Common Recall Risks in Pet Food Processing: Part II

common recall risks in pet food processing

In our previous post, we discussed a number of recall risks in pet food processing, including bacteria, chemicals and heavy metals. In this post, we’ll discuss additional recall risks affecting the pet food processing industry. This includes two of the most common and most dangerous recalls risks; mycotoxins, specifically aflatoxins, and trace mineral inaccuracies.

Common Recall Risks in Pet Food Processing

Mycotoxins, Storage and Testing

Bacteria and chemicals are not the only recall risks in pet food processing. Mold toxins are another common cause of recalls in pet food processing. Molds that grow in a wide variety of grains, seeds, nuts and grasses produce mycotoxins, which are toxic to animals and people. The most harmful among these are aflatoxins, potent carcinogens and mutagens commonly affecting corn. Effects of aflatoxicosis include liver damage, liver failure, cancer, and an inability to process or metabolize nutrients, among other effects. Due to their high toxicity, the acceptable level of aflatoxins set by the FDA is low, at 20 parts per billion for human and pet foods.

Aflatoxins Thriving in Dry Weather

Aflatoxins are common in corn and can be found in a wide variety of products using corn-based ingredients. These toxins are also very difficult to manage, and continue to be a source of recall risks for pet food processors. According to the FDA, “In 1998, 2005, 2011, and 2013 aflatoxin
contamination of dog and cat food resulted in illness, dog mortalities, and extensive recalls of
affected dog and cat food.”

While many harmful molds and toxins proliferate during warm, humid, wet conditions, aflatoxins are particularly difficult to manage because of their unusual tendency to thrive during hot, dry conditions. Aflatoxin risks are high in 2020 due to hot, dry weather across regions with high corn and grain production. Other damaging incidents, such as wind storms, hail and insect damage has made crops more susceptible to aflatoxins.

Relationships With Suppliers Are Key

This pet food recall risk is also difficult for pet food processors to manage. Aflatoxins are resistant to operations like cooking, which kill other contaminants. Reducing the risk of aflatoxins mostly falls on grain harvesters and suppliers. Improper storage, testing, drying and handling before and after harvest can cause grains contaminated with aflatoxins to enter the pet food supply chain. Pet food processors with a high level of vertical integration and supply chain management and visibility may have the best opportunity to mitigate this problem. Other pet food processors must take care to test ingredients for toxins and maintain close partnerships with reliable suppliers. Facility managers must also take care to prevent ingredient mixing; mixing clean grain or ingredients with contaminated ingredients is not a sufficient solution to reduce the level of aflatoxins.

Trace Minerals and Inaccurate Recipes

Both humans and animals require a number of trace vitamins and minerals for optimal health. Pet food processors may use mineral powders or liquids to give pet food the trace minerals and nutrients that animals need to stay healthy. Trace vitamins and minerals may come from organic or inorganic sources. The source can impact whether or not the substance can be effectively absorbed. In many cases, an inaccurate recipe can make pet foods harmful to pets, either by using too much or too little of an ingredient.

A Careful Balance

B-complex vitamins, including B-12, riboflavin, niacin, pantothenic acid, thiamine, pyridoxine, and biotin, all effect metabolism, nervous system function, and skin and fur health. Trace minerals, like zinc, manganese, copper, selenium, iodine and iron, play a variety of roles in an animal’s metabolic system, nervous system, immune system, joint and bone health, and much more. All of these vitamins and minerals are required in very small amounts. However, a deficit will start to weaken essential function. Unfortunately, an excess can also cause health problems.

Excessive vitamin D levels are one cause of recalls in pet food processing. In small amounts, vitamin D is essential for absorbing calcium and phosphorus. It’s particularly important for supporting muscle and bone growth in young animals. However, too much vitamin can be toxic, causing illness, kidney failure and death. Many other trace vitamins and minerals have similar, very narrow requirements.

The Importance of Accurate Formulation

Accurately measuring macronutrients is easier, since the tolerances tend to be wider. However, ensuring the right mix of trace nutrients requires careful ingredient understanding, as well as a highly accurate distribution system. As previously mentioned, the organic or inorganic source of the ingredient will play a role in how it is absorbed and how it reacts during processing. Thiamin, for example, can be easily destroyed during some cooking processes. In other cases, an trace mineral may appear in the formula, but the animal cannot actually absorb the inorganically-derived substance. All of these aspects, and many more, play a role in the optimal recipe.

With the right vitamins and minerals selected, a reliable micro ingredient system is also essential. Using too much or too little of these ingredients can have deadly consequences, so it’s essential to keep weighing instruments well-calibrated. Automation at this stage can also help to prevent costly errors, and ensure that a recipe is consistent. Integrating a tracking and tracing system is also important. This way, if an error occurs and a lot contains too much of a trace ingredient, it can be removed or recalled more easily.

