BUTTER AND GHEE
There are four types of butter that can be made from fresh or fermented milk, from cream, or from the whey that remains after cheese making (Table 1). Butters are made by separating the fat in milk. They contain more than 80% fat with a small amount of water dispersed through the fat as tiny droplets, which are so small that the butter looks dry. Butters have a pale yellow/cream colour, and a smooth consistency so that they spread easily and melt in the mouth. They are used as spreads, for cooking, or as bakery ingredients. Heat is used to destroy food poisoning bacteria and most spoilage bacteria. The heat also inactivates some of the enzymes in the cream. Secondary preservation is due to the low moisture content, by keeping the butter cool and packaging it so that it cannot become recontaminated by dirt, insects or micro-organisms. This also slows the development of rancidity.
Ghee is a golden oil or fat (depending on the room temperature), made from cow’s or buffalo milk. It has a high demand in some countries as domestic cooking oil and as an ingredient for bakeries. It is made by heating cream to boil off the water and then filtering out the solidified proteins. Ghee is preserved by a combination of heat, which destroys enzymes and contaminating micro-organisms, and by removing water from the oil to prevent microorganisms growing during storage. It has a long shelf life if it is stored in a cool place, using airtight, lightproof and moisture-proof containers to slow down the development of rancidity. Further details of the principles of preservation are given in Technical Brief: Dairy Processing – an overview, which is intended to be read alongside this Technical Brief.
Type of butter
Lactic (or ‘cultured’) butter
Made from soured milk or cream, may be salted or unsalted. Slightly acid taste
Fresh (or ‘sweet’) butter
Made from cream, may be salted or unsalted, mild creamy flavour
A clear golden brown oil with a characteristic flavour of milk fat, made by heating cream to remove the moisture and filtering out the solids.
Made from whey separated from curd during cheese making. It is strong tasting with a slight cheesy and slightly acidic flavour. It can taste salty if salt is added to the cheese before the whey is drained off. It is less shiny than fresh butter, more oily, and with a deeper yellow colour.
Table 1: Types of butter (Adapted from Dairy Science and Technology Education).
Most butters contain about 16% water, and any contaminating micro-organisms are found in the water droplets. When salted butter is made, the salt (1-2%) dissolves in the water droplets, so the effective salt concentration is approximately 10% in the water. It acts as a preservative to improve the shelf life by suppressing the growth of any micro-organisms that are present, and also improves the flavour.
Methods of processing
Fresh milk is first separated into skim milk and cream and the cream is then used to make fresh butter or ghee. These processes are described in more detail below. To make lactic butter, milk is fermented to yoghurt (see Technical Brief: Soured milk and yoghurt), and this is then churned as for fresh butter. Whey has a butterfat content of 3.5 – 8.75%, depending on the type of cheese being made (see Technical Brief: Cheesemaking). It may also contain residual starter culture from the cheese whey. The process is similar to that used to make fresh butter.