1. WET MILLING CHARACTERISTICS OF TEN LINES FROM THE
GERMPLASM ENHANCEMENT OF MAIZE PROJECT
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.
outcrossing
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.
Figure 2. The Modified 100 g Wet-Milling Process
200-ml 0.2% SO2,
0.5% Lactic Acid
STEEP WATER
GERM/
COARSE FIBER
SEPARATION
7 mesh
4-L Blender
WASHING
(Sieve Shaker, 5 min)
Germ/
Coarse Fiber
100-g
CORN
200-ml water
800-ml water
GERM
SETTLING
(60 min)
Wash Water
1-L Decant Water
Fine Fiber
500-ml Water
Pan
FIBER
Mill Starch
MIXING
TABLING
(50 ml/min,
0.6° slope)
Overflow +
250-ml Water
(in wash bottle)
1.6-L
Decant Water
Gluten Slurry
COARSE
GRINDING
(1-L Waring Blender,
60% speed, 4 min)
200 mesh
FINE FIBER
FINE GRINDING
(4-L Waring Blender,
90% speed, 2 min)
DRYING
(50°C, 24 hr)
STEEPING
(50°C, 40 hr)
STARCH
Starch
ASPIRATING
(550 mm Hg)
(Specific gravity
adjusted to 1.04)
Starch Layer
Modified 100-g Wet-Milling Procedure
Gluten
GLUTEN
DECANT
RINSE WATER
CENTRIFUGATION
(6000 rpm, 20 min)
The wet-milling characteristics of the lines presented a great variation and statistical differences (p ) were found among the recovered milling fractions. Total solids recovered did not show statistical differences (Table 2).
AR16035:S B, CUBA117:S B, and CH05015:N 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)
Table 3. Correlation Coefficients Between Compositional and Wet-Milling Characteristics of Ten Lines from the GEM Project
STARCH1
PROT.
OIL
STARCH2
FIBER
GERM
GLUTEN
SWATER
STARCH
0.2122
0.7068
0.0683
0.2489
0.5895
0.1712
0.0149
0.5253
0.6553
0.0865
0.4206
0.6412
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:S B and AR16035:S B), Chile (CH05015:N B and CH05015:N B), Cuba (CUBA117:S B and CUBA117:S B), Florida (FS8B(T):N B and FS8B(T):N B), and Uruguay (UR13085:N B and UR13085:N 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 (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.
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.
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
PEDIGREE
COMPOSITIONAL CHARACTERISTICS (db)
STARCH
PROTEIN
OIL
AR16035:S B
70.12
11.41
4.35
AR16035:S B
69.65
10.94
4.71
CH05015:N B
69.76
11.88
4.00
CH05015:N B
68.23
12.71
4.47
CUBA117:S B
69.06
12.35
4.59
CUBA117:S B
68.82
4.82
FS8B(T):N B
69.41
11.53
5.06
FS8B(T):N B
70.71
11.06
UR13085:N B
71.06
3.76
UR13085:N B
69.53
12.12
4.12
B73 (Singh et al, 2001)
69.70
11.90
4.30
AR16035:S B
CH05015:N B
CH05015:N B
CUBA117:S B
CUBA117:S B
FS8B(T):N B
FS8B(T):N B
UR13085:N B
UR13085:N B
AR16035:S B
Figure 1. The ten GEM lines used in this study. Phenotypic differences, such as color, shape , and size of the kernels, can be observed.
Table 2. Wet-Milling Characteristics of Ten Lines from the GEM Project
REFERENCES
AOAC Official Methods of Analysis of the Association of Official Analytical Chemists. 14th ed. Method The Association: Washington, DC.
Fox, S. R., L. A. Johnson, C. R. Hurburgh, C. Dorsey-Redding, and T. B. Bailey Relations of Grain Proximate Composition and Physical Properties to Wet-Milling Characteristics of Maize. Cereal Chem. 69(2):
Singh, S. K., L. A. Johnson, L. M. Pollak, S. R. Fox, and T. B. Bailey 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 Compositional, Physical, and Wet-Milling Properties of Accessions Used in the Germplasm Enhancement of Maize Project. Cereal Chem. 78(3):
PEDIGREE
WET-MILLING FRACTIONS (% of db)
STARCH
FIBER
GERM
GLUTEN
SWATER
TSR (%)
AR16035:S B
61.61cd
11.03d
4.00f
17.87b
5.29c
99.80a
AR16035:S B
64.25a
10.06g
5.20d
14.98d
5.22cd
99.70ab
CH05015:N B
62.48bc
10.08g
4.53e
17.36bc
5.10de
99.54ab
CH05015:N B
56.40g
10.69ef
7.54a
19.50a
5.51b
99.64ab
CUBA117:S B
63.14b
10.54f
4.19f
16.88c
5.05e
99.79a
CUBA117:S B
60.98de
10.87de
5.01d
17.22bc
5.33c
99.40b
FS8B(T):N B
60.67e
10.18g
6.51b
16.73c
5.78a
99.87a
FS8B(T):N B
59.08f
12.57e
5.69c
17.47bc
4.97e
99.77ab
UR13085:N B
60.90de
13.56a
3.60g
16.77c
99.91a
UR13085:N B
61.91c
11.37c
4.71e
16.84c
5.06e
99.88a
B73 (Singh et al, 2001)
62.40
11.40
5.10
SWATER = Steepwater Yield, TSR = Total Solids Recovery.
a-g = Values with different letter on the same column are statistically different at p=0.05
CONTACT INFORMATION
Linda M. Pollak: Professor in Charge Agronomy Hall, Iowa State University, Ames, Iowa, Phone: (515)