Contribution to the characterization of acetylated protein fractions of vicia faba in view of their functional properties

Abstract

Whilst the emulsifying properties of the protein fraction of vicia fabu are almost independent on the acetylation degree, the shear modulus of the gels produced by heat denaturation increases at first with increasing acetylation degree, decreases with further increase of the acetylation, and comes finally to zero for very high acetylation degrees.By changes of pH and by influence of added NaC1, CaCI,, AICI,, and starch, the shear modulus of gels of acetylated protein fractions of vicia f u h can be increased, by addition of sunflower oil it can be decreased.On the base of studies on the fraction p d i l e and on the changes of the content of sulthydryl and disulfide groups of the protein fractions of vicia fabo and the corresponding gels in dependence on the acetylation degree, an interpretation of the results is given, As a continuation of our already published results on the modification of the functional properties of vicia faba proteins by acetylation [l] this paper contains results on emulsifying and gel properties of vicia faba proteins in dependence on the degree of acetylation and on other influencing factors. Material and methodsThe acetylated fractions of viciajiaba protein which are very soluble in water (I) (degree of acetylation: 42, 78.92, and 97 :d) and the corresponding non-acetylated fraction of vicia faha protein (11) were prepared as described previously [I] from an viciafaba protein isolate (111).The acetylation degree of the proteins is given as the percentage of the blocked lysine and has been determined according to [2,3].The determination of the content of sulfhydryl and disulfide groups has been carried out by an amperometric technique described in [4].The gel chromatographic investigations were accomplished using Sepharose 6 B (Pharmacia, Sweden) in a 9/50 column with glass filter, combined with a 21 15 type Multiperpex peristaltic pump (LKB, Sweden) and an Uvicord I1 spectrophotometer (LKB, Sweden); 5.0 mg protein in 1.0 ml solution were given on the column. The flow rate was 6 ml/h and the fraction size 2 ml. To estimate the molecular masses a calibration was carried out with cytochrom C, chymotrypsinogen A, ovalbumin (SERVA, Heidelberg) and bovine serum albumin (FERAK, Berlin-West). The proteins were separated in borate buffer (pH 8.4; p = 0.25), in borate buffer (pH 8.4: p = 0.25 + 0.1 % sodium dodecylsulfate), and in borate buffer (pH 8.4 p = 0.25 + 0. I 7; sodium dodecylsulfate -4-0.1 % 2-mercaptoethanol).

Relationships between adsorption and emulsifying of acetylated protein isolates from fabe beans (Vicia faba L.)

“…This is in accordance with results of previous studies on faba bean protein isolates [7,8,9, 241 where a decreasing droplet size and increasing centrifugal stability with progressive acetylation was found.…”

“…Chemical analysis reveals a marked contribution of O-acetylation to the total degree of acylation which enhances significantly the hydrophobicity of the proteins [5, 61. It has been reported that acetylation of faba bean protein isolates (FBPI) causes an increase of emulsion stability at an extremely high degree of modification but results in a considerable enhancement of emulsifying capacity already at a moderate degree of modification [7,81. Despite the structural changes of the isolates no 191 or only slight differences [8] were found in the adsorption behaviour between unmodified and acetylated FBPI at planar oil-water-interfaces.…”

Isolation and study of the functional properties of pea proteins

“…Functional properties of pea protein isolates and also of protein macro fractions (globulin, legumin, vicilin, albumin) were studied by several researchers [5][6][7][8][9][10][11] and were evaluated as moderately goods.…”

Digestibility and Dietary Quality of Nonacetylated and Acetylated <i>Vicia faba </i>Proteins in Maintenance

“…For example, 1 The authors are grateful to Dr. K. Adam for help with l5N analysis. acetylation of Vicia faba protein improves the characteristics of gels formed by thermal denaturation [12,13].…”