Spray drying technology for manufacturing egg powders
By: Ib Haugaard Sørensen Niro A/S, Copenhagen, Denmark
Benefits of Spray dried Egg Powders
The largest consumers of eggs have long recognized that shell eggs are unsuitable as raw material in a food industry geared to modernization. Frozen eggs have been found much more reliable and convenient. In the course of modernization, however, large egg consumers, faced with the need to further improve product quality and expand product varieties, had to reduce manufacturing costs. More efficient processing techniques were sought. This led to a fuller use of spray drying due to spray dried products being found a most suitable dry raw material for the food industry. The advantage to the food industry of spray dried egg products can be summarized as follows:
- Spray dried products are successfully handled in fully automated processing lines.
- Spray dried products possess more standard constant compositions and overall properties than any other previous form of egg products.
- Spray dried products are readily tailormade to meet required product specifications. This means it is possible to ensure the standardized properties of bakery constituents, an important aspect for mechanized product handling and packaging.
- Spray dried products are always ready for use. (They require no overnight swelling or melting etc.).
- The costs of product transport and storage are considerably reduced, and thus long distance and even overseas transport is possible.
The main users of egg products are bakeries, confectionery, macaroni, and noodle manufacturers, the meat handling industry, large scale catering, hotels, etc.
Spray Drying Process
The spray drying process enables removal of nearly all the water from a heat sensitive biological product like eggs in such a way that the valuable constituents are not only unaffected but even further refined. The basic feature of spray drying that enables this is the atomization of the liquid egg product into a spray of droplets that is dispersed into hot air. The spray has an extensive surface area and moisture evaporation is virtually instantaneous. Because of that the product temperature is maintained well below levels that cause potential heat damage and deterioration in the valuable properties of egg products.
Successful application of spray drying requires obtaining a spray of well defined characteristics (droplet size and size distribution) and optimum spray-air mixing through control of atomization, drying air properties and air distribution.
Atomization of liquid to form a spray can be achieved by several methods. Each one results in sprays of different characteristics. The most important ones utilize centrifugal pressure, or kinetic energy.
Rotary atomization based on centrifugal energy is the type of atomization that most readily produces the required characteristics for egg products. Sprays are formed from a rotating wheel. Atomizer wheels have the advantage of flexibility by successfully handling liquids of widely varying properties. Atomizer performance is controlled by the wheel diameter and speed of rotation. Values of the variables are selected according to the liquid product and required dried properties.
Careful selection of all processing stages and especially close control of the spray drying stage enable the meeting of desired dried egg properties. These include moisture content, particle and bulk density, particle size distribution, colour, baking and foaming properties, etc.
The spray drying process has been used for a long time within the egg processing industry, however, there are other methods of drying eggs. The oldest method is tray drying, which has been used for many decades to produce a so-called crystallized egg white. This has now been replaced by spray dried egg white, which besides the same excellent functional properties has a superior microbiological quality and is more ready-to-use. Some other drying principles than spray drying have been investigated recently, for example foam drying (inert gas is introduced in the feed prior to drying) and freeze drying (under high vacuum the water content of the frozen product is removed by sublimation). With the continuing advances in spray drying technology, it seems unlikely that these other techniques will replace spray drying in the future.