Composition

Ice cream is composed of a mixture of ingredients such as milk products, sweetening agents, stabilizers, emulsifiers, flavours, or egg products. The effect of these ingredients upon the finished product is influenced by the constitution of these ingredients. An ice cream mix is the unfrozen blend of the ice cream ingredients, and consists of all the ingredients of ice cream with the exception of air and flavouring materials. The composition of ice cream is usually expressed as percentage of its constituents, i.e. percentage of milk fat, MSNF, sugar, egg yolk solids, stabilizer, emulsifier and total solids. Its composition varies in different markets.

In developing the formulation of satisfactory composition, some factors which need consideration are: customer demands for flavour, body and texture and colour characteristics of the finished produce, i.e. natural or fortified flavour with artificial flavouring; chewy to heavy, higher overrun or more cooling effect characteristics.

Composition is also influenced by demands of customers, volume of operation,quality of ingredients and ingredient costs.Although the methods of processing and filling influence the characteristics of the mix and the finished product, the effect of constituents supplied by the ingredients is also important. Therefore, the role of each constituent is important in contributing to the characteristics of the ice cream.

i) Milk fat: It contributes a rich flavour to ice cream. It is a good carrier for added flavour compounds and promotes desirable tactual qualities. It is also essential to use the correct percentage of milk fat to balance the mix properly and to satisfy the legal requirements. Milk fat does not lower the freezing point.It tends to retard the rate of whipping. High fat content limits consumption, will increase the cost and increase caloric value.Generally, the fat content of a good average ice cream is considered to be 12%. The best source of milk fat is fresh cream. Other sources are frozen cream, plastic cream, butter, butter oil, and condensed milk blends.

ii) Milk solids-not-fat (MSNF): It includes the protein, the milk sugar lactose and the mineral matter. MSNF is approximately 36.7% protein, 55.5% lactose and 7.8% minerals. It contributes to the body and texture, and storage properties.It is inexpensive, high in food value and adds very little to flavour, except indirectly by improving the body and texture. Lactose supplements the sweet taste produced by added sugars. The minerals impart a slightly salty taste which rounds out the flavour of the finished ice cream. The proteins of MSNF make the ice cream more compact and smooth and tend to prevent a weak body and coarse texture.

However, excessive amounts of MSNF results in a salty or cooked flavor and soggy and sandy body and texture defect. A sandy body and texture defect is caused by high concentration of lactose. Although statistically it is impossible to state the limit of MSNF that may be used in ice cream mix, the following thumb rule is adopted to calculate the maximum MSNF content. Subtract from 100 the sum of the percentage of all the solids of the mix, except MSNF and divide by a factor of 6.4 to 7.4 depending on whether the turnover is expected to be rapid or slow respectively.

Thus, for a mix having 12% fat, 15% sugar solids and 0.3% stabilizer, the highest percentage of MSNF for expected rapid turnover (to be consumed within a week) would be

(100 – (12 +15+ 0.3) )/((6.4)(6.4)) =72.7 =11.36

This much MSNF can be added without possibility of getting the sandiness defect. Too high concentrations of MSNF may impart objectionable condensed milk flavour defect. Though MSNF increases viscosity and resistance to melting, it lowers the freezing point of the ice cream mix.

iii) Sweetener solids: Sweeteners are added to ice cream to enhance palatability and also to improve handling properties. The most common sweetener used in ice cream is can sugar (sucrose). The sugar is used in liquid or dry form. Of all the sweeteners available, sucrose imparts the most desirable properties.However, many good sugar blends are available. Blends of sucrose with low,medium or high conversion corn solids are also used to gain solids and maintain product properties and sweetness. The proportion of sweetening agent to be used along with sucrose depends on:

i. the total solid content of the mix

ii. the desired concentration of sugar in the mix

iii. the effect on the properties of the mix, such as viscosity, freezing point and whipping ability

iv. the concentration and relative sweetening power of the sweetening agent itself.

