The Improved Nutritional And Functional Quality Of Soybean Sprouts By Calcium

In recent years, the consumption of soybean sprouts has been growing, because they are often perceived as a part of a healthy diet. First of all, soybean is an important source of protein and unsaturated fatty acids in Chinese diet. In addition, soybean sprouts are rich in health-promoting phytochemicals, such as gamma-aminobutyric acid (GABA) and isoflavone, compared with their mature counterparts. Ca2+ is a central regulator of plant growth and development. It has been reported that Ca2+ involved in the activation of some enzymes. Soybean sprout is packed with key nutrients like GABA, isotlavone, and so on,which are synthesized in a large amount during germination, but less work has been done on the effect of Ca2+ on their synthesis. At present, supplemental Ca2+ has been supplied on fruits and vegetables to keep them fresh. Balanced and timely application of calcium sources for fruit and vegetable crops during growing seasons and at postharvest stages, will improve the shelf life and nutritional quality of horticultural products. Unlike other vegetables, the effects of Ca2+ on soybean sprout, such as yield and nutritional quality, have received little attention. Soybean has a high amount of calcium content, but most of which is unavailable for being chelated by phytic acid. These findings in this study indicate that supplemental Ca2+ can increase soybean sprout yield and improve its nutrition qualities.1. Effect of germination on phytic acid degradation and mineral bioavailability of soybean sproutWe investigated variation of mineral bioavailability with phytic acid content in soybean after germination and incubation. Phytase and phosphatase activities of germinated soybeans increased, compared with raw beans. The phytic acid contents declined in germinated soybeans by 57.5%. Zn and Fe bioavailability values increased in germinated beans but Ca bioavailability decreased. For incubation, the bioavailability values of Zn, Fe,and Ca in endogenous phytase-incubated group were higher than those using an exogenous phytase treatment. Soybeans exhibited values of 64.7%, 60.6%, and 47.9%, respectively,after a combined treatment with endogenous and exogenous phytases. Incubation is more efficient for improvement of Zn, Fe, and Ca bioavailability values in a short period of time.2. Temporal and spatial distribution of phytic acid and its degradation enzymes during soybean germinationAfter 6 days of germination, phytic acid contents in soybean sprouts decreased by 70%,compared with day 0 soybeans. Zn and Fe bioavailability of 6-day-old germinating soybean both significantly increased (p<0.05),by contrast,Ca bioavailability decreased compared with control. Phytic acid was detectable only in cotyledon of soybean sprout during germination. Inorganic P content increased in embryo while decreased in cotyledon.Phytase and phosphatase activities of embryo were higher than these of cotyledon. Phytase and phosphatase activities of embryo and cotyledon increased first and then decreased.3. Effect of supplemental Ca2+ on the yield and nutritional qualities of soybean sproutsEffects of supplemental Ca2+ on growth and selected qualities of soybean sprout were investigated. Ca-treated sprouts had 40?47% higher length and 31?39% higher yield than water-treated ones. Phytic acid content of Ca-treated soybean sprouts decreased, which hence increased Zn, Fe, and Ca bioavailabilites. Supplemental Ca2+ increased content of GABA, isoflavone, vitamins, and total phenolics, respectively. These findings indicate that supplemental Ca2+ can increase soybean sprout yield and improve its nutritional qualities.Ways to supplement were related to the synthesis of bioactive substances. Soybean sproutsproduced by soaking Ca2+ had more isoflavone. Soybean sprouts treated by soaking plus spraying Ca2+ contained more GABA and VB1 compared to the control.4 A comparative transcriptome and proteomic analysis between water- and Ca-treated soybean sproutThe comparative transcriptome and proteomics between water-treated and Ca-treated soybean sprouts was studied. As consequence 1,912 genes and 460 proteins were up- or down-regulated after 4 days of Ca2+ treatment. The functional classification of these differentially expressed genes and proteins indicated their connection with cell growth, cell division, cell wall synthesis, root hair elongation, longitudinal growth, plant morphogenesis,auxin signal transduction, inositol phosphate metabolism, protein metabolism, conversion of amino acids, lipid metabolism, starch and soluble sugar metabolism, amino acids/lipids carbohydrates/sucrose transporter, oxidation reduction process, transcription regulation and secondary metabolites synthesis/transport/catabolic processes.