Manufacturing of popcorn

Almost all of the popcorn consumed throughout the world in grown in the United States.

Popcorn is ideally harvested when the moisture content of the grain is about 17%. Unlike most of other grains, the outer hull of the popcorn kernel is both strong and impervious to moisture and the starch inside consists almost entirely of hard, dense type.

Once the grain is harvested, it is slowly dried using aeration and low heat. This slow drying, low heat method is used to avoid kernel breakage and damage while reducing the moisture content to about 13.5 to 14% which is ideal for popping.

The kernels of popcorn are smaller than flint corn. When heated rapidly, they turn the moisture in the kernel, which has a moisture-proof hull, into a superheated pressured steam.

The pressure continues to increase until the breaking point of the hull is reached: a pressure of about 135 psi and a temperature of 180 °C. This pressure burst the outer shell and the entire inside of the kernel puffs into a mass of flaky starch.

Upon popping, the volume is 25 to 30 times greater than original kernel.
Manufacturing of popcorn

Grain cleaning

Cleaning is accomplished by:
*Screening out the larger particles with the chaffer and sieves
*Blowing out the lighter particles with a fan blast, or
*Screening out the smaller particles in a recleaner

The impact of grain breakage and fine materials on all aspects of the system has resulted in the need to clean grain.

The modern combine harvester produces remarkably clean grain compared with the manual and partially mechanized processes.

Cleaning decreases the airflow resistance, increases airflow, and increases the cooling rate of the grain if aeration is used.

For good storage the chaff, dust and straw must be removed. Broken and foreign grains should not be present: the former encourage insect attack, the latter lower market value.

Broken grains, grain dust and other fine grains have the greatest effect in the performance of insect control interventions.

A typical grain cleaner, often called a scalperator or scalping machine, consist of two parts, a shaking screen and a fan, driven from the same more. Straw and other large objects are removed by screening and the dust and other lightweight material are blown out by aspiration.

The amount of grain cleaning required prior to storage involves the factors of risk to grain deterioration as a result of mold and insect invasions and the costs associated with maintaining quality.

Grain cleaning

Grain Milling Functions

Grain Milling Functions
Threshing removes the grain from the stem. However, the grain is not usually ready for cooking until the husk (glumes) has been removed. Wheat, sorghum and pearl millet usually thresh naked that is without the glumes. Maize is on a cob covered with a sheath: the sheath must be removed and the grain taken from the cob.

A combine harvester threshes the maize free from both sheath and cob. Barley, oats, rice and most of the small millets thresh with the glumes adhering tightly to the kernel so that even a modern threshing machine or a combine harvester cannot remove the grain from this husk.

The first step in any milling process for this latter group is to remove the glummer. This is done by rubbing the grains one against the other in a mortar or by simple rotary machine, by splitting off the glumes in a disk huller, or by use of rubber rollers rotating at a differential speed. The objective at this stage of milling is to obtain as high an out-turn as possible of whole grains.

Once free from glumes, all grains may be treated in the same way. Cereals have an outer layer and a gem, known collectively as bran, which is rich in lipids that rapidly oxidize to give off-flavors. The bran also tends to be less easily digested than the endosperm.

The objective of the second stage of milling is, therefore, to remove the bran. In the case of rice, the grain is required whole, so great care is taken not to break the grain. Most other cereals are eaten as flour or meal (a coarse flour). The more of the bran that is removed, the better the flour will keep.
Grain Milling Functions

Wheat Cleaning and Milling

Wheat Cleaning and Milling
Wheat is harvested by combines that cut the stalk remove and collect the seed, and either return the straw to the soil, to be plowed under with the stubble and thus provide hummus or compress and bale it for future use as litter, ensilage and so on.

Wheat may be bagged in jute sack and stored in warehouses or it may be stored in bulk in elevators. The latter method provides the best protection against rodent and insect infestation. The moisture content of bulk stored wheat should not be higher than 14.5% and that of sack stored wheat not higher than 16%. Otherwise, microorganism may grow and cause heating and spoilage. When it is necessary to lower the moisture content of wheat it may be dried in bins by blowing hot air (not higher in temperature than 175 degree F) across the bins.

In preparing wheat for milling, it is blown into hopper scales that record the quantity of uncleaned wheat. Some of the coarser impurities are removed by this process. The grain then passes over a series of coarse and fine sleeves that further remove contaminating materials, including chaff and straw. Still in dry states stones may be removed by passing wheat over short openings that allow the heavier stones to fall out of mass and be trapped.

The wheat is next passed over discs or cylinders containing indented surface that remove seeds short or longer than wheat following a pass through a magnetic separator to remove any metals present. The next cleaning process is dry scouring to remove adhering dirt. The wheat is then washed in water, a process that both removes dirt and adds 2 – 3% water to the grain. The added water is necessary to provide desirable conditions for milling. A stone trap is including in the washer. Excess water is removed by centrifugation. A second wet cleaning with a light brushing action is ordinarily used, followed by aspiration (blowing air through the grain), which is the final cleaning operation. The grain is then carried into a bin from which it is fed to the milling operation. This bin is located on the top floor of the flour mill, the grain having been elevate do this position during the various cleaning operation.

In milling, grain is fed automatically though scale hoppers that regulate the flow of the seeds at rates corresponding to those of the following operations: Milling may be carried out by passing the grain through a series of corrugated rolls rotating toward each other, which remove chunks of the endosperm from the bran. After each passage through the break rolls, the material is sifted through cloth, or wire sieve and separated according to particle size.

The various streams of different sized flour particles are finally blended to provide the different grades of flour. The more finely ground flour is nearer to white but less nutritious than the coarser ground flour. This results from the more effective removal of bran and germ from finely ground flour. Impact milling is now used in some operations. With this method, the seed is broken open by impact in a machine. Flour particles of different sizes are separated by air classification or by centrifugation.
Wheat Cleaning and Milling

Ready to Eat Cereals

Ready to Eat Cereals
Ready to eat cereals are processed grain formulations suitable for human consumption without further cooking in the home. They are relatively shelf-stable, lightweight, and convenient to ship and store. There are made primarily from corn, wheat, oats or rice, in about that of order of the quantities produced, usually with added flavor ad fortifying ingredients.

Hot cereals, on the other hand, are made primarily from oats or wheat; those made from corn or rice are of minor importance, being produced in relatively small quantities. The original hot cereals required cooking in the home before they were ready for consumption, but now some varieties are preprocessed so that they are ready for consumption with the addition of either hot water or milk to the cereal in the bowl.

The processing of ready to eat cereals typically involves first cooking the grain with flavor material and sweeteners. Sometimes the more heat stable nutritional fortifying agents are added before cooking, Two general cooking methods are employed in the industry today – direct steam injection into the grain mass in rotating batch vessel, and continuous extrusion cooking , with the latter very much on the increase in recent decades.
Ready to Eat Cereals