Partial Hydrolysis of Granular Potato Starch Using α-Amylase - Effect on Physicochemical, Molecular, and Functional Properties

Abstract

Potato starch (PS) is enzymatically modified using α‐amylase and comprehensively characterized. Modified PS is prepared by adding different amounts of α‐amylase (0.04, 0.08, 0.16, and 0.33 mL of an enzyme solution (LpHera, Novozymes A/S) to 400 g of a 40% w/v aqueous starch suspension and reacting for 15 min at 40 °C. Morphological characteristics (SEM), pasting (viscosity profile, thermal behavior‐DSC) and molecular properties (SEC‐MALS‐DRI), carbohydrates solubility, hot paste shear viscosity, and gel strength are analyzed. The morphological characteristics are significantly affected by the α‐amylase. The surface of the granules shows small cracks and holes. In regard to the characteristic pasting parameters, there are significantly decreased values after hydrolysis. However, the DSC gelatinization properties are slightly impacted by the modification. The solubility of the starch polymers is increased by the increase of both the enzyme dosage and the disintegration temperature applied (95 and 145 °C). Moreover, the molecular composition of the solubilized starch is impacted, too. The investigation of molecular dispersed solutions demonstrates the strong degradation of both amylose (AM) and amylopectin (AP). An increasing enzyme concentration led to a systematically decreased Mw in the samples. The degradation within the amorphous areas is presumed to be faster, similar to acid hydrolysis in native granular starch. However, gelation properties of the enzymatically modified starches are not perceptible. The gradual depolymerization effected the reduction of the hot paste viscosity accordingly.

Enzymatic Modification of Granular Potato Starch ‐ Effect of Debranching on Morphological, Molecular, and Functional Properties

“…Commercial native PS (Superior) was obtained from Emsland‐Stärke GmbH, Emlichheim, Germany. The contents of the dry matter and the total AM as well as the ratio of AM/AP were about 83.10% w/w, 24.3 ± 0.2%, and about 25:75, respectively . The protein content (≤0.1 % w/w), ash content (≤0.5 % w/w), and the lipid content (≤0.1 % w/w) were provided by the supplier.…”

“…The native PS was specifically modified by partial hydrolysis using PUL enzyme according to the description elsewhere with modifications. Based on the dry matter content, a mass of 80.0 g native starch was weighed.…”

“…DSC method (DSC 204 F1 Phoenix fitted with an intracooler, Netzsch, Selb, Germany) was used to determine the thermal gelatinization behavior of the starch samples according to the description elsewhere . About 5 mg of a starch sample and a fourfold amount of deionized water were mixed in an aluminum pan (Netzsch, Germany), hermetically sealed, stored at 20 ± 2 °C for 24 h, and subsequently measured.…”

“…Regular starches feature an AM:AP ratio of about 25:75 w/w. Especially PS possesses conspicuous properties, most likely due to its comparable high contents of phosphate ester groups in the AP affecting several interesting characteristics …”

“…However, the intact molecular structure of the AM is a requirement for the development of a 3‐dimensional AM‐based network, and hence favored. Unfortunately, the acid‐modification is widely non‐specific, but the enzymatic approach could be a promising alternative . In particular debranching enzymes like PUL could effectuate a more specific and additionally very fast molecular degradation of the starch polymers.…”