Popping Methods

Popcorn pops when it is heated to the correct temperature. That heating can be accomplished in several different ways, popping in Hot Oil, popping in Hot Air, and popping in Microwave Ovens.

Oil pop

Popping with oil is the process that Charles Cretors patented in 1893. This process is the one most commonly used in point of purchase popping in concession stands, and in homes before the advent of the microwave.

To pop popcorn in oil, corn and oil are placed in a container in a ratio of three parts corn and one part oil by volume. When the corn and oil reach the proper temperature, the corn begins to pop. Enough heat needs to be applied to heat the corn to approximately 450⁰F (250⁰C) within about three minutes. A normal popping cycle would be 2-1/2 to 3-1/2 minutes. At this time the corn will expand to its greatest volume. The time cycle may be adjusted by either changing the heat rate or, if the heat rate is fixed, by increasing or decreasing the amount of corn and oil put into the cooking pan.

During the popping process the corn and oil must be agitated to produce an even transfer of heat. In commercial machinery, a motor turns an agitator on the bottom of the popper kettle. In the home, the pot in which the corn is being popped is shaken over a burner on a stove.

Popping corn in oil is probably the simplest snack production process available and permits the manufacture of the end product at the point of purchase. The aroma, animation and the obvious freshness of the product make it ideal for concession stands where the consuming public can view the process.

Oil popping (Machinery)

Machinery for popping corn in oil is primarily used in the concession industry and as such the range of equipment available is generally sized for a concession stand. The standard poppers are gas or electrically heated. Individual poppers suitable for industrial applications are typically 40 Pounds (18 Kg) per hour production.

As volume requirements increase production lines made up of one or more banks of the large oil poppers are set up on a conveyor belt. Typically six poppers are set side by side and one operator to adds corn, oil and salt to the machines. Operating on a typical three-four minute cycle the operators will dump and empty and refill a popper every thirty seconds. Corn is usually fed by hand with sized measuring cups.

Oil may be added to the kettle in several different ways. Oil is circulated from a large central oil storage tank to volumetric measuring points above each popper. When it is time to recharge a popper the dry ingredients are added to the kettle and the oil measure is emptied into the kettle. Another approach is to have a timed metering pump at each popper. This pump may draw oil from a manifold that circulates from a central tank or from individual 50 Pound (22.68Kg) pails. In another option the pumps are immersed in the pails themselves and are equipped with a heat element to melt oil that is solid at room temperature.

Popping Oils

The oil in the oil popping process serves two purposes. The first is to transfer the heat from the bottom of the popping pan or kettle to the popcorn kernels. The second is to add flavor to the finished product.

In general terms any shelf stabile oil that will tolerate the high temperature of the popping process can be used. When choosing popping oil several factors should be considered.

1. Melting point. If the melting point is above body temperature, 98.6⁰F (37⁰C), the finished product will leave a waxy coating on the inside of the mouth of the consumer. Popcorn is often consumed in conjunction with cold drinks, which will accentuate this waxy sensation and create an undesirable product.
2. Usability. Melting point also affects usability. Liquid oils are generally easier to handle. Coconut oil has a melt point of 76^OF (24^OC) and can solidify in pipes in cold weather climates. Some Canola oil varieties will separate into liquid and solid phases at lower temperatures.
3. Clean ability. The temperature in a popping kettle usually exceeds 450⁰F. This temperature will carbonize and burn oil left in the kettle. Some oils are more inclined to creating a carbon buildup the kettles. This has a direct relationship to the amount of polyunsaturated fat in the oil. The oil chosen should not smoke at the popping temperature. Oils heated to their smoke points begin to decompose and will have a very short shelf life.

Popular popping oils in the United States

• Coconut
• Corn
• Peanut (Potential allergy problems should be considered)
• Sunflower
• High Oleic Sunflower
• Canola
• Soybean
• Commercially sold oil blends

The oils listed above are popular and may be found in many locations. All have melting points below body temperature and some are liquid oils that do not have a solid phase. The primary differences are their flavors and how the perform in the popping kettles.

For many years Coconut oil was the most popular popping oil. It was relatively inexpensive, It is a 76⁰F melting oil, is very stable, and has a good flavor. From the manufacturing point of view this oil is also desirable for the fact that it does not create a lot of carbon in the popping kettle. The only negative is that it is highly saturated and is considered to be unhealthy by some consumers

Oil Pop Process

1- Salted (Savory) Corn

This is the simplest oil pop product to make and most commonly seen product in the United States. Corn, Oil and Salt are added to a popping Kettle and the kettle is heated. The corn will pop and the product as it exits the kettle only needs cleaning of unpopped or undersized kernels before packaging for sale.

If the popcorn kettle is still hot from the last cycle the full popping cycle from loading raw materials to dumping the kettle will be between 3 and 4 minutes. If the time cycle is significantly less the corn is probably being popped too quickly and will have hard centers and be undersized. If it takes much longer the kettle is being overloaded. A good indication the kettle is ready to dump is when you can count to four between pops.

The popping oil used usually has Beta carotene and butter flavor added to give the finished popcorn a yellow color and butter flavor.

2- Sugar (Sweet) Corn

Sweet Popcorn is very similar to Salted corn in its process. In this process the amount of corn and oil placed in the popping kettle is reduced and an amount of sugar equal to approximately 75% of the normal corn is added. On the surface this appears to be a very simple change. The situation is complicated by the fact that the corn requires a kettle temperature of 450⁰F (250⁰C) to pop the corn. Sugar begins to burn at a much lower temperature, about 320⁰F (160⁰C). The temperature of the popping kettle must be reduced to reduce burning of the sugar and as a result the time for the popping cycle is increased and the output of the kettle reduced from its capacity for salted corn.

