Whey has very high nutritional value. Consequently, the use whey powder and whey fractions as nutritional supplements as well as ingredients in foodstuffs for human and animal consumption have been constantly growing regardless of the quite troublesome processing steps. Today, whey is an important and valuable product for the dairy and cheese-making industries.
Whey can be categorized into two main groups, namely sweet whey and sour whey - both types can be spray-dried but requires different types of spray dryers as well as different handling techniques. The drying system can vary from the very simple to highly sophisticated depending of the quality of the feed and well as the required use. Anyway, sweet whey (a.k.a. cheese whey) is easier to dry than acid whey. The following processing steps are normally used (required) to manufacture of whey powder:
This process requires the following unit operations / processes: preheating, concentration, spray drying and pneumatic cooling (in a vibrating fluid bed).
Ordinary whey powder obtained by this process is fine, dusty, hygroscopic and therefore caking. Hygroscopic and caking are influenced by the type of whey and by local climatic conditions. The stickiness, caking and the associated problems of normal whey powder are mainly due to lactose being present (and that in an unstructured crystalline condition).
In the spray drying of milk products, lactose is in an amorphous state and is not stable in normal humidity and atmospheric air. Only the a-lactose monohydrate form of lactose that is stable to humidity. Since the lactose content of whey powder comprises more than 70% of the total solids in comparison with 30% in whole milk the problem of the lactose content in whey powder is more severe. Anyway it is possible to steer the drying process in a way that enable the majority of the lactose to be transformed to the stable a-lactose monohydrate.
The basic process layout is modified by conducting a pre-crystallization before spray drying.
During the pre-crystallization process, it is easy to keep ideal conditions for crystallization. Viscosity of the concentrate is reasonably low, temperatures may be exactly adjusted and controlled, displacement of used solution from the surface of crystals may be accelerated by agitation, and the required amount of suitable crystals of lactose may be ensured by proper seeding. Furthermore, there is normally sufficient time for the pre-crystallization process so reach the optimal (theoretical) degree of crystallization. The product made by this process is non-caking and, being agglomerated, is dustless and free flowing. The agglomerates tend to be small and thus the bulk density is relatively high.
The drying chamber with integrated fluid bed should be fitted with pressure-release vents and a fire-extinguishing system. Cyclone, bag filter and the external vibrating fluid bed should have similar safety features. A new alternatively is the advanced Integrated Filter Dryer - IFD. Niro has further developed and refined the successful MSD dryer by the addition of the CIP-able SANICIP bag filter. The location of the bag filter assembly inside the drying chamber improves powder quality and enables better powder recovery and cleaning (CIP). The combination of the integrated fluid bed and filter arrangement simplifies powder handling, because the need for external cyclones, bag filters, and fines recycling has been eliminated. The compact design reduces the amount of equipment in contact with the product.
If you have the choice - normally you have the whey look for ways to value-add. Anyway, the choice of process depends upon the type of whey available, the intended market (human or animal feed) for the whey powder and the plant location. The ability to handle sweet whey and yet produce a non-caking product enables the use of a less complicated system compared to a sour whey processing plant. If the dried powder is intended for dry powder mixes, the flowability is essential and the process must be equipped with crystallization and cooling stages to guarantee that these properties are achieved. Local climate conditions (and seasonal changes) should also be considered. If the climate is very humid, it is advisable to use a process that produces a less hygroscopic product with low caking tendencies.
For information about fractionation of whey please access this page: http://www.geafiltration.com/glossary/filtration_terms_f.asp
US Patent References:
|3345683||Oct., 1967||Eirich et al.||23/313.|
|3711254||Jan., 1973||McGowan et al.||23/313.|
|3819332||Jun., 1974||Jaccard et al.||159/11.|
|4490403||Dec., 1984||Pisecky et al.||159/DIG.|
|4629771||Dec., 1986||Candlin et al.||526/125.|
For information about Lactose crystallization and early Maillard reaction in skim milk powder and whey protein concentrates please access this page: http://publications.edpsciences.org/articles/lait/pdf/2005/03/L05S4507.pdf
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