Locations of hypochlorite oxidation in corn starches varying in amylose content

Synergistic effects of oxidized konjac glucomannan on rheological, thermal and structural properties of gluten protein

Oxidation is an effective way to prepare depolymerized konjac glucomannan (KGM). The oxidized KGM (OKGM) differed from native KGM in physicochemical properties due to different molecular structure. In this study, the effects of OKGM on the properties of gluten protein were investigated and compared with native KGM (NKGM) and enzymatic hydrolysis KGM (EKGM). Results showed that the OKGM with a low molecular weight and viscosity could improve rheological properties and enhance thermal stability. Compared to native gluten protein (NGP), OKGM stabilized the protein secondary structure by increasing the contents of β-sheet and α-helix, and improved the tertiary structure through increasing the disulfide bonds. The compact holes with shrunk pore size confirmed a stronger interaction between OKGM and gluten protein through scanning electron microscopy, forming a highly networked gluten structure. Furthermore, OKGM depolymerized by the moderate ozone-microwave treatment of 40 min had a higher effect on gluten proteins than that by the 100 min treatment, demonstrating that the excessive degradation of KGM weakened the interaction between the gluten protein and OKGM. These findings demonstrated that incorporating moderately oxidized KGM into gluten protein was an effective strategy to improve the properties of gluten protein.

Dibasic Magnesium Hypochlorite as an Oxidant to Tune Pasting Properties of Potato Starch in One Step

Modified starches are used widely in the food industry but often have a low nutritional value, lacking minerals vital for the human body, such as magnesium. Magnesium addition to native starches has been shown to result in changes in pasting properties. However, little work has been done on the addition of magnesium and other divalent cations to highly oxidised starches. In this work, we used dibasic magnesium hypochlorite (DMH) to oxidise potato starch to an industrially relevant degree of oxidation while at the same time introducing magnesium into the starch structure. We found that magnesium incorporation changes the pasting properties of starch and increases the gelatinisation temperature significantly, possibly due to an ionic cross-linking effect. These properties resemble the properties found for heat-moisture-treated potato starches. This change in properties was found to be reversible by performing a straightforward exchange of metal cations, either from sodium to magnesium or from magnesium to sodium. We show in this work the potential of the addition of divalent cations to highly oxidised starches in modifying the rheological and pasting properties of these starches and at the same time adding possible health benefits to modified starches by introducing magnesium.

Effect of chemical treatments on the functional, morphological and rheological properties of starch isolated from pigeon pea (Cajanus cajan)

Different chemical treatments (cross-linking, oxidation, and hydroxypropylation) were used to modify pigeon pea starch, and its effect on physiochemical, pasting and rheological properties were studied. Cross-linking and oxidation decreased while hydroxypropylation increased the swelling power of pigeon pea starch. All starch samples showed a decrease in their paste clarities. FTIR spectra of all starch samples displayed characteristic absorption bands of starch at wave numbers 1076, 1148, 1376, and 1632 cm⁻¹. A significant reduction occurred in peak, cold paste, hot paste, and setback viscosity after chemical modification. Rheological determinations showed that starch pastes had viscoelastic behaviour. G′ and G″ of all starch paste increased after chemical modification. Native and chemically treated starches revealed oval to elliptical-shaped granules and no change was observed after modification when examined in SEM. These results confirmed that the undesirable properties of native pigeon starch can be suitably altered via chemical treatments to make them suitable for several food applications.

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Chemical modifications significantly (p˂0.05) affect the amylose content, paste clarity, gel hardness, swelling power, and solubility.

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SEM analysis showed no significant changes after modifications.

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Pasting properties of starches were significantly reduced (p˂0.05) after the modification, whereas pasting time and peak time were increased.

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The cross-linked starch structure was more stable than the other modified starches.

