Most of the principles of making breakfast cereals are similar to all products. Trix cereal is made with corn. The process of converting corn into the delicious product many children as well as adults will be discussed in this section. The corn from the field is dried milled, sifted and cleaned to separate the germ from the bran, oils and debris collected from the field and the milling process. The goal of this separation is to get to the endosperm where most of the starch that will be used for production is located.
Most cereals produced are produced as flakes. Prior to flaking the grits are cooked and mixed with sugar, malt syrup, proteins, and salt into a large amount of water to create what is called cooking liquor. This cooking liquor provides the Milliard reaction that occurs during cooking and is what provides most of the flavor to the flakes or in the case of Trix, corn puffs. This mixture is loaded into a cylindrical industrial steam pressure cooker for about two hours at a 15-18 psig steam pressure (Smith & Hui, 2004).
In the case of Trix the cooking process is done by puffing. Puffing is done either through high temperature ovens, guns or extrusion. The use of any of these three methods is to expose the moist grain to high temperatures where its moisture will be converted to steam. The steam released by the grain expands and puffs the kernel. Prior to placing the grits into any of these three methods, the grains are delumped in lump-breaking machines which incorporate large volumes of air. The air supplied through the machine helps with the cooling of the product.
The cooling of the grit in the lump-breaking machine helps with the initial drying step of the process of making ready to eat cereal. Grits usually have a moisture content of 28-34% (Smith & Hui, 2004) are dried to about 14-17% through the use of forced air dryers at a temperature of 250°F (Smith & Hui, 2004). Once the grains have gone through this initial drying, the grains are controlled cooled to 100°F to prevent hardening of the grain and to allow the grain to return to ambient temperature. (Smith & Hui, 2004).
Once the grain is dried to the moisture levels desired, the grain is tempered. Tempering of the grits takes about 2-3hours, helps reduce the darkening the product that occurs during Milliard reactions, and allow the grit to retrograde. This process uses temperature of 80o F and increases the firmness of the cooked grit (Smith & Hui, 2004). From this point the grit is ready for flaking, shredding, or any of the methods of puffing grits. General Mills utilizes puffing guns to make Trix cereals. The science behind the puffing gun utilized by General Mills and some of its competitors, works by introducing the grains to high (500-800 ° F) temperatures. This high temperature evaporates the moisture within the granules creating a steam pressure build up (100 to 200 psi) inside the chamber. When this pressure is released the moisture attempting to escape the grain, causes the endosperm to expand and simultaneously puff.
Puffing guns have come long ways from when they were first introduced in the cereal business. Today General Mills utilizes a continuous puffing gun systems and extrusion puffing. Continuous puffing guns work the same way as it predecessors. The continuous gun contains a rotating cylinder that is set a specific angle. The cylinder is heated either by gas flames or electrically, and it is fed through a rotary valve. The pressure in the cylinder remains constant via the exit, thus continuously discharging the product. The contents explode into a bin provided with a floor opening leading to a conveyor belt. The product is directed to a rotating heating cylinder to dry, and then cooled. At this point the product is visually inspected for stickiness and color and sent to the packaging line.
Direct expansion or extrusion puffing is the other method used by many cereal manufacturers. This type of technology was received with open arms by the cereal industry because it allows the combination of the steps in the process into one. Cereals ingredients are introduced in one batch into long barrels equipped with single or twin screws. The screws mix, shear, and pressurize the barrel and transport the “dough” to a forming die. As the mixture flows through the extruder, vitamins, flavors and colors are introduced and then the mixture exits through the die.
The same principle of the puffing gun is applied to extruders. As the moisture vapor expands and the excess pressure is released, the volume of the mixture increases. The temperature in the barrel increases the mixture to about 300o-350 o F and the pressure to about 350-500 psi at the die head. As the dough exits through the orifices of the die, it is sliced off in to the different shapes and the slices expand immediately. Despite this quick expansion, the pieces still maintain moisture content of about 27% and are further dried on vibrating screens in hot air puffing ovens where the final cooking of the product occurs (Smith & Hui, 2004). Pieces are inspected and sent to the packaging line. Although extruded and gun puffed mixtures products are enriched and fortified during the cooking process, the puffs receive a final spray of vitamins, sugar and flavors inside rotating spray drums. Both final sprays assist with the reduction of lipid oxidation and moisture which improve the overall quality of the product as it relates to its texture and crispiness.
