Jun Lin

Document Type

Dissertation - University Access Only

Award Date

2005

Degree Name

Doctor of Philosophy (PhD)

Department / School

Biology

Abstract

Soy isoflavones and saponins are two major classes of health promoting phytochernicals in soybeans and soy products. lsoflavones have been reported to have estrogenic/anti-estrogenic, antioxidant, tyrosine kinase (TIC) inhibiting, and antifungal properties. These properties play important roles in the prevention of chronic diseases such as cancers, cardiovascular diseases, and osteoporosis. Saponins also have physiological properties including cholesterol lowering, cancer preventing, human immune virus (HIV) infection inhibiting, and anti-oxidative properties. An high-performance liquid chromatography/evaporative light scattering detection (HPLC/ELSD) method was developed to determine natural forms of soyasaponin Bs with (cxg, j}g, j}a, yg, ya) and without (V, I, II, III, IV) 2,3-dihydro-2,5- dihydroxy-6-methyl-4H-pyran-4-one (DDMP) in soybean. The coefficient of variance of intra-day assays was< 9.51 %, and that of inter-day assays was < l 0.91 %. The soyasaponin I was used as external standard for quantification of all soyasaponins, because it was established that their ELSD signal responses were essentially the same under the specific operating conditions. The extraction conditions were optimized and the extract storage conditions were established for analysis of soyasaponin Bs in their natural state. The energy of activation of soyasaponin 􀂼g was 40. 76 KJ/Mole. The recovery rates for soyasaponin I and II were 98.3% and 93.1 %, respectively. The average of total soyasaponins content from 5 soybean samples was 3.37 μmoVg with ranges from 2.78 to 4.03 μmoVg. This method is simple and easy to use and the sample preparation takes less time than existing methods. A new procedure for simultaneous determination of isoflavones and soyasaponin Bs in soybeans using HPLC/UV /ELSD has been developed. This method has quantified twelve isoflavones, three non-DDMP soyasaponin Bs (V, I, and II) and five DDMP (2,3- dihydro-2,5-dihydroxy-6-methyl-4H-pyran-4-one) soyasaponin Bs (ag, 􀂼g, 􀂼a, yg, and ya). Sample preparation for this method is unique and required significantly less time than previously published methods. A gradient elution comprising 0.05% trifluoroacetic acid in water and acetonitrile was used. Soyasaponin I was used as an external standard for saponin quantification. Three isoflavone standards (genistin, daidzein, and genistein) were used for isoflavone quantification. The recovery for soyasaponin I and isoflavones were 81 % and 85%, respectively. The intra-day assay CV was less than 6.26%, and the inter-day assay CV was less than 7.83%. The detection limit and the quantification limit were determined to be 33 ng and 110 ng injected on column for soyasaponin Bs, and 1.5 ng and 5.0 ng injected on column for isoflavones. The mass balance of saponins during processing of soy protein isolates (SPis) was established and the effects of precipitating and washing (P/W) temperatures (0°C, 10° C, 25° C, 40°C, and 50° C) on the retention of isoflavones and saponins were investigated also. Isoflavones and saponins were measured by a HPLC/UV/ELSD method. It was found that about 41 % of total saponins in soy flour (SF) remained in SPis during processing, while 42% remained unextracted in the solid waste. None was detected in the whey or wash water. The study also revealed that only about 27% of total isoflavones from SF remained in the final SPis when P/W was performed at 50°C. However, lowering the P/W temperature improved the isoflavone retention significantly. As much as 40% of total isoflavones can be retained in SPI, when P/W was conducted at 25°C, IOOC, or 0°C. When the P/W temperature was 50°C, the percentages of total isoflavones lost during extraction, precipitation, and washing were 28, 22, and 6%, respectively. When the temperature was changed to OOC, the percentages of isoflavones lost during extraction, precipitation, and washing were 28, I I, and 5%, respectively. The P/W temperatures did not affect the distribution of saponins in different streams during the processing of SPls. The isoflavone and saponin profiles of the SPis were different from those of SF. Lowering the P/W temperature did not significantly lower the protein content in SPls, unless the temperature was reduced to 0°C.

Library of Congress Subject Headings

Soybean
Phytochemicals
Saponins -- Analysis
Isoflavones -- Analysis
Proteins in human nutrition

Format

application/pdf

Number of Pages

160

Publisher

South Dakota State University

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