Functional properties of hydrothermally cooked soy protein products

Abstract

The effects of hydrothermal cooking on the functional properties of defatted soy flour, aqueous alcohol washed soy protein concentrate, and soy protein isolate were determined in samples that were treated at 154°C by infusing steam under pressure for 11, 19, 30, and 42 s, and then spray dried. Hydrothermal cooking increased the nitrogen solubility index (NSI) of the concentrate from 15 to 56% and altered the solubility profile from a flat profile to one more typical of native soy protein. Hydrothermal cooking also improved foaming and emulsifying properties of the concentrate. For isolate, hydrothermal cooking also improved NSI and foaming and emulsifying properties, although the improvements were less dramatic than with concentrate. NSI and emulsifying properties of the flour were improved by some processing conditions, but foaming properties were not improved by hydrothermal cooking. Dramatically increased protein solubility of concentrate and modestly improved protein solubilities of flour and isolate by hydrothermal cooking, which will also inactivate trypsin inhibitors and microorganisms, have considerable practical significance to protein ingredient manufacturers and those who use these ingredients in foods and industrial products.Paper no. J9745 in JAOCS 78, 189-195 (February 2001). KEY WORDS:Functional properties, hydrothermal cooking, jet cooking, protein functionality, soybean protein, soy flour, soy protein concentrate, soy protein isolate.Soybeans are an abundant source of proteins that have long been recognized for high nutritional value and excellent functional properties in food (1). However, flatulence caused by fermentation of oligosaccharides in the colon, undesirable flavors formed by lipoxygenase-catalyzed lipid oxidation, and low protein digestibility because of trypsin inhibitors (TI) are obstacles for increasing acceptance of soy-protein ingredients in food, and processing procedures are selected based on their abilities to minimize these problems. Procedures such as heat treatment to inactivate lipoxygenase and TI and aqueous alcohol washing to remove oligosaccharides and off-flavors, usually denature and insolubilize proteins, rendering them poorly functional in foods (2) and industrial applications (i.e., paper coatings and adhesives).Defatted soy flour (referred to as flour), alcohol-washed soy protein concentrate (referred to as concentrate), and soy protein isolate (referred to as isolate) are three major soy protein products having different protein contents and functional properties; they are used in different applications. Flour, the least refined form of the three, contains 40-50% protein (moisture-free basis, mfb) depending on whether refined fat or lecithin is added. Flash desolventizing produces flour with minimal protein denaturation and high protein solubility. Different degrees of subsequent heat treatment produce flour with widely divergent functional properties (3). However, flour contains oligosaccharides and high TI activity (unless extensively heat-treated). The nitroge...

Functional properties of protein ingredients prepared from high‐sucrose/low‐stachyose soybeans

“…The LCSPC had emulsification properties superior to those of EWSPC, which was consistent with both solubility and surface hydrophobicity data. EWSPC have very low emulsification capacities (14). The LCSPC had emulsification properties similar to those of SPI on a dry-weight basis.…”

“…The LCSPC had significantly higher solubilities than either EWSPC and similar solubilities to those of SPI. The solubility of EWSPC was quite poor unless it was jet-cooked or alkalinehomogenized to break up denatured protein aggregates (14). The solubilities in the high (7-11) and the low (2-3) pH ranges for the LFSPC extracted at pH 8.5 were significantly higher than the solubilities for SPI, whereas the LFSPC extracted at pH 7.5 was less soluble.…”

Application of genetic algorithm to optimize extrusion condition for soy-based meat analogue texturization

“…3, the minimum OAC has been predicted for mid temperatures near 175°C which is similar to the minimum WAC near this temperature. Wang and Johnson (2001) stated that functional properties like OAC were attributed to the changes in protein hydrophobicity accompanied by protein denaturation. A similar result has been also reported on the OAC increase of soy protein isolate due to hydrothermal processing (Wang and Johnson 2001) and in another study, higher extrusion temperatures led to an increased OAC of extruded navy and Pinto bean (Gujska and Khan 1990) (Fig.…”

Functional Properties of Soy Protein Isolates Produced from Ultrasonicated Defatted Soy Flakes

“…Soy protein isolate (SPI) is a commercial soy protein product having at least 90% protein [dry basis (db)] [1]. SPI holds a unique place in the human diet, not only because of its use as a low-cost substitute for animal food proteins, but also because of the health benefits associated with soy protein consumption, including blood cholesterol reduction and cardiovascular disease prevention [2].…”

“…These properties are affected by the intrinsic, extrinsic and process parameters [6], and could be modified by using alternative processing techniques [5]. Extensive research has been done on enzymatic [7][8][9], mechanical [5] and thermal [1,10] modifications of soy proteins to improve their functional properties.…”