Food recalls in pet food processing can come from many different directions, just like recalls in food processing for humans. It is impossible to account for all of these risks 100% of the time. Even the most detailed testing and sanitation procedures can leave invisible toxins, microbes, and chemicals untouched. This is why preventative as well as reactive measures are necessary. Preventive measures, like detailed maintenance, proper equipment design, testing, and hazard analysis and help to stop risks before they start. When contamination does occur, reactive measures like tracking and tracing, and recall procedures will help to reduce harm.

Common Recall Risks in Pet Food Processing: Part I

recall risks in pet food

Even when recall procedures are well-practiced and well-known throughout the company, a recall is still a turbulent time. Sometimes recalls take place due to improper sanitation procedures or a lack of testing, and other times it may simple result from an unfortunate accident. Food for human consumption as well as animal consumption can all face recalls. Understanding the biggest recall risks in pet food processing, and how to mitigate these risks, can help you avoid these instances.

Common Recall Risks in Pet Food Processing

Bacteria and Improper Cooking

Bacteria present perhaps the biggest recall risk in pet food processing, just like food for human consumption. A number of bacteria can harm pets in similar ways as humans, though the risk of human infection from handling pet food is much higher. This is one of the reasons that pet food and food for humans are held to similar sanitation standards.

Just like food for human consumption, pet food is also susceptible to contamination from Salmonella, Listeria, and E.Coli bacteria, the most common causes of contamination and food recalls. Cooking at high temperatures generally destroys these bacteria and makes pet food safe for consumption. However, a number of things can go wrong. Fats and oils can create safe pockets for bacteria during this process, ovens may not reach the right temperature, or contamination can occur at other points during the process.

Wet pet food or treats often contain raw ingredients as well, which presents greater risks of foodborne illness. However, all types of pet food can be susceptible to harmful bacteria. Maintaining and verifying proper sanitation procedures, hazard analysis, testing, and recall procedures can help to mitigate the risk of a bacteria-related recall in pet food processing.

Chemicals and Contamination

One of the most well-known and widespread pet food recall cases was the melamine-related recall in 2007. Thousands of pets around the world sickened and died during this time, and the cause eluded researchers for weeks. The pets showed signs of kidney failure, though the chemical responsible for the illness, as well as which pet food brands were affected, was difficult to pinpoint.

Tracing the Cause

The cause of the widespread illness was ultimately found to be contaminated wheat gluten, rice protein and vegetable protein. These raw materials made their way into many different pet food types and brands, making it difficult to trace and stop the spread. The ingredients were contaminated with melamine, an industrial chemical, and possibly cyanuric acid. Melamine has many uses, including an industrial binding agent, flame retardant, and even a fertilizer. However, the presence of melamine and cyanuric acid caused kidney failure in pets.

How melamine and cyanuric acid got into pet food remains uncertain. Accidental chemical contamination during the processing of wheat gluten, rice protein and vegetable protein may have occurred. Since melamine, cyanuric acid and other additives can increase the apparent protein content of these ingredients, the contamination may have been deliberate, though the effects were unexpected.

Challenges in Detection

Testing is one way to prevent chemical contamination through raw ingredients. Ingredient testing can show the presence of many other contaminants, though it is more difficult with melamine. In testing, melamine mimics the appearance of protein, so it is difficult to detect. With difficult contaminants like this, effective tracking, tracing and recall measures are vital.

Heavy Metals and Pollution

Heavy metals such as arsenic, lead, cadmium and mercury are also causes of recalls in pet food processing. In very small amounts, heavy metals are not necessarily toxic, and may even be helpful, as many trace minerals are. However, in higher concentrations, heavy metals are highly toxic and can have many negative health effects. The FDA provides maximum allowable concentrations of these metals to inform testing and recall procedures.

Bioaccumulation and Heavy Metals

In some cases, heavy metals may find their way into pet food from outside sources, such as paint chips or chemicals. In many cases, however, heavy metals enter pet food in the same way that they enter food for human consumption. This is generally through polluted air, water, and soil. A number of industrial processes generate arsenic, lead, cadmium and mercury as byproducts, which then make their way into the air through smoke and ash, water through effluent, and into soil through dumping or through the water cycle. Vegetation absorbs these metals, and transfers them to other animals, including chicken, beef, and fish. These metals then transfer up the food chain and accumulate inside predatory animals. When heavy metal concentrations are particularly high, accumulation speeds up and can sicken animals faster.

While humans generally consume a wide variety of meats, grains, fruits and vegetables, pets often consume the same ingredients throughout their lifetime. Since pets, like humans, cannot process larger doses of heavy metals, the elements build up in their system over time (bioaccumulation). Toxicity builds up until it creates health problems. When pet foods do not contain high levels of heavy metals, this generally does not impact pets until much later in life, if at all. However, high levels of heavy metals can cause health problems quickly.

