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Enzymatic Milling Product Yield Comparison with Reduced Levels of Bromelain and Varying Levels of Sulfur Dioxide

¹Crop Conversion Science and Engineering Research Unit, Eastern Regional Research Center, Agricultural Research Services, U. S. Department of Agriculture, 600 East Mermaid Lane, Wyndmoor, PA 19038. Mention of trade names or commercial products is solely for the purpose of providing specific information and does not imply recommendation or endorsement by the U.S. Department of Agriculture. ²Corresponding author. Phone: 215-836-3756. Fax: 215-233-6406. E-mail: djohnston@errc.ars.usda.gov ³Department of Agricultural Engineering, University of Illinois, 360G, AESB, 1304 West Pennsylvania Avenue, Urbana, IL 61801.

Enzymatic milling (E-Milling) is a process that could potentially replace the sulfur dioxide procedure currently used in all commercial wet-milling facilities. E-Milling incorporates the use of a short water soaking step (≤6 hr), a coarse grind, and the use of a protease to release the starch granules from the corn endosperm. E-Milling does not require sulfur dioxide to obtain starch yields equivalent to conventional wet milling; however, the important antimicrobial effects of sulfur dioxide are not duplicated by the enzymatic process. The use of low levels of sulfur dioxide (sufficient for antimicrobial activity) is being proposed as an easily implemented means of microbial control during E-Milling. To assess the effectiveness of E-Milling under these conditions, fraction yields for milling experiments adding sulfur dioxide with and without added enzyme were compared with fraction yields from conventional 24-hr steeping with 2,000 ppm SO₂ and 0.55% lactic acid. Because adding enzyme and SO₂ can both improve product yields and compositions independently, it was necessary to use a reduced level of enzyme (much less than necessary to generate “product quality” material) to observe differences in terms of product yields. The results show significant differences in starch, fiber, total gluten, and insoluble gluten recoveries between samples milled with SO₂ and enzyme compared with those at the same SO₂ level without enzyme addition. No significant differences were observed for soakwater or germ yields regardless of the SO₂ level used. The yield benefits from adding both enzyme and SO₂ are clearly shown over the addition of each individually, for all coproduct yields with the exception of the yields for germ.