Powders (Milk, WPC)
Several methods of analysis can be used during the production of powders such as near infrared (NIR), image and wet chemistry analysis. Dairy powders consist of many different product sources. Basic dairy powders include WMP (Whole Milk Powder), SMP (Skim Milk Powder), MPC (Milk Protein Concentrate), whey powder, WPC (Whey Protein Concentrate), butter milk powder etc. Whey and WPC (Whey Protein Concentrate) powders are derived from the whey by-product in cheese manufacturing. WMP is manufactured by concentrating and drying whole milk. These powders are high in fat and protein. SMP is the product of concentrating and drying skim milk. The milk is skimmed to take the cream off, generally for butter manufacturing or other cream based products. These powders are low in fat and high in protein. MPC is produced from skim milk with the protein concentrated, typically by membrane filtration. Whey and WPC by-products from cheese making are concentrated and dried.
WPC has the protein concentrated by membrane filtration. Basically the valued constituents, specifically protein, are recovered from process by product streams and used in other food/dairy manufacturing. In order to economically ship these products, and to extend the shelf life, the water is removed. Typically water above 4% in a dried product significantly reduces the shelf life. So, the goal is to dry the product to the specified target but not too dry because of costs: loss in revenue due to volume/weight and the cost of energy for drying.
The control of the target moisture is the most important parameter in the analysis of dairy powders. Other constituents of interest include protein, fat and lactose. Lactose may also be removed by membrane filtration.
Since the products that need to be dried consist mainly of water, the water must be reduced before drying. Evaporators have been used to remove most of the water by heat. More recently, the water is being removed by membrane filtration. This technique uses much less energy to remove the water. The concentrated product is then fed to a dryer and sprayed into a heated air flume. This heated air removes the moisture to a much lower level (<4%) to produce a powder.
Currently, dairy powder manufacturing companies are either performing no analytical testing or are using time consuming methods that do not provide “real time” analysis. Much of the control is based on process parameters i.e. temperature, flow rates and other process conditions.
Moisture content is analyzed as the product comes out of the dryer using a variety of methods. Primary methods to analyze moisture include an oven method or a moisture balance. Both methods use loss on drying to measure moisture content. The drawback to the vacuum oven method is that the testing time is 5-16 hours, meaning this test will have no impact on real time process control. The moisture balance can analyze a sample in approximately 15 minutes, but it almost 2-3 times less accurate than a vacuum oven.
The Unity SpectraStar 2400 provides a NIR solution for improving the analytical testing methods at the dairy powder manufacturing plant. NIR is a fast, safe, and reliable technology that will rapidly analyze the product in various stages of the process. NIR is a secondary technique and is calibrated by analyzing a set of known samples. The SpectraStar 2400 can be used to analyze powder in the different stages of the dryer, and for moisture, fat, protein and lactose in the finished product. Analysis time is approximately 30 seconds per sample. This speed can provide “real” time results necessary to properly control the process.
The SpectraStar can measure moisture at similar accuracy to the oven test or moisture balance that it is calibrated against. Typical performance of the SpectraStar 2400 for moisture analysis when calibrated against a vacuum oven that is working properly is approximately 0.10%.