Structure, Protein Interactions and In Vitro Protease Accessibility of Extruded and Pressurized Full‐Fat Soybean Flakes

Abstract

The objectives of the present study were to determine how extrusion (barrel temperature of 100°C) and high-pressure processing (HPP, 200 and 500 MPa, 15 min, 25°C) of full-fat soybean flakes (FFSF) modified the structure of soybean cotyledon cells, the protein interactions and the in vitro protease accessibility. Cellular disruption of the cotyledon cells was only observed for extruded FFSF. Extrusion and HPP at 500 MPa favored formation of insoluble protein aggregates, in which oil was entrapped. High pressure size exclusion chromatography (HPSEC) and extraction methods using buffers containing SDS and 2-mercaptoethanol suggested that noncovalent interactions were the main forces in protein aggregate formation during HPP 500 MPa and extrusion. Intermolecular cross-linking by disulfide bonding was also involved in insoluble aggregates, but at a lesser extent than noncovalent interactions. Extrusion and HPP 500-MPa treatment enhanced the proteolytic attack, while treatment at 200 MPa had no impact. Drastic changes in the peptide profile of the extracted proteins were, however, only observed for the enzyme-treated 500-MPa FFSF. Optimal oil and protein extraction yields required cellular disruption of cotyledon cells and hydrolysis of protein aggregates, which were obtained with enzyme-assisted aqueous extraction of extruded FFSF.

Aqueous Extraction of Oil and Protein From Soybean and Lupin: A Comparative Study

“…Extrusion pretreatment of soybean and lupin flakes caused significant increase in oil extraction (Table 2), from 56.5 to 64.8% and 48.1 to 62.7%, respectively. This increase can be attributed to severe cellular disruption promoted by the treatment (Jung et al. 2009).…”

“…2009). Extrusion decreased AEP soybean and lupin protein extraction yields by 19 and 12%, respectively, when compared to aqueous extraction of the flakes, which can be attributed to the protein insolubility caused by extrusion (Jung et al. 2009).…”

“…Prerequisites to achieve high extraction yields of soybean oil and protein include the pretreatment of the flakes by extrusion and the use of a protease during the aqueous extraction (Lamsal et al. 2006; Jung et al. 2009).…”

Efficiency of pretreatments for optimal enzymatic saccharification of soybean fiber

“…The FFSF were extruded as described by Jung et al (2009) using a Micro ZSE-27 twin-screw extruder (American Leistritz Extruders, NJ, USA). EAEP of extruded FFSF was carried out as described in Fig.…”

31P NMR Phospholipid Profiling of Soybean Emulsion Recovered from Aqueous Extraction

“…A reduction of soy flour particle size from 1200 to 100 μm increased AEP oil extraction recovery from 22 to 65% (6). Extrusion treatment formed insoluble aggregates that trapped the released oil (9) and led to a yield of 68%, although it disrupted cotyledon cells (8). However, an extraction yield comparable to hexane extraction can be obtained with protease treatment of extruded soy flakes (10).…”