Precooked masa flour snacks are now very much part of the ethnic food scene due to an influx of southern Americans into the USA and Canada. Manufacturers have catered for this type of product exploiting the power of precooked masa flour. A great range of different masa flour are now on the market for tortilla chips, nachos etc.
Traditional corn cooking methods have been replaced in the snack industry for example with extrusion and larger-scale cooking technologies. In this instance, corn is cooked and ground immediately with hardly any steeping if any at all.
Processing masa flour
Five steps are needed in producing corn or masa-style snacks. Corn from a bulk hopper is ground up and passed through a 1.5-mm screen before transfer to a batch or in many cases continuous blending and mixing system.
The ground corn is kneaded with water and calcium hydroxide to a moisture content of between 20 and 25% w/w with the calcium hydroxide level between 0.5 and 1.0%w/w. About 15 minutes is needed for water to penetrate the mass. The final moisture content and the ability of the alkali to modify the masa corn depends on the varieties used and the manner in which the calcium hydroxide is applied to the mixture.
Extrusion of masa flours
Masa corn is fed via a hopper which ultimately controls the rate of flow through the extruder. Most extruders used nowadays are twin-screw but single-screw extruders are relatively as effective if handled appropriately.
The flow-rate is one of the main controlling factors because the final product quality will depend on uniformity of heating and pressure application which also depends on flow rate. Live steam is injected into a mixing cylinder so that the corn is tempered prior to extrusion. This also ensures that all particles have been fully penetrated with water as moisture.
Temperature of processing is between 90 and 95 Centigrade (194 to 203 Fahrenheit).
Preconditioned corn is extruded through a 1/6 to 1/4 inch (6 to 9 mm) die orifice. The number of holes in the die depends on the size of the equipment. The minimal amount of shear energy put into the system is highly desirable to avoid disrupting the gelatinizing starch. The temperature of the extruder barrel is between 120 and 150 Centigrade and barrel pressures are set between 10 and 15 atmospheres.
A rotating knife cuts the extrudate as it leaves the die orifices. These are conveyed mechanically or pneumatically to a dryer.
In the dryer, the cooked and moist extrudate is reduced to between 10 and 12% moisture content. Drying needs to be very rapid to produce a high quality nonstick precooked masa flour. The best drying technology delivers a temperature of 300 Fahrenheit for 15 minutes of residence time.
The processed corn is passed through a 40 or 60-mesh sieve screen and packaged.
Precooked masa flours are temperared before further extrusion to create tortilla chips, corn chips and so on.
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