Flow behavior and mechanical properties of water chestnut (Trapa natans) under steady shear as affected by acid and autoclave treatment

Abstract

The flow behavior and mechanical properties of the water chestnut as influenced by acid and autoclave treatment (AT) are envisaged. The water chestnut flour (WCNF) was exposed to 1 M HCl, acid hydrolysed (AH) in the ratio of 1:1 (wt/vol) and AT at 121°C for 15 min, and cooled for 24 (AT‐24) and 72 (AT‐72) hr at 4°C. The acid hydrolysis and autoclaving resulted in significant changes in physico‐functional, flow behavior, and mechanical properties of the water chestnut. The WCNF showed a non‐Newtonian behavior, and the viscosity decreased with an increase in the shear rate for both acid and autoclave treated WCNF samples. The mechanical spectra, storage modulus (G′), and loss modulus (G″) observed dominance of the elastic component over viscous component in both acidic and autoclaving conditions. The flow behavior and mechanical spectrum data were fitted to the power‐law model and the Ostwald‐de Waele equation. The relationship among the power‐law coefficients (n, K, n′, and n″) was assessed by linear regression of the fitted models. The swelling power of WCNF and AH was lower than AT samples. However, the increase in swelling power with the rise in temperature from 55 to 95°C was more for WCNF and AH samples than AT samples. The autoclaving‐cooling changed the A‐type X‐Ray Diffraction (XRD) pattern to a B‐type XRD pattern representing the loss of molecular order and the disintegration of the internal structure. Practical applications Since different stresses cause different reactions in materials, it is critical to measure liquid flow in a way that mimics the mechanism it might encounter in an industrial or commercial setting. Many processing operations that include slurries or pastes, such as beneficiation (wet mixing and milling, filtration); shape formation (extrusion); and coating or deposition, require knowledge of rheological behavior. Although various nuts and seeds are extensively being studied for their physicochemical and functional behavior in different environments, the data of water chestnut on feasibility in industry‐related process operations is scarce. Therefore, the rheology of the water chestnut in acid and autoclave environment can help to decide the process feasibility and, hence, use in a particular industrial operation.

Esterified unpopped foxnut (Euryale ferox) starch: molecular and rheological characterization

“…The swelling power, solubility, flow curve, and frequency sweep tests were performed as previously described 20 with slight modifications. A parallel plate of 25 mm dia with 1 mm gap size was used (MCR‐302).…”

“…The pans were sealed and left to equilibrate at room temperature (25 °C) for 3 h. With N 2 as the inert gas, a heating cycle from 32–120 °C (5 °C min −1 ) was performed. Using the instrument software (TA‐60), the thermograms were evaluated for onset (To), peak (Tp), conclusion (Tc) temperatures and enthalpy of gelatinization ( ∆ H) 20 …”

“…The electron high tension (EHT) value was fixed at 3.00 kV. The images were taken at different resolutions from 1kX to 10kX 20 …”

“…The z-average was used to describe the particle size of starches. 19 Functional and rheological properties The swelling power, solubility, flow curve, and frequency sweep tests were performed as previously described 20 with slight modifications. A parallel plate of 25 mm dia with 1 mm gap size was used (MCR-302).…”

“…Using the instrument software (TA-60), the thermograms were evaluated for onset (To), peak (Tp), conclusion (Tc) temperatures and enthalpy of gelatinization (ΔH). 20…”