faster and easier to control. Higher overruns of 55-60% can be achieved in more controlled ways and mixes with higher solids (fat content up to 8%) can be used.

Horizontal freezers are more effective and overruns in excess of 100% can be obtained. A wider range of mix formulations can be used but the ice cream will be lacking in body and texture if mixes of too low a solids content are overbeaten.

Continuous freezers tend to produce a more uniform product and because the air is pumped or drawn into the mix rather than beaten in, the overruns can be controlled effectively. Freezing is more rapid and this benefits the ice-cream. When a continuous freezer is used, the air incorporation does not depend so much on the character or the viscosity of the mix. Shorter ageing times will suffice and it has been said that less stabilisers are used.

Hardening the Ice Cream

Ice cream from the freezer is semi-solid in consistency and hardening is really a continuation of the freezing process. It involves further chilling without agitation. It involves storing the ice cream at a temperature of -20°F for a time sufficient to ensure that the centre of the package reaches the hardening room temperature, generally at least 12 hours.

During the process, more water is frozen to ice and as the process is relatively slow, and without agitation, texture defects will appear if the mix is not well balanced. An excess of water will produce an icy product, and if the solids content is too high, graininess will result as the solids come out of the solution. If the ice cream weighs less than 36 ounces per gallon, the texture may also be poor.

Storing the Ice Cream

Storage should be at a uniform temperature around -20°F. Defects will occur if the temperature varies excessively.