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In order to investigate the varied effects of repeated annealing treatment (RANN) and continuous annealing treatment (CANN) on the structural, physicochemical, and digestibility properties of the sweet potato. The 75% starch-water suspensions were prepared and incubated at 65 °C for 8 cycles and 96 hr. The results exhibited that RANN and CANN did not influence the starch granules and polarization cross obviously. The crystal type of RANN and CANN starches still maintained A-type, while the relative crystallinity increased. The solubility, swelling power, peak viscosity and breakdown of RANN and CANN starches decreased, but the gelatinization transition temperatures, trough viscosity, final viscosity, setback, and pasting temperatures of starches increased after annealing treatments. Furthermore, RANN and CANN decreased the RS and RS + SDS contents with the increase of annealing cycles and time. The RANN was more effective in modification of the crystallinity, solubility, swelling power, pasting, gelatinization transition temperatures and enthalpy, and digestibility of starch before four times compared with the CANN ones. By and large, RANN may be a potential way for modification of structural, physicochemical and digestibility properties. PRACTICAL APPLICATION: The described RANN and CANN starch provide new ideas for the study of modified starch. Furthermore, this study revealed the mechanism of annealing treatment and it was concluded that the repeated annealing treatment could provide a new potential way for the modification of starch., (© 2019 Institute of Food Technologists®.)

The study was undertaken to reveal the effects of freeze-thaw cycles at different freeze temperature (-20 °C, -40 °C and -80 °C) and the number of freeze-thaw cycles (3, 6, 12, 18, 24 times) on physicochemical and structural properties of waxy corn starch. The number of pores on the surface of starch granules increased, but there was no significant (P < 0.05) effect on molecular weight, transparency, freeze-thaw stability and the crystal structure of starch after repeated freeze-thaw cycle. But the crystallinity intensity decreased after freeze-thaw cycles treatment and a tiny decrease in onset, peak, conclusion temperature and gelatinization enthalpy were found. The RVA analysis exhibited an increase in gelatinization temperatures and a decrease in breakdown and setback value after freeze-thaw treatment, which manifested an increase in the aging and heat resistance of waxy corn starch paste. However, there was no statistical (P < 0.05) difference between different freeze temperatures at the same number of freeze-thaw cycle on physicochemical and structural properties of starch. The obtained data could be helpful in evaluation of the repeated freeze-thaw treatment of waxy corn starch-based foodstuffs and providing the theoretical basic for revealing the effect of repeated freeze-thaw processes in manufacture applications., (Copyright © 2019 Elsevier B.V. All rights reserved.)

The influence of repeated and continuous dry heat treatments on structural, physicochemical, and digestive properties of sweet potato starch was investigated. The results showed that the original A-type crystallinity of sweet potato starch remained unchanged after dry heat treatments. The light transmittance, gelatinization temperature, and pasting temperature of sweet potato starch increased; while the pasting viscosities, swelling power, and solubility decreased after dry heat treatments. Relative crystallinity, solubility, swelling power, light transmittance, and thermal parameter values (T o , T p , T c , ΔT) were found to be significantly higher for the continuous dry heat (CDH) treated starch than those of the repeated dry heat (RDH) treated starch after treatment for the same duration. However, CDH treated starch samples showed lower paste viscosity and digestibility than those of RDH treated samples after treatment for the same duration. In addition, the CDH treatment highly influenced the structure of starch granule surface compared with the RDH treatment. Generally, it can be concluded that RDH treatment highly influenced structural, physicochemical, and digestive properties of sweet potato starch compared with CDH treatment., (Copyright © 2019 Elsevier B.V. All rights reserved.)

The altered morphology, amylose content, microstructure, viscosity and thermal properties of potato starch after heating by radio frequency (RF) and microwaves (MW) were studied and contrasted with the native potato starch. The results showed that the MW treatment roughens the starch surface and lowers the amylose content of the starch, even more than the RF-treated starch does. The starch granule size of MW treated was larger than RF treated. RF treatment altered the structure and reduced the crystallinity of the starch, but the MW treatment did not affect the crystal form. The gelatinization temperature of the MW-treated starch was higher than the native potato starch, while the RF-treated starch was lower than the native starch. The results also indicated that the peak viscosity and the breakdown viscosity values of the RF-treated starch consistently surpassed that of the MW-treated starch. The results exposed the facts that RF treated starch showed the same trend on crystal and pasting properties compared with the hot water annealing starches, which suggested RF can be an efficient method for starch annealing., (Copyright © 2018 Elsevier B.V. All rights reserved.)

Native potato starch was suspended in distilled water at starch: water ratio of 1:3 (w/v). The starch-water suspensions were then subjected to repeated annealing treatments (RANN) at 55 °C for 12 h, repeated for 8 cycles or continuous annealing treatments (CANN) at 55 °C for 24, 48, 72 and 96 h. The structural, physiochemical and digestive properties of the annealed starch samples were studied and compared with those of the native starch. The scanning electron microscopy and light microscopy analysis showed that the repeated and continuous annealing treatments could keep the integrity and surface perfection of the starch granules. The growth rings of the annealed starch granules were more distinct than those of the native starch granules as revealed by confocal laser scanning microscopy. The crystallinity degree increased and the crystalline retained the B-type pattern after the annealing treatments. There were no chemical bonds and functional groups produced or disappeared during the applied annealing treatments. Infrared absorption peak intensity of starch decreased and short-range ordered structures increased after treatments. The swelling power and solubility decreased at low temperature (50 to 60 °C) and increased at relatively high temperature (70 to 90 °C). The rapid visco-analyzer and differential scanning calorimeter analysis revealed an increase in the setback, final viscosity, pasting temperature and gelatinization transition temperature, and a decrease in breakdown value of the starch after the annealing treatments. On the other hand, the repeated and continuous annealing treatments resulted in starch with low in vitro digestibility degree, indicating formation of resistant starch. Generally, the repeated annealing treatment resulted in starch with high improved properties compared with the starch resulted from the continuous annealing treatments. Therefore, the repeated annealing treatments can be suggested as an effective method for producing of modified starch for food industrial applications., (Copyright © 2018 Elsevier Ltd. All rights reserved.)

