Food First Blog | Tip of the Week: Shredded Food Products

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Tip of the Week: Shredded Food Products
Tip of the Week: Shredded Food Products

Shredded products such as ready-to-eat cereals and snacks have been around for at least 100 years. In 1892, Henry Perky from Denver, Colorado invented a machine for pressing wheat into strips. From the beginning, shredded wheat was marketed as a health food. People added it to mashed potatoes, cakes, ice cream, sweets, and even coffee to further enhance the nutrition of the foods they consumed.

Most shredded products are made with whole grain wheat. Certain percentages of other whole grains or multiple whole grains may be used in combination with wheat. For example, wheat may be shredded with rye, with or without caraway seeds. Soft wheat with a low level of protein is preferred for producing shredded products of a desirable texture. Soft wheat can be white, red, or a mixture of both. Shredded products made with white wheat are light colored, whereas those made with red wheat have visible pieces of red bran specks in the finished product. Even though hard or durum wheat could conceivably be used, they would result in much harder and crunchier products.

The Process of Shredding

The process of shredding begins with using clean wheat kernels, free of any foreign material such as chaff, dust, other grains, stones, sticks, and so forth. Once cleaned, the wheat is ready for cooking by one of two methods. The first option is to cook the kernels in water that is slightly below the boiling point (at about 210°F) under atmospheric pressure. This process is called immersion cooking. The second method is called pressure cooking, where the kernels are cooked under pressure using a limited amount of water.

Immersion Cooking

In immersion cooking, whole wheat kernels are used since they maintain their free-flowing integrity. Similar-size kernels are used to attain uniform cooking. The cooking vessel for immersion cooking has a horizontal, perforated basket that rotates within a stationary housing (about 3.5 feet in diameter and 8 feet long) and is sufficient to hold 50 bushels (approximately 3000 lbs.) of raw wheat. It is equipped with a water inlet and drains. The water is heated by injecting steam inside the cooker; a set temperature is maintained with temperature-sensing probes.

In order to achieve the set cooking temperature rapidly, preheated water may be used. Cooking is achieved when the kernel endosperm turns from starchy white to translucent gray, which usually requires 30 to 35 minutes. Analytical technical methods such as differential scanning calorimetry (DSC) or microscopy are also used to quantify the extent of starch gelatinization. The moisture content of the cooked wheat after draining the water will range from about 45% to 50%. Undercooking and overcooking are both undesirable — undercooked grains cause white starchy streaks in the final product, and overcooked grains cause overgelatinization, which can make the material very moist, sticky, and difficult to handle and process.

Pressure Cooking

In the pressure–cooking process, either whole or milled/cracked wheat may be used. Wheat is milled using a desired screen opening (such as in a Fitz mill) to reduce the wheat into smaller particles. Instead of milled wheat, partially bumped or flaked wheat may also be used. Pressure cooking provides the ability to blend in additional ingredients, such as other whole grains, starches, proteins, fibers, sugar or sugar derivatives, salt, colors, flavors, processing aids, or inclusions.

When pressure cooking, a precise amount of water is added, which is fully absorbed by the wheat and other ingredients. A pressure-cooked grain or material has a relatively lower moisture content than its immersion– cooked counterpart. Pressure cooking occurs at a steam pressure of 5 psig to about 25 psig at a temperature of 227°F to 267°F for 10 to 30 minutes. The cooking time is relatively short due to cooking at a higher temperature, which results from higher steam pressure. The pressure–cooked whole wheat berries coming out of the cooker are free flowing. However, when milled wheat is used, the exposed starch gelatinizes in the presence of water and forms agglomerates of various sizes. The agglomerated lumps are reduced in particle size using a lump–breaker, and further sized using a screening device.

Even though shredding technology is more than 100 years old, it is still being underutilized in comparison to other snack technologies. Shredding technology can be used to develop health–oriented products because shredding generally uses whole grains. Whole wheat is the preferred grain of choice for producing shredded products. Many other whole grains or starchy materials are generally unsuitable for shredding. However, it is possible to overcome their limitations by modifying formulas and processes. More work is needed to transition this technology from breakfast cereals to new snack opportunities.

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