Preventing Heavy Metal Toxicity with Testing

The process of bioaccumulation is generally out of pet food processors’ hands. This process can only be reduced by regulating environmental pollution, monitoring potentially hazardous industrial processes and chemicals, and properly cleaning toxic waste and spills. When ingredients are exposed to toxic chemicals or heavy metal contamination, testing is key. High levels of heavy metal toxicity can be shown through proper testing. Raw ingredients, generally animal products though sometimes polluted grains, should be tested regularly. Once again, recall, tracking and tracing measures are also essential.

Preventative measures, such as good manufacturing practices for equipment and product testing can help to prevent these recall risks. However, no system is 100% effective. Reactive measures, such as track and tracing systems and recall simulations, can help to mitigate the damage if a recall does occur. Both of these measures are essential. In our next blog post, we’ll discuss additional recall risks and how to prevent them, including the risk of aflatoxin contamination and trace mineral inaccuracies.

Process Improvements to Increase Efficiency in Pet Food Processing

process verification in manufacturing

Increasing efficiency can mean many things. It might mean decreasing waste, lowering costs, improving speed, or increasing overall production. There are many ways to go about this. These improvements can also be difficult to compare or analyze. In this blog post, we’ll discuss a few of the most readily available process improvements specifically in pet food processing. These improvements can help to decrease waste, improve process speed, and improve overall efficiency at your pet food processing facility.

Process Improvements to Increase Efficiency in Pet Food Processing

Optimizing Liquid Coating Systems

Liquid coating systems present a number of challenges to pet food processing facility managers, as well as opportunities for improving efficiency. Pet food facilities working with liquid coatings that are high in fat content, like many dry pet food processing plants, often struggle with clogs and pressure backups. Liquid coating nozzles can easily become clogged in these situations, requiring frequent cleaning, maintenance and replacements. Overall, this requires downtime and eats into production time. Pressure backups also reduce the equipment’s lifespan. When clogged nozzles do not coat products evenly, this can also result in product defects and losses.

Comparing Liquid Coating Equipment

Finding the right liquid coating process and equipment can increase the efficiency of this process dramatically. Your coating system must be designed to suit your liquid coating product, as well as the surrounding processes. The liquid coating must also have enough time and opportunity to evenly coat the product and properly absorb.

Considering alternative liquid coating solutions can help to optimize coating quality, reduce maintenance, and even speed up the process. Even making slight alterations to the mixing process, such as reducing screw conveyor flights or introducing pitched paddles can increase the mixing action and improve the uniformity of the coating. If the spray nozzles are consistently causing problems, consider a system that bypasses spray nozzles, such as a spinning disk atomizing system.

Automated Micro Ingredient Systems

Some pet food formulas require the addition of micro ingredients, such as vitamins and minerals. A reliable system for adding micro ingredients can help to reduce waste, improve organization, reduce process time, and improve tracing. Adding ingredients by hand introduces the opportunity for waste and error. Automated micro ingredient systems allow you to measure ingredients quickly and exactly. With the right micro ingredient systems and tracking system integration, you can also save time on FSMA-required lot tracking.

Scale Calibration

An important aspect of an efficient micro ingredient system is accurate weighing devices. When weighing small amounts of ingredients, accuracy is essential. Be aware of effects that can make your load cells inaccurate, such as temperature changes, load cell creep, interference, or a lack of calibration. Keep in mind that small mistakes in measurements can add up; a minor weighing error with as little as .5% overuse ultimately means wasting .5% of the total product purchased.

FSMA rules require that pet food processing facilities track and trace ingredients, just like food for human consumption. Automated ingredient systems can help trace ingredients from the start of the process until the finished product. A fully integrated system can keep necessary documentation and also work with your labeling system.

Process Improvement Assessments

Go through process improvements step by step, and compare all the costs and expenses equally. Remember to include not only upfront investment costs on one side of the equation, but also maintenance, training, or installation. On the other side, include all the benefits you’ll receive, such as process speed improvements, reduced waste, decreased downtime, and lowered maintenance costs long term. Take a look at the process improvements and efficiency upgrades that present the biggest opportunities first. Equipment or processes that are causing waste and delays should be examined first, as these will present the biggest opportunities for improvement.

With the right systems, equipment upgrades and process speed coordination, you can optimize the most essential aspects of your pet food processing facility. Assess each process first to find where opportunities exist. Prioritize each improvement, and take them on step-by-step, as opportunities become available.

