Effect of different drying methods on the structure and digestibility of short chain amylose crystals

Differences and Mechanism of Waxy Corn Starch and Normal Corn Starch in the Preparation of Recrystallized Resistant Starch (RS3)

This study prepared resistant starch (RS) from waxy corn starch and normal corn starch and analyzed the effects of its molecular and microstructural characteristics on RS content. The RS content of waxy corn resistant starch (RS-WCS) was highest at 57.8%, whereas that of normal corn resistant starch (RS-NCS) was 41.46%. The short-chain amylose contents of RS-WCS and RS-NCS were 47.08% and 37.24%, respectively, proportional to their RS content. Additionally, RS content positively correlated with crystallinity, short-range order degree, and degree of polymerization (DP), exceeding 25. Electron microscopic images, before and after enzymolysis, revealed that RS-WCS was hydrolyzed from the surface to the center by pancreatic α-amylase, while RS-NCS underwent simultaneous hydrolysis at the surface and center. These results indicate that the higher RS content in RS-WCS, compared to RS-NCS, is attributable to the synergistic effects of molecular structure and microstructure.

Large flour aggregates containing ordered B + V starch crystals significantly improved the digestion resistance of starch in pretreated multigrain flour

The starch digestibility of flour is influenced by both physicochemical treatment and flour particle size, but the interactive effect of these two factors is still unclear. In this study, the effect of pullulanase debranching, combined with heat-moisture treatment (P-HMT), on starch digestibility of multi-grain flours (including oat, buckwheat and wheat) differing in particle size was investigated. The results showed that the larger-size flour always resulted in a higher resistant starch (RS) content either in natural or treated multi-grain flour (NMF or PHF). P-HMT doubled the RS content in NMFs and the large-size PHF yielded the highest RS content (78.43 %). In NMFs, the cell wall integrity and flour particle size were positively related to starch anti-digestibility. P-HMT caused the destruction of cell walls and starch granules, as well as the formation of rigid flour aggregates with B + V starch crystallite. The largest flour aggregates with the most ordered B + V starch were found in large-size PHF, which contributed to its highest RS yield, while the medium- and small-size PHFs with smaller aggregates were sensitive to P-HMT, resulting in the lower ordered starch but stronger interactions between starch and free lipid or monomeric proteins, eventually leading to their lower RS but higher SDS yield.

Study of the self-assembly, drug encapsulating and delivering characteristics of short chain amylose-based type 3 resistant starch nanoparticles from Canna edulis

In developing type 3 resistant starch (RS3) from Canna edulis for use as functional food ingredients, we investigated the synthesis of C. edulis RS3 nanoparticles. Simultaneously, we explored the potential of C. edulis short-chain amylose (SCA)-based RS3 nanoparticles (RS3N) as a targeted delivery system, with a specific focus on colon targeting, yielding promising insights. Our study revealed that the degree of polymerization (DP) of C. edulis SCA, particularly the chains of DP 36- 100, exhibited a robust correlation with the particle size and physicochemical characteristics of C. edulis SCA-based RS3N. Additionally, recrystallization temperature variation (4, 25, and 45 °C) significantly influenced the self-assembly behavior of C. edulis SCA, with the preparation at 4 °C resulting in more uniform particle size distributions. In further expanding the scope of applications for C. edulis SCA-based RS3N, we harnessed the potential of Fe3O4 and curcumin (CUR) as guest molecules to assess drug encapsulation and colon-targeting capabilities. Incorporating Fe3O4 into the self-assembly system led to the production of magnetic RS3N, confirming the successful encapsulation of Fe3O4 within C. edulis SCA-based RS3N. Furthermore, in vitro experiments have demonstrated that CUR-RS3N was stable in the gastrointestinal tract and gradually released curcumin with fermentation in the colonic environment. Collectively, these findings provide invaluable insights into the intricate self-assembly behavior of C. edulis SCA with varying fine structures and recrystallization temperatures during RS3N formation. Moreover, they underscore the colon-targeted properties of C. edulis SCA-based RS3N, opening promising avenues for its application within the food industry, particularly in advanced controlled drug delivery systems.

