Confocal laser scanning microscopy of dextran–rice starch mixtures

Alteration of the Morphological and Physicochemical Characteristics of Corn and Wheat Starch via Dry Heating with Whey Protein Isolates

This study investigated the impact of whey protein isolate (WPI) addition on the dry heat modification of corn (CS) and wheat starch (WS). Starches were treated under dry heating conditions at 130 °C for 2 and 4 h. The physicochemical and structural properties of the modified starches, such as color, particle size, thermal behavior (DSC), crystalline structure (XRD), and surface morphology (SEM), were analyzed. The results show that adding WPI significantly altered the gelatinization properties, surface morphology, and crystalline structure of both starches. DSC indicated that the gelatinization properties of starch/WPI mixtures varied, with corn starch showing a decreased gelatinization temperature and increased enthalpy, whereas wheat starch exhibited a more complex response, likely due to different structural changes. The XRD and FTIR results revealed WPI-enhanced crystallinity and structural changes, highlighting WPI-induced aggregation. Wheat starch, in particular, exhibited stronger interactions with WPI than corn starch, as evidenced by the accumulation patterns in the SEM images. The oil-binding capacity of native starches increased with dry heating and WPI addition, suggesting an improved hydrophobicity of starch granules. Dry heating and WPI addition significantly altered starch properties, highlighting the potential of thermal modulation to enhance starch-protein systems for targeted food applications.

Understanding the Molecular Interactions Between Pandan Pigment and Food Components for Enhanced Thermal Stability

Pandan pigment (Pandanus amaryllifolius) is widely used as a natural food coloring and flavoring agent. However, its application in food is limited because of its susceptibility to thermal degradation during food processing, which affects both pigment stability and color. Despite its growing use, there is limited research on how common food ingredients can mitigate this degradation. This study addresses this gap by exploring the effects of sucrose, lactose, rice starch, whey protein, and soy protein isolate on the thermal and color stability of pandan pigment under various heating conditions (65 °C, 95 °C, 115 °C, and 121 °C for 15 min). Spectroscopic techniques (UV-visible, infrared, and fluorescence) and laser confocal microscopy were used to elucidate the molecular interactions. The results revealed that rice starch provided the strongest protection, followed by whey protein, soy protein isolate, lactose, and sucrose, although the protective effects decreased at higher temperatures. These findings offer new insights into the use of sugars and proteins to increase the thermal stability of natural pigments in food applications.

Mild steam treatment: Enhancing the rehydration performance of instant rice noodles by changing the physicochemical properties and gel structure of rice starch

The "instant" quality of instant rice noodles is significantly affected by slow rehydration during cooking. This happens as a result of the native rice starch's low ability to gelatinize as well as the high shear and pressure utilized in industries during the widely used extrusion molding process. In order to address this issue, the rice flour was pretreated with mild steam (MS) technology. The results revealed that the rehydration qualities of the rice noodles that were extruded from the steam-treated flour significantly improved. There was a reduction of 25.5% in the rehydration time, from 443 to 330 s. The MS-treated rice starch's peak viscosity increased to 4503 from 4044 mPa/s. Decreases in gelatinization enthalpy (ΔH) and short-range ordering also suggest a reduction in difficulty in accomplishing starch gelatinization. Scanning electron microscopy studies showed particle aggregation increased as the treatment duration lasted longer. In conclusion, our findings indicate that we successfully addressed the issue of slow rehydration in instant rice noodles while presenting a novel approach for their manufacturing in the manufacturing sector.

Effect of Pulsed Electric Field Treatment on the Protein, Digestibility, and Physicochemical Properties of Starch Granules in Wheat Flour

The effect of pulsed electric field (PEF) treatment depends mainly on the electric field strength and treatment time. In this study, wheat flour-water suspensions were treated with PEF at an electric field strength of 3 kV/cm for 0 to 1400 pulses to obtain a specific energy input of 0 to 656 kJ/kg. The effect of PEF on the removal or unfolding of proteins from the starch surface, digestibility, starch granule structure, and physicochemical properties of wheat flour was studied. The removal of proteins from the surface and the damage to the internal structure of wheat starch granules after PEF treatment was detected by confocal laser scanning microscopy (CLSM) and FTIR. The damage of the PEF-treated wheat starch granules was observed by scanning electron microscopy (SEM). From CLSM results, penetration of dextran (Mw 10,000 Da) into starch granules of wheat flour was dependent on the energy input of PEF. The high the energy input showed the intense penetration of the biopolymer. The benefits of the accessibility of biopolymer in starch granules are to increase enzyme digestion, especially rapidly digestible starch (RDS). The RDS of wheat flour treated with PEF at 656 kJ/kg was 41.72%, whereas the RDS of wheat flour control was 27.59%.

