Hardening and Storage

Hardening is a continuation of freezing process. Only part of water in ice cream mix is converted into small ice crystals in the ice cream freezer. When ice cream is removed from freezer and put in the packaging materials it has a semi fluid consistency not stiff enough to hold its shape. Therefore freezing process is continued without agitation in a very low temperature room until the temperature of ice cream reaches –18 °C or below, preferably –30°C. This process is called hardening of ice cream.

The refrigerated place where the hardening takes place is called hardening room or hardening chamber or cabinet.

Quick freezing of ice cream during hardening is also desirable. Slow hardening will favour large ice crystals formation in ice cream and hence the texture of ice cream will be coarse. Time required to complete hardening process depends on the following
factors:

• Initial composition of mix
• Temperature of ice cream drawn from freezer
• Over run in ice cream
• Size and shape of packages
• Temperature of air in hardening room
• Rate of air circulation in hardening room
• Sections of the hardening room where the ice cream containers are stored.

Hardening time of 6- 8 hr may be considered normal for the operation to be completed. However large containers may take more time as compared to small packages.

1. Hardening Methods: The following hardening methods are used for fast hardening of ice cream:
i) Hardening room: This is a low temperature cold store maintained at – 30 °C or lower with large storing space. Also a good air circulation is maintained throughout the room for uniform cooling effect.

ii) Hardening tunnel: This is a hardening room constructed in the form of an insulated tunnel through which large volume of air is discharged. The air circulated in the tunnel may be at –35 to – 40 °C and this helps in fast hardening of ice cream. Small blast tunnel hardeners may also be located in hardening room for faster hardening. Manufacturers of large volume of
ice cream prefer to have this type of system.

iii) Hardening cabinet: This is a small, refrigerated cabinet maintained at –25 °C or below. It may have two or more compartments separated from each other. Ice cream cups are tightly packed and stored in these compartments. This unit serves as hardening and storing cabinet. This type of unit is useful where volume of operation is low.

2. Storage: After ice cream is hardened it is ready for sale. Until such time it is marketed ice cream should be stored at temperature at which it is hardened.

Hardening rooms or cabinet can be used as storage rooms for ice cream. If separate storage room is used the following precautions should be taken:
i) Room temperature should be maintained uniformly (-11 to –15 °C)
ii) Ice cream packages should be piled very closely
iii) Cold air should be circulated uniformly throughout the room
iv) Frequent opening and closing of the room should be avoided.

Indigenous Frozen Dairy Products

i. Kulfi

It is a frozen dessert characterized by slight whitish to brownish appearance, compact body, icy texture and nutty, cooked, caramelized flavour. It is popular in the northern and western parts of India. In the traditional process, milk is thickened in a shallow pan with constant agitation. Sugar, nuts, essence and colour are added towards the finishing stages. Concentrated mass is poured into metallic moulds and frozen in a mixture of ice and salt.

In the industrial process, the ingredients used are the same as for ice cream – milk,cream, skim milk powder, sugar and stabilizer. Water is added to dilute the mixture(not having stabilizer and a small amount of sugar), and the fat: MSNF ratio is maintained at 1.4:1. usually, the fat in the finished product is about 16%. The required quantity of ingredients are taken in an open steam kettle and the contents heated with vigorous agitation. When the mixture has been concentrated approximately two times, the stabilizer blended with little sugar (1:3 parts by weight) is added to the concentrated mix, and the heating and agitation is continued till the mixture has been concentrated three times. The concentrated mass is then cooled promptly and frozen in a batch freezer to an overrun of 20-30%. Chopped nuts, almonds, pistachio,flavour and colour are added in the freezer. The frozen mix is transferred immediately into the moulds having freezing pockets. Wooden sticks are inserted and the mix hardened in a brine tank maintained at -23 to -30 C. The mould is then transferred into a tank having lukewarm water to defrost the bars so that they can be easily lifted from the freezing pockets. The bars are wrapped in papers, put in corrugated boxes and placed in cold store until further distribution.

ii. Malai ka baraf:

It is popular in northern and western parts of India. It is similar to kulfi and prepared by freezing a mixture of malai (heat desiccated/clotted milk), sugar, nuts and essence.This product has a plastic body, crunchy, icy texture , and delicate, nutty and caramel flavour.