4 Key Sanitation and Safety Regulations in Pet Food Processing

minimizing risk in food processing

Clean, safe food and a clean, safe work environment are important in processing food for human consumption as well as animal consumption. Many of the rules and guidelines for maintaining sanitation and preventing workplace hazards are the same between both of these environments. Taking precautions to create a sanitary pet food processing plant and prevent workplace hazards also has similar benefits; a good reputation, avoiding expensive fines, reducing downtime and improving efficiency. Be aware of these sanitation and workplace hazards in pet food processing, and you can take advantage of these benefits.

4 Key Sanitation and Safety Regulations in Pet Food Processing


A hazard analysis and critical control points (HACCP) assessment is an essential part of food safety, and a major component of the Food Safety and Modernization Act (FSMA). Manufacturers of food for human consumption as well as animal consumption both have to follow FSMA regulations. FSMA applies to both manufacturers in very similar ways. A good understanding of FSMA regulations and requirements will help you to maintain a clean workplace, prevent contamination, and respond appropriately if contamination does occur.

The FDA outlines a HACCP assessment with the following 7 principles. Keep these in mind as you make your plan.

  • Principle 1: Conduct a hazard analysis.
  • Principle 2: Determine the critical control points (CCPs).
  • Principle 3: Establish critical limits.
  • Principle 4: Establish monitoring procedures.
  • Principle 5: Establish corrective actions.
  • Principle 6: Establish verification procedures.
  • Principle 7: Establish record-keeping and documentation procedures.

2. GMP in Equipment Design

Good manufacturing practices (GMP) are an important part of workplace sanitation that can easily be overlooked. In some cases, GMP can be even more important in pet food processing facilities, since these facilities commonly work with materials that present sanitation risks.
Consider the following GMP and sanitation standards in your pet food processing facility:

  • Welded seams: if machines are not welded properly, fats and oils can find their way into cracks, and breed mold and bacteria.
  • Metal sharps: metal burrs that aren’t eliminated during the equipment construction phase can break off into the product.
  • Rust: steel machines without the right finish can rust and flake off into the product. Stainless steel construction, protective finishes and regular inspections can help to prevent this.
  • Hermetic sealing: control panels, weighing devices and other electronics must be properly sealed to protect the device, but also to prevent bacteria from getting in.

3. Bacteria in Fats and Oils

A number of pet food processing procedures involve working with fats and oils, which present unique challenges in preventing the spread of bacteria. Fats and oils are difficult to clean without the proper cleaning solution, and can also make bacteria more resistant to the cooking process. Keep the following in mind:

  • Thorough cleaning: dangerous bacteria tend to build up in forgotten areas, or build up when cleaning procedures are neglected. Cracks in floors and dirty drains, for example, often harbor listeria bacteria. Be sure to use the right cleaning solutions and tools, so debris are scrubbed off first and come in full contact with sanitizing agents.
  • Proper temperatures: Storing fresh food in appropriately cold temperatures and cooking raw foods at appropriately high temperatures is an essential part of preventing disease. Be aware of conditions that can affect storage and cooking, such as opening a freezer door too often during loading or unloading, or ensuring that fats and oils are not compromising the cooking process.

4. Workplace Hazards

Working with fats and oils also presents workplace hazards. For example, if the pet food coating process is not contained, fats and oils can make their way onto floors, creating slip-and-fall hazards. When these coatings make their way into the air, it also presents air quality problems. Containing this process and preventing fugitive particles from escaping is the best way of preventing these hazards.

Pet food processing equipment can also present hazards to workers if the equipment is not properly maintained, or if the equipment is tampered with. For example, safety grates and stopping mechanisms should never be removed or tampered with. Power cords and connection lines should not present trip-and-fall hazards. Cords and power boxes should also be regularly inspected for damage and a secure ground to prevent electric shock or sparks.

Prioritizing safety, providing time and resources for inspections, and providing clear instructions for how to resolve safety issues is the best defense against workplace injuries. Take a preventative stance, not a reactive one; it should not take a tragic accident or expensive lawsuit to emphasize the need for safety protocols.

Comparing and Contrasting Liquid Coating Equipment Solutions

comparing liquid system pumps

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

Screw Conveyor

spray coating screw conveyorAs 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.

Rotating Drum

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.

Rotating Disk

spray coating rotating diskThe 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.

Batch Mixer

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.

Spray Equipment and Coatings: Problems and Solutions

Two spray nozzles and a screw conveyor.

Spray equipment and coatings present a number of challenges to food and pet food manufacturers. Spray coating systems, as well as the coating liquids, can be difficult to work with. Workplace hazards, equipment maintenance problems, expenses, down time and other problems may arise. In this blog post, we’ll discuss some of the most common problems with these systems, as well as some solutions.

Spray Equipment and Coatings: Problems and Solutions

Clogging and Crystallization During Spray Coating

spray coating rotating disk
The mistcoater system eliminates the need for spray nozzles and prevents nozzle clogs.

