Discover your next big idea in food packaging & processing this Sept.
Experience a breakthrough in food packaging & processing—explore solutions from 2,300 suppliers spanning all industries at PACK EXPO Las Vegas.
REGISTER TODAY & SAVE

Size reduction: How to select the proper milling equipment

With numerous milling options available, food processors face a challenging landscape when sifting through the range of available machines.

Different types of milling machines may be suitable for reducing the size of the same food product. Selecting the right milling machine requires an understanding of the product and its desired characteristics. Hosokawa Micron Powder Systems
Different types of milling machines may be suitable for reducing the size of the same food product. Selecting the right milling machine requires an understanding of the product and its desired characteristics. Hosokawa Micron Powder Systems

Food manufacturers and ingredient suppliers have access to a wide range of high-tech milling methods. Each one offers advantages for achieving product characteristics such as particle size and moisture content, along with other considerations such as cost, footprint and the need for ancillary equipment. Each method has also given rise to a diverse range of size reduction equipment. In fact, there may be more than one solution when selecting milling equipment.

According to Suha Ozsoylu, director of operations at ‎Hosokawa Micron Powder Systems, the most important step in selecting size reduction equipment is establishing the target size reduction of the end product. This target is typically based on the particle size and particle size distribution desired, typically expressed in terms of milling the material down to a given particle size distribution in microns. "End products that demand the vast majority of particles consistently measure the same size. For example, cake flour, often requires a different approach to milling than end products that include a range of different sizes, such as cookie crumb or chopped walnuts. The particle size directly affects the amount of surface area and the interactions among the flour, water and other ingredients. For cakes and other baked goods to achieve a desired delicate, heavy or fluffy texture every time, the baker needs the flour to meet the same particle size every time."

Testing and particle size analysis

Despite the importance of determining the required particle size, many product developers do not know the size of their existing products or the particle size needed for new products, says Ozsoylu. When asked about the target particle size, “something like flour,” “as fine as possible” or “just like cereal” are common responses, he adds. In these cases, develops should consider checking with a milling machinery manufacturer that has a track record with the product. Identifying systems that are proven to work with a given product can accelerate the specification process by weeks or months.

Whether the product matches existing test data or you are starting from scratch, today's milling equipment manufacturers offer configurations and custom options that can meet tight specifications. Testing the actual product on lab-size and/or full-size machinery is recommended. The first step in testing often involves evaluating a sample on a particle size analyzer that uses pneumatic sieving to determine the particle size distribution and provides a target end point. Other product characteristics can be addressed such as the size at the infeed, bulk density, flowability, hardness, moisture content, heat sensitivity, toxicity and even explosivity.

Milling selection: Hammer and screen mill

Check to see if a low-cost technology can meet the requirements, Ozsoylu suggests. One of the least costly types of milling machinery for food products is also the most frequently used. The hammer and screen mill style uses the impact of swinging hammers that rotate at high speeds inside a round housing to reduce the particle size. When the particles meet the targeted size, they fall through a screen and into collection. Screens are available in a variety of sizes and configurations to suit dry, sticky, fibrous or abrasive ingredients. Today's most effective hammer mills grind down to D90 <75 µm. If a finer end product is required, a more advanced impact systems may be considered.

Break out of the ordinary: see what’s new in food packaging & processing
<strong>At PACK EXPO Las Vegas you’ll see machinery in action and new tech from 2,300 suppliers, collaborate with experts and explore transformative solutions. Join us this September to experience a breakthrough in food packaging and processing.</strong>
REGISTER NOW AND SAVE!
Break out of the ordinary: see what’s new in food packaging & processing
Researched List: Engineering Services Firms
Looking for engineering services? Our curated list features 100+ companies specializing in civil, process, structural, and electrical engineering. Many also offer construction, design, and architecture services. Download to access company names, markets served, key services, contact information, and more!
Download Now
Researched List: Engineering Services Firms