PROTEOLYSIS AND FERMENTATION OF GRAIN-CORN ENSILED AT SEVERAL MOISTURE LEVELS AND UNDER SEVERAL SIMULATED STORAGE METHODS

Abstract

Proteolysis of ensiled grain corn (Zea mays L.) was studied in both whole-kernel and ground forms at initial grain moisture levels ranging from 22 to 36%. Three trials simulated and examined the effects of anaerobic fermentation, aerobic pre-ensiling and aerobic postensiling environments on soluble nitrogen (SN) formation (Trials 1, 2 and 3, respectively). Sealed mason jars (1.2 L) with fermentation locks, polyethylene-lined metal pails (23 L) and polyethylene-lined metal pails with fermentation locks were used as storage containers in Trials 1, 2 and 3, respectively. Soluble nitrogen as a percent of total nitrogen (TN) increased substantially during anaerobic fermentation (0–90 d), but increased only slightly and not at all during aerobic storage pre-ensiling (0–5 d) and postensiling (0–8 d). As moisture level increased, rates and extent of fermentation and proteolysis increased in both whole and ground grain (Trial 1). Soluble nitrogen contents after 90 d of sealed storage were approximately double for ensiled corn above compared to below 30% moisture. Grinding increased the rate but not the extent of proteolysis at grain moisture levels above 30%; grinding had little effect on SN formation or fermentation parameters at lower moisture percentages. A fourth trial compared the effect of three low-rate organic acid treatments to ground and sealed corn and an unsealed 1.5% (wt/wt) acetic:propionic acid (20:80) treatment on whole kernels for proteolysis in grain corn at 28% moisture. Only a 0.2% (wt/wt) acetic:propionic:formic acid:formaldehyde (10:40:20:30) treatment partially inhibited proteolysis; it did not control mold growth. A 1.5% acetic propionic acid treatment inhibited fermentation, but produced SN contents similar to the ensiled control. Key words: Proteolysis, corn, simulated, storage methods, moisture level