Tofu Characteristics Influenced by Soybean Crop Year and Location (continued)

Keywords

Introduction

Materials and
Methods

Results and
Discussion

Conclusions

References

Project
Background

Results and Discussion
There were significant differences between years for grain yield, tofu yield, protein content, and oil content (Table 1). Pooled across the two years, there was a significant difference among locations within each year for grain yield, protein content, oil content and 11S/7S ratio.

Grain yield, tofu yield, protein content, and oil content were all greater in 1994 than in 1993 (Table 2). In 1993, the protein content of soybean grown at Kragnes, MN was lower than at Dwight, ND. This shows that protein content can vary with location within the same year. Processors can use this information to test the protein content of soybean grown in different locations to determine which location has produced the highest protein content. Oil content and 11S/7S ratio also differed among locations within each year. These results show that the effect of location within the same year can have a great influence on chemical constituents of soybean for both the amount of protein and type of protein fraction.

There was a genotype X location within-year interaction for protein content and 11S/7S ratio. The magnitude of the differences between Proto and M86-356 for 11S/7S ratio varied among locations within each year (Table 3). However, Proto was significantly greater than M86-356 only at the 1994 Casselton, ND location.

There were differences in redness and yellowness among years (Table 4). Tofu produced in 1993 was less red and more yellow than tofu produced in 1994 (Table 5). There were differences in tofu firmness and yellowness and soymilk Brix among locations within years (Table 4). In 1993, the firmest tofu was produced from soybean grown at Northwood, ND and Kragnes, MN (Table 5). Location within a year can have a large influence on tofu firmness. However, the soymilk was not closely associated with tofu firmness. In 1993 at Northwood, ND, the firmest tofu was produced with the highest soymilk Brix. However, in 1993 at Kragnes, MN, firm tofu was produced with a low soymilk Brix. Differences in yellowness among locations within 1993 were small. However, in 1994, there were large differences among locations for yellowness.

There was a significant genotype X location within-year interaction for whiteness (Table 4). M86-356 was significantly whiter than Proto only at the 1993 Hendrum, MN environment (Table 6). The genotype X location within year interaction for whiteness was primarily due to differences in magnitude rather than changes in rank.

Tofu produced from soybean grown in 1993 was less red and more yellow than tofu produced from soybean grown in 1994 (Table 5). In both 1993 and 1994, soybean grown at some locations within a year produced tofu that was less yellow than other locations within each of these years. Differences in the yellowness of tofu also depend on the year in which the soybean was grown. Processors can produce tofu that is less yellow by identifying soybean grown at specific locations within a year that produce less yellow tofu.

The cooler weather in 1993 compared to 1994 (Table 7) was associated with lower protein and oil content, decreased tofu yield, and lower grain yield (Table 2). On average, tofu from soybean produced in 1993 was less red and more yellow than soybean produced in 1994. Precipitation was above normal in both 1993 and 1994 at most locations (Table 8). Soil properties and soil fertility differed among locations (Table 9). The greatest association between tofu quality factors and environmental conditions appears to be due to the difference in temperature between 1993 and 1994. However, the unique combination of temperature, precipitation, soil fertility, and soil type associated with the different environments could not be replicated. Factors such as weather and soil were confounded at each environment and cannot be separated. If locations within years are considered a random effect, then averaged across locations within a year, the effect of years can be evaluated in this context.

Conclusions
Due to the influence of environment, genotypes should only be compared for tofu firmness, soymilk solid content, and color when grown in the same environment. Processors can benefit by evaluating the tofu quality of soybean grown at different locations within a year and purchasing soybean from those locations that produces the best quality tofu. Rather than discard soybean genotypes based on an absolute standard, tofu quality of experimental lines should be compared to that of a known check cultivar.

References

AOAC. 1990. Official Methods of Analysis; Association of Official Analytical Chemists: Washington, DC, 1990.

Bourne, M.C. 1978. Texture profile analysis. Food Technol. 32(7): 62-66.

Laemmli, U.K. 1970. Cleavage of structural proteins during assembly of the head of bacteriophage T4. Nature 227: 680-685.

Lim, B.T., J.M. DeMan, L. DeMan, and R.I. Buzzell. 1990. Yield and quality of tofu as affected by soybean and soymilk characteristics. Calcium sulfate coagulant. J. of Food Sci. 55:1088-1111.

Murphy, P.A., and A.P. Resurreccion. 1984. Varietal and environmental differences in soybean glycinin and B-conglycinin content. J. Agric. Food Chem. 32:911-915

Orf, J.H., J.W. Lambert, and B.W. Kennedy. 1991. Registration of 'Proto' soybean. Crop Sci. 31:486.

Smith, A.K., T. Watanabe, and A.M. Nash. 1960. Tofu from Japanese and United States soybeans. Food Tech. 14:332-336.

Wang, C.C.R. and Chang, S.K.C. 1995. Physicochemical properties and tofu quality of soybean cultivar Proto. J. Agric. Food Chem. 43: 3029-3034.

Wang, H.L., E.W. Swain, W.F. Kwolek, and W.R. Fehr. 1983. Effect of soybean varieties on the yield and quality of tofu. Cereal Chem. 60:245-248.

Project Background

Authors
T.C. Helms, Associate Professor
Deptartment of Plant Science
North Dakota State University
helms@badlands.nodak.edu

T.D. Cai, Food Technologist II
Department of Food and Nutrition
North Dakota State University
tcai@plains.nodak.edu

K.C. Chang, Professor
Departments of Food and Nutrition and Cereal Science
North Dakota State University
schang@plains.nodak.edu

J.W. Enz
Department of Soil Science
North Dakota State University

Corresponding author
T.C. Helms

Location where the research was (primarily) done
Soybean Research and Utilization Lab
Department of Food and Nutrition
North Dakota State University, Fargo, North Dakota

Funding source of the project
USDA-CSREES
Great Plains International Trade Research Program
North Dakota Soybean Council

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Table of Contents – Fall 1998