One aspect of producing cereal is its quality. The cereal industry uses multiple methods to assess the quality of its product during the production process. The biggest issue for a good cereal product is moisture. Moisture is measured through near infrared analysis (NIR), wet chemistry, and image analysis. During the process the product the raw material is analyzed for moisture to ensure it can be flaked, shredded, shaped, maintained for control of oven temperatures, and to control the sugar content applied to the product. This type of testing can also be done to the final product where the fat, sugar, and moisture are analyzed to ensure the operation is working at optimum conditions. These test is necessary due to any unacceptable moisture content could lead to poor product quality as well as possible bacteria growth.
At present, cereal industries are performing little or no analytical testing, and are relying on the vendors to provide them with highest quality level of product for their market. This can present a problem in production process. Despite the fact that the cereal industry does little or no analytical testing, most of the moisture content testing is performed as the product exits the oven using a 16 hour vacuum oven method or a moisture balance method (Unity Scientific, 2014). According to Unity Scientific, “both methods use loss on drying to measure moisture content.” The main problem with the 16 hr oven method is the time it takes to get results, and when these are received they “have no impact on real time process control” (Unity Scientific, 2014). When it comes to the moisture balance method Unity Scientific says, although the sample can be “analyzed in 15 minutes it is “2-3 times less accurate the vacumm oven method.” The key to cereals is the control of its moisture and texture. Moisture as mentioned previously, is critical to maintaining a cereal’s integrity, and it is crucial that the moisture of a cereal product is not greater than 3%. Anything less or greater could reduce its crunchiness as well as make it brittle. Therefore, NIR is one of the best methods of testing for moisture as well as fat content in any step of the process.
In regards to its crunchiness the cereal industry uses mechanical as well as sensory evaluation methods to ensure the products texture. Nonetheless, sensory evaluations can be subjective. One of the best ways to analyze texture is the use of mechanical instruments as these provide a quantitative measure of texture. Currently instruments used by the cereal industry include Stevens, Instron and Ottawa Texture Analyzer. The purpose of these crunch evaluation methods is to find the bowl life by exposing the product to milk for a small period of time and then performing a shear test. Other equipments used are the multiple crunching probes and the Ottawa Cell shearing test.
The final step in the production process is packaging. Different equipment and films are used across the board in the cereal industry. Some of the machinery used include Ishida multi-head weighers, Bosch vertical form fill seal machines and Triangle bag in box packaging. When it comes to films, they either use wax paper or various polymer films (Smith & Hui, 2014). However, before selecting a packaging film, cereal manufacturers consider whether the location the product is going to be sold is humid or arid. Based on these conditions the film is selected and used for production. One of most common packaging materials used in the cereal industry is polyethylene films (Smith & Hui, 2014). The packaging film must protect from water vapor transmission and flavor loss. As mentioned previously, moisture plays a big role in the process and any sign of moisture gain could lead to potential loss of crispiness and acceptability of the product. Another issue for cereals is the instability of lipids. Lipid oxidation leads to rancidity thus, creating a bad aroma in the product.
To prevent lipid oxidation and moisture gain in the product, the cereal industry utilizes different antioxidants. The antioxidants commonly used are butylated hydroxyanisole (BHA) and butylated hydrooxytoluene (BHT) (Smith & Hui, 2004). Although their use is limited in the production process, these can be added before cooking. However, after several trials, it was discovered that due to their non polarity and their volatility these would not hold during the manufacturing process. Nonetheless, it was discovered it was better to apply these antioxidants to the packaging material as the antioxidants would transfer to product after packaging (Smith & Hui, 2014). Packaging does more than protect from decay, it provides the identification, and it provides consumer attraction and appeal to the product.
Producing cereals entails more than what is see in the grocery store shelves or what is consumed at homes. Essentially behind all of this manufacturing process is the effort to make profit, but no matter what idea the manufacturer may have, protecting the product and providing the best quality of product to consumer becomes primordial. Accurate shelf lives, quality of stored cereal, its freshness are what attract and appeal the consumer.
How Products Are Made. Cereal. 2014. Available at: http://www.madehow.com/Volume-3/Cereal.html. Accessed September 03, 2014.
Smith, J. (2004).Food processing: Principles and applications. Ames, Iowa: Blackwell Pub.
Kulp, K. (2000).Handbook of cereal science and technology(2nd ed., pp. 626- 627). New York: Marcel Dekker.
Breakfast Cereal. (2014, January 1). Retrieved October 18, 2014, from http://www.unityscientific.com/industries/food-dairy/cereal.asp