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

Three different methods, including autoclaving, autoclaving-debranching, and purification, were used to prepare Kudzu-resistant starch (KRS) from Kudzu starch (KS). The physicochemical properties, such as thermodynamic properties, pasting properties, solubility, swelling, and coagulability, as well as the in vitro digestive characteristics of the three kinds of KRS were studied. The results showed that the morphology of starch granules of KRS prepared by autoclave, autoclave enzymatic hydrolysis, and purification methods was changed and the relative crystallinity was significantly decreased compared with the original starch. X-ray diffraction (XRD) showed that KRS exists in the form of C and C+V crystalline form. There was a significant increase in the pasting temperature and a remarkable decrease in the peak viscosity and the expansion degree of the KRS prepared by all three methods. The solubility of the resistant starch (RS) obtained by autoclaving-debranching and that by purification were both increased compared to that of native KS, while the solubility of the RS obtained by autoclaving was decreased. Meanwhile, the retrogradation of the three RS was also improved to varying degrees. The contents of RS in the samples were: P-KRS (71%) > DA-KRS (43%) > A-KRS (42%) > KS (9%). Simulated human in vitro digestion experiments showed that RS has stronger antidigestibility properties than native starch. Among them, the RS prepared by the purification method has stronger antidigestive properties, and it is predicted that it may have a better potential value in regulating blood glucose. These results indicated that the processing properties of KRS, especially the digestibility, are significantly improved and can be used as a new functional food ingredient, which deserves thorough study.

Ultrasonication effects on physicochemical properties of starch-lipid complex

The starch-lipid complex between the pea starch (PSt) and glycerol monolaurate (GM) was prepared using ultrasound with different amplitudes, durations and application sequences. Fourier-transform infrared and nuclear magnetic resonance spectra showed the formation of amylose-lipid complex between PSt and GM in the ultrasonic field. Stronger diffraction intensities were observed in samples treated by ultrasonication, whereas the thermogravimetric analysis indicated that the thermal stability of starch was improved by the formation of the V-type inclusion complexes. An ultrasound pre-treatment prior to the addition of a guest molecule (UC) was more favorable to induce the formation of an amylose-lipid complexes than ultrasound treatment after PSt was incorporated with GM (CU). The UC-treated samples showed stronger diffraction intensities, higher melting enthalpy values and enzyme-resistant than that of CU-treated PSt-GM complexes.

Physicochemical, Pasting Properties and In Vitro Starch Digestion of Chinese Yam Flours as Affected by Microwave Freeze-Drying

Microwave freeze-drying (MFD) is a new freeze-drying technique, which differs from single microwave treatment; it involves simultaneous effects of microwave power, time, and the moisture state applied to the materials. In this study, the effects of MFD under various microwave power densities (0.5, 1.0, and 1.5 W/g) on the drying characteristics of Chinese yam slices and the physicochemical, pasting, and thermal properties as well as the starch digestibility of the flour were investigated using conventional hot air drying (HAD) at 50 °C as a control. Compared to HAD, MFD shortened the drying time up to 14.29~35.71%, with a higher drying efficiency at a high microwave power density (1.5 W/g). MFD yam flours provided benefits over HAD products in terms of color, water/oil absorption capacity, and solubility, exhibiting high hot-paste viscosity but low resistant starch content. The content of total starch and free glucose of the yam flour and its iodine blue value were significantly influenced by the drying method and the MFD process parameters (p < 0.05). MFD processing could disrupt the short-range ordered structure of yam starch. Among the MFD flours, samples dried by MFD at 1.5 W/g presented the highest ratio of peak intensity at 1047 and 1022 cm−1 (R1047/1022) value, gelatinization enthalpy, and resistant starch content. These results gave a theoretical foundation for the novel freeze-drying method that MFD applied to foods with a high starch content, enabling the production of a product with the desired quality.

Polymeric Microparticles: Synthesis, Characterization and In Vitro Evaluation for Pulmonary Delivery of Rifampicin

