Carl J. Bern

Small-Scale Extrusion of Corn Masa By-Products

ABSTRACT Corn masa by-product streams are high in fiber and are amenable for utilization in livestock feed rations. This approach is a potentially viable alternative to landfilling, the traditional disposal method for these processing residues. Suspended solids were separated from a masa processing waste stream, blended with soybean meal at four levels (0, 10, 20, and 30% wb), and extruded in a laboratory-scale extruder at speeds of 50 rpm (5.24 rad/sec) and 100 rpm (10.47 rad/sec) with temperature profiles of 80-90-100°C and 100-110-120°C. Processing conditions, including dough and die temperatures, drive torque, specific mechanical energy consumption, product and feed material throughput rates, dough apparent viscosity, and dough density, were monitored during extrusion. The resulting products were subjected to physical and nutritional characterization to determine the effects of processing conditions for these blends. Extrudate analysis included moisture content, water activity, crude protein, in vitro...

Implementing a Computer Vision System for Corn Kernel Damage Evaluation

A computer vision system was developed for evaluation of the total damage factor used in corn grading. Major categories of corn damage in the Midwestern U.S. grain market were blue–eye mold damage and germ damage. Seven hundred twenty kernels were obtained from officially sampled Federal Grain Inspection Service (FGIS) corn samples and classified by inspectors on the Board of Appeals and Review. Inspectors classified these kernels into blue–eye mold, germ–damaged, and sound kernels at an 88% agreement rate. A color vision system and lighting chamber were developed to capture replicate images from each sample kernel. Images were segmented via input of red, green, and blue (RGB) values into a neural network trained to recognize color patterns of blue–eye mold, germ damage, sound germ, shadow in sound germ, hard starch, and soft starch. Morphological features (area and number of occurrences) from each of these color group areas were input to a genetic–based probabilistic neural network for computer vision image classification of kernels into blue–eye mold, germ damage, and sound categories. Correct classification by the network on unseen images was 78, 94, and 93%, respectively. Correct classification for sound and damaged categories on unseen images was 92 and 93%, respectively.

PHYSICAL AND NUTRITIONAL PROPERTIES OF CORN MASA BY-PRODUCT STREAMS

Production of corn masa-based products is flourishing in the United States, as is the generation of masa processing waste. Masa by-products have potential for value-added utilization, an option which could produce less pollution in the environment and economic benefits for masa processors. Physical and nutritional properties of these by-products are needed for the proper design of processing operations and by-product applications, but information concerning masa byproducts is not currently available. Thus the objective of this study was to fully characterize typical masa by-product streams. The masa by-products studied had moisture contents between 88.15% and 89.29% (w.b.), water activity values between 0.999 and 1.000, densities between 1030.85 and 1047.32 kg/m 3 , yield stress values between 1440.04 and 1618.08 N/m 2 , pH values between 6.17 and 6.30, Hunter L values between 35.15 and 49.13, a values between 0.27 and 0.98, and b values between 6.85 and 9.38. Drying curves were developed to predict drying behavior. The dried by-products had protein contents between 4.76% and 4.90% (d.b.), crude fat contents from 0.74% to 5.76% (d.b.), ash contents between 17.41% and 19.09% (d.b.), and carbohydrate contents from 71.93% to 75.41% (d.b.), which was due primarily to fiber, with hemicellulose levels of 20.82% to 24.06% (d.b.) and cellulose between 30.55% and 31.83% (d.b.). Dry masa by-products also consisted of 4.68% (d.b.) calcium. Therefore, dehydrated masa by-products seem very suitable for use as livestock feed additives.

Background segmentation and dimensional measurement of corn germplasm

An automatic thresholding technique was developed to segment the background from the images of corn germplasm (ears of corn). The technique was a modification of Otsu’s algorithm using probability theory. Three different measures were used to evaluate the performance of the modified Otsu’s algorithm for background segmentation and subsequent dimensional measurement of corn germplasm. Modified Otsu’s algorithm was found to perform better than Otsu’s algorithm and was successful in automatic background segmentation of all 80 images of corn germplasm included in the study. This modified algorithm also eliminated the misclassification of exposed cob in the image as background which occurred with Otsu’s algorithm. Subsequent dimensional measurements based on the segmentation by the modified algorithm were also highly accurate.

Airflow Resistance of Mixtures of Shelled Corn and Fines

ABSTRACT TESTS were carried out to define the effects on airflow resistance of adding various percentages of various sizes of fines to whole corn kernels. The relationship between clean corn multiplier and percentage fines was defined for seven size grades of fines. Effect of fines on fan power requirements for aeration and drying was estimated.