Freeze Moisture Treatment and Ozonation of Adlay Starch (Coix lacryma-jobi): Effect on Functional, Pasting, and Physicochemical Properties

Adlay starch has great potential as a cereal starch, but it has several weaknesses, namely a low swelling volume, low solubility, and low stability. The purpose of this study was to improve the characteristics of adlay starch, such as porosity, functional properties, and pasting properties, through starch modification using freeze moisture treatment (FMT) and ozonation. This study consisted of several treatments, namely FMT, ozonation, and a combination of FMT + ozonation. The results show that the FMT and ozonation generally increased water absorption capacity, swelling volume, solubility, and number of pores of the starch granule. The pasting properties showed an increase in the viscosity of the hot paste and caused a decrease in the gelatinization temperature, breakdown, and setback viscosity. FMT 70% + ozonation produced modified adlay starch with a porous granular surface, swelling volume value of 21.10 mL/g, water absorption capacity of 1.54 g/g, a solubility of 9.20%, and an increase in the amorphous structure but did not cause the emergence of new functional groups. The combination of FMT + ozonation was effective in improving the functional, pasting, and physicochemical properties of adlay starch.

Removal of Lead, Cadmium, and Aluminum Sulfate from Simulated and Real Water with Native and Oxidized Starches

The separation of toxic pollutants such as Pb2+, Cd2+, and Al3+ from water is a constant challenge as contamination of natural water bodies is increasing. Al3+ and especially Pb2+ and Cd2+ are ecotoxic and highly toxic for humans, even in ppb concentrations, and therefore removal below a dangerous level is demanding. Herein, the potential adsorber material starch, being ecofriendly, cheap, and abundantly available, was investigated. Thus, four different native starch samples (potato, corn, waxy corn, and wheat starch) and two oxidized starches (oxidized potato and corn starch) were comprehensively analyzed with streaming potential and charge density measurements, SEM-EDX, ATR-FTIR, 1H-NMR, and TGA. Subsequently, the starch samples were tested for the adsorption of Pb2+, Cd2+, and Al3+ from the respective sulfate salt solution. The adsorption process was analyzed by ICP-OES and SEM-EDX, and the adsorption isotherms were fitted comparing Langmuir, Sips, and Dubinin-Radushkevich models. Oxidized starch, for which chemical modification is one of the simplest, and also native potato starch were excellent natural adsorber materials for Al3+, Cd2+, and especially Pb2+ in the low concentration range, exhibiting maximum adsorption capacities of 84, 71, and 104 µmol/g for oxidized potato starch, respectively.

Iron Tetrasulfonatophthalocyanine-Catalyzed Starch Oxidation Using H2O2: Interplay between Catalyst Activity, Selectivity, and Stability

Oxidized starch can be efficiently prepared using H₂O₂ as an oxidant and iron(III) tetrasulfophthalocyanine (FePcS) as a catalyst, with properties in the same range as those for commercial oxidized starches prepared using NaOCl. Herein, we performed an in-depth study on the oxidation of potato starch focusing on the mode of operation of this green catalytic system and its fate as the reaction progresses. At optimum batch reaction conditions (H₂O₂/FePcS molar ratio of 6000, 50 °C, and pH 10), a high product yield (91 wt %) was obtained with substantial degrees of substitution (DS_COOH of 1.4 and DS_CO of 4.1 per 100 AGU) and significantly reduced viscosity (197 mPa·s) by dosing H₂O₂. Model compound studies showed limited activity of the catalyst for C6 oxidation, indicating that carboxylic acid incorporation likely results from C-C bond cleavage events. The influence of the process conditions on the stability of the FePcS catalyst was studied using UV-vis and Raman spectroscopic techniques, revealing that both increased H₂O₂ concentration and temperature promote the irreversible degradation of the FePcS catalyst at high pH. The rate and extent of FePcS degradation were found to strongly depend on the initial H₂O₂ concentration where also the rapid decomposition of H₂O₂ by FePcS occurs. These results explain why the slow addition of H₂O₂ in combination with low FePcS catalyst concentration is beneficial for the efficient application in starch oxidation.

Carioca bean starch upon synergic modification: characteristics and films properties

BACKGROUND

The use of damaged beans for starch isolation comprises an end-use alternative for a product that is not accepted by the consumer. For that reason, isolation and modification of Carioca bean starch should be explored and evaluated as a suitable source for biodegradable material. The present study aimed to evaluate the synergism of physical and chemical modifications on Carioca bean starch with respect to improving the properties of biodegradable films. A heat-moisture treatment (HMT) followed by oxidation by sodium hypochlorite was performed and vice versa.

RESULTS

Synergism was noted in the starch properties compared to the single modification. When the oxidation was applied first, a higher amylose and carbonyl content was noted. HMT, isolated and as a second modification, caused a more pronounced effect on viscosity profile than the oxidized starch, with an increase in paste temperature and a decrease in viscosity, breakdown and final viscosity.

