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Understanding variability of soybean sucrose, oligosaccharide, and NSP content

Ali, M., M. Alfaro-Wisaquillo, G. Quintana-Ospina, K. Englyst, G. Gomes and E. Oviedo-Rondón

Sucrose is the main soluble sugar in soybeans, and it is highly related to meal energy value. Soybean oligosaccharides and the non-starch polysaccharides (NSP) are poorly digested by poultry. Understanding variability of these compounds in soybeans can help improve their nutritional quality. In this study, the content of sucrose, raffinose, stachyose, total, soluble and insoluble NSP, as well as its relationship with CP, AA, and trypsin inhibitor (TI), were evaluated. The sources of variation were 4 commonly grown soybean varieties (A to D) planted in 3 North Carolina counties (X, Y, Z) in 2 maturity groups double crop (growing two successive crops per year) and full season (growing one traditional crop per year). 24 treatments resulted from a 4 x 3 x 2 factorial arrangement of treatments. A completely randomized design with four plot replicates was used. Raw soybean samples were cleaned from foreign material and standardized to be USDA grade 3 or 2. NSP content, including solubility fractions, was determined by GC analysis of constituent sugars, while sugars and oligosaccharides were determined by ion chromatography. Other nutrients (CP, AA, and TI) were determined by AOAC standard methods. The data was standardized to dry matter and later analyzed using a three-way ANOVA and mean separation was done by Tukey’s test. Correlation analyses were conducted between carbohydrates and CP, AA, and TI content. Three-way interaction effects (P < 0.01) were detected in all parameters evaluated. Soybeans grown in double-crop with varieties A, C, and D in location Z had the highest sucrose. tNSP and raffinose content were higher in varieties A and D in location X regardless of maturity group. Variety C had the highest iNSP in location Y in both maturity groups. Variety C also had the lowest stachyose independently of location or maturity group. Location X and Z had lower CP and AA than Y. Negative correlations (P < 0.001) were detected between CP and total sugars (r = -0.74) and sucrose (r = -0.71). In contrast, TI resulted in positive correlations (P < 0.001) with total sugars (r = 0.53) and sucrose (r = 0.51).

In conclusion, soybean variety, planting location, and maturity group affected soybean carbohydrate profile and their relationship with CP, AA, and TI.