Enzymatic and Acidic Hydrolysis of Cationized Waxy Maize Starch Granules

Abstract

A series of wet‐cationized starch granules from waxy maize with different degrees of substitution (DS) were solubilized with either 2.2M HCl (lintnerization) or with the α‐amylase of Bacillus amyloliquefaciens. The maximum rate of the enzymatic hydrolysis occurred in starches with intermediate DS. It appeared that the cationic substituents interfered with the binding to the active site of the enzyme at high levels of substitution. The DS remained fairly constant in the granular residues after the enzymatic attack. The rate of the acidic hydrolysis increased with increasing DS but the final level of solubilization slightly decreased. The DS of the residual starch material decreased to 40% of the original level, showing that a large part of the cationic groups was found within the amorphous parts of the granules. A dry‐cationized sample with a high DS was also treated with the acid and lost a major part of its substituents at low levels of lintnerization. Probably most of the substituents were associated with the surface and channels of these granules. The cationized starches possessed branches that were resistant to isoamylase attack and the samples also contained β‐amylolysis resistant dextrins. The proportion of resistant dextrins in the granular residues decreased after lintnerization, but remained constant after the enzymatic hydrolysis.

Characterisation of Fractions Obtained by Isoamylolysis and Ion-exchange Chromatography of Cationic Waxy Maize Starch

“…Dextrins with a degree of polymerisation (DP) < 50 corresponded to the unit chains of the amylopectin of waxy maize starch [28], whereas dextrins of DP 50-500 represented fragments that contained resistant branches [20]. As also shown earlier [20], the DC sample contained less resistant branches, but these were apparently more concentrated locally, thus resulting in a low amount of large dextrins that eluted at the void volume of the column. from the DC starch was more than twice that obtained from the WC sample.…”

“…The samples of wet-cationised (WC) and dry-cationised (DC) waxy maize starch were identical to those described in an earlier investigation [20]. Both samples had a degree of substitution (DS) of 0.046, which represented a level commonly used in commercial applications.…”

“…Both samples had a degree of substitution (DS) of 0.046, which represented a level commonly used in commercial applications. When treated with isoamylase, the samples were not completely debranched because substituents at, or close to, the α-(1→6)-linkages blocked the action of the enzyme [20].…”

“…Preparation and characterisation of the wet-and drycationised waxy maize starches used has been described previously [20]. Both samples had a degree of substitution (DS) of 0.046.…”

Modificação enzimática da farinha de arroz visando a produção de amido resistente

“…A farinha de arroz com menor granulometria, possuindo maior área de contato com a enzima, favorece a ação enzimática nas cadeias proteicas e amiláceas e aumenta, desta forma, o grau de hidrólise do amido, alterando, consequentemente, a digestibilidade da farinha. 24 A lipase pancreática, por ser uma enzima impura contém outras hidrolases (como amilases e proteases), que podem ser benéficas ao tratamento atuando diretamente nas camadas externas do grânulo e hidrolisando os complexos lipídio-amilose e proteína-amilose e, com isso, chegando às regiões mais internas, frágeis e susceptíveis à hidrólise amilolítica. Entretanto, a hidrólise das camadas mais internas (amorfas) pela ação da lipase pancreática ocorre em menor intensidade quando comparada à ação da amiloglicosidase, o que pode explicar o fato desta farinha ter perdido menos massa (medida através da massa específica), em relação à ação com a amiloglico- sidase, tendo em vista que quanto menor a perda de massa menor a quebra de ligações entre as moléculas.…”