Effects of Extraction Temperature and Preservation Method on Functionality of Soy Protein

Abstract

The effects of extraction temperature and preservation method on the functional properties of soy protein isolate (SPI) were determined. Four extraction temperatures (25, 40, 60, and 80°C) were used to produce SPI and yields of solids and protein contents were determined. Three preservation methods were also tested (spray-drying, freeze-drying, and freezingthawing) and compared to fresh (undried) samples for each extraction temperature. No differences in yields of solids and protein were observed among SPIs extracted at 25, 40, and 60°C; however, SPI extracted at 80°C yielded significantly less solids and protein. Extraction temperature significantly affected SPI functionality. As extraction temperature increased, solubility and emulsification capacity decreased; surface hydrophobicities, emulsification activities and stabilities, and dynamic viscosities increased; and foaming properties improved. Preservation method also significantly affected SPI functionality. Drying method did not affect the denaturation enthalpies of SPIs, but spray-dried SPIs had higher solubilities, surface hydrophobicities, and emulsification stabilities, and lower viscosities, emulsification activities and rates of foaming than freeze-dried SPI exhibited. Emulsification and foaming capacities and foaming stabilities were similar for both methods of drying. There was significant interaction between extraction temperature and preservation method for all functional properties except emulsification capacity.

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

“…The control SPI exhibited two thermal transitions at approximately 77 and 92°C corresponding to the denaturation peak temperature (T d ) of b-conglycinin (7S) and glycinin (11S), respectively [24,25]. The enthalpy (DH) value of b-conglycinin and glycinin for control SPIs, 0.98 and 5.19 J g -1 , respectively, were consistent with those of Deak and Johnson obtained at the same extraction temperature of 60°C [4]. After 60 s at low power level, T d of b-conglycinin and glycinin decreased significantly, while increasing after 120 s at high power level, when compared to the control, suggesting protein conformation changes [25].…”

“…Ultrasound treatment of the soy flakes significantly decreased the SPI consistency and increased their flow behavior index except for the sample treated for 30 s at low power level. Some of these changes could be due to the effect of the treatment on the protein native state [4].…”

“…SPI can also be used in non-food applications including the production of biodegradable plastics and paper coatings and sizing [3]. The versatile uses of SPI can be attributed to the wide range of functional properties that SPI can confer to a food product [4,5]. These properties are affected by the intrinsic, extrinsic and process parameters [6], and could be modified by using alternative processing techniques [5].…”

Rheological properties of African yam bean (Sphenostylis stenocarpa Hochst. Ex A. Rich.) calcium proteinate and isoelectric protein isolates

“…The shear rate (€ g) and apparent viscosity h over the course of the analysis as well as power law formula were used to determined the consistency coefficient (k) and flow behavior index (n). Shear stress was then obtained as described by Deak and Johnson (2007) and Lamsal, Jung & Johnson (2007). The temperature dependence of apparent viscosity was studied by fitting the rheological data into the Arrhenius model:…”

Value-Added Production of Nisin from Soy Whey

“…A method for lab-scale production of soy whey from hexane-defatted, desolventized dry soybean flakes was developed, yielding a final product with properties similar to soy whey generated through commercial-scale wet milling of soy beans. Briefly, ground and defatted soybean flakes (50 g) were mixed in a 1:10 ratio (w/v) with tap water [19]. The pH was raised to 8.5 with 2 N NaOH, and the resulting slurry was stirred for 30 min at 60°C.…”