Improved Fractionation of Glycinin and β-Conglycinin and Partitioning of Phytochemicals

Abstract

Glycinin-rich and â-conglycinin-rich products are prepared by soy protein fractionation. Physicochemical characteristics of these proteins affect their unique, important functionality in food systems and industrial applications. Soybean isoflavones and saponins are phytochemicals with potential health benefits. Objectives of this protein fractionation research were to (1) improve protein and phytochemical extraction from defatted soy flakes and recovery in product fractions and (2) evaluate phytochemical partitioning and profile changes during fractionation. Extraction environments (pH, ethanol concentration, temperature, and water-to-flake ratio) were each varied during bench-scale optimization. Optimized conditions of 45 °C and 10:1 water-toflake ratio were compared with previous conditions of 20 °C and 15:1 water-to-flake ratio and a soy protein isolate process at pilot scale. Optimized conditions yielded more â-conglycinin with higher isoflavone and saponin concentrations, but fraction purity was diminished by glycinin contamination. Bench-scale data demonstrated that increased phytochemical extraction did not translate into increased concentrations in product fractions. KeywordsCenter for Crops Utilization Research, Glycinin; â-conglycinin; soy protein; protein fractionation; pilot plant; isoflavones; saponins Glycinin-rich and -conglycinin-rich products are prepared by soy protein fractionation. Physicochemical characteristics of these proteins affect their unique, important functionality in food systems and industrial applications. Soybean isoflavones and saponins are phytochemicals with potential health benefits. Objectives of this protein fractionation research were to (1) improve protein and phytochemical extraction from defatted soy flakes and recovery in product fractions and (2) evaluate phytochemical partitioning and profile changes during fractionation. Extraction environments (pH, ethanol concentration, temperature, and water-to-flake ratio) were each varied during bench-scale optimization. Optimized conditions of 45°C and 10:1 water-to-flake ratio were compared with previous conditions of 20°C and 15:1 water-to-flake ratio and a soy protein isolate process at pilot scale. Optimized conditions yielded more -conglycinin with higher isoflavone and saponin concentrations, but fraction purity was diminished by glycinin contamination. Bench-scale data demonstrated that increased phytochemical extraction did not translate into increased concentrations in product fractions.

Interactions between isoflavones and soybean proteins: Applications in soybean-protein–isolate production

“…In previous studies between 18% and 26% of total isoflavones remained in the whey fraction after SPI production (Rickert, Meyer, et al, 2004;Speroni et al, 2007). Rickert, Johnson, and Murphy (2004) reported that when the amount of water was high relative to the quantity of soybean flakes during the purification of glycinin and b-conglycinin, a greater portion of the related isoflavones remained in the whey, thus indicating that they were released from the soybean matrix and partitioned into the water phase. Therefore, a higher polarity may favor the partitioning of the genistin into the aqueous phase.…”

Compositional characteristics of protein ingredients prepared from high‐sucrose/low‐stachyose soybeans

“…The LFSPC extracted at pH 8.5 contained significantly less malonylglucosides (43.2%) and acetylglucosides (1.5%), and higher amounts of glucosides (49.1%) than the same products extracted at pH 7.5 (63.2% malonylglucosides, 2.3% acetylglucosides, and 28.0% glucosides). The conversion from malonylglucoside to the glucoside isoform has been previously reported (17,18), and alkali extraction significantly favors conversion. The aglucon isoform contents for both extraction pH values significantly increased, from 3.5% in the flour prepared from HS/LS soybeans to 6.4% in the LFSPC.…”

“…The isoflavones commonly found in soybeans and soy protein products are genistein, daidzein, and glycitein, which occur in four forms: the aglucon, the β-glucoside, the malonyl-β-glucoside, and the acetyl-β-glucoside. Of these four isoforms, the β-glucosides and the malonyl-β-glucosides predominant in soybeans (13) and the isoflavone profile and isoforms distribution are altered during processing (17,18).…”

“…The aglucon isoform contents for both extraction pH values significantly increased, from 3.5% in the flour prepared from HS/LS soybeans to 6.4% in the LFSPC. This result was partly attributed to the action of native soybean β-glucosidases during the extraction step (18).…”

Novel Health Ingredients and Their Applications in Salad Dressings and Other Food Emulsions

“…In addition to the major components, soybean protein also contains minor components such as isoflavones that may be beneficial for human health. About 30% of the total isoflavones are lost in the insoluble fraction during soy protein isolate production (Rickert et al 2004). Studies carried out by Erdman and Potter (1997) suggested that consumption of 40 g of soy protein isolates containing 90 mg total isoflavones per day increased both bone mineral content and density in the lumbar spine by about 2% over a period of 6 months.…”