Sweet whey products. Also referred to as cheese whey, it is produced during cheese-making, when rennet is applied. This group forms a large family of products with very similar composition, whereas their properties are very different. The pH value of sweet whey can range between 5.2 and 6.7
Sour whey products. These may include acid whey, quark or cottage-cheese whey and sour sweet whey. Acid whey, also known as casein whey, originates from the manufacture of casein by means of lactic acid and hydrochloric acid. The origin of quark or cottage-cheese whey is self-explanatory. Lactic acid created through natural fermentation gives the whey a high acidity. The pH values of this group range from 3.8 to 4.6. If insufficient care is provide to the cheese whey, natural fermentation makes it sour. This process is obviously undesirable since soured (not sour) whey is not considered a natural product
SPRAY DRYING WHEY PRODUCTS
Whey products can be spray-dried, but do, however, require their own handling techniques. Layouts for spray-dried whey may vary from simple to sophisticated. Generally speaking, sweet (cheese) whey is easier to dry than acid whey. The main operations used for the production of whey powder are as follows:
Preheating
Concentration
Flash cooling
Pre-crystallization
Spray drying
Cooling in a vibrated fluid bed
SPRAY DRYING WITHOUT CRYSTALLIZATION TREATMENT
This process consists of preheating, concentration, spray drying and pneumatic cooling.
Whey powder obtained by this process is very delicate, dusty, hygroscopic and therefore caking. Hygroscopicity and caking are influenced by the type of whey and by local climatic conditions. The hygroscopicity, caking and all the problems associated with the stickiness of ordinary whey powder are mainly due to the presence of lactose in the amorphous state.
Lactose is in an amorphous state and unstable in atmospheric air or normal humidity, during the spary drying process. The a-lactose monohydrate is the only form, which remains stable when encountering humidity. The lactose content of whey powder comprises more than 70% of the total solids in comparison with 30% in whole milk, which makes the problem of the lactose content in whey powder is more severe. However, since the solubility of lactose is 17 g/100 cm3 H2O at 20°C, it is easy to guide the drying process in such a way that a majority of the lactose can be transformed to the stable a-lactose monohydrate form during the drying process.