Ice Cream Novelties

The term ‘novelty’ means something unique. As it related to ice cream, we mean any single-serve portion-controlled product. Worldwide, especially in Europe, ice cream novelties enjoy an even bigger market. Every shape size, and flavour are being offered : from ice cream and frozen yoghurt to sorbets and non fat products.

Methods of Preparation

Ice cream novelties are prepared either on a brine system or through an extrusion system. Using the brine system, semi-frozen ice cream is poured into molds that are placed inside a brine tank to freeze the product at -20 F. The extrusion method enables a manufacturer to produce unusual types of novelties that are impossible to produce on a brine system.

Using the extrusion method, the ice cream must be frozen to certain stiffness so that it retains its form between the time it is extruded until it enters a hardening tunnel.The ice cream is drawn from the continuous freezer at 20-22 F. The external contour of the slice can be almost of any desired shape of the extrusion nozzle. Complex extrusions utilizing more than one flavour or colour can be produced from multiflavour extrusion nozzles supplied by more than one continuous freezer barrel. By placing different extrusion devises inside each other, faces with eyes, noses and mouths can be formed, as well as other intricate designs.

Semisolid ice cream is drawn either vertically or horizontally. As the stiff extruded ice cream flows through the extrusion nozzle, portions of appropriate size are cut off by an electrically heated wire. In vertical extrusion, the flat portion of ice cream falls precisely onto a continuous row of stainless steel supporting plates fastened to a conveyor chain which carries the portions into the hardening tunnel for rapid freezing.The temperature in the hardening tunnel is usually in the range -45 F to -50 F. A 10% ice cream butter fat mix with 85-100% overrun is most commonly used.

i. Chocolate Coatings

More than 1/3rd of all ice cream novelties produced have some kind of exterior chocolate coating. Chocolate bars consist of vanilla ice cream stick which has been dipped in chocolate coating. The composition of chocolate coating can be the following (on weight basis):

Chocolate mass : 65-70 parts

Coconut oil : 27-32 parts

Cocoa butter: 1-1.5 parts

Dextrose : 1-1.5 parts

Lecithin : 0.3 – 0.4 parts

Refined deodorized coconut oil is added as a thinner, to increase the coating ability.The quantity of coconut oil will vary with the amount of chocolate mass. Higher amount of chocolate mass will require more quantity of coconut oil to avoid the excessive viscosity. Coconut oil is preferred since other oils have melting points which are too low for satisfactory use in coatings

ii. Ice Cream Cakes and Pies

These products can be made with freezer attachments designed for filling the cake or the pie plate. The cake plate is usually inserted into a cardboard package the support the form of cake during handling and delivery.Ice cream pies can be modified by using fruit flavoured gelatin, instead of the filling of preserved fruit or fruit ice cream which is ordinarily used. The pie crusts are about ½ inch thick and can be made by hardening vanilla ice cream between two plates. Closed or open pies can be made by this procedure. The pies and cakes can be decorated with whipped cream.

iii. Aufait Ice Cream

Aufait ice cream usually consists of a layer of fruit between two layers of ice cream.

iv. Other Novelties

Variegated or rainbow ice cream is made by mixing several different colours as the product is packaged. The variegated ice cream sundae, and other colourful products are packaged in transparent plastic container to have a good consumer appeal.

v. Cassata Ice Cream

This is essentially ice cream on a sponge cake. Hemispherical moulds of aluminum are used in making this ice cream. The outer layer is usually made of chocolate ice cream. Different varieties of ice cream constitute the middle and inner layer. The ice cream which constitutes the outer layer is first filled in the mould (outer mould) from the freezer. Another mould which is smaller in size, is inserted into the first mould and pressed so that the ice cream occupies the annular space between the two moulds.

