It is indeed quite impressive the change in mass of a seed corn, when during its heat treatment it transforms into pop corn. The following describes briefly the process of this change.
Each corn seed consists of the endosperm and the perisperm. The corn seeds used for the production of popcorn is a special type of corn because they should have some specific features which are not found in all types of corn. The perisperm is the durable and impermeable part of the seed which holds the endosperm. The endosperm consists of two substances, which are responsible for and involved in the “miracle” of pop corn production: starch and water in the form of moisture.
Upon heating a corn seed, water content is vaporized within the seed increasing the internal pressure inside the seed. As the heating progresses, the internal pressure is increased but because the perisperm is particularly resistant it continues to withhold the grain structure. At the same time, due to the heating process, starch content have its physical structure changed, a process called gelatinization, a form of liquidation. When the internal pressure is increased enough, the perisperm can no longer retain the structure of the seed, causing it to “explode”. In “burst” release the steam content and the fluid starch which momentarily cools and resolidifies giving the popcorn the known irregular shape. At the time of the explosion, the internal pressure reaches a pressure of 135 psi and a temperature of 180 oC. To achieve the best possible explosion, it has been found that the moisture content of the seed must be, ideally, at about 14%.
If the humidity is less, the internal pressure delays to increase and because of the prolonged heating of the seed, the elasticity and consistency of the perisperm varied delaying the time that has to rupture so as to generate a large “flakes” popcorn.
If the seed contains more moisture, then the internal pressure will increase rapidly, before complete gelation and liquefaction of the starch content occurs, and the “flakes” popcorn that will be produced will be small. The same result we will have if the heating temperature of the seed is not the appropriate. The “flakes” popcorn obtained will be small and in some cases the corn seeds will not burst at all. In conclusion, we could say that for the creation of large corn flakes, which are desired, the following conditions must take place at the same time:
– The type of the seed so that there is an adequate internal rate of moisture, starch and specific elastic strap. – The appropriate time and the heating temperature in order for the seed to explode.
THE “EXPANSION” (swelling) of POP CORN
A type of corn which gives large “flakes” popcorn is more desirable commercially and financially. This is because it increases the volume of the product (popcorn) while its weight remains the same. For this reason, a measuring unit was developed which expresses the size of corn produced in a popcorn preparation. The unit is called expansion and is essentially, volume unit of the produced popcorn per unit of corn weight. To calculate the expansion a specific methodology (Metric Weight Volume Tester – MWVT) is used, for popcorn preparation and for measurement of the produced volume. Briefly, 250 g of corn thermally processed after mixing with 150 ml of oil in specialty maker popcorn of 1400 watts and a temperature of 232.2 oC.
The volume of the produced popcorn, measured in concrete measuring cylinder dimensions, expressed in cubic centimeters, divided by the grams of maize used and the quotient is the expansion of corn to be measured. The expansion rates of course vary and fluctuate depending on the type of corn from 35: 1 to 51: 1. Of course the longer the expansion the greater the commercial value of corn because large expansion means higher volume of produced popcorn hence more product for sale therefore more profit.