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ABSTRACT This study was conducted to identify the key volatile compounds that characterize whether silage has deteriorated and to investigate the intrinsic link between the key compounds and silage odor. First, silages with different aerobic exposure durations were sampled, and sensory evaluation integrating aerobic stability monitoring was used to distinguish whether the silage had deteriorated. Subsequently, headspace solid-phase microextraction gas chromatography-mass spectrometry (HS-SPME-GC-MS) was utilized to determine the relative content of the compounds. Using the relative content of the compounds in each silage as input, relative odor activity value (ROAV) calculations and orthogonal partial least squares discriminant analysis (OPLS-DA) were performed to determine the odor contribution of the compounds and the compounds with significant differences in relative content (based on variable importance for the projection, VIP) between the deteriorated and non-deteriorated silages. Next, the key compounds were identified by combining the conditions of average ROAV (aROAV) ≥ 1 and VIP > 1. Finally, the OPLS algorithm was used to analyze the intrinsic link of key compounds with the silage odor. The results showed that three out of 63 compounds—4-ethyl phenol, eugenol, and ethyl linoleate—were key compounds to characterize whether the silages deteriorated or not. In addition, ortho-guaiacol, 4-ethyl guaiacol, and 2-methoxy-4-vinyl phenol were the specific key compounds for deteriorated silage. Eugenol and ethyl linoleate were correlated with fruity, sour, and spicy odors. In addition, guaiacol, 4-ethylphenol, 4-ethyl guaiacol and 2-methoxy-4-vinyl phenol contributed to roasted, musty, and putrid odors.

ABSTRACT To improve the working performance of hammer mill, cutting-edge hammer and oblique hammer were designed in this study. The advantages of new hammers were theoretically analyzed. The grinding process of corn grain with different hammers was studied by discrete element method (DEM) and experiments. Discrete element simulation results showed that under same rotor speed conditions, the cutting-edge hammer had highest bond-breaking efficiency in corn grain model. The oblique hammer could reduce the incident angle of corn grain and improve sieving efficiency. The motion trajectory of corn grain in grinding chamber was relatively dispersed and similar when using common hammer and cutting-edge hammer, and the motion trajectory was more concentrated when oblique hammer was used. The experimental results showed that both cutting-edge hammer and oblique hammer could improve the working performance of hammer mill. The productivity of hammer mill could be improved by using cutting-edge hammer, electricity consumption per ton and temperature rise of feed could be reduced by using oblique hammer, and the experimental results were consistent with simulation results and theoretical analysis results. The research results can provide references for the design of new hammer and the grinding process simulation of other agricultural materials.

ABSTRACT The harvesting of straw by the flail knife type straw cutting device will cause loose contacts between straw roots and soil, affecting the straw feed's impurity content. In this study, a theoretical analysis of the straw cutting process was conducted to explore the factors influencing the root-soil disturbance. A pulling force test device was designed to test the pulling force of the corn stalk. The response surface method was used to study the effects of various factors on the straw pulling force under different conditions of draft angles (20°, 30°, 40°), soil moisture content (15.23%, 17.62%, 20.47%), and different straw root diameters. The test results showed that the straw pulling force was directly proportional to the straw root diameter and inversely proportional to the soil moisture content. The straw pulling force decreased first and then increased with the increase of the draft angle. According to the established second-order regression model, when the draft angle was 28.5°, the soil moisture content was 20.47%, the root diameter was 22 mm, the minimum pulling force of straw was 189.635N. The test results can provide a reference for the design of straw feed harvester.