Lack of sweetness produces a flat taste while too much sugar tends to mask desirable flavours. Generally, 14-16% sugar seems most desirable. Sugars increase the viscosity and total solids concentration of the mix. This improves the body and texture characteristics provided the total solids content does not exceed 40%, or the sugar content does not exceed 16%. Beyond these limits the ice cream tends to become soggy and sticky. The sugars, being in solution,depress the freezing point of the mix. This results in slower freezing and requires a lower temperature for proper hardening.

iv) Stabilizers: Stabilizers are used to prevent the formation of objectionable large ice crystals in ice cream. They have high water holding capacity which is effective in giving smooth body and texture to the finished product. Besides, they prevent ice crystal formation in storage, give uniformity to the product, give desired resistance to melting and improve handling properties. The effect of stabilizers on flavour is indirect. They increase viscosity, have no effect on the freezing point and generally decrease whipping ability. The amount of stabilizers varies with its properties, with the solids content of the mix, with the type of processing equipment, and other factors.

Generally, stabilizers are added at the rate of 0.2 to 0.3% of the ice cream mix.Stabilizers commonly used are sodium alginate, CMC (sodium carboxyl methyl cellulose), guar gum, locust bean gum, carrageenan, gelatin, and pectin. It is not necessary to age the mix when sodium alginate is used. CMC produces a chewy characteristic in the finished period. Gelatin produces a thin mix and requires ageing period. Pectin is used alone or in combination with gums as a sherbet or ice stabilizer. Addition of excessive amounts of stabilizers results in soggy or heavy body and high resistance to melting.

v) Emulsifiers: Emulsifiers are used to produce ice cream with a smoother body and texture, to impart dryness and to improve whipping ability to the mix.Emulsifiers extensively used are monoglycerides or diglycerides, sorbitan esters and polyoxyethylene sorbitan esters (polysorbates). They are added at the rate of 0.1 to 0.4% of the finished product. Egg yolk solids are also used as emulsifiers. Excessive amounts of emulsifiers result in an ice cream having slow melting characteristics and body and texture defects.

vi) Total solids: Total solids replace water in the mix and, thereby, increase the viscosity, and improve the body and texture of ice cream. Addition of sweet cream butter milk solids, dextrin and eggs significantly improves the body and texture of ice cream. However, the total solids content should not be too high.When it is above 40-42%, a heavy, soggy product is obtained.

vii) Water and Air: Ice cream is a physico-chemical system having a gas (air) dispersed in a liquid (water), a solid or a mixture of liquid and solid. Thus, a partly frozen emulsion with ice crystals and solidified fat globules embedded in unfrozen water phase constitute a continuous phase. The source of water in ice cream mix is mainly from fluid dairy products or added from the water supply.

The amount of air in ice cream is important because it influence quality, profits and legal standards. In order to maintain quality, it is important to have a uniform amount of air. Studies have been conducted on gases other than air in ice cream. It has been found that addition of finely shredded solid carbon dioxide to ice cream during the manufacturing process helps in obtaining an improved, very acceptable product.

viii) Flavour and Colour: Flavour is generally considered the most important characteristic of ice cream. The kind of flavouring material to be added is influenced by the quality of the ice cream mix since slight off-flavour can obscure the delicate flavour of the flavouring material to be added. Local preference of the consumers will determine the type and intensity of flavour to be added.Natural and synthetic flavour substances are available for the flavouring of ice cream.

Ice cream should have a delicate, attractive colour which can be readily associated with the flavour. Most colours are of chemical origin. Colours are available in liquid of powder form. Most ice cream manufacturers prefer to purchase dry colours since these are more economical and can be dissolved in boiling water as needed.

The chemical composition of ice cream differs mainly with regard to fat content and three grades of ice cream can by usually found in most market areas in the US. One grade just meets the minimum fat content, and usually contains relatively inexpensive flavour ingredients. At the other extreme are the so called premium ice creams that are high in fat, low in overrun, and usually contains natural flavours. Representative formulae for these grades are given in Table below.

The composition of ice cream varies in different regions and different markets.Generally, a good ice cream contains 12% fat, 11% milk solids-not-fat (MSNF),15% sugar, 0.3% stabilizer and emulsifier, and 38.3% total solids. One serving of a good ice cream of average composition (100g) supplies approximately 200 cal, 4 g protein, 0.13 g calcium, 0.105 g phosphorus, 0.1 mg iron, 490 IU Vitamin A, 0.38 mg thiamine and 0.24 mg riboflavin.

Representative formulae for ice creams of different grades (%)