Many spray equipment systems and coatings are not well-suited for each other. Suspended solids in the coating can clog the spray nozzles in the machine, requiring repeated cleaning and maintenance. Salt and sugar solutions work similarly, creating crystals that clog the nozzle. If the spray nozzles aren’t regularly cleaned, the liquid coating can’t break through, creating problems with uniformity and back pressure (we’ll discuss these in more detail later in the post).


Spray nozzles aren’t ideal for coatings with suspended solids, or salt and sugar solutions. Consider spray equipment can atomize coatings without the need for a narrow outlet. APEC’s Mistcoater uses a rapidly spinning disk to atomize liquid coatings into fine droplets. This eliminates opportunities for clogs and crystallization.

Inconsistent Coating

Different liquid coating characteristics can affect their compatibility with different spray equipment. As previously mentioned, suspended solids and salt or sugar content, as well as liquid percentage and viscosity can affect the uniformity of the coating. As a thick solution moves through the spray nozzles, the high viscosity creates inconsistent flow. Or, some spray nozzles may be clogged, while others continue to work, creating inconsistencies across the product. Some pieces can be coated too heavily, and others might not be coated at all. This means food and pet food manufacturers must take special considerations to ensure uniform coatings across the product.


Spray nozzle coating systems present a variety of challenges in choosing the right coating. A liquid that is too thick or has too many suspended solids can render the entire system ineffective. An atomizing system which removes the need for spray nozzles can provide uniform coating over a longer period of time. Thinning the liquid may also be effective, however this may also affect how well the coating sticks to the product.

Back Pressure Build-up

When crystals and clogs build up on spray nozzles, it causes pressure to build up throughout the rest of the spray equipment. This means the machines require more horsepower to operate, wearing them down prematurely and using excessive power.


Once again, removing the opportunity for clogs provides an easy solution to this problem. When the fat, oil, salt or sugar solution is atomized over a spinning disk instead of being forced through a small outlet, there is no back pressure build up. Regularly cleaning spray nozzles or reducing the liquid’s viscosity can also help to reduce problems with back pressure.

Workplace Hazards and Sanitation

Spray equipment and coatings can also present a number of workplace challenges. Coatings on food and pet food not only get sprayed onto the product, but also move through the air, stick to the floor, stick to workers, equipment, and any exposed surface. When working with fats and oils, this also introduces sanitation problems. These coatings can make their way into cracks in the floor, small spaces on machines, and other areas that are difficult to clean. This creates perfect opportunities for mold and bacteria to build up. Sprayed coatings in the air and oily, slippery floors also create workplace hazards for employees.


The best solution for these sanitation problems and workplace hazards is enclosing the spray coating system. The Mistcoater spray coating system is fully enclosed, keeping the coatings inside and preventing them from entering the air or sticking to other surfaces. Enclosing spray coating systems can help to dramatically reduce the amount of housekeeping and safety measures needed to keep your workplace safe and sanitary.

Consider your spray equipment and coatings carefully in the equipment design phase, and you can avoid many of these issues. If you’d like to learn more about the fully-enclosed Mistcoater spray coating system for your food or pet food products, contact us.

Liquid Coating Processes for Uniform Snack Coating

Whether for flavor, vitamin content, shelf life, or texture, liquid coating is the preferred application method for many cereals, snacks, pet food mixes, and more. Though this provides a number of efficient, time-saving advantages for snack coating, it can introduce some challenges if the process isn’t correct. Consistency and uniformity in liquid coating are two of the most common challenges in pet food and snack coating. With careful process design considerations, you can find the right process for your coating and substrate.

Liquid Coating Processes for Uniform Snack Coating

Before Application: Measurement

A standard mass flow system.

Before applying the liquid coating to the substrate, it’s essential to accurately measure the flow of each material. There are several way to do this, and which you choose will depend on the accuracy you require, moisture or temperature conditions, the composition of the carrier ingredient, and the layout of your facility. The carrier ingredient will be the “master flow” and the liquid coating process will depend on it, making accuracy even more important. You may need to consider potential flow problems at this stage.

You might choose the following flow measurement systems for continuous snack coating:

  • Volumetric: A screw conveyor, rotary feeder, or belt conveyor measures solid flow through RPMs (or Hz). A nutating disk, positive displacement pump, piston pump or turbine measures liquid flow through RPMs (or Hz) or pulses. Volumetric measurement is sensitive to changes in density, and not recommended for applications with high accuracy. Calibrate often to adjust for elevated temperature or moisture content,
  • Mass flow: Mass flow measurements have more versatility, with a variety of measurement systems. Weigh belts, weigh screws, impact scales, and nuclear gauges more accurately measure flow through RPMs and weight simultaneously.
  • Loss in weight: This measurement system works similarly to mass flow systems, however it measures weight as the material flows out. A garner hopper and scale hopper work in unison to take accurate measurements in a continuous flow system. This system is also quite accurate, however a facility’s height restrictions may be problematic. The scale hopper operates in weight exception mode during re-filling to accommodate continuous operation, and this should not exceed acceptable tolerances.