Starch granule size: Does it matter?

Nature has developed starch granules varying in size from less than 1 μm to more than 100 μm. The granule size is an important factor affecting the functional properties and the applicability of starch for food and non-food applications. Within the same botanical species, the range of starch granule size can be up to sevenfold. This review critically evaluated the biological and environmental factors affecting the size of starch granules, the methods for the separation of starch granules and the measurement of size distribution. Further, the structure at different length scales and properties of starch-based on the granule size is elucidated by specifying the typical applications of granules with varying sizes. An amylopectin cluster model showing the arrangement of amylopectin from inside toward the granule surface is proposed with the hypothesis that the steric hindrance for the growth of lamellar structure may limit the size of starch granules.

Infusion efficiency of fluorescein derivatives of different molecular sizes into various starches under atmospheric and high hydrostatic pressures

Fluorescein isothiocyanate-dextrans (FDs) of different molecular weights were infused into corn, waxy rice, tapioca, and potato starches under atmospheric and high hydrostatic pressures (HHP). FD4, FD10, FD20, and FD40 (Mw 4000, 10,000, 20,000, and 40,000, respectively) were used as infusion materials. Confocal laser scanning microscopy confirmed that all FDs except FD40 infused into corn, waxy rice, and tapioca starches. However, no FDs infused into potato starch. Corn starch had the highest amounts of infused FDs. As molar mass increased, the amount of infused FD decreased in all starches. The infused amounts of FDs in corn starch were similar at 200-300 MPa and atmospheric pressure. Infusion of FDs at 400 MPa was reduced due to partial gelatinization. These results confirm that infusion efficiency is inversely proportional to the molecular weight of the infused material and large materials (Mw > 40,000) cannot be infused into starch granules under atmospheric pressure or HHP.

SUPPLEMENTARY INFORMATION

The online version contains supplementary material available at 10.1007/s10068-021-00972-2.

Impact of starch granule-associated channel protein on characteristic of and λ-carrageenan entrapment within wheat starch granules

This study investigated the physicochemical characteristics of protease-treated wheat starch (PT-WST) to understand the role of starch granule-associated proteins (SGAPs) and the potential capability of PT-WST to provide a nutrient delivery system (NDS). Protease treatment was conducted at 4 °C and 37 °C (PT04 and PT37), respectively. A model delivery system was assessed with PT37 granules infiltrated by λ-carrageenan (λC) under variations of molecular size (λC hydrolysates produced from 0, 2.5, 100, and 500 mM HCl solution), agitation time, and temperature. Protein-specific (3-(4-carboxybenzyl)quioline-2-carboxaldehyde) or non-reactive (methanolic merbromin) fluorescent dye staining revealed that removal of SGAPs on surfaces and channels were more effective for PT37 than for PT04. Consistent amylose content, swelling, and gelatinization temperature before and after protease treatment suggested minimal impact on the starch structure. PT37 presented higher solubility and pasting viscosity than PT04. This resulted from excessive SGAP removal, which enhanced entrapment capacity. λC molecular size and agitation temperature showed a negative correlation with the content of λC entrapped within PT37, and this content depended on the interplay between the agitation time and λC molecular size. As λC molecular size decreased, the λC distribution became uniform throughout the granules, which confirmed the potential of PT-WST as a carrier for NDS.

Characterizing internal cavity modulation of corn starch microcapsules

Swelling of normal corn starch granules through heating in water leads to enlargement of the starch particles and a corresponding increase in internal cavity size. Through control of the swelling extent, it is possible to tune the size of the internal cavity for the starch microcapsules (SMCs). The swelling extent can be controlled through regulation of the swelling time and the swelling temperature. Since the swelling extent is correlated with particle size and solubility, these aspects may also be controlled. Imaging the SMCs at increasing levels of swelling extent using scanning electron microscopy (SEM) allowed for the internal cavity swelling process to be clearly observed. Brightfield and polarizing light microscopy validated the SEM observations. Confocal laser scanning microscopy provided further validation and indicated that it is possible to load the SMCs with large molecules through diffusion. The highly tunable SMCs are novel microparticles which could have applications in various industries.