CONCLUSION

The results obtained in the present study reflect a decrease in water vapor permeability, although a higher tensile strength was noted when oxidation was applied, as a single and as a first modification. © 2020 Society of Chemical Industry.

The ex-situ and in-situ ultrasonic assisted oxidation of corn starch: A comparative study

The objective of this study was to evaluate the differences in ex-situ (starch treated by ultrasonication and oxidation sequentially, U-OS) and in-situ (starch treated by ultrasonication and oxidation simultaneously, UOS) ultrasonic assisted oxidation process of corn starch, which were studied in contrast to the traditional oxidized starches (OS). Fourier-transform infrared spectra confirmed the successful oxidation of all modified starches samples. In comparison to the OS, the carboxyl contents of U-OS and UOS increased by 56% and 112%, respectively. The same increase trend was also found for the carbonyl contents. The significance raise was attributed to the great increase of pores and specific surface areas in the starch granule after ultrasonic irradiation which promoted the penetration of the sodium hypochlorite into the starch granules with higher chances for chemical reactions. SEM and pore size distribution characterizations further verified this result. However, the method of in-situ ultrasonic assisted oxidation can simultaneously accelerate the increase of pores and the penetration process. Consequently, the starches with higher oxidation degree can be more efficiently prepared by the strategy of in-situ ultrasonic assisted oxidation.

Effect of CaCl2 pre-treatment on the succinylation of potato starch

Potato starch was pre-treated with CaCl₂ solutions prior to modification with octenyl succinic anhydride (OSA). Starch pre-treated with 1.0 M CaCl₂ showed higher degree of substitution (DS) and reaction efficiency (RE) on OSA modification, whereas pre-treatment with CaCl₂ solutions at 0.05 M, 0.1 M and 0.5 M had no effect on DS and RE. CaCl₂ pre-treatment decreased the swelling power, paste clarity, peak viscosity (PV), breakdown (BD) and some textural parameters of potato starch, with the effects being greater at higher concentrations of CaCl₂. Pre-treatment with 1.0 M CaCl₂ caused a small disruption to starch crystallinity and granule morphology. OSA modification significantly decreased the textural parameters, PV, BD, relative crystallinity, swelling power, gelatinization temperatures and enthalpy of potato starch, but it increased the paste clarity and emulsifying activity. OSA-1.0 M-starch showed improved functional properties over OSA-starch, indicating that CaCl₂ pre-treatment provides advantages for improving the functional characters of succinylated starch.

Preparation and Characterization of Superabsorbent Polymers Based on Starch Aldehydes and Carboxymethyl Cellulose

Superabsorbent polymers (SAPs) are crosslinked hydrophilic polymers that are capable of absorbing large amounts of water. Commercial SAPs are mostly produced with acrylic acid that cannot be easily biodegraded. Therefore, in this study, polysaccharide-based SAPs using carboxymethyl cellulose as a major component were prepared. Starch aldehydes and citric acid were selected due to their environment-friendly, non-toxic, and biodegradable properties compared to conventional crosslinking agents. Starch aldehydes were prepared by periodate oxidation, which forms aldehyde groups by taking the places of C–OH groups at C-2 and C-3. Furthermore, starch aldehydes were analyzed through the change in FT-IR spectra, the aldehyde quantitation, and the morphology in FE-SEM images. In the crosslinking of polysaccharide-based SAPs, the acetal bridges from starch aldehydes led to a large amount of water entering the network structure of the SAPs. However, the ester bridges from citric acid interfered with the water penetration. In addition, the swelling behavior of the SAPs was analyzed by the Fickian diffusion model and the Schott’s pseudo second order kinetics model. The relationship between swelling behavior and morphology of the SAPs was analyzed by FE-SEM images. In conclusion, polysaccharide-based SAPs were well prepared and the highest equilibrium swelling ratio was 87.0 g/g.