Liquid Coating Applications

With the measurement system determined, you have the right amount of liquid coating and substrate, but you still need to decide how to apply an even, consistent coating in the continuous process. You might use a screw conveyor, rotating drum, or mist coater.

Screw Conveyor and Spray

liquid application screw conveyor
Two spray nozzles and a screw conveyor.

As the screw conveyor moves the substrate, spray nozzles apply the liquid coating. In a simple screw conveyor very little agitation of the product takes place. To get a uniform coating, the substrate will require agitation. Some of the screw conveyor flights can be cut away to form more of a ribbon to agitate the product while moving it forward. Lifting flights and paddles on the screw conveyor will provide more movement, and there should be enough space for the material to tumble through.

The tumbling action through the screw conveyor must be gentle for fragile materials, which can slow down the process. Liquids moving through the spray nozzles can also present problems. If the liquid flow rate changes a great deal, then additional spray nozzles may be needed so the quantity being sprayed does not drop below or go above the rated capacity for flow and pressure, which can affect the quality of the atomization. If the liquid has suspended solids, spray nozzles will easily clog.

Rotating Drum and Spray

This liquid coating process works similarly to the screw conveyor, except the material moves through an open-ended cylinder. Flights lift and tumble the material, and spray nozzles coat the material as it moves through. This method is generally gentler and ideal for fragile snacks or foods.

Since the rotating drum is open on both sides, fugitive liquid and dust can quickly become an issue. Without proper ventilation or cleaning, the liquid or dust can create slip and fall hazards, unpleasant or hazardous working conditions, or it may damage equipment. The required length of the drum may also be a concern for facilities with limited space.

Spinning Disk and Mist Coating

liquid coating spinning disk atomization
Liquid application through spinning disk atomization.

During this process, the material moves across a spinning disk and flows over the edges. As it falls, the liquid coating hits additional disks moving much faster in the opposite direction below. The liquid atomizes into a mist that coats the material as it falls.

Atomization through spinning disks solves many of the liquid coating problems presented by spray nozzles. Since pressure is not required for the liquid coating application, density changes and solid suspensions are no longer a concern. This also allows for multiple liquid coatings simultaneously, regardless of changes in density or viscosity. Finally, the system is completely enclosed, which prevents fugitive dust and liquid from escaping.

Finding the right pet food or snack coating process will help you not only increase product quality and consistency, but it can also reduce costs, product loss, labor, and maintenance needs. Always test the process before installation, and work closely with your equipment manufacturer to get the right system.


Part 2: Ingredient System Planning Pitfalls For Micro-Ingredient Scales, Conveyance and Controls

In the previous post, we discussed common problems that can occur with the start of a micro-ingredient system, including ingredient bins and feeders. The latter half of the system is generally more complex, and more issues usually arise here. In this blog post we’ll cover micro-ingredient scales, conveyance and controls, and what you can do to design the most effective system.

7 Ingredient System Planning Pitfalls for Micro-Ingredient Scales, Conveyance and Controls

1. Miscalculated Scale Error

To find the right scale for your formula, you’ll need to to add all of the possible ingredients and the quantity of each. This will tell you the size of the scale that you need, but you also need to consider the margin of error. If the scale can accurately measure within +/-5 grams and the required accuracy of the formula is 1%, you won’t be able to measure 10 grams of a micro-ingredient, because the possible error will be 50%.

Reduce error and improve efficiency. Download the Engineer’s Guide to Weighing and Batching >

2. Miscalculated Resolution and Accuracy

The scale resolution is also important to consider. The minimum increment a scale will display is generally one 10,000th (1/10,000) of the total scale capacity. So, a 100 kg scale would display in increments of .01 kg. If this isn’t suitable for your accuracy measurements or your feeder output, you may have to reconsider your scale capacity. Using the 100 kg scale example, if your feeder puts out more than .01 kg of material a second, and the control system can only time shut-off to within a second, the system will be inaccurate by this amount.

3. Incorrect Scale Hopper Design

The type of materials, the available height in the facility, and the downstream conveyance must all be considered to design the right scale hopper. Limited vertical space in some facilities can prevent the use of some types of scale hoppers, like a conical scale. Use of a roll-over tub with a slide gate may be a better choice then for facilities with lower ceilings. However, since a roll-over tub discharges material all at once, this will only work if the downstream conveyance or next process can accommodate all materials. If your materials are better suited to pneumatic conveying, like fine powders, then a conical scale hopper will transition into the pneumatic system easier. If you prefer to skip conveyance and discharge into the mixer, a conic scale hopper or roll-over tub will work.  

