Blending and Processing Nutrient Premixes

Blending and processing techniques can make the difference between producing a reliable, high quality, homogenous, shelf-stable nutrient premix and an inferior one that may cause poor consumer confidence, potential regulatory issues or recall situations. Particle size, blending equipment used and the type of ingredients used are primary blending and processing considerations, as are potential ingredient interactions.

The challenge in blending ingredients with different particle sizes is that bulk density and variable particle sizes can lead to segregation. Therefore, minor nutrients should be diluted with another carrier to get the two different materials to blend well in order to make a homogeneous product. In the nutraceutical and functional food industries, combination products are the norm, and the most common nutrients are vitamins, minerals, amino acids, nucleotides and other functional food ingredients offered in singleserving powdered products—tablets or capsules. The average premix formulation contains at least 10 to 14 active nutrients and three to six functional ingredients, or carriers (excipients). Some formulations contain more than 30 active nutrients and carriers.

To comprehend the challenges when producing a homogeneous, correctly-proportioned blend of these active ingredients, imagine trying to create a uniform blend of one spoonful of granular sugar, three spoonfuls of flour and five spoonfuls of rice—then add to that blend a one-half teaspoon of salt and a quarter spoonful of color. Presuming success in combining these ingredients into a homogeneous blend, the next challenge is compressing small amounts of the blend into a capsule/tablet or serving of a nutritional product.

There are basic steps to follow when dry-blending a multipleingredient formula to make a homogeneous premix:

• Test all active ingredients for identification and potency limits. If raw materials are not tested prior to use, it may be difficult to determine whether a problem with the final product is related to blending or to the ingredients.
• If possible, render all ingredients free-flowing. This can be done with milling, particle coating, granulation, making preblends, tituration, spray drying and other techniques.
• Purchase ingredients that have consistent particle size distribution or that have a narrow range of variation.
• Screen lumpy or cohesive ingredients as you add them to the blender. It will reduce agglomeration during mixing.
• Always add a portion of the largest quantity ingredient to the blender first. It will coat the blender and prevent lesser ingredients from sticking to the walls.
• Before adding small-quantity active nutrients to the blend, be sure that each one is geometrically diluted to prevent loss from ingredients adhering to the blender wall or because the material had not been dispersed enough for uniform blending. Never add ingredients that account for less than one percent of the total blend into an empty blender.
• When using a V-type blender divide the ingredients into equal parts, and then add one portion to one side and the other portion to the other side. This improves distribution, blending time and the level of fill in the vessel, all which play critical roles in determining the adequacy of blending.
• Finally, take adequate samples from the top, bottom and center of the blender. List at least three of the lower potency ingredients to determine the adequacy of the blend. Take samples again after discharge to identify any segregation that may have occurred during material transfer.

Most experts on formulation agree there is no exact science to blending powders that are part of the finished product and that will work for every product. However, blending powders is very different from blending liquids. Where over-blending is almost impossible, powder-to-powder blends can be “un-mixed” when particles segregate. There are two common blending processes employed in the nutraceutical/dietary-supplement industry to achieve a homogeneous product: dry-blending and wet-granulation. Dry blending is the most common method used to manufacture premixes. A critical aspect of dry blending is the physical make-up of powders— including flowability, particle size, shape and density.

The incorporation of nutrient premixes in food fortification is an essential element in nutrition strategies to alleviate micronutrient deficiencies. It is a dynamic area developing in response to the needs of population groups and global industries. Efforts should continue to develop new systems of delivering micronutrients to target populations through appropriate fortification procedures. To facilitate this, those involved in the establishment of food fortification programs must have ready access to information concerning fortification techniques and procedures being used all over the world. A multi-disciplinary approach is essential for successful fortification based on active collaboration with all parties involved. Adequate monitoring of food fortification is essential and should include both monitoring of critical control points in both the production and distribution of fortified foods, and the strict monitoring of micronutrient status for target populations.

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