Meng Niu

Effects of concurrent ball milling and octenyl succinylation on structure and physicochemical properties of starch

This work concerns the effects of concurrent ball milling (BM) and octenyl succinic anhydride (OSA) modification on the starch microstructure and physicochemical properties (swelling, emulsifying, and rheological). Unlike normal OSA-modified starches, the BM/OSA-modified starch displayed new features such as reduced viscosity and rigidity but increased paste stability during shearing, heating and cooling, regardless of the substitution degree. More interestingly, while the physicochemical properties could be regulated by simply altering the BM treatment time, BM/OSA was more efficient and effective at modulating starch properties during the initial period (approx. 10h), as seen by the rapid evolutions in starch structural disruption and OSA esterification. Thus, the BM/OSA modification can serve as a viable and cost-effective approach for producing octenyl succinate starches where low viscosity (at relatively high concentrations) and high paste stability are desired.

Microstructural, textural, and sensory properties of whole-wheat noodle modified by enzymes and emulsifiers.

With the utilization of enzymes including endoxylanase, glucose oxidase (GOX) and transglutaminase (TG), and emulsifiers comprising sodium stearoyl lactate (SSL) and soy lecithin, the microstructural, textural, and sensory properties of whole-wheat noodle (WWN) were modified. The development time and stability of whole-wheat dough (WWD) were enhanced by TG due to the formation of a more compact gluten network, and by SSL resulting from the enhanced gluten strength. Microstructure graphs by scanning electron microscopy (SEM) verified that TG and SSL promoted the connectivity of gluten network and the coverage of starch granules in WWN. TG increased the hardness and elasticity of cooked WWN, while two emulsifiers increased the noodle cohesiveness. Additionally, TG and SSL improved the sensory properties of noodle such as bite, springiness, and mouth-feel. The results suggest that TG and SSL are effective ingredients in enhancing the gluten strength of WWD and improving the qualities of WWN.

An improved approach for evaluating the semicrystalline lamellae of starch granules by synchrotron SAXS

A fitting method combined with a linear correlation function was developed as an improved approach for the SAXS analysis of the semicrystalline lamellae of starch granules. Using a power-law function with two Gaussian plus Lorentz functions, the SAXS pattern was resolved into sub-patterns of the net lamellar peak and the power-law scattering plus scattering background (PL+B). The ratio of the net lamellar peak area (Apeak) to the total scattering area (Atotal) was proposed equal to the proportion of the lamellae within the starch granule (PSL). Along with this fitting method, we obtained a better profile of linear correlation function, with the elimination of the interference of non-lamellar amorphous starch (i.e., amorphous growth rings). Then, we could accurately calculate the lamellar parameters, e.g., PSL, the thicknesses of semicrystalline (d), crystalline (dc) and amorphous (da) lamellae, and the volume fraction (φc) of crystalline lamellae within semicrystalline lamellae. Quantitative analysis revealed that PSL was positively correlated with the crystallinity (Xc) of starch. It was confirmed that the distribution of lamellar thickness was more important than the starch botanical origin in affecting the validity of the developed fitting method. We also proposed a criterion to test the validity of the proposed method. Specifically, the total SAXS pattern should be mostly tangent to the profile of PL+B at a high q tail (close to 0.2Å-1).

Understanding the fine structure of intermediate materials of maize starches

Here we concern the molecular fine structure of intermediate material (IM) fraction in regular maize starch (RMS) and Starpro 40 maize starch (S40). IM had a branching degree and a molar mass (Mw) somewhere between amylopectin (AP) and amylose (AM). Compared with AP, IM had more extra-long (Fr I) and long (Fr II) chains and fb3-chains (degree of polymerization (DP)>36), with a higher average chain length (CL). Also, IM contained less A-chains but more B-chains (both BS-chains with DP 3-25 and BL-chains with DP≥26), accompanied by longer B- and BL-chains, total internal chains (TICL) and average internal chains (ICL), and a similar average external chain length (ECL). Furthermore, relative to RMS-IM, the IM of S40 (with higher apparent amylose content than RMS) showed increases in relatively-long chains, e.g., Fr II, fb3-chains and BL-chains, but reductions in Mw, relatively-short chains (those with DP 6-12, etc.).

Influence of Lactobacillus/Candida fermentation on the starch structure of rice and the related noodle features

With screening of Lactobacillus fermentum M9 and Candida santamariae Y11 from a natural fermentation broth (Jinjian) for rice noodle production, this work concerns how fermentation with M9:Y11 suspensions of different volume ratios affects the texture and sensory features of rice noodles. The M9:Y11 strains regulated rice structures and thus the physicochemical features of rice noodles. In particular, 5:5 and 8:2 v/v M9:Y11 strains endowed rice noodles with better texture and sensory performance than did Jinjian. The underlying mechanism regarding evolutions in rice noodle properties was discussed from a rice structural view. Specifically, the fermentation disrupted rice ordered structures (e.g., starch crystallites) and broke starch granules, which was preferable for the swelling and molecule leaching of rice noodle matrixes with enhanced molecule interactions. Such noodle matrixes were robust to resist imposed force, thus exhibiting increased hardness, chewiness and mouthfeel. More interestingly, the 5:5 and 8:2 v/v M9:Y11 strains less prominently altered starch granule integrity, contributing to increasing hardness, chewiness and mouthfeel of rice noodles associated with robustness of swollen granule shell within rice gel matrixes. These two ratios of M9:Y11 strains also improved the color, aroma and taste for rice noodles.

An insight into the multi-scale structures and pasting behaviors of starch following citric acid treatment

Using combined analytical techniques, this work discloses how citric acid (CA) treatment affects the pasting features of starch from a view of multi-scale structural evolutions. The treatment induced disruption events in starch multi-level structures and thus modulated the pasting behaviors. A structure-property relationship was proposed to rationalize CA effects on starch pasting properties. Specifically, CA disrupted starch structures from molecular scale to micron scale, eventually reducing pasting temperature and paste viscosities. Interestingly, unlike previous findings that acid hydrolysis normally reduces the breakdown viscosity, the CA here resulted in regulated breakdown viscosity (paste stability under shearing and heating) related to concurrent effects from granule surface corrosion and molecule degradation. Moreover, the molecule degradation of starch weakened its chain rearrangement tendency, allowing increased paste stability during cooling. Also, simply altering CA concentration effectively regulated starch structural and pasting features. Hence, compared to untreated counterpart, the CA-treated starch may serve as food agents with reduced paste viscosity, regulated paste stability under heating and increased paste stability during cooling.

Multi-scale structures and pasting characteristics of starch in whole-wheat flour treated by superfine grinding

The multi-scale structures and pasting properties of starch in WWF were investigated after superfine grinding. Five particle size distributions of WWF and their corresponding starch were obtained. The grinding process reduced the particle size of WWF and starch. However, a slight increase of fragments from starch granules was observed with enhanced grinding strength because of the small decrease in starch particle size and the existence of other WWF components that undertook some of shearing force and friction during grinding. A prominent reduction in starch crystallinity was resulted due to the destruction of crystalline structure by grinding. Small-angle X-ray scattering analyses indicated the disordering in starch semi-crystalline lamellae with thinner lamellae thickness. Additionally, the 13C Nuclear Magnetic Resonance spectra demonstrated the alterations in starch chain conformation by varying peak areas of starch carbons (C1 and C4). Along with these structural changes, Starch pasting characteristics showed substantial variations, indicating decreased viscosities and higher pasting stability. The results suggest that the grinding treatments influenced the structures and pasting properties of starch even at a non-separated state, the changes in starch structures were related to the variations in starch gelatinization characteristics.