7 Dairy products All the ingredients included here are derived from milk or eggs. In biscuit manufacture their principal value is for flavour although there are also tenderising properties associated with the fats and emulsifying compounds which they contain. Milk, butter, cheese and eggs have been traditional ingredients for baking due to their exceptional nutritional values as well as their flavour. The technology of milk production has now developed to such an extent that there are a large number of distinct derivatives each with special value for the food industry. Only a few are commonly used in biscuit manufacture. 7.1 Milk Fresh milk is now rarely used in biscuits because of its short storage life, the tendency for the cream to separate and its large bulk (it has about 87% water). It is usual to use the dried products, either full cream milk powder (FCMP) or skimmed milk powder (SMP) or products where the water content has been reduced (condensed milks) because of ease of handling, good storage life and low moisture content. If it is decided to use fresh milk, thorough cleaning of containers and pipes is essential to avoid serious bacterial contamination and bad smells. The fatty nature of milk demands that detergent sterilisers are required. There are many cleaning chemicals specially prepared for use in dairies which allow CIP (clean in place) cleansing of pipe work and other equipment that would be tedious to dismantle and reassemble. 7.2 Full cream milk powder, FCMP This material is usually derived from whole fresh milk by a process of evaporation under vacuum followed by roller or, more commonly, 46 Dairyproducts 47 spray drying. It is important to control the maximum temperatures of the milk as it is processed as this affects both flavour and solubility of the resultant powder. Freeze drying techniques have the advantage of causing less damage to the proteins but the process is much more expensive and therefore rarely used. FCMP is now rarely used in biscuit manufacture due to its high cost and the limited storage life (up to six months) which is determined by rancidity development in the fat. FCMP, however, has an exceptionally pleasant flavour and when prepared mixed with sugar under special conditions of heating as a crumb, it is valuable for giving a distinctive flavour in the manufacture of milk chocolates and coatings. Storage in moisture-proof containers at 15°C will give a satisfactory product for about six months. To reconstitute the powder it is necessary to mix with about 3.5 parts of water to 1 part of FCMP. Dispersion is best if part of the water is used first to make a paste. 7.3 Skimmed milk powder, SMP When the fat is separated from milk for cream or butter manufacture, a white fluid, rich in lactose and proteins, remains. This is known as skimmed milk and may be concentrated and dried in a similar manner to FCMP. The flavour is strong and this powder is used in many ways during the manufacture of biscuits. The lactose is a reducing dissacharide which is only about 16% as sweet as sucrose but combines with proteins by the Maillard reaction, under appropriate conditions of heat, at the biscuit surface during baking to give attractive reddish brown hues and surface ‘bloom’. Thus, SMP has found widespread use as a minor dough ingredient both to give subtle flavour and textural improvements and to aid surface colouring. It is a rather expensive ingredient for these roles and the use of cheaper sources of reducing sugars (whey powder, glucose and invert syrups) have tended to replace it. If SMP is nor well dispersed in the dough, small lumps will appear as dark brown or black specks in the baked biscuits. This problem is normally overcome by dispersing the powder in some cold water before it is added to the mixer. Reconstitution requires vigorous agitation but a powder/water ratio of 1 : 2 is all that is needed. A similar procedure is required when FCMP is to be used in dough. The dispersed ‘milk’ will sour rapidly like fresh milk. Thus, dispersions of milk powder should be made daily and containers and other equipment which come into contact must be cleaned 48 Biscuit, cookie and cracker manufacturing manuals thoroughly. Storage in moistureproof containers at the optimum temperature of 15°C should maintain the SMP in good condition for at least twelve months. 7.4 Evaporated milks Some manufacturers find it more convenient to use milk in an evaporated form. Unsweetened condensed whole milk has a long shelf life if aseptically packed. High storage temperatures may cause a brown tinge to develop. Sweetened condensed milk, with 62.5% sugar, inhibits bacterial growth. 7.5 Whey powder Whey may be regarded as skimmed milk less the casein (protein). It is the liquid fraction obtained when milk is used for cheese production. Casein is coagulated by acids or enzymes and is separated with the fat to form cheese, leaving the whey. Whey is rich in lactose and minerals but also includes serum proteins, the albumins. Depending upon the type of cheese being formed, whey may be ‘sweet’ (from cheddar and Swiss type cheeses) or acid (for example, from cream cheeses). Whey is dried in a similar way to the other milk powders and because of its lower cost is now used extensively in biscuits in place of SMP. The function of whey powder in dough is very similar to SMP. Separation techniques have been developed which have allowed the preparation of lactose, demineralised whey and whey protein concentrate. Lactose is used where low sweetness and savoury flavour enhancement is required, but the mineral content of normal whey powder may contribute a salty flavour which is not as pleasant as SMP. Demineralisation reduces this saltiness. 