Preparation and Functional Properties of Enzymatically Deamidated Soy Proteins

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...

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“…Protein solubility profiles were determined by using the method of Hamada and Marshall (12). (iii) Foaming properties.…”

Section: Soymentioning

confidence: 99%

Functional properties of hydrothermally cooked soy protein products

Wang

Johnson

2001

J Americ Oil Chem Soc

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“…Enzymatic modification is usually performed through limited proteolysis (Puski 1975, Feeney and Whitaker 1977, Hamada and Marshall 1989, Bernardi et al 1991. Adler-Nissen and Olsen (1979) reported improved emulsifying capacity, solubility, and foaming capacity of soy protein after a1calase and neutrase treatment.…”

Section: Enzymatic Methodsmentioning

confidence: 99%

“…For soy proteins to have the desired functional properties, several methods of protein modification have been used, including physical. chemical, and enzymatic methods (Puski 1975, Feeney and Whitaker 1977, Kinsella 1979, Sung et aL 1983, Hamada 1989.…”

Section: Modification Of Soy Proteinsmentioning

confidence: 99%

Soybean Protein Products

Hettiarachchy¹,

Kalapathy²

1997

Soybeans

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“…Deamidation has been shown to affect protein functionality. Functional properties, such as solubility, emulsifying and foaming properties, of gluten have been reported to improve upon low levels of deamidation brought about by mild acid hydrolysis (Hamada & Marshall, 1989;Matsudomi et al, 1982Matsudomi et al, , 1985. Deamidation also was reported to increase exposed hydrophobicity of gluten induced by a conformational change and, subsequently, to increase surface activity (Matsudomi et al, 1982).…”

Section: Deamidationmentioning

confidence: 99%