Moisture in Cookie and Cracker Production

Manufacturing Process Summary

Cookies and crackers are enjoyed by billions of people every day. Similarly, biscuits and crispbrea are available in a variety of diverse types and flavors, making them all a staple in the snack food industry.  

Control of moisture in these baked products is necessary in order to optimize the quality of the product and the production process. A moisture content that is too high will adversely affect the texture and taste, while also shortening shelf life. A moisture content that is too low will result in crackers that damage easily, leading to wastage both before and after packaging. Additionally, low moisture causes crackers to “burn” to a greater extent when they pass through the ovens, leading to an undesirable flavor.

Dough Forming

To form the dough for cookies, crackers and the like, raw solids and liquid ingredients are transferred to mixing tanks. Ingredients are then mixed together in specific quantities, as specified in the product’s recipe—and the order that ingredients are added to the mixture is important. These doughs are then mixed with either vertical spindle mixers or high-speed horizontal drum mixers.  

Sheet Forming & Cutting

The doughs used for crackers, cookies and similar baked products are ostensibly the same. In the machining process, dough is delivered from a hopper onto a conveyor belt and rolled thin by a series of metal gauging rolls. The thickness of the sheet is reduced by each of these rollers. Some manufacturers stack multiple sheets on top of each other in a process known as laminating.  

The dough sheets are then rolled out further, allowed to relax and then sent along a conveyor belt to the cutting machines. The edges of the dough sheets are cut smooth by rotary cutting machines, and excess dough is sent back to the hopper for reuse. After this stage, sugar, cinnamon or honey is applied to the top of the dough if the recipe requires it.

Baking

The cookies, crackers or other products are baked in a tunnel oven. The dough is first transferred to a metal conveyor belt and then moved through the oven, which can be 100–300 feet (30–90 m) long. Baking takes place in three stages: development, drying and coloring. In the development stage, the dough sets, taking on the size and shape of the final product. Then comes the drying stage, where the greatest amount of water is lost. Then in the coloring stage, the dough is changed from pale white to a light golden brown.

Post Conditioning & Packaging

After the cookies, crackers and baked products come out of the oven, they travel on a series of conveyors to cool. At some point in this process they are flipped over and then flipped back to ensure that cooling is throughout. The total cooling time can be twice as long as the baking time.

Depending on the recipe, other coatings such as icings, chocolate coatings, sugar, etc. can be put on the baked goods after they have cooled.  

The final step in the manufacturing process is packaging, where the products are parcelled by weight for shipment.

Quality Parameters and Measuring Points

The online NIR transmitter is usually located several feet down line from the oven exit. While it might be useful to locate it closer to the exit from the point of automatic control of the ovens or inlet belt speed, it is not recommended due to the fact that NIR measurements are essentially surface measurements, and a degree of equilibration needs to occur in order to obtain a stable and meaningful measurement.

A food grade MCT-566SF (NIR) transmitter is designed to meet the strict hygiene and safety requirements of a food manufacturing plant. It is coated in electro-less nickel and houses a Kel F or sapphire window.  

Bench NIR Analyzers, such as the QuikCheck or the SpectraStar™ XT-3 are used either in the laboratory or at-line for quick, accurate and reliable sample testing.  

Value and Quality

Moisture measurements can be made on-line or off-line. On-line measurements greatly improve efficiency; they eliminate the need for routine laboratory moisture testing and provide an instantaneous measurement so that necessary process changes can be implemented sooner.

Off-line moisture measurements are simple, sample a greater product area and are quicker to effect than using Infrared balances or oven tests.

Further analysis of the product after seasoning ensures a consistent product quality before packaging. This will fortify shelf life and ensure that the final product meets the nutritional label specifications on the package.