Upon delivery to the milling plant, chaff, rocks, other grains, and other foreign material are removed from the oats.
Step 1: Dehulling
Separation of the outer hull from the inner oat groat is effected by means of centripetal acceleration. Oats are fed by gravity onto the center of a horizontally spinning machine which accelerates them towards the outer ring. Groat and hull are separated on impact with an impact ring. The lighter oat hulls are then aspirated away while the denser oat groats are taken to the next step of processing. Oat hulls can be used as feed, processed further into insoluble oat fibre, or used as a biomass fuel.
Step 2: Kilning
The unsized oat groats will then pass through a heat and moisture treatment to balance moisture, but mainly to stabilize the groat. Oat groats are high in fat (lipids) and once exposed from their protective hull, enzymatic (lipase) activity begins to break down the fat into free fatty acids, ultimately causing an off flavor or rancidity. Oats will begin to show signs of enzymatic rancidity within 4 days of being dehulled and not stabilized. This process is primarily done in food grade plants, not in feed grade plants. An oat groat is not considered a raw oat groat if it has gone through this process: the heat has disrupted the germ, and the oat groat will not sprout.
Step 3: Sizing of groats
Many whole oat groats are broken during the dehulling process, leaving the following types of groats to be sized and separated for further processing: Whole oat groats, coarse steel cut groats, steel cut groats and fine steel cut groats. Groats are sized and separated using screens, shakers and indent screens. After the whole oat groats are separated, the remaining broken groats get sized again into the 3 groups (coarse, regular, fine), and then stored. The term steel cut is referred to all sized or cut groats. When there are not enough broken to size for further processing, then whole oat groats get sent to a cutting unit with steel blades that will evenly cut the groats into the three sizes as discussed earlier.
Three methods are used to make the finished product:
This process uses two large smooth or corrugated rolls spinning at the same speed in same direction at a controlled distance. Oat flakes, also known as rolled oats, have many different sizes, thicknesses and other characteristics depending on the size of oat groat passed between the rolls. Typically the three sizes of steel cut oats are used to make instant, baby and quick rolled oats, whereas whole oat groats are used to make regular, medium and thick rolled oats. Oat flakes range from a thickness of 0.36 mm to 1.00 mm.
Oat bran milling
This process takes the oat groats through several roll stands that flatten and separate the bran from the flour (endosperm). The two separate products (flour and bran) get sifted through a gyrating sifter screen to further separate them. The final products are oat bran and debranned oat flour.
Whole flour milling
This process takes oat groats straight to a grinding unit (stone or hammer mill) and then over sifter screens to separate the coarse flour and final whole oat flour. The coarser flour gets sent back to the grinding unit until it's ground fine enough to be whole oat flour. This method is used very much in India and other countries.
Go to www.wheatfree.com.au to order your Australian GF Oats.