Principle and Methods of Manufacture

As compared to conventional butter (80% fat), low-fat dairy spreads have much reduced concentration of fat and correspondingly increased level of non-fat constituents viz. water and non-fat milk solids. This altered composition, together with additives, imparts the desired spreadability to the product. In case of non-dairy and mixed spreads blending of liquid and solid fats and the use of other ingredients results in the required plasticity properties. Further, the emulsification and fat-crystallization processes in spread-making ensure the desired body and texture characteristics. Thus, the formulation and processing of spreads generally determine the final product characteristics such as appearance, spreadability and keeping quality.

Processing basically comprises preparation of aqueous and fat phases and their mixing, emulsification, cooling/crystallization, working, filling, packaging and setting.Heat treatment is given to the separate phases prior to blending and/or to the blended mix. As there is a wide range of spread formulations and these could be either an O/W or W/O type emulsion, the processing protocol will largely depend on the type and level of ingredients to be used as well as the kind of emulsion desired. Accordingly, for most O/W type spreads homogenization of a hot spread mix using a pressure homogenizer or a colloid mill or a similar device followed by cooling and fat crystallization, whereas in order to obtain a W/O type spread the finishing steps are usually cooling, crystallization, working and pre-packaging or post-packaging setting. Thus, spread processing is specific to the finished-product formulation. An example of the spread-manufacturing method is shown in Fig.

Schematic Diagram of Manufacture of Low Fat Butter Spread

 

i. Preparation of the Aqueous Phase

Aqueous phase preparation involves dissolving/dispersing of water soluble ingredients namely, protein product, stabilizer, salt, etc. in water or the aqueous medium to be used. Blending temperature between 40-80°C is generally used for faster dispersion and solubilization of ingredients. Cultured buttermilk or synthetic flavour or starter distillate should be incorporated at the end of heating to minimize loss of volatile flavour. Treatments like pasteurization (75-95oC for up to 30 min) and cooling are commonly followed for the aqueous phase before addition/blending it into the fat phase.

 

ii. Preparation of the Fat Phase

Preparation of the fat phase involves melting of fat and mixing it with fat soluble vitamins and colour. Pretreatments of the fat phase depend upon the source or form of fat. Low-fat or medium-fat cream is often pasteurized as is the aqueous phase before being concentrated into a high-fat cream, if so desired, and cooled/precrystallized for blending with the aqueous phase. Phase inversion (O/W to W/O) may also be followed depending on the formulation. This can be achieved by using a continuous butter-maker or a ‘transmutator’ (worm cooler).

Butter- or Butteroil-based processes involve tempering (preferably to the emulsification temperature e.g. 21oC) before converting it into a spread. In a continuous method for low-fat spread-making, butter (80% fat) requires vacuum working, deaeration and warming before blending with the aqueous phase.In case of non-dairy or mixed-fat spreads, partial hydrogenation or interesterification of vegetable oils or their blends followed by refining, bleaching, deodorization, etc. is commonly practiced in preparation of the fat phase.

 

iii. Blending and Emulsification

Separately prepared aqueous and fatty phases are often blended to form a ‘pre-emulsion’. Such a premix may be subjected to heat treatment if the individual phases were not so treated. The heat treatment is then followed by cooling,crystallization, etc. Sometimes one phase, usually the pasteurized and cooled aqueous phase, may be continuously introduced into the pre-treated fatty phase during cooling or crystallization, thus combining the blending and emulsification steps.

Emulsification is carried out by means of a suitable agitating device such as a mixer or a churn, which may involve shearing action with or without simultaneous cooling.It ensures adequate distribution of the dispersed or discontinuous phase into the continuous phase.Homogenization, an emulsification method, particularly suitable for O/W-type spreads,is carried out after pasteurization / heating of the spread base mix. Two most important parameters of homogenization are temperature and pressure. Generally,a single-stage pressure of 5-36 MPa (50-360 bar) is used. In two-stagehomogenization, the pressure used is 7-18 MPa (70-180 bar) in the first stage and 3-5 MPa (30-50 bar) in the second. In general, homogenization of the spread mix is carried out at a temperature employed for pasteurization/heating. However, the temperature may range from 25o to 85oC. Homogenization can also be used for achieving phase inversion in spread-making. Emulsification can also be brought about by churning of cream either in a batch or continuous churn. Churning is often done at 14-16oC.

 

iv. Cooling, Crystallization and Working

Scraped surface coolers are used to achieve the water-in-oil emulsion. Such equipment also known by various generic names such as ‘Votator’, ‘Kombinator’ or ‘Perfector’ are cylindrical devices with a rotor/scraper housed in a double–walled tube provided with an evaporating refrigerant. These multifunctional units are used for carrying out cooling, crystallization and working. Solidification of fat into the desired crystal size and type is important for a smooth, plastic spread. The process of working ideally disperses the fat crystals throughout the emulsion and if the process is carried out satisfactorily, the product will be plastic and spreadable;if not, it will be greasy.