Study on structural characteristics, physicochemical properties, and in vitro digestibility of Kudzu-resistant starch prepared by different methods

Preparation of fern root resistant starch by pullulanase and glucoamylase combined with autoclaving-enzymatic method: physicochemical properties and structural characterization

BACKGROUND

Fern root starch has a high percentage of amylose and has great potential for application in the field of slow-digesting foods. Clarifying the effect of treatment conditions on fern root starch is key to achieving industrialized production of fern root resistant starch. In the present study, fern root starch was treated by the autoclave-enzymatic method with pullulanase, glucoamylase and mixed enzyme.

RESULTS

The content of resistant starch in fern roots treated with mixed enzyme was the highest (24.07 ± 1.11%), which was approximately 320% times that of the native starch, had the best water-holding capacity (151.08%), vital transparency and freeze-thaw stability. By contrast, the solubility, swelling and viscosity were lower than natural starch. In addition, mixed enzyme shows a denser structure, and the crystal form changes from C-type to V-type, with a high relative crystallinity and significantly enhanced thermal stability.

CONCLUSION

After mixed enzyme combined with autoclave treatment, the content of resistant starch in fern root was greatly increased. The modified starch molecules did not produce new functional groups, which made the crystal structure of starch molecules more compact, and resistance to enzymatic hydrolysis and high temperature thermal stability were significantly enhanced. This provides a positive reference for further in-depth study of fern root starch, improvement of utilization value, development and innovation of new food health products, and diabetes treatment. © 2024 Society of Chemical Industry.

Exploring the formation mechanism of resistant starch (RS3) prepared from high amylose maize starch by hydrothermal-alkali combined with ultrasonic treatment

In this study, type III resistant starch (RS3) was prepared from high amylose maize starch (HAMS) using hydrothermal (RS-H), hydrothermal combined ultrasonication (RS-HU), hydrothermal-alkali (RS-HA), and hydrothermal-alkali combined ultrasonication (RS-HAU). The role of the preparation methods and the mechanism of RS3 formation were analyzed by studying the multiscale structure and digestibility of the starch. The SEM, NMR, and GPC results showed that hydrothermal-alkali combined with ultrasonication could destroy the granule structure and α-1,6 glycosidic bond of HAMS and reduce the molecular weight of HAMS from 195.306 kDa to 157.115 kDa. The other methods had a weaker degree of effect on the structure of HAMS, especially hydrothermal and hydrothermal combined ultrasonication. The multiscale structural results showed that the relative crystallinity, short-range orderliness, and thermal stability of RS-HAU were significantly higher compared with native HAMS. In terms of digestion, RS-HAU had the highest RS content of 69.40 %. In summary, HAMS can generate many short-chain amylose due to structural damage, which rearrange to form digestion-resistant crystals. With correlation analysis, we revealed the relationship between the multiscale structure and the RS content, which can be used to guide the preparation of RS3.

Multi-scale structural characteristics of black Tartary buckwheat resistant starch by autoclaving combined with debranching modification

The impact of autoclaving or autoclave-debranching treatments on the multi-scale structure of resistant starch (RS) and the relationship with starch digestion remains unclear, despite their widespread use in its preparation. This work investigated the relationship between RS structure in black Tartary buckwheat and its digestibility by analyzing the effects of autoclaving and autoclave-debranching combined treatments on the multi-scale structure of RS. The results showed that black Tartary buckwheat RS exhibited a more extensive honeycomb-like network structure and enhanced thermal stability than either black Tartary buckwheat native starch (BTBNS) or common buckwheat native starch (CBNS). Autoclaving and autoclaving-debranching converted A-type native starch to V-type and possibly the formation of flavonoid-starch complexes. Autoclaving treatment significantly increased the proportion of short A chain (DP 6-12) and the amylose (AM) content, reduced the viscosity and the total crystallinity. Notably, the autoclave-debranching co-treatment significantly enhanced the resistance of starch to digestion, promoted the formation of perfect microcrystallines, and increased the AM content, short-range ordered degree, and the proportion of long B2 chain (DP 25-36). This study reveals the relationship between the multi-scale structure and digestibility of black Tartary buckwheat RS by autoclaving combined with debranching modification.