Submitted to: Journal of Dairy Science
Publication Type: Abstract Only
Publication Acceptance Date: 3/1/2010
Publication Date: 7/11/2010
Citation: Hoffman, P.C., Esser, N.M., Shaver, R.D., Coblentz, W.K., Scott, M.P., Bodnar, A.L., Schmidt, R. 2010. Influence of Inoculation and Storage Time on Alteration of the Starch-Protein Matrix in High Moisture Corn. Journal of Dairy Science. 93:726. Interpretive Summary:
Technical Abstract: The fates of hydrophobic prolamin (Zein) proteins, which encapsulate corn starch creating vitreous endosperm, have not been investigated in high moisture corn (HMC). To assess influences of inoculation and storage time on hydrophobic proteins in HMC, quadruplicate samples of two random corns (A and B) containing 25.7 and 29.3% moisture were ground (± 900 um), inoculated (I) with or without 500,000 cfu/g of LB500 (Lallemand Inc., Milwaukee, WI), ensiled, and stored for 0, 15, 30, 60, 120, and 240 d. Nutrient composition (CP, prolamin, starch, ADF, NDF), fermentation (pH, lactate, acetate) and protein degradation markers (buffer-soluble CP, NH3-N) were evaluated. At 0 and 240 d, a, ß, ', and d zein regions were profiled using HPLC. Data were evaluated as a split-split plot using PROC MIXED procedures of SAS. Inoculation and storage time reduced pH, and altered lactate and acetate contents of HMC. Lactate and acetate contents of A, AI, B, and BI at 240 d were 0.40, 0.32, 1.11, 0.73, and 0, 0.35, 0.30, and 0.87% of DM, respectively. Buffer-soluble CP of HMCs increased from 1.5-2.0% of DM at 0 d to > 4.0% of DM at 240 d. Inoculation had no effect on buffer-soluble CP, but increased NH3-N content of HMC. Corn A contained more prolamin (5.8 vs. 4.6 g of prolamin/100 g starch) than corn B. Peak areas for 6 a, ', and d zein regions were higher for corn A and fermentation (0 vs. 240 d) reduced all zein subunits with the exception of 2 a and 1 d region. Fermentation reduced (> 50%) 27kDa ' zein which cross links and lies peripheral to a zein. Despite altering lactate and acetate contents, inoculation had no effect on hydrophobic proteins in HMC endosperm. Data suggest altering fermentation acids via inoculation has a minimal effect on hydrophobic proteins in HMC, but hydrophobic proteins in HMC are highly influenced by origin and storage time (proteolysis).