This ice cream is hardened and the smaller mould is taken out.Ice cream is now filled again into the mould and another smaller mould of a different size is inserted and pressed lightly. This ice cream layer now forms the middle layer.The ice cream is hardened and the smaller mould taken out. Now a third variety of ice cream is filled into the outer mould and this ice cream constitutes the innermost layer. The mould is hardened and ice cream is taken out by dipping the mould in slightly warm water. Now the three layer ice cream is inverted on the sponge cake to which thin coating of whipped cream has been applied. The whipped cream serves the purpose of an adhesive between the cake and ice cream. This cassata ice cream is transferred to the cold store or hardening tunnel so that it becomes sufficiently hard for slicing into small pieces.

vi. Chocolate Jam Sticks

These are made by coating vanilla sticks with white chocolate and injecting the vanilla portion with a flavoured syrup of jam base which constitutes the innermost core.

A white chocolate coating is made by adding a thinner, cocoa butter and an emulsifier.Usually coconut oil is added as a thinner and lecithin is added as an emulsifier. An appropriate amount of colour (oil soluble) is added to the coating so that it is characteristic of the flavour added to the syrup or jam base. The total solids content of the syrup or jam base is so adjusted that its freezing point is much lower than the vanilla portion. But the syrup should have a sufficiently high viscosity so that it does not drip while eating. A syrup or jam base consists of sucrose, glucose syrup, citric acid, stabilizer, water, fruit pulp or concentrate and flavour.

vii. Quiescently Frozen Stick Items

These items include water ice frozen without overrun in a stick and cream on a stick which has ice cream centre with quiescently frozen outer section.

Water ice: The following formula is suggested for an ice base (on weight basis)

Water : 85-95 parts

Cane sugar : 20-23 parts

Glucose syrup : 5-7 parts

Stabilizer : 0.25-0.35 parts

Citric acid : 0.35-0.50 parts

Brix : 22-24

1. Weigh the stabilizer carefully and mix it with cane sugar in the ratio 1:3 parts by weight and add the required amount of water. Then agitate until it is fully suspended. It is necessary to maintain the temperature of the mixture between 60-70 C to fully dissolve the stabilizer.

2. Add the remaining amount of cane sugar and the required amount of glucose syrup, and agitate until it is fully dissolved. If necessary, homogenize at 100 bars to obtain homogenous mix.

3. Pasteurize at 80-85 C for 20-40 sec and cool the mixture; add citric acid,desired colour and flavour.

4. Ageing for 4 hours to impart a smooth body when gelatin or agar agar is used as a stabilizer.

Pour the mix into the mould and allow sufficient space in the pocket for expansion during freezing. Place the moulds in the brine tank at -25 to -30 C.

On partial freezing, insert the sticks into the mould pockets (the water ice should be just sufficiently firm and hard to hold the sticks).

Freezing us usually accomplished in 15-20 min. The frozen sticks are then taken out by immersing the mould in hot water for a few seconds.For a cream-on-a-stick item, a special filler attachment can be used so that in one operation, a freezer can be used to freeze the ice cream to 100% overrun for the centre, and a second freezer to freeze the ice or sherbet shell to 10-15% overrun for the shell.

Manufacturing Procedures

i) Selection of ingredients: Fresh, sweet dairy products should be preferred for making soft serve mix in order to obtain a good quality product. Generally,cane sugar is used but a part of it is replaced with dextrose or corn syrup. The selection of ingredients should be based on the composition given in section above.

ii) Mixing of ingredients: To avoid difficulties in mixing, pre-calculated quantities of dry ingredients, i.e. milk power, sugar and stabilizer should be mixed in a lot.Similarly, the liquid ingredients, viz., milk and cream, etc. should be mixed separately in a container. The dry mixture shall be incorporated within the liquid ingredients mixture gradually with constant stirring and heating to the homogenization temperature of 65.5 C.

iii) Homogenization: In order to avoid fat separation, clumping of fat and fat churning in soft ice cream, the mix should be homogenized in two stages. First at a pressure of 2500 psi. and then at a pressure 500 psi.

iv) Pasteurization: To safeguard health consumers by means of destroying all the pathogenic and disease producing organisms present in the mix, it must always be pasteurized. Pasteurization is normally done at 80 C for 25 seconds by High Temperature Short Time (HTST) method or at 69 C for 30 min. by Batch method.

v) Ageing of mix: The mix is to be aged at temperatures 2-5 C for at least 4 to 6 hours before freezing.

vi) Freezing: A soft ice cream freezer, apart from freezing a portion of water of ice cream mix, also incorporates the air in the mix to obtain a swell in volume or ‘overrun’. A soft ice cream freezer is very similar to the batch freezer of ice cream. It is usually a self contained machine in which the low pressure refrigeration system is either directly attached, or is adjacent to the freezer.

