title: Impact of acid and alkaline pretreatments on the molecular network of wheat gluten and on the mechanical properties of compression-molded glassy wheat gluten bioplastics.
abstract: Wheat gluten can be converted into rigid biobased materials by high-temperature compression molding at low moisture contents. During molding, a cross-linked protein network is formed. This study investigated the effect of mixing gluten with acid/alkali in 70% ethanol at ambient temperature for 16 h followed by ethanol removal, freeze-drying, and compression molding at 130 and 150 °C on network formation and on types of cross-links formed. Alkaline pretreatment (0-100 mmol/L sodium hydroxide or 25 mmol/L potassium hydroxide) strongly affected gluten cross-linking, whereas acid pretreatment (0-25 mmol/L sulfuric acid or 25 mmol/L hydrochloric acid) had limited effect on the gluten network. Molded alkaline-treated gluten showed enhanced cross-linking but also degradation when treated with high alkali concentrations, whereas acid treatment reduced gluten cross-linking. β-Elimination of cystine and lanthionine formation occurred more pronouncedly at higher alkali concentrations. In contrast, formation of disulfide and nondisulfide cross-links during molding was hindered in acid-pretreated gluten. Bioplastic strength was higher for alkali than for acid-pretreated samples, whereas the flexural modulus was only slightly affected by either alkaline or acid pretreatment. Apparently, the ratio of disulfide to nondisulfide cross-links did not affect the mechanical properties of rigid gluten materials.
authors.affiliation: Laboratory of Food Chemistry and Biochemistry, KU Leuven , Kasteelpark Arenberg 20, B-3001 Leuven, Belgium.
authors.forename: Koen J A
authors.initials: KJ
authors.lastname: Jansens
authors.forename: Bert
authors.initials: B
authors.lastname: Lagrain
authors.forename: Kristof
authors.initials: K
authors.lastname: Brijs
authors.forename: Bart
authors.initials: B
authors.lastname: Goderis
authors.forename: Mario
authors.initials: M
authors.lastname: Smet
authors.forename: Jan A
authors.initials: JA
authors.lastname: Delcour
mesh_terms: D000148:Acids, Noncarboxylic / Q000737:chemistry*; D063566:Biodegradable Plastics / Q000737:chemistry*; D055598:Chemical Phenomena; D055119:Elastic Modulus / Q000187:drug effects; D005983:Glutens / Q000737:chemistry*; D006358:Hot Temperature; D006851:Hydrochloric Acid / Q000737:chemistry; D006878:Hydroxides / Q000737:chemistry*; D007202:Indicators and Reagents / Q000737:chemistry*; D055595:Mechanical Phenomena; D009994:Osmolar Concentration; D017680:Potassium Compounds / Q000737:chemistry; D011487:Protein Conformation; D012639:Seeds / Q000737:chemistry*; D012972:Sodium Hydroxide / Q000737:chemistry; D012995:Solubility; D013464:Sulfuric Acids / Q000737:chemistry; D014908:Triticum / Q000737:chemistry*
chemical_list: D000148:Acids, Noncarboxylic; D063566:Biodegradable Plastics; D006878:Hydroxides; D007202:Indicators and Reagents; D017680:Potassium Compounds; D013464:Sulfuric Acids; D012972:Sodium Hydroxide; D005983:Glutens; C033158:sulfuric acid; D006851:Hydrochloric Acid; C029943:potassium hydroxide