María Antonia Martínez–Anaya

Effects of flour type and enzymes on total pentosans (TP) and water‐soluble pentosans (WSP) and composition of isolated water‐extractable pentosans (WEP) during a straight breadmaking process were investigated. Two wheat flours (F1, F2) and 3 enzymes (pentosanase, glucose‐oxidase (GOX) and lacasse (LAC)), and their combinations were used. The presence of pentosanase increased the WSP content while oxidases produced a decrease. Extractability of pentosans was greater for dough than for bread but the latter had higher purity. Major sugars were xylose (Xyl) and arabinose (Ara) with a xylose/arabinose ratio between 1.00 and 1.56. Molecular weight profiles (MWP) of WEP comprised 5 fractions with the same distribution for the 2 flours but different relative proportions.

Eleven commercial enzyme preparations, based on pentosanase and/or amylase activities, were added to wheat doughs and were processed to bread. Changes in free sugars, maltodextrins and carbohydrate polymer degradation—starch and pentosans—during fermentation, baking and storage are reported, and their possible relationship to functional properties is evaluated. The main activity of preparations was endo-type, although some arabinosidase action was present, even in•-amylases without other declared activity. Dextrinogenic (low molecular weight) properties of•-amylases depended on the source, and within the same manufacturer, on the enzyme characteristics. The majority of preparations solubilized part of pentosans, changes consistent with reported enzyme composition. Storage of breads induced variations in soluble starch and solids, which were affected by the enzymes. Some low molecular weight dextrins correlated with fresh bread properties, favored crumb and starch solubilization and did not induce changes in texture during storage, whereas water-insoluble pentosans correlated with crumb elasticity and hardness during storage.

Water soluble pentosans (WSP) from doughs and breads made with different enzyme preparations are characterized according to extraction yield, sugar composition, xylose/arabinose ratio and molecular weight (MW) distribution. Extraction yield was greater for dough than for bread samples, ranging from 0.94 to 1.64%, but bread extracts had a higher purity. Percent of pentoses in purified WSP was greater in pentosanase supplemented samples (28-55%) than in control and amylase containing samples (23-32%). Major sugars were xylose and arabinose, but glucose and mannose also appeared in the extracts. The xylose/arabinose (Xyl/Ara) ratio was 1.3-1.6 and underwent small changes during processing. Enzyme addition caused an increase in Xyl/Ara ratio, attributable to a debranching of arabinoxylans (AX) with higher degree of Ara substitution by arabinofuranosidase. Addition of pentosanases had a significant effect in increasing WSP with MW over 39 000, whereas those of low MW changed only slightly. MW distribution depended on enzyme source, and whereas some enzymes showed activity during fermentation others increased their activity during baking. No synergistic effects were observed in studied variables due to the combination of amylases with pentosanases. Protein in WSP extracts eluted together with ferulic acid suggesting they were linked, but not associated with a determined carbohydrate fraction.