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Harvest Timing May Influence Bean Color
During the 2001 harvest, it was observed that pinto beans
harvested near the end of September were darker than beans harvested near the
beginning of September. Darker beans may have a $1 to $6 per hundred weight
lower value than lighter colored pinto beans. Eleven farmers from different
areas in North Dakota collected bean samples while harvesting during September
2002. There was a lot of variability, but the lightness trended lower with later
harvest dates. The measured reduction in lightness values from 57 to 55 is
visually observable darkening. A difference in lightness for the different
varieties was noted, but the sample sizes were not large enough to validate a
difference. The lightness values observed at the various harvest dates are shown
in Figure 1. A darkening of the
pinto beans was noted when the length of the growing period exceeded 120 days.
Beans harvested after a 110 days growing period had a 57 L-value and
those harvested after a 130 days growing period had a 54.5 L-value. The data is
shown in Figure 2. Some increase in
the �redness� of the beans was noted with later harvest dates and longer
growing periods. The harvest moisture content did not affect the lightness of
the pinto beans.
Figure 1. Harvest
date versus L value for all samples.
Kenneth Hellevang, Ph.D., PE
Extension Engineer, Professor
NDSU Extension Service
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