Starch hydrogels: The influence of the amylose content and gelatinization method

Gelatinization and retrogradation, influenced by amylose and amylopectin ratio, are important characteristics for starch hydrogels elaboration. The objective of this study was to evaluate the influence of amylose content and the gelatinization method on the physicochemical characteristics of native and cross-linked rice starch hydrogels. The native and cross-linked starches were gelatinized with heating or alkaline solution, added polyvinyl alcohol, frozen and then freeze-dried. The cross-linked starch had a low final viscosity (101.38 RVU), which made the heat-induced gelatinized hydrogel readily disintegrated in water. However, modified starch hydrogels obtained by alkaline-induced gelatinization resulted in a more rigid structure than the native starch hydrogels. In addition, the starch sample with high amylose content had lower water absorption (322.2%) due to the greater stiffness of the hydrogel structure that resisted swelling. The alkaline-gelatinization resulted in stiffer hydrogels with lower water absorption (322.2 to 534.8%), while the heat-gelatinized behaved as a superabsorbent (658.7 to 1068.5%). The variability of the hydrogels properties of this study can enable a range of applications due to different amylose contents and gelatinization methods.

Potato starch oxidation induced by sodium hypochlorite and its effect on functional properties and digestibility

The effects of different concentrations of sodium hypochlorite (active chlorine content at 0.1, 0.2, 1.0, 2.0, 3.0, and 4.0 g/100 g) on the properties of potato starch (PS) were investigated by determining the morphological, physicochemical, crystallinity, pasting, gel texture and digestive properties. The starch granules of PS oxidized with high oxidant concentrations caused cracks and pores, and oxidation mainly acts on the amorphous regions of the starch granules. As the sodium hypochlorite concentration increases, the carbonyl content, carboxyl content, solubility, and pasting temperature of PS increased, as measured using a Rapid Visco Analyser (RVA). The swelling power, breakdown, setback, and peak and final viscosities decreased according to the RVA (P<0.05). The gel strength increased under low-intensity oxidative treatments and decreased under high-intensity oxidative treatments. Oxidative treatment decreased the digestibility of gelatinized potato starch. The slowly digestible starch and resistant starch contents increased significantly, while the rapidly digestible starch content decreased after the oxidation modification (P<0.05). Overall, PS oxidation with sodium hypochlorite improved the functional characteristics of starch and decreased starch digestibility.

Distribution of octenylsuccinic substituents in modified A and B polymorph starch granules

The octenylsuccinic (OS) substituent distribution in octenylsuccinic anhydride (OSA)-modified normal maize and potato starches with different degrees of subsititution (DS) was studied using confocal laser scanning microscopy (CLSM) and surface gelatinization. The remaining non-gelatinized portions of starch granules after removal of surface-gelatinized starch (remaining granules) were studied with light microscopy, scanning electron microscopy, Fourier transform infrared spectroscopy (FTIR), and the level of succinylation. Results showed that greater proportions of the OS groups were present at the periphery than at the core of the granules. However, the granular interior of OS maize starch has higher fluorescent intensity than that of OS potato starch, as shown by CLSM. The DS of OS maize starch degraded less than that of OS potato starch under the same degree of gelatinization. In addition, the characteristic peaks of the remaining OS maize granules in the FTIR were more protruding than that of the OS potato granules after 50% chemical surface gelatinization. The results implied that maize starch displayed much more homogeneous OSA reaction pattern when compared to potato starch. With the special architectures (pinholes and channels) of maize, it is easier to change the location of OS groups than with potato starch by changing reaction conditions or starch pretreatments.

Effect of alkali and oxidative treatments on the physicochemical, pasting, thermal and morphological properties of corn starch

BACKGROUND

Few studies on starch modifications using different chemical agents are available in the literature, and no reports were found on the combined effect of oxidation and alkaline treatment of corn starch. Thus this work evaluated the physicochemical, pasting, morphological, cystallinity and thermal properties of chemically modified corn starch, after either the isolated or combined action of alkaline (sodium hydroxide) and oxidative (sodium hypochlorite) treatments.

RESULTS

The highest values for the sum of carbonyl and carboxyl and enzymatic hydrolysis occurred in starches submitted to oxidative treatment at high active chlorine concentrations. The alkali treatment in isolation modified the pasting properties, reduced the paste temperature and increased the peak viscosity, breakdown, final viscosity and setback of starches. Starch modified by the action of sodium hypochlorite and hydroxide in combination presented more severe damage on granule surfaces.

CONCLUSION

The results show that corn starch modified by the combined action of oxidative and alkaline treatments should be studied more, especially at the concentration limit of sodium hydroxide where gelatinization occurs. Under these conditions the effect of oxidation can be more intense and thus allow the production of starches with different properties and an increase in their industrial applications.