Oats, the only grain referred to in the plural form, is the third largest crop in the United States. It is mainly considered as a breakfast cereal, but is also used in the manufacture of breads, cookies, and muffins. This cereal is available in many forms like whole oat groats, steel-cut oats, rolled oats, quick oats, oat flour, oat bran, etc. Raw oat grains undergo various stages of processing to get transformed into different forms.
Like most of the other grains, oats is also harvested when ripe. The grains are then dried before being transported to the milling plant. Here, the grains undergo various stages of processing; starting from cleaning and sizing or grading, dehulling, groat separation, steaming, kilning, and the final processing steps that make the end product. It is the final processing that determines the nature of the end product. Go through this NutriNeat article to understand the milling process of oats.
Field of oats
Ripe oats ready for harvest
Different Stages of Oat Processing
Cleaning and Grading
Cleaning is the first step in the processing of oat grains. This is done to remove impurities, like sand and stones, other grains, chaff and weeds, etc. Even lightweight oats are removed by air aspirators, and are used as fodder for animals. Once the cleaning is done, the grains are sized and separated into different grades.
The next step involves removal and separation of the husk from the grains, to obtain oat groats. The cleaned raw oats are fed to a large machine, which throws the grains to a hard surface. The impact of the collision of the grains with the hard surface and the resultant abrasion cause separation of the hull from the kernel called groat. The speed of the machine is set in such a way that the only the husks are removed without breaking the groats. In other words, care is taken to ensure maximum yield, by minimizing the number of broken groats. Then, the hull is removed using air aspirators, and is used as feed for livestock or to produce oat fiber. The resultant groats are further cleaned by scouring machines.
Whole oat groats
Oats contain lipolytic enzymes, which break down the fat in the grain to free fatty acids, which, in turn, makes the grains rancid. This enzymatic activity gains speed once the protective husk is removed. In order to avoid this, cleaned groats are subjected to steam treatment, and the heat radiators in the kiln absorb the moisture from the grains. This process is unavoidable because, after dehulling, the flavor of groats will turn rancid within four days, unless stabilized by the above said process. Kilning also gives a nutty flavor to the oats.
Sizing and Cutting
The groats are fed to sizing systems, where machines separate the groats as per their size. After separating the large groats, the small groats and the broken pieces are directed to the cutting system. Here, the steel cut oats are made from the small groats and broken pieces. Sifters are used to sort out small and large pieces. Small pieces are called baby steel cut, while large pieces are referred to as large steel cut. A mixture of both large and small pieces is termed as regular steel cut. In case of shortage of broken pieces, whole oat groats are cut into required sizes using steel blades.
Steel cut oats
This process results in the production of oat flakes or rolled oats, depending upon the raw material used ― groats or steel cut oats. Whole or steel cut oats are steamed (for softening) and then passed to the rolling mill, which is usually, two large corrugated rolls spinning at the same speed in opposite directions. Steel cut oats in different sizes are used to produce quick rolled oats, baby oat flakes, and instant oats. Whole groats produce old-fashioned types like regular, medium, and thick rolled oats. Before packaging, the flakes are dried and cooled in a fluid-bed dryer and cooler.
Thick rolled oats
The milling process involves two methods ― oat bran milling and whole flour milling. In the first method, oat groats are sent through roll stands, which separate the bran from the flour. This process results in two products ― oat bran and oat flour without bran.
The second method is used exclusively to produce whole oat flour from whole groats. Groats are fed to hammer mills, where it is converted into fine oat flour. The coarse flour, left behind after sifting, is again fed to the hammer mill, and this process continues.
This is only a brief overview of processing oats, to produce the different forms in which the grain is marketed. It is said that whole oat groats and steel cut varieties are more nutritious than the rolled ones, as they are not processed further. Oats are also considered a rich source of carbohydrates, proteins, vitamins, minerals and dietary fiber. So, including oats in your diet can definitely add to the nutrition value and impact your health in a positive way.