AbstractThe increasing sophistication of customers has put pressure on corn wet‐millers to improve product quality. One quality requirement is that glucose and corn syrups be free of material stained blue or green by iodine, i.e. free starch. Observations from a number of corn wet milling plants indicate that liquified corn starch may test negative for free starch but yield a positive iodine test after saccharification. Such dextrose hydrolyzates are difficult to process into product and often fail to meet customer specifications. The problem has been traced to small (0.2 to 1.0 μm) particles which are present in the starch supply. The particles exhibit an iodine spectrum similar to that of gelatinized corn starch. Enzymatic degradation of the particles was compared to that of gelatinized and non‐gelatinized starch, and lipid‐amylose complexes; the behavior of the particles most closely resembled nongelatinized starch. Extended liquefaction reduces, but does not eliminate the problem. Cellulase, hemicellulase, amylase, and proteasewere tested as adjuncts to normal glucoamylase products; none of these were effective in assisting hydrolsis of the particles under saccharification conditions. The particles can be completely eliminated by microporous filtration of liquefact or dextrose hydrolyzate.