Issue link: https://www.e-digitaleditions.com/i/1325722
80 / January 2021 powderbulk.com PBE SUPPLIERS' TIPS How can I prevent an ingredient from smearing or building up during mixing? T here are several things that can cause buildup and smearing in a mixer. The first is that the mixer's construction materials and methods can contribute to a buildup of material. Avoid rough surfaces whenever possible. Basically, the smoother the surface the better, such as stainless steel in a food grade or sanitary finish or a coating such as Teflon that can be applied to the mixer. Also, try to select a mixer without sharp internal cor- ners to prevent buildup. Even with a smooth interior finish, mixer cleaning should be done on a regular basis. Quite often buildup in a mixer will be compounded if there's material in areas of the mixer that other material can stick to. Choosing a mixer that's appropriate to the mate- rial being mixed is important. Some mixers have high shear, which can introduce heat to the mix and can cause some ingredients to smear. Mixing at the right temperature for the ingredient is also important. Some ingredients can solidify on sur- faces at low temperatures and cause buildup, unless the mixer is heated. This problem is especially true of mixtures containing fats and resins. The placement and timing of liquid introduction to a dry mix is also important. The liquid should be introduced in an area within the mixer where the liq- uid sprays on to the surface of the ingredients being mixed and not the mixer's internal surfaces. The liq- uids should also be sprayed slow enough so they can be absorbed by the dry solids and not create a slurry that can stick to the mixer. When introducing a sticky ingredient into the mixer, make sure that it goes in after other ingredients, so the contact surface where the ingredient lands isn't the mixer's bare surface. Another thing to check is the clearance between the mixer agitator and the mixer walls. Some mixers are designed with scrapers to aid in keeping the mixer clean, but over time the scrapers, agitator, or both can wear and material can build up in the gap. Terry Stemler, president, APEC, 616-374-1000 P reventing materials from smearing, building up, or experiencing both issues on interior blender surfaces can be challenging, and, in most cases is unavoidable. These issues can be minimized by using a blender with low shear or through timing the order of material additions with your blend cycle, which may require experimentation. Material buildup on vessel interior surfaces can sometimes be minimized through the use of a jacketed vessel and using a heated or cooled surface. The temperature only needs to be 15°F or 20°F lower or higher than the normal operating temperature to make a difference in blend quality. Steve Schloemer, senior product specialist – APS, Eirich Machines, 847-336-2444 W hen handling soft or low-melting-point ingredients, the causes of smearing and material buildup are likely the result of fric- tion or applied pressure. An agitator with too much velocity can create fric- tion, which can soften or melt the ingredient and lead to smearing and buildup. In other equipment, such as a ribbon blender, these problems could be caused by pres- sure applied to the material as it contacts the blades or blender's walls. If I'm seeing issues, I'd slow down the agitator or shearing device and analyze the material. There are likely physical limits to the problem materials that weren't properly examined or researched. I've also seen this smearing and buildup problem with organic powdered botanicals. Customers thought the materials were dry, but they still smeared and built up on the agitator blades because the powder con- tained oils that weren't behaving as volatiles. A mois- ture test wouldn't reveal this issue and the material only required the agitator blades' velocity to release the oils and cause smearing and buildup. This oil usu- ally requires a similar solution to the first issue — slow down shear points and remove potential friction or applied pressure sources. George Paffendorf, technical director, Gemco, 732-752-7900