Sugar corn is usually a white product and is the result of popping oil that has no color added to it and is popped with white sugar.

In the actual process there are two approaches to the addition of the sugar to the kettle. Sugar can be added with the corn and oil. The result is a slightly browned product near the end of the popping cycle. The sugar may also be added just as the corn begins to pop. This will give a whiter corn but the sugar on the corn may not melt completely and have a flat grainy appearance. The choice of method will depend on the local market.

In the actual operation of the kettle the operator must be more attentive when making sugar corn due to the fact that the kettle must be emptied as soon as the corn is done popping. If it is allowed to remain in the kettle the sugar will begin to burn. Even with careful operation the sugar will create leave an accumulation of carbon on the surface of the kettle. A kettle making sugar corn will require more frequent cleaning than a kettle making salted corn.

3- Kettle Corn

Kettle Corn is Sugar corn with a little salt added. The product has been made for many years but has become popular at Fairs and Carnivals when it was made with a great deal of fanfare in a large open top copper kettle. The operator would stir the corn, oil, salt, sugar mix with a wooden paddle and wore leather chest and arm covers to protect him from the hot sticky popcorn that often flew out of the kettle.

The process for Kettle Corn is the same as Sugar corn with the exception of the addition of salt to the recipe. The salt must be added in to the kettle near the end of the popping cycle. If it is included from the beginning with the rest of the ingredients the salt will cause the corn to burn and darken.

Strictly speaking, Kettle Corn is corn popped in a kettle with oil. However, due to the availability of large dry popping lines, and automated continuous caramel coating lines, most large-scale production is now done by this method. A light coating of sugar is added to the popcorn to simulate the sugar in Kettle Corn. A small amount of salt completes the flavor sensation. The “cooked in oil” flavor is usually missing.

4- Dry pop Process

When popcorn is popped without the use of oil the process is referred to as dry popping. This process is found in the home, commercial, and in industrial situations.

The first hot air poppers were wire baskets containing a small amount of popcorn that were held over a fire. The baskets were shaken rapidly to agitate the corn and keep it from burning. Today commercial versions of this process use a motorized rotating wire drum over an open flame or electric heat elements.

Today dry-popped or hot-air popped corn is used mainly in the Snack Food industry. Many specialty popcorn shops also use dry popcorn as a base for the many products they make and sell. Industrial hot air poppers are continuous automatic machines that have many applications. The industrial hot air corn popper is essentially a continuous-feed, fluidized-bed oven. While it is primarily a popcorn machine, it is also used to puff third generation snacks, roast peanuts and it will process any type of snack that requires precise temperature and time control and where a continuous process is needed. The dry pop machine used in specialty shops uses a rotating wire screen to simulate the shaken wire basket used in the 1800’s.

5- Dry popping Machinery

There are two basic types of Dry poppers on the market today, batch and continuous hot air poppers.

5- 1- Batch Dry Poppers

Batch poppers are made with a rotating wire drum with a fine mash that supports raw popcorn over an open flame or electric heat element. A coarse wire mesh shaped like a helix is fitted inside the drum. The mesh in the helix is coarse enough that the raw popcorn grain will fall through and popped corn will not. When the corn sitting on the fine mesh outer screen pops it becomes too large to fall through the inner screen. The shape of the inner screen feeds the popped corn out of the drum as the drum rotates.

5- 2- Batch Popper operation

The operation of the batch dry popper is much like that of the batch wet popper. A volume of corn corresponding to the amount recommended by the manufacturer is put into the popper. As the corn begins to pop, it will be discharged from the machine by the helical sifter screen in the popper. Before all the corn is popped, another charge of corn is placed into the popper. Experience will determine the correct timing. The net result is a nearly continuous flow of popped Corn. The sifter that carries popped corn out of the machine does not carry out unpopped kernels; the unpopped corn remains in the popping drum and must be emptied periodically.

6- Continuous Dry Poppers

Hot air poppers are continuous automatic machines that have many applications. The commercial hot air corn popper is essentially a continuous feed fluidized bed oven. While it is primarily a popcorn machine, it is also used to puff third generation snacks, roast peanuts and will process any type of snack that requires precise temperature and time control and where a continuous process is needed.

The basic design of a hot air popcorn machine incorporates a horizontal rotating perforated metal cylinder. Popcorn or any other product to be processed is introduced into one end of the cylinder. Heated air is forced up through the perforations in the cylinder with enough pressure to fluidize the raw popcorn lying on the bottom surface of the drum. The high velocity of the air agitates the corn and provides for very rapid and uniform heat transfer.

Popcorn kernels are a raw grain, the only processing they have been exposed to is that of drying to the correct moisture and cleaning to remove undersized kernels. The variables of a natural product require that the popcorn machine operator be able to adjust the machine to compensate for variation in kernel size, shape, hybrid and moisture content. In addition to accommodating the variables in the raw grain control of the process variables permit the operator to modify the shape of the finished popcorn kernel and the scrap rate.

7- Microwave

With the advent of Microwave ovens in the kitchen popcorn moved from a covered pot on the stove to a prepackaged bag in the oven. Today it is the predominant method of popping corn in the home. Due to the cost of the machinery and the cost of operation Microwave has not been developed in industrial markets.

Popcorn has been around for a long time and it should not be underestimated. It is perceived as a healthy snack and can be flavored to appeal to many consumer groups. There are a number of options on how popcorn can be produced and marketed. Popcorn only requires a little imagination to develop a marketing plan and the discipline to deliver a high quality product to take advantage of the potential sales.