There are a number of ways to apply liquid coatings to foods and pet food. Using the right liquid coating equipment solutions for your coating type and product can improve product quality, and reduce waste, maintenance expenses, and downtime. In this blog post, we’ll discuss different liquid coating equipment solutions.
Comparing and Contrasting Liquid Coating Equipment Solutions
As extruded products move through a screw conveyor, they can also be coated. This requires the use of spray nozzles over the screw conveyor. However, the spray nozzles actually coat a relatively small portion of the product. This means the coating relies on mixing action to properly and uniformly coat the product. Spray liquid coating equipment solutions using screw conveyors don’t provide much mixing action and comparatively little retention. Reducing the screw conveyor flights or using ribbons in place of solid flights can improve the mixing action. Paddles with a slight pitch between the ribbon flights will move the product in the opposite direction of the conveyor, which can also improve the mixing action.
The rotating drum is a common liquid coating equipment solution in food and pet food production. With this method, the product tumbles through a tilted drum, across raised flights on the inside. This system provides the unique advantage of adjustable retention. The drum also eliminates pinch points, which can cause fragile products to break. However, this method also has some disadvantages. Similar to the screw conveyor, the rotating drum requires mixing action to work. By putting the spray nozzles into a plenum prior to entry into the drum, this process can be improved.
The previous systems all use spray nozzles to coat the product. Systems using spray nozzles have a number of challenges. Spray nozzles can easily clog, especially when working with coatings with heavy fats, oils, sugars or salts. Liquid coating equipment solutions that bypass spray nozzles can avoid many problems resulting from clogs. Rotating disk applicators like the Mistcoater use spinning disks to apply liquid to the product. The liquid coating drops onto a disk spinning at a high RPM, which atomizes it into a fine mist and covers the product. This method not only provides uniform coating, but also requires less maintenance.
These liquid coating equipment solutions are usually located just before load-out or packaging. These mixers used paddles, or a combination of ribbons and paddles to move coatings over the material. This allows the product to move through the mixer quickly without getting damaged. A vacuum can also be drawn on this mixer, allowing it to draw the air out of the product and then draw liquid into the product when the vacuum is released. With this system, it’s also easier to add a light level of liquid to the product. The disadvantage is that this system requires more headroom, and it can be expensive.
Each of these methods has advantages and disadvantages. Finding the right liquid coating equipment solutions means finding a good fit for your product, coating, and the rest of your existing equipment. Work closely with your system engineer and provide as much information as possible about the coating and materials you’re working with. This will help you to optimize your system.