Synthesis, characterisation and in vitro digestibility of carboxymethyl potato starch rapidly prepared with microwave-assistance

Chemical Modifications of Starch: Microwave Effect

This paper presents basic methods of starch chemical modification, the effect of microwave radiation on the modification process, and the physicochemical properties of starch. It has been shown that the modifications contribute to improvement of the material performance and likewise to significant improvement of its mechanical properties. As a result, more and more extensive use of starch is possible in various industries. In addition, methods of oxidized starch and starch esters preparation are discussed. Properties of microwave radiation and its impact on starch (with particular regard to modifications described in literature) are characterized.

Recent progress in chemical modification of starch and its applications

Starch has received much attention as a promising natural material both in biomedical fields and waste water treatment due to its unique biological and adsorptive properties.

Characterization of different substituted carboxymethyl starch microgels and their interactions with lysozyme

A carboxymethyl starch (CMS) microgel system was prepared for the control of uptaking and releasing proteins (lysozyme). The physicochemical properties of microgels in various degrees of substitution (DS) were determined by thermal gravimetric analysis (TGA), swelling degree, and rheological analysis. The microgel particle size mostly ranged from 25 µm to 45 µm. The result obtained from the TGA studies indicated that carboxymethylation decreased the thermal stability of starch, but crosslinking increased the thermal stability of CMS. The CMS microgels showed typical pH sensitivity, and the swelling degree of microgel increased with the increasing of DS and pH, because of the large amounts of carboxyl group ionization. The samples (2.25%) could behave as viscoelastic solids since the storage modulus was larger than the loss modulus over the entire frequency range. The protein uptake increased with increasing pH and DS at low salt concentration. The optimal pH shifted to lower pH with increasing ionic strength. The saturated protein uptake decreased with increasing ionic strength at each pH. The protein was easily released from the microgel with high pH and high salt concentration.

Interactions of ε-polylysine with carboxymethyl sweet potato starch with an emphasis on amino/carboxyl molar ratio

The interaction between ε-polylysine (ε-PL) and anionic polysaccharides has gained considerable attention recently because of its scientific impact on the stability and appearance of liquid food systems. The purpose of this study was to characterize the interactions between ε-PL and carboxymethyl sweet potato starch (CSS) using isothermal titration calorimetry (ITC), electrical charge, and turbidity measurements. The results showed that the interaction between ε-PL and CSS was electrostatic and mainly dependent on the molar ratio of amino groups in ε-PL to carboxyl groups in CSS. Additionally, the interaction between ε-PL and CSS was also associated with pH, degree of substitution (DS) of CSS, and ionic strength of the system. For the interaction of ε-PL with high DS (>0.235) CSS, three states of the ε-PL/CSS mixture were observed as transparent, turbid, and precipitated with a successive increase in amino/carboxyl molar ratio. Distinguishingly, a transparent mixture could be obtained for CSS with low DS (0.114) at a sufficiently high amino/carboxyl molar ratio. The present study provided basic guidance in designing liquid food systems containing both ε-PL and CSS.

Effect of microwave treatment on the physicochemical properties of potato starch granules

Background

The degree of polymerization of amylose starch in potato was so large that the gel was hardness after gelatinization. Therefore, it is one of the most important ways that the microwave treatment was used to change the physicochemical properties of starch gel to make it suitable for the preparation of instant food.

Results

The effect of microwave treatment on the physicochemical properties including morphology, crystalline structure, molecular weight distribution and rheological properties of potato starch granules was evaluated by treating time of varying duration (0, 5, 10, 15, 20 s) at 2450 MHz and 750 W. Scanning electron micrographs (SEM) of potato starch granules showed flaws or fractures on the surface after 5 to 10s of microwaving and collapse after 15 to 20 s. Polarized light microscopy (PLM) indicated that microwave treating damaged the crystalline structure of potato starch, such that the birefringence of starch granules gradually decreased after 5 to 10s and even disappeared after microwaving from 15 to 20 s. The molecular weight (Mw) values of potato starch and the proportion of large M_W fraction were considerably reduced with increasing the microwave treating time from 0 to 20s. The molecular weight slowly decreased over 5 ~ 15 s microwave treating but decreased abruptly at the time of 20s microwave treating. The apparent viscosity decreased as shear rate increased and presented shear-thinning behavior. The magnitudes of the storage modulus (G’) and loss modulus (G”) obtained at each shear rate increased with duration of microwave treating from 0 to 15 s but decreased from 15 to 20 s.

Conclusions

These results demonstrated that the morphology and crystalline structure was damaged by microwave treatment. The high molecular weight of potato starch above 2 × 10⁸ Da was so sensitive to the vibrational motion of the polar molecules due to the application microwave energy and broke easily for longer dextran chains. The fracture of starch granules, molecular chains leached from the starch granules and degradation of dextran chains contributing to the development of rheological properties.

Optimization of Reaction Conditions for Preparing Carboxymethyl Cellulose Guaze

Chemical modification was employed for converting cotton gauze to carboxymethyl cellulose (CMC) gauze by treating them with sodium monochloroacetate and sodium hydroxide. Fourier Transform Infrared spectra (FTIR) were used to characterize the product. The reaction was optimized against temperature, concentration and reaction time for obtaining high degree of conversion. Under optimized conditions, the CMC gauze has a large degree of substitution (DS) of 0.43, and it has shown better moisture absorption ability than that of common cotton gauze.

Preparation and Application of Carboxymethyl Starch

Carboxymethyl starch (CMS) was used as printing thickener, it was synthesized by carboxymethylation reaction with acid-hydrolyzed maize starch and chloroacetic acid(MCA). The optimum conditions of synthesized CMS were as follows: the ratio of nNaOH/nAGU was 3, the ratio of nMCA/nAGU was 1.5:1, etherification temperature was 65°C. The highest degree of substitution(DS) was 0.45. The maximum value of printing viscosity index(PVI) was 0.513, the best water-retention property was 0.2cm and the solid containing rate was 8%. Compared the synthesized CMS with sodium alginate, the results on printing experiments showed the properties of the CMS were almost the same as sodium alginate. Form FT-IR, it was found carboxyl functional group were show at absorption peak of 1604cm-1,1425cm-1 and 1325cm-1, it indicated that the maize starch were substituted.

Synthesis and characterization of carboxymethyl potato starch and its application in reactive dye printing

Carboxymethyl potato starch (CMPS) was synthesized with a simple dry and multi-step method as a product of the reaction of native potato starch and monochloroacetic acid in the presence of sodium hydroxide. The influence of the molar ratio of sodium hydroxide to anhydroglucose unit, the volume of 95% (v/v) ethanol, the rotation rate of motor driven stirrer and the reaction time for degree of substitution (DS) were evaluated. The product was characterized by Fourier transform infrared spectroscopy (FTIR), scanning electron microscopy (SEM) and X-ray diffractometry (XRD). FTIR spectrometry showed new bonds at 1618 and 1424 cm⁻¹ when native starch underwent carboxymethylation. SEM pictures showed that the smooth surface of native starch particles was mostly ruptured. XRD revealed that starch crystallinity was reduced after carboxymethylation. The viscosity of the mixture paste of carboxymethyl starch and sodium alginate (SA) was measured using a rotational viscometer. In addition, the applied effect of mixed paste in reactive dye printing was examined by assessing the fabric stiffness, color yield and sharp edge to the printed image in comparison with SA. And the results indicated that the mixed paste could partially replace SA as thickener in reactive dye printing. The study also showed that the method was low cost and eco-friendly and the product would have an extensive application in reactive dye printing.