The design of the dasher is such that it gives a good degree of aeration to the mix as it freezes and can operate for a long period of time without undue breaking down of the ice cream mix. Excessive speed of the dasher causes too much air to be incorporate, and adversely affects the body of ice cream if the dasher ran for extended periods of time. The refrigeration system is so designed that the freezer cylinder is kept at the proper temperature for a soft serve ice cream for an indefinite period of time. Most of these freezer use Freon as a refrigerant. In this case, they often use a thermo valve control rather than the flooded system. Care and maintenance of this type of freezer consists mainly of keeping the scraper blades properly sharpened,and ensuring that the refrigeration system is properly adjusted.

The automatic cycling of ice cream can cause major problems including fat separation, occurrence of sandiness due to lactose crystallization and coarse texture.

Soft server frozen products are usually drawn from the freezer at -6.5 to -7.5 C.The overrun of soft serve varies between 40-60% depending on the total solids content. It is possible to achieve high overrun and desired body and texture characteristics on a product with a high solids content.

Overrun and serving temperatures for different types of ice

cream

Composition

The differences between soft serve and regular ice cream include:

•  Composition
•  Freezing procedures
•  Stability and whipping properties of the mix
•  Maintenance of dry, smooth, stiff characteristics of the product as drawn from the freezer.

i) Fat: Soft serve ice cream has a lower butter fat than the hard product, but it is difficult for the consumer to tell because the soft state allows full flavour. Soft serve ice cream normally has a fat content between 6 to 10% range. If fat content is low, i.e. less than 4%, the product tends to become coarse, weak and icy. If the fat content is high (above 12%) freezing problem is encountered.This involves possible fat separation, and also, the product becomes too rich and less palatable.

ii) Milk Solids-Not-Fat (MSNF): The MSNF content of soft frozen products varies somewhat inversely with the fat content and can be as high as 13% for a low fat formula. MSNF serves for provide proper firmness of body. In products having a high MSNF content, the lactose may separate during freezing and cause a sandy defect. Normally soft serve products consists of 11-14% MSNF.

Soft serve mixes should have a slightly lower MSNF than normal ice cream, as a slightly lower MSNF (MSNF factor 16-16.5) contributes to a higher degree of fat destabilization, thus, ensuring better stand-up and slower meltdown (a MSNF factor of 17 is recommended for plain, hardened ice cream).Since the soft-serve mix is exposed to a mechanical treatment for alonger period of time in the freezer, this can cause excessive churning of fat, resulting in a greasy texture. This can be avoided by incorporating whey proteins which impart greater stability to fat emulsion, and consequently less fat destabilization and ‘churning out’ effect of the emulsifier. Replacement of 10-15% MSNF with whey powder adds to the freshness of soft-serve ice cream and fat destabilization is also brought under control.

iii) Sugar: The sugar content of soft serve products is 13-15%, which is slightly lower than for regular ice cream. The amount of corn sugar used to replace cane sugar is limited to about 25% in order to avoid too low a freezing point.However, corn syrup solids, instead of corn syrup, can be added as they provide firmness and also raise the freezing point slightly (corn syrup solids depress the freezing point less than corn syrup and sucrose) thereby enabling the drawing of ice cream at almost the same temperature as normal ice cream.Stiffness and dryness of mix is extremely important for getting a smooth, creamy finished product from the soft serve freezer. Those characteristics are achieved by two ways:

•  By reducing the sugar content of mix by 2-3% of that used for a hard ice cream product
•  Drawing the product at lower temperature 21 to 22 F. This lower temperature not only produces a stiffer product, but makes it immediately suitable for serving to public.

 iv) Emulsifiers and stabilizers: Higher amounts of emulsifiers and stabilizers are added to provided desirable whipping properties, smoothness, firmness and melting resistance.

