Retrogradation of Maize Starch after High Hydrostatic Pressure Gelation: Effect of Amylose Content and Depressurization Rate

Azo dye anaerobic treatment in anaerobic reactors coupled with PVA/Fe/Starch gel bead

A novel bio-carrier, PVA/Fe/starch gel bead, was fabricated and developed to enhance the anaerobic treatment performance of synthetic azo dye-containing wastewater. PVA-gel beads with 5 % magnetite and 0.5 % starch were optimal for physical strength and treatment performance. A pair of 2 L-up-flow anaerobic sludge blankets (UASB), one with the bead (UB) and another without (U) as a controller, operated continuously at 30 °C and an HRT of 11-24 h for 302 days. UB showed better performance than U in most phases, especially with influent dye of 200 mg·L-1, suggesting a greater tolerance to dye toxicity of UB than U. Microbial analysis revealed that the PVA/Fe/starch gel beads successfully captured the dye degrader Clostridium. Diversity indices indicated that PVA/Fe/Starch gel beads effectively support microbial diversity and resilience under varying dye concentrations. Overall, these findings demonstrate the potential of PVA/Fe/Starch gel beads to improve the stability and efficiency of the dye treatment system.

Comprehensive investigation of pressure-induced gelatinization of starches using in situ and ex-situ technical analyses

The pressure-induce gelatinization of pea starch, potato starch and corn starch was investigated by a combination of in situ and ex-situ technical analyses. According to in-situ observation of gelatinization process and the analysis of granular morphology by scanning electronic microscopy (SEM), the pressure that caused potato starch gelatinization was the highest at 600 MPa. This was followed by pea starch, and the pressure that caused the gelatinization of corn starch was the lowest at 400 MPa. In situ Raman spectral analysis revealed the molecular mechanism of starch gelatinization. This indicated that high pressure treatment resulted in the modification of the structure of the double helical polymers and the degree of a double helix of the starch crystalline varied as well. This study dynamically monitors the starch gelatinization process, aiming to better understand the gelatinization mechanism and provide a theoretical basis for the application of pressure in the starch field.

Pre-gelatinized high-amylose starch enables easy preparation of flexible and antimicrobial composite films for fresh fruit preservation

While high-amylose starch (HAS) possesses advantageous properties such as high resistant starch content and favorable mechanical attributes, its gelatinization constraints have limited its applicability. This study enhances its versatility by focusing on pre-gelatinized (PG) HAS with exceptional rehydratability, achieved by disorganizing native HAS granules (with amylose contents of 55 % and 68 %, respectively) using a 33 % CaCl2 solution, followed by water-ethanol precipitation and freeze-drying. The resulting PG-HAS exhibited elevated amylose content (61 % and 75 %) with minimal changes in amylose molecular weight. PG-HAS displayed superior water-absorption index (WAI) and water-soluble index (WSI) compared to native HAS, further improved by 2 % CaCl2 solution incorporation. Furthermore, composite films were prepared by mixing PG-HAS with PVA at a 6:4 (w/w) ratio. The PG-G50 (61 % amylose content)/PVA composite film exhibited remarkable elongation (131.1 ± 5.4 %), nearly three times that of a normal corn starch (NCS, with 27 % amylose)/PVA film, attributed to improved starch dispersity and higher amylose content. Nonetheless, the PG-G70 (75 % amylose content)/PVA film at the same ratio showed lower elongation (54.7 ± 8.0 %), potentially due to strong cohesive forces between amylose chains that impede starch-PVA interactions. Moreover, the PG-HAS/PVA composite films, enriched with antibacterial agents, demonstrated effective antibacterial properties with a gradual and sustained release of active compounds. Notably, the PG-G50/PVA/tannic acid (TA) film effectively preserved fresh apple slices by inhibiting bacteria growth and preventing browning. These findings underscore the excellent rehydration of PG-HAS and its potential as an inner packaging material for irregularly shaped foods, such as sliced fruits or meats, due to its nontoxic nature, softness and flexibility, which allows the film to maintain close contact with food surfaces.

The effects of high-pressure treatment on the structure, physicochemical properties and digestive property of starch - A review

High hydrostatic pressure (HHP) is a novel technology used in the food-processing industry. Starch is an important renewable natural resource. The applications of starch are determined by its properties, which in turn are determined by its structure. In this study, the effects of HHP treatment on starch structure (granular structure, crystalline structure, molecular structure, and molecular conformation) and properties (pasting, retrogradation, thermal, digestive, rheological, swelling, solubility, water absorption, and oil absorption properties) are summarised. Additionally, the mechanism of HHP-induced gelatinisation is discussed. First, the strong hydration ability of starch molecules under high pressure facilitates the binding of water molecules to starch molecules via hydrogen bonding. These bound water molecules may block the channels inside the starch granules, leading to the formation of a sealed space. Finally, the granules disintegrate because of the intra/extra pressure difference. This study provides a reference for the application of HHP to starch processing and modification.

