Use of two endoxylanases with different substrate selectivity for understanding arabinoxylan functionality in wheat flour breadmaking

A Bacillus subtilis endoxylanase (XBS) with a strong selectivity for hydrolysis of water-unextractable arabinoxylan (WU-AX) and an Aspergillus aculeatus endoxylanase (XAA) with a strong selectivity for hydrolysis of water-extractable arabinoxylan (WE-AX) were used in straight-dough breadmaking with two European wheat flours. Dough, fermented dough, and bread characteristics with different levels of enzyme addition were evaluated with a strong emphasis on the arabinoxylan (AX) population. The WU-AX solubilized by XBS during breadmaking were mainly released during mixing and had higher molecular weight, in contrast to their counterparts solubilized by XAA, which were mainly released during fermentation and had lower molecular weight. This coincided with increased loaf volume with XBS and a negative to positive loaf volume response with XAA. Bread firmness and dough extract viscosity also were affected by endoxylanase addition. Results confirmed that WU-AX are detrimental for breadmaking, while WE-AX and solubilized AX with medium to high molecular weight have a positive impact on loaf volume.status: publishe

Amylose-lipid complexation: a new fractionation method

Amylose fractions of different peak Degree of Polymerisation (DP) (DP20, DP60, DP400, DP950) were complexed with docosanoic acid (C22) and glyceryl monostearate (GMS) at 60 and 90degreesC. Complexation yields, relative crystallinities, dissociation temperatures and enthalpies increased with amylose chain lengths (DP20-DP60-DP400). Relative crystallinities and thermal stabilities of the DP950-complexes were slightly lower than those of the other amylose fractions, probably due to increased conformational disorders, resulting in crystal defaults. Molecular weight distributions of the complexes revealed that, irrespective to the complexation temperature, the critical DP for complex formation and precipitation was 35 and 40 for complexes with GMS and C22, respectively, corresponding to the length needed to accommodate two GMS- or C22-molecules within an amylose helix. Complexation of dextrins with a well-chosen lipid, allows to separate starch derived dextrins with a predictable critical chain length as border. Dextrins, of sufficient DP will complex and precipitate, while the shorter dextrins will remain in solution. (C) 2004 Elsevier Ltd. All rights reserved.status: publishe

Enzyme and acid resistance of amylose-lipid complexes differing in amylose chain length, lipid and complexation temperature

To study parameters that influence enzyme and acid resistance of amylose-lipid complexes, complexes were formed between amylose of different average chain lengths [Degree of Polymerisation (DP); DP60, 400, 950] and docosanoic acid (C22) or glyceryl monostearate (GMS) at 60 or 90 °C. Complexes were hydrolysed with hog pancreatic alpha-amylase or acid (2.2 N HCl). DP400- and DP950-complexes were of type I when formed at 60 °C and of type II when formed at 90 °C. Enzyme and acid resistance increased with increasing amylose DP, lipid chain length and complexation temperature. DP60 yielded only type I complexes, independent of the complexation temperature. Enzymic and acid hydrolysis of all complexes gave rise to two or more dextrin subpopulations, which are interpreted to originate from a sequence of lamellar units (the smallest peak DP) with interconnecting, amorphous amylose chains. The peak DP of such lamellar unit increased with increasing amylose DP and complexation temperature, but remained constant when higher enzyme dosages were applied. Synthesis of amylose-lipid complexes from amylose and lipids of variable structure under variable temperature conditions followed by hydrolysis can yield dextrin populations of defined and relatively narrow molecular weight distributions.status: publishe

Fractionation of starch hydrolysates into dextrins with narrow molecular mass distribution and their detection by high-performance anion-exchange chromatography with pulsed amperometric detection

Low levels of high-molecular-mass dextrins in starch hydrolysates can be detected by high-performance anion-exchange chromatography with pulsed amperometric detection in spite of their low responses by dialysis of the starch hydrolysate and fractionation of the resulting adialysate with ethanol (final concentration 30-80% at 6degreesC). In doing so, dextrin fractions with a relatively narrow molecular mass distribution were obtained. (C) 2003 Elsevier Science B.V. All rights reserved.status: publishe