Wet-milling of grain sorghum of varying seed size without steeping

Experimental lines of hybrid grain sorghums were produced with thousand-kernel-weights (TKW) varying between 23.1-44.9 g. The proportion of germ in the normal-seeded hybrids with TKW 23-27 g was similar to 9.9-10.2% of dry kernel weight, whereas that in the large-seeded hybrids with TKW 37-45 g was similar to 10.8-11.2%. Starch in grain decreased similar to 4% as kernel weight increased which was offset by an increase in protein level. Wet-milling of the grain was done without steeping after an initial coarse-grinding step in two parts of water with 0.3% sodium bisulfite. Three of four samples of large-seeded and soft-textured grain sorghums gave 77-82% recovery of starch with 0.5-0.7% protein, while one gave 59% recovery and 0.6% protein. The starches had < 0.5% damaged starch, gave no rancid off-odor after storing 26 months at 25 degrees C in a sealed glass container, and had lightness (L*) values of 93.1-93.7 vs. 95.2 for a commercial corn starch. Their pasting curves were similar to that of commercial corn starch. The bran/germ/endosperm fraction obtained by limited wet-milling of one large-seeded hybrid was separated by flotation to recover one-half the germ in 98% purity as estimated by fat content.