Whether a starch conversion plant is using rice starch, corn starch or potato starch the liquefaction process is generally accomplished using a jet cooking (direct steam injection) system. After first prepping the slurry and making pH adjustments, the slurry is pumped through a direct steam injection heater where it is quickly heated to a temperature of 105°C or more. The slurry is then passed through a series of holding tubes for 5 to 7 minutes; time to allow the starch to gelatinize fully.
When considering a new process line, production facilities should examine the type of Direct Steam Injection Heater used. Many think of the jet cooking equipment as simply a high shear device, but that couldn’t be further from the truth, and when maximizing production, high shear isn’t always the best approach.
As taught in various food science courses, collapsing a swollen starch granule or breaking a granule before it reaches its full potential decreases gel formation and reduces gel strength. The key to maximizing gelatinized starch granules is to get them to uniformly swell to their maximum extent, while maintaining whole granule integrity without the need of heavy chemical modifications. Often times granular breakage is the results of crude high velocity eductor and choke-flow type steam jet eductors.