Content area
Full text
ABSTRACT
Cereal Chem. 81(5):626-632
Enzymatic milling is a modified wet-milling process that uses proteases to significantly reduce the total processing time during corn wet milling and eliminates the need for sulfur dioxide as a processing agent. To optimize the overall enzymatic milling procedure and minimize the amount of enzyme, a series of experiments were done to determine the best first grind parameters and the optimal enzyme additions. The yields lor germ, germ quality, and starch recovery were used for evaluation of first grind and enzyme addition, respectively. The specific processing conditions evaluated were the soaking time and first grind parameters. After soaking and first grind optimization, enzyme concentration and pH determinations were evaluated using bromelain as an example. The first grind procedure was optimized by evaluating a combination of different soaking and grinding conditions followed by a fixed enzyme addition and incubation step. The pH profile of bromelain for enzymatic milling was evaluated for pH 3.5-6.5 and the optimum was determined to be pH 5.0. Enzyme addition was then evaluated using the optimized first grind conditions and bromelain additions with 0-1.9 g of enzyme (based on protein)/kg of corn. Results showed that the minimum addition of bromelain to reach starch yields equivalent to conventional yields were [asymptotically =]0.4 g of protein/kg of corn. This amount is significantly less than what was previously used and reported.
The development of a two-step wet-milling process for corn that uses proteases to significantly reduce processing time and eliminates the need for sulfur dioxide as a processing agent was previously reported (Johnston and Singh 2001). For the new process to be commercially viable, the costs associated with enzyme usage need to be offset by the savings generated through decreased processing time and energy consumption. The amount of enzyme necessary for processing is believed to be the single most important factor for minimizing enzyme-associated processing costs. The soaking time and the first grind procedures have also been identified as critical factors for effective enzyme treatment and germ recovery.
The initial work done on developing the enzymatic milling process (E-milling) was done using a small-scale (100-g) corn wet-milling procedure that has a high degree of precision in predicting yields in conventional corn wet-milling operations (Eckhoffet al 1996). There were a...