Kd. Rausch et al., EVALUATION OF THE DISPLACEMENT VALUE AS A METHOD TO DETECT REDUCED CORN WET-MILLING QUALITY, Cereal chemistry, 74(3), 1997, pp. 274-280
A procedure based on the resistance and capacitance (RC) properties of
corn to calculate a displacement value (DV) was evaluated for detecti
on of corn that had reduced wet-milling quality. In 1991 and 1992, thr
ee hybrids were dried at air temperatures between ambient and 115 degr
ees C in batch dryers. Additional samples, obtained from commercial el
evators in 1992, had been dried with air temperatures ranging from 52
to 136 degrees C. A baseline reference relationship was developed betw
een log(10)-resistance and capacitance with data from ambient-dried sa
mples. A DV was defined as the horizontal distance along the capacitan
ce axis from a sample RC data point to the baseline reference. RC prop
erties of samples dried at air temperatures >50 degrees C were compare
d to the baseline and the DV determined. Selected drying treatments we
re wet-milled by a laboratory-scale procedure to verify milling qualit
y and correlation with DV. The effects attributed to hybrid and harves
t moisture content on the RC properties of ambient-dried samples were
small, allowing the baseline reference to be applied to a wide range o
f corn samples. In 1992, the baseline shifted upward from the 1991 bas
eline by 0.5 units on the log(10)-resistance axis. DV increased signif
icantly at drying air temperatures >50 degrees C for batch-dried sampl
es. While DV correlated with drying temperature in batch-dried samples
(r = 0.66), it did not correlate with starch yield or recovery of com
mercial samples (r less than or equal to 0.10). Although the specific
causes could not be determined, the shift in the baseline indicates th
e method would be difficult to implement on a practical scale. Althoug
h not indicated by DV, starch recovery decreased significantly for sam
ples batch-dried at air temperatures greater than or equal to 70 degre
es C. All samples dried at 115-136 degrees C had significantly lower s
tarch recoveries.