Emulsifiers have several main effects in ice cream:

•  To facilitate the dispersion of the fat in fine, uniform globules during whipping
•  To promote and control destabilization of the fat and to secure a good fat protecting membrane around the air cells
•  To aid aeration during freezing by permitting better air distribution with a smaller air cell size.

 Thanks to these effects an ice cream with a creamy consistency, slow meltdown and improved storage stability can be produced. These are exactly the properties that are needed in scoopable ice cream. It is advantageous to increase the addition of emulsifier in scoopable ice cream, due to increased level of the liquid water phase at any given temperature.

The main effect of stabilizers in ice cream systems is to bind water resulting in higher mix viscosity and superior body in the finished ice cream as well as controlling the mobility of the residual aqueous phase. As mentioned above,there is more liquid phase in scoopable ice cream, which means that more stabilizer is needed to bind the water present. A 5 to 10% increase in emulsifier/ stabilizer content is advisable.

v) Other additives: Products like calcium sulphate can be used at the rate of 0.12% to produce dryness and stiffness in ice cream.

Formulation of Soft Serve Ice Cream

There are several ways of obtaining softness in ice cream, and sometimes these may be combined if required. The following techniques are used:

•  Addition of an anti-frost preparation of carbohydrate nature, including MSNF
•  Increase of the overrun
•  Selection of specific emulsifiers/ stabilizers.

 The first is the most important point, and the effect of using freezing point depression factors is discussed below:

i. Lower the Freezing Point

In traditional ice cream there are various ingredients, but not all of them have an influence on the freezing point of ice cream mix

                 Degree of freezing point depression

Fat	: Of no importance
MSNF:	Limited importance (contains lactose and salts)
Sugars	Great importance (give the main effect)
Emulsifier/stabilizer	No importance
Overrun	Great importance

Consequently, the freezing point depression is sought from lactose and salts of MSNF as well as the sugars.

ii Effect of MSNF on Freezing Point Depression

It is known that MSNF consists of approximately 8% minerals, 39% protein and 53% lactose. Lactose is a disaccharide that is in the dissolved state. It lowers the freezing point just like ordinary sugar. The salt content will also have an influence on the freezing point and generally it may be assumed that the MSNF will depress the freezing point to the same extent as a 40-50 DE glucose syrup.

Lactose, is an important part of MSNF, but is only partially soluble. If the MSNF factor (i.e. parts of MSNF per 100 parts of water):

i.e. (%MSNF 100)/ %water

is increased to more than 17, the result will be the risk of a sandy ice cream. By means of enzyme lactase, the lactose may be hydrolyzed into monosaccharides, glucose and galactose which are more soluble and these sugars will lower the freezing point more than the lactose.However, MSNF has a limited effect on the freezing point depression. The main effect is achieved by the sugars, which are present.

iii. Effect of Sugars on Freezing Point Depression

The freezing point of an ice cream mix is first of all dependent on the amount of dissolved solids. The more are the solids dissolved (in the genuine solution), the lower the freezing point. The sugars produce a lowering of the freezing point and it is its molar concentration that determines the freezing point of the ice cream mix.In order to survey the effect of different products, it is necessary to introduce two factors that are related to lowering of the freezing point and the sweetening ability of sugars.

The factors are: Freezing point depression factor (FPDF) and Relative sweetness 

Freezing point depression and relative sweetness of some

sweeteners

In the above table, sucrose was chosen as the datum point and the FPDF and relative sweetness of each sweetener is compared with it.For example, the same amount of dextrose will lead to greater freezing point depression than sucrose due to the difference in molecular weights, and conversely  glucose syrup will produce a less freezing point depression than sucrose. By combining different sweeteners, it is possible to produce desired softness and relative sweetness.Experience has shown that ice cream with FPDF of about 15 will be relatively hard at -18 C and not scoopable, whereas scoopable ice cream should have a FPDF of around 20-25.

