Cereal Chem. 75(1):156-161To investigate relationships of wheat single kernel (SK) characteristics with end-use properties, we used 12 hard winter wheat cultivars harvested at six regions in Kansas in 1993. Significant positive correlations occurred among wheat hardness parameters including near-infrared reflectance hardness score, SK hardness index (SK-HI), and SK peak force (SK-PF) obtained by the Single Kernel Characterization System (SKCS). The SKCS characteristics also were significantly correlated to conventional wheat quality parameters such as test weight, kernel density, and kernel sizing. Flour yields were significantly correlated with SK-PF, SK-HI, and SK weight (SK-WT), suggesting the usefulness of SKCS in evaluating milling quality. The negative correlation of milling score with the standard deviation of SK-HI and SK-PF indicated that uniformity of SK hardness is desirable for good milling performance. However, bread loaf volumes had significant negative correlations with SK diameter and SK-WT, mainly due to the inverse relationship between wheat protein contents and kernel weights or sizes. Loaf volume regression values, the changes in loaf volumes per one percentage point of flour protein, also had significant negative correlations with SK-HI, SK-PF, and SK-WT.

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T HE effect of heat on trypsin inhibitor (TI) activity during steam-infusion cooking of soymilk was studied. At 154°C only 40 s process time reduced TI to the same level as conventional cooking at 99°C for 60 min. Between 99 and 154°C the kinetics of TI inactivation followed behavior exemplified by the summation of two first-order reactions. Spline fitting functions effectively modeled the data with r 2 ranging from 0.984 to 0.999. The heat-labile reaction was attributed to Kunitz inhibitor and the heat-stable reaction, to Bowman-Birk inhibitor. The former accounted for approximately 85 percent of the iriginal TI activity. Arrhenius equation kinetic constants for each reaction were calculated.

Traditional soymilk is boiled for approximately 60 min at 99°C pH 6.7, which reduces trypsin inhibitor (TI) activity by more than 90% to improve nutritional value. We evaluated continuous, direct steam-infusion cooking that facilitated higher temperatures (99-154°C) than that traditionally used for cooking soymilk. At temperatures above 120°C in steam-infusion cooking we observed consistent temperature-dependent patterns in yields of soymilk, solids, andyprotein, characterized by an initial decrease, followed by a rise to maximum recovery, then by a final decrease. At 154"C, pH 6.7, maximum recovery occurred at the same point as did adequate inactivation of TI. As much as 90% of the slurry, 86% of the soybean solids, and 90% of the protein were recovered as soymilk after centrifuging at 1050 x G for 5 min. Under optimum conditions for steam-infusion cooking the soymilk also retained less than 8% residual TI activity, and less chemical browning. Using traditional cooking methods, about 72% of the slurry, 61% of soybean solids, and 7 3% of the protein are recovered.

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