The multi-scale structures and in vitro digestibility of starches with different crystalline types induced by dielectric barrier discharge plasma

The effects of plasma treatment on multi-scale structures and in vitro digestibility of starches isolated from Tartary buckwheat (TBS), potato (PTS), and pea (PS), were investigated. The results from SEM and CLSM showed that plasma treatment resulted in the extension of pores from the starch hilum to the surface. The XRD and 13C CP/MAS NMR spectra demonstrated that the crystalline type of three starches was not changed by plasma treatment, while the RC and double helix content of TBS increased. Besides, the single helix content and the proportion of amorphous phase decreased following the treatment, which was consistent with the result of SAXS. However, the PTS and PS showed the opposite results by plasma treatment. In addition, the modification significantly changed the molecular weight (Mw) and chain length distribution of all the starches, among which the Mw of PTS fell drastically from 2.45 × 107 g/mol to 1.74 × 107 g/mol. The in vitro digestibility of starches increased significantly when treated with plasma, in which TBS exhibited the biggest increase for its inside-out and side-by-side digestion manners. Therefore, plasma treatment led to different alteration trends for multi-scale structures with quite various change extent for in vitro digestibility about different crystalline starches.

Multi-scale structural disruption induced by radio frequency air cold plasma accelerates enzymatic hydrolysis/ hydroxypropylation of tapioca starch

This study investigated the effects of radio frequency air cold plasma (RFACP) pretreatment on the multi-scale structures, physicochemical properties, enzymatic hydrolysis, and hydroxypropylation of tapioca starch. The results showed that cold plasma (CP) made starch granules rough on the surface and disrupted long- and short-range ordered structures, reducing relative crystallinity from 43.8 % to 37.4 % and R1047/1022 value from 0.992 to 0.934. Meanwhile, the starch molecules were depolymerized and oxidized by CP, reducing weight-average molecular weight from 9.64 × 107 to 2.17 × 107 g/mol, while increasing carbonyl and carboxyl groups by up to 118 % and 53 %. Additionally, CP-treated starches exhibited higher solubility and swelling power, along with lower gelatinization enthalpy. Short-time CP pretreatment (10 min) promoted the hydroxypropylation of starch and increased the molar substitution (0.081-0.112). Also, CP pretreatment accelerated enzymatic hydrolysis of starch, as indicated by the increase in hydrolysis rate (1.846 × 10-3-2.033 × 10-3 min-1) and degree of hydrolysis (51.45 % - 59.92 %). Overall, the multi-scale structural disruption induced by CP treatment facilitated the accessibility of enzymes/chemical reagents into starch granules and glucan chains. This study suggested that RFACP could be used for starch pretreatment to increase production efficiency in modified starch production, as well as in brewing and fermentation industries.

Prevents kudzu starch from agglomeration during rapid pasting with hot water by a non-destructive superheated steam treatment

Superheated steam (SST) at different moisture contents (10% ∼ 30%) was used to prevent the agglomeration of kudzu starch during rapid pasting with hot water. Changes in pasting-related properties and multi-scale structures were investigated. At moisture content of 20%, SST dramatically reduced the agglomeration rate from 42.20% to 2.97% without destroying the microstructure of kudzu starch or deteriorating the rheological properties of kudzu starch paste, which was superior to the conventional pre-gelatinization treatment. The agglomeration was prevented mainly by decreasing the swelling power and increasing the pasting temperature of kudzu starch. The slight disruption of multi-scale structures may facilitate faster water absorption by kudzu starch, but it was not the primary prevention mechanism. Moreover, the solubility of kudzu starch was not related to the agglomeration, since it was significantly decreased by SST. Our findings could provide new insights into the rapid pasting of starchy powders or flours with hot water.

Multi-scale structures and physicochemical properties of waxy starches from different botanical origins

The multi-scale structures and physicochemical relationships of three different types of waxy starches (maize, tapioca, and potato) were investigated. The maize and tapioca starches exhibited A-type crystalline polymorph compared to potato starch (B-type). The WMS showed higher amorphous content (5.56 %) than other waxy starches. The WTS exhibited a low tendency of retrogradation with its high f_a (DP 6-12) and low f_b3 (DP ≥ 37) proportion of chains. Double helix content of WPS was observed highest with a high pasting viscosity (952.3 BU). Low f_a (DP 6-12) and high f_b3 (DP ≥ 37) chain proportions of the WPS retrograded easily. The compactness of the semi-crystalline aggregation structure influenced the retrogradation properties of waxy starches with a positive correlation. Furthermore, the peak viscosity of pastes was correlated with the proportion of f_b3 (DP ≥ 37) chains, mass fractal dimension, and double helix content. The results provide guidance to design the application of waxy starches in the production of clean-labels.