Summary: The normal and waxy corn starch gels were subjected to repeated freeze–thaw treatment at 0, 1, 2, 3, 4,5 and 6 cycles with an interval of 24 h, and the effects on structural, physicochemical and digestible properties were investigated. The normal starch gels formed a honeycomb structure while waxy starch gels exhibited a lamellar structure, and the number of holes and lamellas increased with increasing cycles. The X‐ray analysis showed that the A‐type pattern of starches was converted into the B‐type after treatment, and their relative crystallinity increased with the number of increased freeze–thaw cycles. The hardness increased in both normal and waxy starch. The solubility and pasting breakdown viscosity decreased in normal starch while they increased in waxy starch. The pasting peak time, peak viscosity, and setback viscosity increased in normal starch but decreased in waxy starch. The rapidly digested starch (RDS) and slowly digested starch (SDS) content in normal starch increased and non‐digestible starch (RS) content decreased whereas the RDS, SDS and RS content in waxy starch was almost unchanged as the freeze–thaw cycles increased. In the meantime, the molecular weight of both normal and waxy starch decreased with freeze–thaw treatment. Therefore, the repeated freeze–thaw treatment can change the physicochemical and digestible properties which could be a basis for starch‐based food processing. [ABSTRACT FROM AUTHOR]

Potato starches were pretreated with 600 W microwave and then acetylation was carried out with acetic anhydride and glacial acetic acid (1:1 in volume). The microwave-pretreated-acetylation remarkably modified the physicochemical properties of starch compared with the single acetylation method. The starch granules exhibited rough surfaces but maintained integrity and the crystal structure changed to C-type after microwave-pretreated-acetylation. Meanwhile, the microwave-pretreated starch esters exhibited the higher substitution degree, the higher infrared absorption peak intensity and the lower relative crystallinity compared to un-microwave-pretreated ones. The solubility of microwave-pretreated starches was higher at 80–90 °C than un-pretreated samples, while the swelling power of microwave-pretreated starches was lower at 60–90 °C under a same esterification level. Particularly, the solubility of microwave-pretreated samples at 90 °C was 2.11 times higher than un-pretreated ones, while the swelling power of microwave-pretreated starches exhibited 52.8% lower than un-pretreated samples at 90 °C under the 12 mL/100 g esterification level. The peak viscosity and the gelatinization enthalpy of microwave-pretreated starches were lower than un-pretreated ones under the same esterification level. Particularly, these values of microwave-pretreated starches were 2332 mPa s lower and 8.46 J/g lower than un-pretreated ones at the 12 mL/100 g esterification level, respectively. [ABSTRACT FROM AUTHOR]

To explore the mechanism of heat-moisture treatment on starches and innovate the starch modification method, the wheat starch-water suspensions were subjected to repeated and continuous heat-moisture treatment (RHMT and CHMT) and investigate the changes and connections of molecular, morphological and physicochemical properties. The results showed that treated starches had many scallops but their shape unchanged compared with native starch. Primarily, the molecular weight emerged an increasing trend of modified starch as the time prolonged, which induced the changes of physicochemical properties. The crystal form of treated starches did not change but their crystallinity decline. The viscosities and swelling force of modified starch decreased while solubility, pasting temperatures and in vitro digestibility increased than that of native starch. The RHMT exhibited a more obvious effect in molecules rearrangement and the RHMT starch had a lower molecular weight, which could be used as a great potential to modify the starch physicochemical and functional properties. • Heat-moisture treatment increased the pasting temperature and digestibility of starch. • Heat-moisture treatment reduced crystallinity, viscosity and swelling power of starch. • Repeated heat-moisture treated starch had a more stable structure than continuous ones. • Repeated heat-moisture treatment had a better effect in rearranging starch molecules. [ABSTRACT FROM AUTHOR]

Starch is isolated from kernel of acorn fruit (Quercus fabri) using different methods, including hot‐water soaking (HWS), alkaline washing (ALW), ultrasonic‐assisted ethanol soaking (UAES), and ultrasonic‐assisted hot‐water soaking (UAWS). Structural and physicochemical properties of starches isolated using these methods are investigated. The surface structure of acorn starch granules varies depending on the isolation method. However, a similar C‐type crystalline pattern is found for all the isolated starch samples. Acorn starches isolated using the ALW and UAES methods exhibit a greater degrees of crystallinity than those of starches isolated using the other methods. FT‐IR spectra analysis reveals that the chemical bonds in starch molecules are not affected during the isolation of acorn starch under different conditions. Moreover, starch isolated using the UAES method exhibits the greatest water solubility, swelling power, and light transmittance values, as well as the lowest tannin content. In addition, the lightest white color is found for starch isolated using the ALW method. Furthermore, the HWS and ALW methods result in acorn starch with greater enthalpy and gelatinization temperatures, whereas the UAES and UAWS isolation methods result in acorn starch with greater peak viscosity. The obtained results provide important knowledge about the differences in physicochemical properties of acorn starch isolated using different methods. [ABSTRACT FROM AUTHOR]