Role of carbohydrates in soya extrusion

Abstract

When extruded under similar processing conditions, soya flour yielded a far more regular, honeycombed structure than soya isolate, though both had similar expansion ratios. A t low concentrations both extrudates were almost totally soluble in solutions containing sodium dodecyl sulphate (SDS) plus 2-mercaptoethanol (ME), although in SDS or ME the extrudates were only partially soluble. These results suggest that, in both cases, the extrudates are primarily stabilized by disulphide bonds and hydrophobic interactions.When rehydrated in water at temperatures in the range 20-120°C all the extrudates exhibited decreasing toughness and increasing protein solubility with increasing temperature. Also, the soya flour extrudates, but not those prepared from the isolate, exhibited a phenomenon at the lower temperatures characterized by minimum hydratability, pH and carbohydrate solubility at about 30-40°C. It is suggested that the soya flour extrudates are additionally stabilized, compared to the extrudates prepared from the isolate, by hydrophobic interactions involving the embedded carbohydrate.

Analysis of sorption properties of starch–protein extrudates with the use of water vapour

“…According to Sheard, Edward, and Mitchell (1984), extrusion of starch-protein blends forms a structure in which carbohydrates are set in a protein matrix, additionally stabilised by hydrophobic effects. Probably, those effects cause a reduction in the water vapour absorption capacity of the tested starch extrudates with various protein material.…”

Post‐denaturational exothermic transition in soya isolate

“…Approximate enthalpies of 3.72 J/g (0.8970.2 cal/g) and 20.1 J/g (4.870.2 callg) have been reported for the denaturation of the 7s and 11s globulins, respectively (Sheard, 1985). Thus, the enthalpy of the exothermic transition is larger than the enthalpy change required for denaturation of the 11s globulin at moisture contents above 90%.…”

Use of near infrared spectroscopy to evaluate the intensity of extrusion‐cooking processing of pea flour

“…Extrudates Table 2. Protein solubility (%) in phosphate buffer-SDS (PB-SDS) alone and also containing 2-mcrcaptoethanol (PB-SDS-ME) and unprecipitable nitrogen (UPN) in TCA of nativc pea flour (NPF) and pea extrudates taken from the groups M, I and S On the other hand, as interpreted in many works (Jeunink & Cheftel, 1979;Rhee et al, 1981;Noguchi et af., 1981;Hager, 1984;Sheard et al, 1984;Pham & Del Rosario, 1984a), the linkages disrupted by SDS were assumed to be noncovalent interactions and those disrupted by 2-ME were disulphide covalent bonds. In our case, these two types of linkages predominated under moderate conditions of extrusion-cooking.…”

“…To determine the nature of the interactions involved in protein texturization by extrusion-cooking, protein solubility in various buffers containing chemical agents known to disrupt non-covalent interactions or disulphide bonds had been extensively studied. The general conclusion was that non-covalent interactions and covalent disulphide bonds were the major linkages involved in the insolubilization of extruded protein (Jeunink & Cheftel, 1979;Noguchi et al, 1981;Rhee et al, 1981;Hager, 1984;Pham & Del Rosario, 1984a;Sheard et al, 1984). However, since these types of linkages are thermally labile, they presumably form on cooling of extrudates rather than in the extruder itself (Ledward & Mitchell, 1988).…”