Grain cleaning

Unmodified Modified Corn Corn Corn Refined Corn Corn Corn 

Prior to wet-milling, the com must be softened by a steeping process developed specifically to produce optimum milling and separation of com components. Steeping is more than simple water soaking of com. It involves maintaining the correct balance of water flow, temperature, sulfur dioxide concentration and pH. Com is normally steeped for 24-40 hours at a temperature of 48°C to 52°C. By the end of the steeping period, the kernels should have (a) absorbed water to about 45% (wet basis)  

The third stage of steeping (the last 8-12 hours) is known as the sulfur dioxide dominated stage because it is characterized by high concentrations of sulfur dioxide (up to 2500 ppm) in the process water being added to the oldest corn. The third stage 

Steeps are large tanks that may be constructed of any material resistant to the corrosive action of solutions of sulfur dioxide and lactic acid at pH 3 1, but stainless steel construction is now the most common. Steep tanks will vary in size and number depending on the capacity of the facility. It is common in newer US facilities for tanks to hold 250-600 metric tons (10000-25000 bushels), but tanks as small as 60 metric tons (2500 bushels) of com are still in use in some plants, with even smaller tanks being used in some other countries. The number of tanks in each separate steep battery varies, ranging from 6 to over 50. 

Steeps are normally operated as countercurrent batteries of 6-12 tanks although, as mentioned earlier, much longer batteries are sometimes used. Process wash water containing 0.1-0.2% sulfur dioxide is placed on corn that has been in the steeps longest and, therefore, has the lowest residual solubles content. This process water is sequentially moved from tank to tank (from oldest corn to newest) while it decreases in sulfur dioxide content and increases in solubles. 

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Organic grains may be contracted prior to planting. Contracts vary considerably, some make producers responsible for grain cleaning or shipping charges or both, while others do not make the producer responsible for either. 

Herbicides reduce transportation and storage costs. A good example of the transportation and storage costs of weed seeds was given by a Canadian weed scientist ( 1). He reported that despite herbicide usage and grain-cleaning processes, 33 railroad carloads of weed seeds are transported across Canada from elevators to ports each day. 

It can be assumed that seeds and dust from PA-containing plants are a major source for a human PA exposure [ 12,13]. In industrialized countries, grain cleaning methods reduce the PA contamination under a level where acute intoxications can occur, but the dust components are still remaining and there are indications that diseases such as cirrhosis, cancer, and pulmonary arterial hypertension are due to a long-time exposure of low doses of PAs [14]. 

Corn and other cereal grains Cleaned, whole corn, wheat, rye, or barley. Canadian whiskey ... 

Why are grain cleaning operations critical to any milling process List at least five reasons why it is critically important to thoroughly clean grains before milling. 

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