Evaluation of lipid peroxidation level in corn dried distillers grains with solubles1

Lipid peroxidation in feed can negatively affect animal health, growth performance, and meat quality. The objective of this study was to determine the lipid peroxidation level in corn dried distillers grains with solubles (DDGS) samples from 31 U.S. ethanol plants and compare results with a corn sample obtained from a corn processing plant. Lipids from each sample were extracted with hexane and analyzed for peroxide value (PV) and thiobarbituric acid reactive substances (TBARS). Peroxide values of DDGS samples ranged from 4.2 to 84.1 milliequivalents (meq)/kg oil (CV = 97.5%). The greatest PV among DDGS samples was 27 times greater than that of the corn sample (3.1 meq/kg oil). The TBARS values for DDGS samples ranged from 1.0 to 5.2 ng malondialdehyde (MDA) equivalents/mg oil (CV = 43.6%). The DDGS sample with the greatest TBARS value was 25 times greater than that of the corn sample (0.2 ng MDA equivalents/mg oil). Color of DDGS samples was measured by Minolta L*, a*, and b*, corresponding to the degree of lightness, redness, and yellowness, respectively. Correlations between PV, TBARS, and color were determined. Values of PV and TBARS were correlated positively (r = 0.81; P < 0.001). Both TBARS and PV were correlated negatively with L* (r = –0.73; P < 0.001, and r = –0.63; P < 0.001, respectively) and b* (r = –0.67; P < 0.001, and r = –0.57; P < 0.001, respectively), which suggests that darker and less yellow-colored DDGS samples were more likely to have a greater lipid peroxidation level, as measured by TBARS and PV, compared with lighter or more yellow-colored DDGS samples. However, a* was not correlated with either PV (P = 0.97) or TBARS (P = 0.66). These results indicate that color can be a preliminary indicator of lipid peroxidation level in DDGS, but a more reliable assessment of peroxidation level is achieved by measuring PV and TBARS.