7.6 Cheese and cheese powder The high cost of cheese determines that only those types with strong flavours like cheddar and Parmesan are commonly used in baking. In the fresh form there may be some incorporation problems in dough, and the dried powdered cheeses tend to have lost some flavour. Choice of fresh cheese should include attention to type and maturity Dairy products 49 characters as both have a strong effect on the flavour and baking performance. Cheese is one of the most acceptable and satisfactory basic savoury flavours for biscuits. This is because the flavour loss and change during baking is relatively small. It is, however, important to obtain the maximum effect of the flavour derived from cheese by paying attention to the salt, monosodium glutamate (if legally permitted) and acidity levels. The biscuit should always be slightly acid, best achieved with lactic acid additions and the cheese can be ‘extended’ with whey powder. Pepper and autolysed yeast prepara- tions compliment cheese flavour and there are also many synthetic cheese flavours which work well when used with some real cheese or cheese powder to back them. Cheese is rich in fat and protein which have shortening effects on doughs making it more difficult to maintain a good cracker structure. Most savoury biscuits are now oil sprayed immediately after baking. In some cases cheese or a cheesy flavour is dissolved in this oil, but this is not recommended because the oil taints conveyors, etc. and the oil lost to the bakery atmosphere can give a strong unpleasant and persistent odour. Cheese and cheese powders have limited storage life due to the fat content. Cool storage is necessary and great care should be given to good stock rotation. 7.7 Butter and butter oil These ingredients are dealt with in Section 6.1 on fats and oils. 7.8 Use of milk products in biscuits Milk, cheese and butter are used principally for their flavour benefits in biscuits. Unfortunately, the flavour and colour is variable due to the season of the year and the condition and feed of the cows producing milk. The melting curve of butter oil may be markedly affected and in extreme cases fat bloom may occur on biscuits made with all butter fat. From a quality control point of view the organoleptic properties of milk products are probably paramount in biscuit manufacture; thus, some degree of blending of different consignments of, at least, butters and cheeses will aid in maintaining uniform levels. Biscuits containing butter are often described in such as way that 50 Biscuit, cookie and cracker manufacturing manuals the purchaser’s attention is drawn to this fact. Labelling regulations usually demand that a certain minimum level is used in the recipe. For example, in the EC, butter biscuits must contain butter at least to the level of 7% of the dry matter and milk biscuits must have at least 2.4% of solid whole milk substances calculated on the weight of the dry matter. Due to their moisture contents butter and cheese can only be used in doughs. However, dried milk, cheese and whey powders are also useful flavour components in sandwich creams. The calcium salt of casein, caseinate, is a valuable protein supplement for high protein or other dietetic biscuits. A reconstituted milk, perhaps with the addition of some egg, is often used as a surface wash on dough pieces and this produces an attractive glossy colour after baking. If colour is the principal requirement it should be remembered that a solution of glucose or lactose will also perform well and costs rather less. Yoghurt, although valued as a ‘healthy’ food, finds little place in biscuits because of its mild and delicate flavour. 7.9 Eggs Due to the difficulties of cracking and subsequent handling of eggs, it is unusual to use whole eggs in biscuit manufacture. Whole egg material is, therefore, purchased either frozen or as a spray dried powder. Spray dried egg does not have the same physical characteristics as fresh egg. Egg is an ideal medium for the growth of microorganisms so great care must be taken to clean and sterilise utensils which come into contact with it. Pathogenic organisms, like Salmonella, are destroyed by pasteurising and all microorganisms are killed when doughs or batters are baked. Frozen egg has always been pasteurised. Thawing the frozen egg must be done carefully if the special characters of egg proteins are to be preserved. Overheating will denature the proteins. Thus it is normal to thaw frozen egg by placing the containers in cool running water for several hours. Egg yolk is rich in fat and lecithin and it is these components together with flavour that have made egg a good and traditional bakery ingredient. For most biscuits, eggs are too expensive and the fat and emulsifier can be obtained from other sources, but in batters for sponge types like Jaffa cakes and sponge finger (Boudoir) biscuits Dairyproducts 51 where a stable foam is required and the only other ingredient is sugar, the delicate taste of egg is still valued. The baking performance of whole liquid egg shows some variation and it is known that both frozen and dried eggs deteriorate in storage.