How to Beat The Challenge of Baked Bread’s Physical Properties During Inspection

When we look at the use of metal detectors for baked bread, one of the biggest challenges is “product effect.” Product effect in the food industry refers to the impact that the physical and chemical properties of a food product have on the performance of inspection and detection equipment. Factors like moisture content, salt levels, temperature, and product density can create false signals or mask contaminants, making it challenging to accurately detect foreign objects. Managing product effect is crucial to reliable inspection results and maintaining food safety standards.

Let’s take a look at how bread is made in an industrial bakery operation and the technologies and techniques used to detect physical contaminants that may enter into the production process.

How Bread is Made

In an industrial bakery, bread is generally made by first mixing flour, water, yeast, and other ingredients to form dough. The dough is then kneaded to develop gluten and allowed to rise. After rising, the dough is divided into portions and shaped into loaves. These loaves undergo a second rise before being baked in large ovens at controlled temperatures. Once baked, the bread is cooled, sliced if necessary, and packaged for distribution. Throughout the process, quality control measures are needed to help ensure consistency and safety, from raw ingredients to final packaging.

Keeping Out Metal Contaminants

Metal detectors are an essential tool in the food industry, used at various stages of the production process to help ensure that metal contaminants — like broken pieces of machinery or a missed metal buried in raw materials — are detected and removed before the food products reach consumers. They work by creating an electromagnetic field using a coil system. When a metal contaminant passes through this field, it disrupts the field, and this disruption is detected by the system. The detector processes the signal caused by the disruption to determine the presence of metal, whether ferrous, non-ferrous, or stainless steel. If metal is detected, the system triggers a rejection mechanism, such as a pneumatic pusher or a diverter arm, to remove the contaminated product from the production line. (You can read about metal detector technology here.)

Inspection Complications and Solutions

Warm bread coming out of the oven, coupled with its salt content, tends to have a high product effect. This negatively impacts the metal detector’s ability to distinguish between actual non-ferrous metal contaminants and the false signal given by the combination of typical product attributes. This is further complicated by the varying densities, air bubbles and other physical characteristics of each loaf, since no two are exactly the same. (There also are variations between bread types.)

In these situations, X-ray detection and inspection systems will produce significantly better results since product effect is not a factor.  X-ray inspection systems can detect a wide variety of metallic and non-metallic contaminants, but also deliver additional quality control capabilities, including the detection of missing product pieces and components, under- and over-fills, and other quality problems. (You can read about X-ray inspection technology here.)

However, other issues need to be considered. For example, the ideal time to run the loaf of bread through the X-ray machine is prior to bagging. Bread is typically conveyed through the X-ray machine with its longest dimension leading. At the point of entry, there is a lead shielding curtain, which sometimes causes the loaf to roll on its side as it passes through. This is not problematic for the X-ray machine; however, incorrect orientation can negatively impact the bagging operation that immediately follows.

On specialty bread lines, where volumes and production speeds are slower, loaves can be positioned so that the short dimension leads. Entering the machine that way minimizes the curtain’s contact with the bread, thereby preventing loaf roll over.

Those are the concerns for loaves of bread.  But for specialty bakery products such as bagels there are additional concerning factors. Since bagel products are typically sold in multiples, the objective is both contamination detection and ability to verify count. Additionally, pieces can break off during the production process. X-ray inspection, which can detect missing pieces as well as contaminants, is ideal for this product type. X-ray inspection can be deployed to spot broken pieces (bagels, pretzels, etc.) or missing components.

Summary

The use of metal detectors in industrial bakeries faces challenges due to “product effect,” where the physical and chemical properties of bread, such as moisture, salt, and density, can create false signals or mask contaminants, making it difficult to accurately detect foreign objects; X-ray inspection systems can offer a better solution by detecting a wide range of contaminants and quality issues without being affected by product effect.

Additional Resources

• Technologies and Solutions to Improve Food Weighing and Inspection

• Infographic: 5 Needed Inspection Points During Baked Goods Production

• White Paper: Market Insights and Solutions: Packaged Baked Goods & Snack Products

Editor’s Note:  This article was originally published in September 2015 under the name Bob Ries but has been updated with additional content and broken links have been fixed.