Effects of the Amylose/Amylopectin Content and Storage Conditions on Corn Starch Hydrogels Produced by High-Pressure Processing (HPP)

In this study, the effects of the amylose/amylopectin content on starch gelation and the physical characteristics of hydrogels produced by HPP were studied by optical and rheological measurements in steady-state conditions. Additionally, the effects of the storage temperature (4 °C and 20 °C) and type of packaging (plastic bags or sealed Petri dishes) on the physical stability of the hydrogels were evaluated for 30 days of storage by evaluating the shrinkage of the granules, as well as the weight loss, water activity, organoleptic, and rheological properties. The experimental findings suggested that amylose plays an antagonistic role in determining the capacity of the starch granules to absorb water under pressure and to create stable and structured gels and on the physical stability of hydrogels due to its influence over the starch retrogradation extent during storage. Twenty per cent amylose was the minimum concentration to form stable corn starch HPP hydrogels with good physical and rheological properties. Moreover, a storage temperature of 20 °C and the use of polymeric bags were evaluated as the most suitable storage conditions and packaging materials enabling the long storage of corn starch hydrogels.

High-amylose maize starch: Structure, properties, modifications and industrial applications

High-amylose maize refers to a special type of maize cultivar with a 50 %-90 % amylose content of the total starch. High-amylose maize starch (HAMS) is of interest because it possesses unique functionalities and provides many health benefits for humans. Therefore, many high-amylose maize varieties have been developed via mutation or transgenic breeding approaches. From the literature reviewed, the fine structure of HAMS is different from the waxy and normal corn starches, influencing its gelatinization, retrogradation, solubility, swelling power, freeze-thaw stability, transparency, pasting and rheological properties, and even in vitro digestion. HAMS has undergone physical, chemical, and enzymatical modifications to enhance its characteristics and thereby broaden its possible uses. HAMS has also been used for the benefit of increasing resistant starch levels in food products. This review summarizes the recent developments in our understanding of the extraction and chemical composition, structure, physicochemical properties, digestibility, modifications, and industrial applications of HAMS.

The effects of HHP (high hydrostatic pressure) on the interchain interaction and the conformation of amylopectin and double-amylose molecules

Starch is an important resource in nature, and HHP (high hydrostatic pressure) is one of the most important physical modification technologies. In this study, molecular dynamics simulation was used to explore the interchain interaction and the changes of molecule conformations of amylopectin and double-amylose helix at atomic level in different pressure. The results shown that, firstly, high pressure increased the content of 4C1 chair conformation, decreased the RMSD (root mean square deviations) and RMSF (root mean square fluctuation), made molecules more stable. Secondly, high pressure increased the interchain VDW (Van der Waals) and electrostatic forces, then caused the decreases of the interchain distances and surface area of both amylopectin and double-amylose, made molecules more compact. Thirdly, high pressure decreased the intramolecular hydrogen bonds, increased the molecule-solvent hydrogen bonds. These findings can explain some existing experimental phenomena from the atomic level, meanwhile, it may also provide importance reference value for using of HHP in starch processing and the studies of starch granule structure.

Physicochemical Properties and Resistant Starch Content of Corn Tortilla Flours Refrigerated at Different Storage Times

The tortilla is a foodstuff that has a short shelf-life, causing great losses to the industry. The objective of this work was to evaluate, for the first time, the physicochemical properties and resistant starch (RS) content of flours. These were obtained from nixtamalized corn tortillas made with traditional and industrial (commercial) methods, stored at 4 °C for 7, 15, and 30 days. The flours were characterized by measuring particle size distribution, color, water absorption index (WAI), water solubility index (WSI), viscosity, calcium, and RS content. Additionally, chemical proximate analysis, scanning electron microscopy (SEM), and thermal analysis were conducted. Storage at 4 °C increased the friability of tortillas and shifted the particle size distribution toward a greater content of coarse particles in corn tortilla flours. The commercial corn tortilla flours showed higher WAI and WSI values than the traditional corn tortilla flours. On the other hand, the traditional corn tortilla flours exhibited higher RS content values than commercial corn tortilla flours as well as peak viscosity. X-ray diffractograms revealed the presence of amylose-lipid complexes (RS5) in experimental samples. The thermograms evidenced three endotherms corresponding to corn starch gelatinization and melting of type I and type II amylose-lipid complexes.