4. Cycle Time Doesn’t Match Mixer Time

For the micro ingredient system to reach maximum efficiency, the cycle time of each ingredient—including the time it takes for the materials to fill, settle, and discharge—must align with the batch mixing time of all ingredients. If, for example, it takes 30 seconds to fill, measure and discharge each ingredient in a 10 ingredient mix, it will take 300 seconds total to weigh the material in the scale so the mixer could be waiting for the weighing process to complete. If the mixing time only takes 150 seconds, it will be idle half the time. To solve this problem and reach maximum efficiency, you might use two scales, each with 5 ingredients.

This will require some careful calculations, as the fastest cycle time time, average time, and slowest time will vary. The times for each ingredient will also vary by density and amount. Be sure to allow some room for timing variation.

5. Vibration Interference

Vibration can be used  i in a micro ingredient system to prevent bridging, ratholing, and other no-flow conditions in bins and hoppers. It’s also desirable to keep the different parts of your system close together to prevent the need for extraneous conveyance. However, if scales are placed too close to vibrating equipment, it can cause fluctuation of the scale reading. If the scale readings are dampened to eliminate the fluctuating readout, the scales may appear to be working normally and showing normal readouts, but the process duct may be weighing  incorrectly. In this case, interference through vibration may be to blame.

6. Conveyance Contamination

The most efficient type of conveyance is through gravity, however this is not always an option, especially for facilities with low vertical clearance. In these cases, you might use pneumatic, belt or drag conveyors. When using belt or drag conveyors, it’s important to prevent contamination from one batch to the next. Materials, powder or coatings that become stuck on the belt can not only damage the belt and cause it to stick or slide, but can also contaminate new material. Use scrapers or brushes to prevent material build-up on the conveyor. It may also be advisable to run a flush material through the conveyor to clean off the residual material.

7. Slow or Damaged Controls

The micro ingredient system cannot function properly without direction from the right controls. The control system, whether you are using a PLC or PC, should be able to sample each scale quickly and stop feeders without a long delay, otherwise overfilling will ruin the batch. The system should also be powerful enough to control all scales, feeders, mixers, metered liquids, and other functions with accuracy. Finally, the control system should be enclosed if dust, moisture, heat, vibration or other hazards are a concern. Often, a PC will be used outside the factory floor for extra processing and data storage power, and communicate with a more durable PLC directly controlling equipment.  

With different ingredients and recipes there are different challenges for each part of the micro ingredient system. If you have questions about the needs and capabilities of your micro ingredient system or ingredient automation system, take a look at the Engineer’s Guide to Weighing and Batching. This guide addresses the issues from this and the previous blog post in more detail, as well as many others not discussed here.

Part 1: Ingredient System Planning Pitfalls from Micro-Ingredient Bins to Feeders

Proper planning before an ingredient system redesign or new installation is pivotal to ensure the system runs efficiently.  With so many moving parts and considerations, it’s not easy to plan for every eventuality, and a few problems are consistently missed. In this blog post, we’ll cover some of the most common problems that can arise at the start of the system with your micro-ingredient bins and feeders.

6 Ingredient System Planning Pitfalls from Micro-Ingredient Bins to Feeders

1. Incomplete, Inaccurate Information

Proper planning starts with accurate information. When your numbers are exact and you have all the information you need on your ingredient system up front, every step in the process will be easier. Whether you are installing a new system or conducting an ingredient system redesign for automation, you will need key information about all of your ingredients. You will also need information about your new or existing facility. Finally, you’ll need some measurements about your recipe as a whole to bring your system together properly. It’s helpful to have all of the following information available and well-organized in a spreadsheet:

  • Number of ingredients
  • Recipe composition
  • Ingredient types
  • Ingredient bulk density
  • Minimum weight required
  • Maximum weight required
  • Daily usage
  • Weekly Usage
  • Monthly usage

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2. Insufficient Ingredient Storage

The usage of each ingredient as well as the delivery means and schedule will both play an important role in determining ingredient storage needs. For micro-ingredient systems and ingredients delivered infrequently, this will be particularly important for planning the rest of the surrounding system. If the daily usage of any ingredient exceeds 250 kg, consider using a super sack unloader to improve efficiency. For this, you’ll need adequate vertical space or design solutions to ensure ingredients flow properly.

3. Flow Problems From Bin Design  

You want to make sure that you have space for all ingredient bins of the correct size, and it’s also important to consider the construction of the bins themselves. Micro-ingredient bins without sloped walls, or without an adequate slope, can introduce flow problems. Generally, an angle of 70° is sufficient, but this will also depend on the characteristics of the ingredient. Ingredients that tend to clump, stick, or don’t flow freely may need additional design considerations, like vibration. If ingredients aren’t flowing properly from the bin, it can create costly downtime and other problems further downstream.