A well known and easy way of obtaining scoopable ice cream is to add 2-3% glycerol. The following recipe shows the effect of keeping the total sweetness constant:

Recipe:

Fat                                                       10.0%

MSNF                                                  10.7%

Sucrose                                                11.0%

Glucose solids                                       3.0%

Glycero                                                 l 2.0%

Emulsifier/stabilizer                                 0.7%

Total solids                                         37.4%

Calculation of FPDF and Relative sweetness

sweetness                                FPDF                                                      Relative

Sucrose,                             11% 11 × 1 = 11                                         11 × 1 = 11

Glucose solids,                    3% 3 × 0.8 = 2.4                                        3 × 0.3 = 0.9

Glycerol,                             2% 2 × 3.7 = 7.4                                        2 × 0.8 = 1.6

                                                             20.8                                                       13.5

The addition of 2% glycerol produces a FPDF of 20.8 which will be sufficient to give the product scoopable properties.

The effect of other combinations can be considered, especially if a combination of saccharides can be used to produce acceptable softness and sweetness in the final product. A recipe which can be considered without the use of glycerol is shown below:

Recipe:

Fat                                                10.0%

MSNF                                          10.6%

Sucrose                                         4.5%

High fructose corn solids                6.0%

Glucose solids                                2.0%

Dextrose                                        4.5%

Emulsifier/stabilizer                         0.7%

Total solids                                    37.3%

Calculation of FPDF and Relative sweetness

	FPDF	Relative sweetness
Sucrose, 4.5%	4.5 × 1 = 4.5	4.5 × 1 = 4.5
Glucose solids, 2%	2 × 0.8 = 1.6	2 × 0.3 = 0.6
High fructose corn solids, 5%	5 × 1.8 = 9.0	5 x 1 = 5.0
Dextrose, 4.5%	4.5 × 1.9 = 8.6	4.5 × 0.8 = 3.6
	23.7	13.7

The correct choice of saccharides can make it possible to produce a scoopable ice cream with the same solids and total sweetness as that of regular ice cream.

Legal Standards

In India there are no separate legal standards for soft serve ice cream. The Prevention of Food Adulteration Act (1954) has specified the same standard for ‘Softy’ as that of ice cream.

Softy and Novelties - Defination,Composition,Legal Standards and Method of Manufacture

Softy or ‘scoop able ice cream’ was first marketed in earnest in England in 1975.The aim was to produce a type of ice cream that was scoopable at -18 C and that had a good creamy consistency, slow meltdown properties and good storage stability.

While hard ice cream has been the dominant frozen dessert produced world wide for many years, other frozen dessert products have their niche, and in many countries are more popular than ice cream. The American market in recent years have seen the introduction of a number of other dairy and non dairy soft serve products, such as frozen yoghurt, sorbets and smoothies.

As the name implies, soft serve products are not hardened, and its is their soft,creamy texture that the public finds so appealing. They are easy to consume, thus providing instant gratification. They are especially easy to lick, a characteristic particularly enjoyed by children, who make up 50 per cent of the consumer base for soft serve products. Such products also lend themselves to decreased labour costs,as evidenced by the growing numbers of consumers willing to serve themselves from soft serve freezers in supermarkets and convenience stores and restaurants.Other than the investment in the equipment, handling soft serve products is a relatively low-cost operation. The equipment takes up little space and is easy to operate. The products increase profit margins and are self-promoting when the machinery is in public view. Two major categories of soft serve products, low fat and non fat soft ice cream and frozen yoghurt, attained amazing sales growth during the late 1980s because of intense consumer interest in the diet and health.

Common Defects and their Remedy

Defects may appear in ice cream due to following reasons:

•  Use of low quality ingredients
•  Improper mixing of ingredients
•  Faulty method of manufacture
•  Faulty method of storage and transport

 Quality of ice cream is judged for its delicate and pleasing flavour, smooth body and texture and attractive colour. The reasons for the development of defects in ice cream and the preventive actions to be taken to remove the defects are discussed in the following paragraphs.

i. Colour and appearance Defects and Preventive Measures:

i) Un-natural colour in ice cream develop due to following reasons:

•  Careless-ness in adding colour
•  Improper use of colour
•  Use of foreign materials

 ii) Uneven colour results if the colour is not added and mixed properly.

iii) Excessive colour is due to addition of too much colour.

