Ultrasound-assisted annealing treatment to improve physicochemical and digestive properties of banana flour.

BACKGROUND: Banana flour can provide a solution to people with gluten intolerance, as it is gluten-free. Native banana flour may have limited functionality in certain applications. In this study, banana flour was modified by ultrasonic (US) and annealing (ANN) treatments at four incubation time spans, namely 12, 24, 36 and 72 h, separately or combined sequentially (US-ANN) to enhance the physicochemical and digestive properties. RESULTS: US led to exposed granular surfaces and damaged non-starch components. Both treatments, at extended incubation time, increased crystallinity, resulting in a narrower starch gelatinization temperature range. The swelling power was significantly lower for ANN and US-ANN compared to US alone, providing a delay of gelatinization temperature. However, none of the treatments affected the gelatinization enthalpy. Furthermore, US increased peak viscosity, breakdown, final viscosity and setback whereas the opposite results were obtained for ANN and US-ANN. Additionally, US prior to ANN significantly increased the resistant starch (RS) content for annealing times over 24 h, especially for the US-ANN treatment for 72 h, which provided the highest RS content (49.3%) compared to ANN treatment for 72 h (44.0%) and native flour (36.3%). CONCLUSIONS: US prior to ANN treatment offers an alternative method to improve the functional and digestive properties of banana flour, extending the range of applications. © 2024 Society of Chemical Industry.

Generation of short-chained granular corn starch by maltogenic α-amylase and transglucosidase treatment.

We describe a method for permitting efficient modification by transglucosidase (TGA), from glycoside hydrolase family 31 (GH31), sequentially after the pre-treatment by maltogenic α-amylases (MA) from GH13. TGA treatment without MA pre-treatment had negligible effects on native starch, while TGA treatment with MA pre-treatment resulted in porous granules and increased permeability to enzymes. MA→TGA treatments lead to decreased molecular size of amylopectin molecules, increased α-1,6 branching, and increased amounts of amylopectin chains with the degree of polymerization (DP)<10 and decreased amounts of DP 10-28 after debranching. Wide-angle X-ray scattering (WAXS) data showed a general decrease in crystallinity except for a long term (20 h) TGA post-treatment which increased the relative crystallinity back to normal. MA→TGA treatment significantly lowered the starch retrogradation of starch and retarded the increase of storage- and loss moduli during storage. This work demonstrates the potential of sequential addition of starch active enzymes to obtain granular starch with improved functionality.

Pre-treatment of granular rice starch to enhance branching enzyme catalysis.

Effects of different pre-treatments of granular rice starch using ethanol (ET) and maltogenic α-amylase (MA), separately or combined sequentially ET→MA, were performed to enable efficient subsequent modification with branching enzyme (BE). The pre-treated samples were characterized with respect to morphology, molecular structure, physicochemical properties and the rate of digestion to amylolytic enzymes. MA produced pores and also eroded the granular surface whereas ET caused coapted granules, noticeable swelling but no pores. Crystallinity and enthalpy of gelatinization dramatically decreased with ET and ET→MA. Subsequent BE catalysis increased the specific surface area, crystallinity, α-1,6-glucosidic linkage ratio and enthalpy. BE catalyzed branching resulted in more intact granules, less swelling capacity, solubility and granular separation as compared to their control. These effects were related to reduced amylolytic susceptibility. Pre-treatment prior to BE catalysis offers an efficient alternative way to modify granular starch with different structure and properties depending on the pre-treatment protocol.

Porous high amylose rice starch modified by amyloglucosidase and maltogenic α-amylase.

Porous starch is attractive by providing high surface area for many applications. In this study amyloglucosidase (AMG) and maltogenic α-amylase (MA) were investigated in direct comparison to elucidate potential effects in producing porous starch using high amylose rice starch as a substrate. Both enzymes generated pores at the surface as illustrated by Scanning Electron Microscopy (SEM). The enzyme-treated granules had higher relative crystallinity as deduced from Wide Angle X-ray Scattering (WAXS). MA treatment increased the number of short amylopectin chains and decreased the molecular weight with extended incubation time. The MA-treated starch had higher solubility whereas swelling capacity, amylose content, peak viscosity, final viscosity, breakdown and setback of both treatments were decreased compared to the control. Enzymatic treatments produced starch with delayed gelatinization temperature and increased the enthalpy. The results demonstrate that porous rice starch can provide different functionalities depending on the enzyme mechanisms, extending the range of applications.

Porous rice starch produced by combined ultrasound-assisted ice recrystallization and enzymatic hydrolysis.

The effects of multicycle ultrasound-assisted ice recrystallization (US+IR) combined with amyloglucosidase (AMG) or maltogenic α-amylase (MA) catalyzed hydrolysis on structure were investigated. Scanning electron microscopy (SEM) showed that the US+IR produced shallow indentations and grooves on the exterior of granules while the combination US+IR and enzyme hydrolysis created additional pores on starch granules. MA displayed a higher number of pores than AMG. The highest values of specific surface area (SBET) and the total pore volume were obtained for US+IR→MA (1.96 m2 g-1 and 7.26 × 10-3 cm3 g-1, respectively). The US+IR treatment significantly decreased the relative crystallinity, amylose content and swelling capacity. Those parameters were further efficiently decreased following enzymatic hydrolysis. The combined treatments generated products with higher initial gelatinization temperature (Ti) compared to the corresponding controls. The US+IR increased the digestion rate constant (k-value) compared to native starch. However, the combined treatment, US+IR→AMG, significantly decreased the k-value from 2.97 × 10-3 to 2.50 × 10-3 min-1 compared to its control. Our study demonstrates that US+IR treatment in combination with enzyme hydrolysis is a useful method to produce specifically functionalized porous rice starch that can be used as e.g. absorbents and for further chemical modifications.