4. Contamination From Bin Design

Sometimes, when ingredients do not flow from the bin properly, the material may stick to the sides or stay in dead zones. When new shipments are loaded into the bins, this can introduce contamination. If the material in the bin becomes rancid and then mixes with a new batch, it will upset the quality of the product. Special coatings inside the bin can further enhance flow and reduce sticking and dead zones, and stainless steel will allow the bin to be easily cleaned at regular intervals.

5. Incorrect Feeder Type

Knowing the maximum and minimum weight for each ingredient, as well as ingredient characteristics, will be particularly important for choosing the right feeder type. You might choose an auger-type feeder for powders or other ingredients that won’t easily break or generate heat through friction. If the materials are susceptible to these problems, use a vibratory feeder instead.

6. Inaccurate Feeder Output

Both auger-type feeders and vibratory feeders must feed ingredients through the system with the proper output. The desired feeder output will vary depending on the accuracy needed and the total volume of the system. Here it is important to have accurate density measurements, as the material density will affect output calculations by weight. Output may also be affected by flushing if the ingredient is free-flowing. Use a knife gate or butterfly gate to prevent this problem.


Problems with ingredient bins and feeders are often overlooked, as these parts of the system are generally simpler than mixers, scales, and controls. However, problems anywhere in the process can affect the end result. Our next post will cover common issues with the later half of the micro-ingredient system, including scales, conveyance and controls.

7 Ways Feed Mill Automation Drives ROI

feed mill automation ROI

In any industry, automation is based on goals: solving problems, minimizing risks, and reducing costs. The same is true for feed mill automation. There are a number of ways that feed mill automation can improve the end product and solve or reduce problems throughout the operation. Though some facilities may automate all processes at once, step-by-step automation is also a viable option. Feed mill automation can drive ROI in the following ways, and many of these benefits may occur simultaneously, depending on which process or processes you choose to automate.

7 Ways Feed Mill Automation Drives ROI

1. Reducing Labor Costs

Automation not only ensures that tasks are completed consistently, but also eliminates the need for manual operation. Repetitive tasks no longer require physical labor, and free up manpower for more sophisticated and important jobs. Automation can also protect workers from safety risks, either by removing them from dirty or dangerous environments, or by putting reliable safety controls in place.

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2. Enhanced Production

Enhanced production is one of the most common factors driving ROI in feed mill automation. With the right design and maintenance, automation can streamline processes and remove the need for breaks and pauses. The right machines can also work at a faster rate.

3. Measureable Regulatory Compliance

Feed mill automation can simplify regulatory compliance for rules like the Food Safety Modernization Act (FSMA), among others. Track and trace is an important part of FSMA compliance, but can be difficult to accurately implement without systematic controls. Tracking lot numbers manually not only introduces error, but takes up workers’ time and energy. Lot tracing can easily be automated, and it will greatly improve accuracy. With a reliable, automatic system in place tracking where your ingredients came from, what they went into, and where the product ultimately went, you can reduce liability and meet compliance requirements with minimal costs.

4. Consistent Testing

To prevent moisture, toxins and other substances from ruining ingredients and the finished product, proper sampling and testing is essential. With automated sampling and testing, you can gather uniform, accurate information about ingredients and products. Detecting excessive moisture in ingredients from the start will prevent product from being contaminated, and allow you to hold suppliers accountable for defects. Detecting aflatoxins and other harmful substances in ingredients also reduces liability, as well as product loss. With feed mill automation for testing and sampling combined with automated track and tracing, any problems with ingredients or products can be accurately recorded.

5. Reducing Batching Errors

Batching is one of the most common areas for feed mill automation, and often offers the highest initial ROI. By automating your batching and mixing processes, you can substantially reduce error and variation. When your recipe is programmatically controlled, corn, soy, vitamins, minerals, enzymes and other additives are each exactly measured. With an easily re-programmable controller, you can even change the recipe without significant downtime.

6. Automatic Routing

Automation of the batching process is usually the first section of the feed mill to be automated, but the addition of downstream routing of material can enhance the payback of the system. If the system has to wait for the operator to setup the routing of material to the downstream packaging or load-out, then valuable production time can elapse while waiting for a route to be selected.


Through most zones, feed mill automation makes hazard analysis and critical control points easier to regulate and monitor. By gathering more data, more often, with less manpower required, you can get holistic, up-to-date information about your production line. You can also eliminate risks altogether by automating repetitive tasks with a high risk of human error. Automated regulation ensures that critical control points are monitored at the same time, in the same way, with no exceptions.

Before starting or continuing feed mill automation, plan and design your system carefully. Conduct ingredient testing to ensure that the system is suitable for your recipe, and be sure to factor any maintenance costs into your ROI calculations. With the right system automating the right process, you can realize a return quickly and eliminate risks at the same time.