To avoid any of the above colour defects in ice cream correct amount of colour should be calculated, added and mixed thoroughly. Also the added colour should reflect the flavour characteristic of the ice cream. Cleanliness and neatness of the pakages should also be carefully observed.

ii. Melting quality defects and Preventive Measures

i) Curdy melt down or curdled melt down: It indicates high acidity in the ice cream mix or the effect of any other factor which causes instability of milk proteins. This defect makes the consumer feel that inferior quality materials were used in the preparation of ice cream. The defect may be corrected by:

•  Using fresh dairy products
•  Avoiding use of any product that might disturb natural salt balance of the mix
•  Avoiding freezing of high acid mixes

ii) Ice cream does not melt: Ice cream shows resistance to melting, retains shape when warmed and takes longer time to melt. The cause and remedial measures of the defect are discussed under soggy body defecs.

iii) Slow meltdown: It indicates use of excessive stabilizer (over stabilization) or faulty processing of the mix. This condition may be corrected by taking the following measures:

•  Reducing amount of stabilizer
•  Using fresh dairy products
•  Homogenizing the mix at proper temperature and pressure

iv) Whey leakage: When ice cream melts separation of whey occurs. This defect may occur due to poor quality of ice cream mix or improper balancing of mix. This defect can be corrected by:

•  Using good quality dairy products
•  Balancing the constituents carefully
•  Using better quality stabilizer

v) Foamy meltdown: This is caused by incorporation of too much air in the ice cream during freezing (excessive over run). Hence the defect may be corrected by reducing the over run and reducing the amount of emulsifier or egg products.

iii. Body and texture defects and Preventive Measures

The body of ice cream refers to firmness and consistency while texture refers to the fineness of the product, which is dependent upon the number, size, shape and arrangement of ice crystals and other particles. The ideal body of ice cream is that which is produced by the correct proportion of milk solids together with proper over run and which melts fairly rapidly at room temperature to a smooth liquid similar in consistency and appearance to sweet cream containing about 40 % fat.

i) Crumbly body: It is a condition in which ice cream does not hold together properly. It lacks cohesion or breaks apart very easily. It is associated with low total solids content, in-sufficient stabilization, excessive over run, imperfect homogenization and large air cells. This defect can be remedied by:

•  Increasing the total solids content
•  Increasing the stabilizer
•  Decreasing the over run

 ii) Soggy body: Ice cream with a dense body and wet appearance is an indication of soggy body. It is due to a low over run, high concentration of sugar that lowers the freezing point, excessive use of stabilizer or delayed packaging of ice cream after freezing. This defect is also similar to other defects such as gummy, doughy, sticky, pasty and gluey. Excessive stabilization or high total solids content produce a chewy or gummy body while certain types of gums and syrups cause pasty or sticky body. Soggy body and other related defects contribute to high melting resistance. These defects can be corrected by:

•  Maintaining correct over run
•  Reducing the quantity of stabilizer
•  Use of a combination of stabilizers
•  Reducing the sugar content

iii) Weak body: Ice cream lacks firmness or chewiness and is invariably accompanied by rapid melting. This defect is due to low total solids content combined with insufficient stabilization. This defect can be corrected by:

•  Increasing the total solids content
•  Adding correct amount of stabilizer
•  Properly ageing the mix

 iv) Texture of ice cream: Ice cream having an ideal texture will be very smooth,i.e., the solid particles too small to detect in mouth.

v) Buttery texture: This defect appears in ice cream when lumps of butter- fat are detected easily in the mouth. This defect is due to high fat content, inadequate homogenization, mix entering the freezer at a higher temperature and partial churning of cream due to slow freezing. This defect may be corrected by:

•  Homogenizing the mix properly
•  Ageing the mix properly
•  Freezing the mix quickly

 vi) Coarse or icy texture: When the ice crystals are large or not uniform in size or that the air cells are too large in ice cream, icy texture is indicated. This defect is most commonly noticed in retailer’s shop. Large ice crystal formation in ice cream may be due to

•  Insufficient stabilizer
•  Slow freezing in the freezer
•  Slow freezing in the hardening room
•  Insufficient ageing of mix

 Formation of large air cells may be due to:

