The main value of using ingredients derived from milk in the manufacture of sugar confectionery is to add flavour. A secondary effect from the presence of the milk solids is the development of body through chemical interaction between the milk protein and reducing sugars.
Most types of milk will produce this effect. The critical factor in choosing a variety to use is the amount of water present in a particular ingredient.
Milk taken from the cow contains some 88 per cent water while comparable figures from other mammals range from 86 to 90 per cent.
This high level of water has to be removed during manufacture and this involves prolonged cooking.
Extended process times lead to excessive inversion of the sugar and to the discolouration of the mix.
This problem can be overcome by the use of condensed milk which may or may not contain a large amount of a sugar as a preservative. The usual grades are :
(i) evaporated milk ( no added sugar )
(ii) full cream sweetened condensed milk
(iii) skimmed sweetened condensed milk.
The difference between the types of milks listed under (ii) and (iii) is in the amount of fat present in the ingredient.
Typical water contents reported for the three grades are 67 per cent - 25 per cent and 27 per cent respectively.
The content and type of milk protein is important as it is this component which under appropriate conditions - combines with reducing sugars to develop flavour and colour.
the added sugar present in both full cream and skimmed sweetened condensed milk is cane or beet sugar. A typical addition is 56 per cent.
This added sugar (sucrose) to "doctor" solids is balanced in a recipe.
Note:- "doctor" sugars are those sugars which inhibit crystallisation.