PRESERVING THE IOWA CORN CROP: ENERGY USE AND CO2 RELEASE

A study was undertaken to estimate energy use and CO2 release due to postharvest preservation of the 38.8 × 106-Mg (1.52 ×109-bu) Iowa corn crop. About 87% of the crop is artificially dried. Other preservation methods include cribbing ear corn (7%), oxygen-limiting storage (5%) and chemical preservative treatment (1%). Preservation of the corn crop requires, in total, 18 200 TJ of energy and releases 1614 Gg of CO2. Combustion of fuel (liquefied petroleum or natural gas) and electricity accounted for 77 and 10% of total energy use, respectively. CO2 from combustion of fuel and generation of electricity accounted for 57 and 32% of the CO2 release, respectively. Preservation methods varied in total energy use and CO2 release from farm natural-air drying at 1020 MJ/Mg corn and 262 kg CO2/Mg corn to chemical preservative treatment at 116 MJ/Mg corn and 9.3 kg CO2/Mg corn.

Soil Strain Under Three Tractor Configurations

Soil compaction can cause significant crop yield reductions. Effective management of soil compaction caused by tractors requires an understanding of the influence of the tractive system on soil compaction. Soil strain under tractors equipped with single rear wheels, dual rear wheels, or steel tracks was measured and compared. Tractors were of nearly equal mass. Strain was measured by using soil-strain transducers installed at 100-, 150-, 200-, and 300-mm depths beneath the soil surface. Soil strain was defined as the change in transducer length divided by the initial length of the transducer when installed in the soil. Soil strain at 100- to 245-mm depth was significantly greater for the tractor with single rear wheels than for the other tractors. The difference in soil strain caused by tractors with different tractive systems decreased with soil depth.

CARBON DIOXIDE EVOLUTION FROM FRESH AND PRESERVED SOYBEANS

Carbon dioxide evolution has proven to be a good indicator of deterioration in studies of stored cereal grains and oilseeds. Since little work has been done with stored soybeans, a study was conducted measuring carbon dioxide from stored soybeans using freshly harvested and preserved soybean samples. The objective of the study was to determine the effects of harvesting method, storage temperature, storage moisture content, and storage time on soybean deterioration. Following storage treatment, samples were held under aeration in a respirometer at 26°C and 21% moisture, and evolved carbon dioxide mass was measured until samples had lost 1.0% of original dry matter. At high harvest moistures, combine-harvested soybeans deteriorated faster, but at low harvest moistures, the deterioration rate of hand-harvested soybeans was greater. After 48 weeks of storage, the soybeans harvested at 22% moisture and preserved at -18°C deteriorated in a respirometer like freshly harvested soybeans, but soybeans harvested at 9% deteriorated in a respirometer significantly faster than those freshly harvested at 13% moisture.

Horizontal and Vertical Airflow Resistance of Shelled Corn at Various Bulk Densities

ABSTRACT Airflow resistance of shelled corn was measured in both horizontal and vertical directions at eight airflow rates between 0.76 and 28.6 mVm2.min and at three different bulk densities. Data were fitted to the Ergun equation and multipliers for horizontal airflow were determined. For airflow rates above 6 mm^-min, horizontal airflow resistance was about 58% of the vertical resistance. For airflow rates at or below 6 mm^-min, horizontal resistance was about 45% of the vertical resistance.

Corn Moisture Measurement Accuracy

ABSTRACT THE four electronic moisture meters most commonly used by Iowa grain dealers were compared with the official United States Department of Agriculture (USDA) air-oven method on 881 samples of corn from the 1979 and 1980 harvests. Samples ranged in moisture from 11% to 38%, wet basis. With the manufacturer-developed calibrations used in 1979, all four brands gave biased readings with respect to the air-oven method. Calibration bias errors differed among brands and ranged from approximately 1.5% to -3.5% moisture content. A recalibration between the 1979 and 1980 harvests reduced both this bias and the discrepancy among meter brands. Random errors originated from three sources: the electrical properties of different samples (contributing about 85% of the total random error), the repeatability of a meter test on a specific sample (contributing about 10%, and the repeatability of the oven method on a specific sample (contributing about 5%. The coefficient of variation of a meter test with respect to the oven varied with moisture content and increased from a minimum of 2.5% to 15.5% moisture corn to a maximum of 4.5% at both 11% and 38% moisture corn.