WET MILLING CHARACTERISTICS OF TEN LINES FROM THE GERMPLASM ENHANCEMENT OF MAIZE PROJECT

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WET MILLING CHARACTERISTICS OF TEN LINES FROM THE GERMPLASM ENHANCEMENT OF MAIZE PROJECT Modified 100-g Wet-Milling Procedure 200-ml 0.2% SO2, 0.5% Lactic Acid 200-ml water FINE GRINDING (4-L Waring Blender, 90% speed, 2 min) GERM/ COARSE FIBER SEPARATION MIXING SETTLING (60 min) COARSE GRINDING (1-L Waring Blender, 60% speed, 4 min) Mill Starch STEEPING (50°C, 40 hr) 100-g CORN 7 mesh SETTLING (Specific gravity adjusted to 1.04) 1-L Decant Water 4-L Blender FINE FIBER SEPARATION Germ/ Coarse Fiber 800-ml water 500-ml Water + 250-ml Water (in wash bottle) Fine Fiber 200 mesh 1.6-L Decant Water TABLING (50 ml/min, 0.6° slope) Pan WASHING (Sieve Shaker, 5 min) 500-ml Water Overflow 7 mesh WASHING Starch Layer Pan 200 mesh Fine Fiber Pan DRYING (50°C, 24 hr) Wash Water Gluten Slurry WASHING Fine Fiber 200 mesh Pan CENTRIFUGATION (6000 rpm, 20 min) ASPIRATING (550 mm Hg) DRYING (50°C, 24 hr) DECANT Gluten Starch Coarse Fiber Fine Fiber DRYING (50°C, 24 hr) DRYING (50°C, 24 hr) GERM STARCH FIBER STEEP WATER RINSE WATER GLUTEN Figure 2. The Modified 100 g Wet-Milling Process Figure 1. The ten GEM lines used in this study. Phenotypic differences, such as color, shape , and size of the kernels, can be observed. AR16035:S19-227-1-B CUBA117:S1520-562-1-B AR16035:S19-285-1-B FS8B(T):N1802-35-1-B CH05015:N15-182-1-B CUBA117:S1520-153-1-B UR13085:N0215-11-1-B FS8B(T):N1802-32-1-B UR13085:N0215-14-1-B CH05015:N15-143-1-B O. R. TABOADA-GAYTAN1, L. M. POLLAK2, L. JOHNSON3, S. FOX3, AND S. DUVICK4 1Agronomy Dept., Iowa State University, Ames, Iowa. 2USDA-ARS Corn Insects and Crop Genetics Research Unit, Ames, IA . 3 Center for Crops Utilization Research, Iowa State University, Ames, Iowa. 4 USDA-ARS Plant Introduction Research Unit, Ames, Iowa. The wet-milling characteristics of the lines presented a great variation and statistical differences (p 0.0001) were found among the recovered milling fractions. Total solids recovered did not show statistical differences (Table 2). AR16035:S19-227-1-B, CUBA117:S1520-562-1-B, and CH05015:N15-182-1-B presented better starch yield than the inbred line B73. Correlations among the values of the compositional and wet-milling characteristics (Table 3) varied largely but followed the same pattern reported in previous studies (Fox et al, 1992; Singh et al, 2001) INTRODUCTION Corn (Zea mays L.) is the main crop in the United States not only due to the area planted but also to the enormous amount of uses and products that can be obtained from the corn kernels. In 2004, corn production was estimated at 11,807.2 million bushels with average yields of 162 bushels/acre. The use of corn to produce food and for industrial purposes has been increasing during the last few years. In fact, in 2004, 22.6% of the total volume was processed to produce starch, sweeteners, and ethanol and other fermentation products, mainly through the wet-milling process. Starch is the most important product obtained from wet milling. However, production of high-starch-yielding hybrids is still a developing objective of corn breeding programs. Additionally, characteristics that are important for the corn processing industry, such as millability and composition of the recovered fractions, need to be studied. This study is focused on the use of exotic materials to obtain useful breeding lines containing both adapted and exotic characteristics. Table 3. Correlation Coefficients Between Compositional and Wet-Milling Characteristics of Ten Lines from the GEM Project RESULTS Corn lines from the GEM project were originally selected for grain yield as testcrosses and then evaluated for wet-milling properties. For this project ten lines were chosen on the basis of starch yield. The highest and the lowest starch-yielding lines for each of the five different germplasm sources (Argentina, Chile, Cuba, Florida, and Uruguay) were selected. The compositional characteristics, obtained from the NIR-T analysis, of the lines are shown in Table 1. MATERIALS AND METHODS Genetic Materials Ten lines from the GEM project (Fig. 1) were used in this study. The lines have 25% exotic genetic background from Argentina (AR16035:S19-285-1-B and AR16035:S19-227-1-B), Chile (CH05015:N15-182-1-B and CH05015:N15-143-1-B), Cuba (CUBA117:S1520-562-1-B and CUBA117:S1520-153-1-B), Florida (FS8B(T):N1802-32-1-B and FS8B(T):N1802-35-1-B), and Uruguay (UR13085:N0215-11-1-B and UR13085:N0215-14-1-B). Seed of the lines was produced in Ames, IA, in the Summer of 2003 by self pollination and bulked at harvest. Compositional Characteristics Near-Infrared Transmittance (NIR-T) technology was used to estimate moisture, starch, protein, and oil contents of bulked whole kernels from each line by using a FOSS Infratec 1241 Grain Analyzer (Tecator, Hoganas, Sweden). Wet-Milling Characteristics Two samples from each line were analyzed in the laboratory by using the 100 g. modified wet-milling procedure (Singh et al, 1997). This procedure (Fig. 2) yields starch, gluten, fiber, germ, and steepwater fractions. Moisture content of the recovered fractions was determined in triplicate by using the AOAC method 14.004 (AOAC, 1984). Statistical Analysis Proc ANOVA and Proc CORR of SAS (SAS Institute, Cary, NC) were used to determine statistical differences and correlations among different values, respectively. 1, 2 = Compositional and recovered starch, respectively. CONCLUSIONS Some lines with exotic genetic background have better wet-milling characteristics, related to starch yield, than the Corn Belt inbred line B73. The results indicate that the use of exotic corn germplasm in a wet milling breeding program will enhance available genetic diversity. Table 1. Compositional Characteristics of Ten Lines from the GEM Project Table 2. Wet-Milling Characteristics of Ten Lines from the GEM Project REFERENCES AOAC. 1984. Official Methods of Analysis of the Association of Official Analytical Chemists. 14th ed. Method 14.004 The Association: Washington, DC. Fox, S. R., L. A. Johnson, C. R. Hurburgh, C. Dorsey-Redding, and T. B. Bailey. 1992. Relations of Grain Proximate Composition and Physical Properties to Wet-Milling Characteristics of Maize. Cereal Chem. 69(2):191-197. Singh, S. K., L. A. Johnson, L. M. Pollak, S. R. Fox, and T. B. Bailey. 1997. Comparison of Laboratory and Pilot-Plant Corn Wet-Milling Procedures. Cereal Chem. 74(1):40-48. Singh, S. K., L. A. Johnson, L. M. Pollak, and C. R. Hurburgh. 2001. Compositional, Physical, and Wet-Milling Properties of Accessions Used in the Germplasm Enhancement of Maize Project. Cereal Chem. 78(3):330-335. CONTACT INFORMATION Linda M. Pollak: Professor in Charge. 1405 Agronomy Hall, Iowa State University, Ames, Iowa, 50011. Phone: (515) 294-7831. E-mail: lmpollak@iastate.edu.