•  Type of freezer used
•  Use of mix of low whipping ability

Sometimes small ice particles are found in ice cream. These ice particles are formed when water droplets get into ice cream. This defect may be eliminated by

•  Increasing total solids in the ice cream
•  Increasing or adding correct amount of stabilizer
•  Freezing quickly and drawing ice cream at a lower temperature from freezer
•  Hardening ice cream quickly
•  Reducing storage period
•  Avoiding frequent heat shocks to ice cream

 vii) Fluffy texture: This defect is due to presence of large amount of air cells. It is due to incorporation of an excessive amount of air either as large or small air cells. This defect may be expected when the total solids content in ice cream is not more than one third of over run. When the air cells are large and the amount of air is excessive the texture is sometimes described as snowy or flaky. This defect may be removed by

•  Decreasing over run
•  Increasing total solids
•  Decreasing the amount of emulsifiers

 viii) Sandy texture: This defect is easily detected by the presence of rough sand like particles in mouth when ice cream is tasted. This defect may be due to presence of more non-fat milk solids, which contribute more lactose. Higher amount of sugar may also lead to lactose crystallization. This defect can be eliminated by

•  Reducing milk solids not fat content
•  Replacing part of cane sugar with other sweetening agents like dextrose, corn syrup etc
•  Maintaining uniformly low temperature during hardening and storage.

iv. Flavour Defects and Preventive Measures:

Ice cream flavour is essentially a blend of flavours from different ingredients used in its preparation. The dairy products and flavouring materials used have profound effect on the delicate flavour characteristics of ice cream. Any defect in these materials will therefore influence significantly the flavour of ice cream.

Defects due to flavouring materials:

i) High flavour: Excess of flavouring material will impart a sharp bitter flavour in ice cream. Poor quality flavouring material also imparts bitter flavour. This can be corrected by checking the quality of flavouring materials and adding correct amount to get the desired delicate flavour.

ii) Low flavour: It is due to insufficient amount of flavouring material. It requires addition of correct amount of flavouring material to overcome the defect.

iii) Harsh flavour: It is due to use of inferior flavouring substances. These substances or artificial extracts lack fine flavour . Also use of excess flavor cause this defect. Therefore correct quantity of superior flavours should be used.

iv) Acid flavour: This is caused by the presence of excessive amount of lactic acid. This can be corrected by:

 Using fresh dairy products

 Prompt and efficient cooling of mix

 Avoiding prolonged storage of the mix at high storage temperature.

v) Bitter flavour: This defect may be caused by the use of inferior quality ingredients. The defect may be controlled by:

 Using good / fresh extracts

 Avoiding use of dairy products stored for long time at low temperature as

certain type of bacteria produce bitter flavour under these conditions.

vi) Cooked flavour: This is caused by over heating the mix or using over heated concentrated dairy products. The defect can be prevented by:

 Carefully controlling pasteurization temperature

 Using concentrated dairy products without cooked flavour

vii) Flat flavour: This results from the use of insufficient flavours, sugars or milksolids. By adding required quantities of various ingredients this defect can be corrected.

viii) Un-natural flavour: This is indicated by the flavour not typical of ice cream.The defect can be controlled by using good quality dairy products and flavouring materials.Synthetic flavours that are not correct imitation of true flavours are also considered un-natural. Similarly flavours due to poor gelation, fermented syrups,over-ripe or under-ripe fruits and rancid nuts are un-natural. Therefore use of such ingredients should be avoided to control this defect.

ix) Oxidized flavour: This defect is also known as tallowy or cardboard flavor and results from use of old or stored dairy ingredients especially fat rich products.This defect can be remedied by use of fresh dairy products and pasteurizing the mix at slightly higher temperature than recommended.

x) Shrinkage: Besides flavour and body texture defects one another defect is also noticed in ice cream, especially in retail shops. Sometimes when well-filled packages are hardened and stored, the volume of ice cream shrinks leaving space either at the top or on the sides of the package. Cups then do not appear full. This defect is known as Shrinkage defect. The main reason for this defect to occur appears to be excessive over run in ice cream and too much fluctuation in storage temperature. Maintaining constant temperature during storage and avoiding rough handling during transportation will prevent this defect to a greater extent in ice cream