Rifampicin, a potent broad-spectrum antibiotic, remains the backbone of anti-tubercular therapy. However, it can cause severe hepatotoxicity when given orally. To overcome the limitations of the current oral therapy, this study designed inhalable spray-dried, rifampicin-loaded microparticles using aloe vera powder as an immune modulator, with varying concentrations of alginate and L-leucine. The microparticles were assessed for their physicochemical properties, in vitro drug release and aerodynamic behavior. The spray-dried powders were 2 to 4 µm in size with a percentage yield of 45 to 65%. The particles were nearly spherical with the tendency of agglomeration as depicted from Carr’s index (37 to 65) and Hausner’s ratios (>1.50). The drug content ranged from 0.24 to 0.39 mg/mg, with an association efficiency of 39.28 to 96.15%. The dissolution data depicts that the in vitro release of rifampicin from microparticles was significantly retarded with a higher L-leucine concentration in comparison to those formulations containing a higher sodium alginate concentration due to its hydrophobic nature. The aerodynamic data depicts that 60 to 70% of the aerosol mass was emitted from an inhaler with MMAD values of 1.44 to 1.60 µm and FPF of 43.22 to 55.70%. The higher FPF values with retarded in vitro release could allow sufficient time for the phagocytosis of synthesized microparticles by alveolar macrophages, thereby leading to the eradication of M. tuberculosis from these cells.

Study of the microstructure of chitosan aerogel beads prepared by supercritical CO2 drying and the effect of long-term storage

In order to investigate the pore properties and effect of storage time on the microstructure of CO₂-dried aerogels, chitosan aerogel beads were obtained from chitosan hydrogels with an initial concentration in the range of 1.5–3.0 wt% through SCCO₂ drying and freeze-drying (as a comparison). The SCCO₂-dried chitosan aerogels showed a three-dimensional network structure, and had higher BET surface area (200 m² g⁻¹) and higher crystallinity (0.62/XRD, 0.80/ATR-FTIR) than the freeze-dried aerogels. The stability of the microstructure of the SCCO₂-dried chitosan aerogel beads during 10 months was studied. The BET surface area of the aerogel beads at each concentration declined by 30.5% at 2 months, 56.7% at 6 months and 67.2% at 10 months. Accelerated aging tests of the chitosan aerogel beads were carried out to study the effect of humidity on the chitosan aerogel beads. The average diameter of the chitosan aerogel decreased from 2.3 mm to 0.9 mm when stored at 65 °C with 90% relative humidity (RH). In contrast, there was no obvious change during storage at 65 °C with 20% RH. The amount of adsorbed water increased from 4% to 12% at 65 °C with 90% RH for 96 h, and the bound water content of the aerogel beads gradually increased. This study demonstrates that SCCO₂-dried chitosan aerogel beads could be better at maintaining their mesoporous structure, and the adsorption of water from the surrounding air had a significant effect on the microstructure and shrinkage of the chitosan aerogel beads.

Chitosan aerogel beads prepared by different drying methods were compared, and the effects of long-term storage and humidity on the structure were investigated.

Influence of waxy proteins on wheat resistant starch formation, molecular structure and physicochemical properties

This study investigated the influence of wheat waxy proteins on type III resistant starch (RS3) formation, molecular structure and physicochemical properties. Waxy deletions led to a significant increase in B- and C-type starch granules, particle size of RS3, and slowly digesting starch content, and a decrease in content of amylose and RS3. X-ray powder diffraction and Fourier-transform infrared spectroscopy analyses revealed high relative crystallinity and long-range (1047/1022 cm-1, IR1) and low short-range (1022/995, IR2) crystalline structures of RS3 in waxy wheat, which suggests that waxy deletions could produce a more ordered crystalline structure and fewer amorphous regions in RS3 crystals. Further laser confocal microscopy Raman spectroscopy analysis found that waxy deletions significantly increased the full width at half maximum and intensity of the bands at 480 cm-1, as well as leading to more ordered RS3 crystals. These changes in molecular structure resulted in improved physicochemical properties of RS3.

Structural factors governing starch digestion and glycemic responses and how they can be modified by enzymatic approaches: A review and a guide

Starch is the most abundant glycemic carbohydrate in the human diet. Consumption of starch-rich food products that elicit high glycemic responses has been linked to the occurrence of noncommunicable diseases such as cardiovascular disease and diabetes mellitus type II. Understanding the structural features that govern starch digestibility is a prerequisite for developing strategies to mitigate any negative health implications it may have. Here, we review the aspects of the fine molecular structure that in native, gelatinized, and gelled/retrograded starch directly impact its digestibility and thus human health. We next provide an informed guidance for lowering its digestibility by using specific enzymes tailoring its molecular and three-dimensional supramolecular structure. We finally discuss in vivo studies of the glycemic responses to enzymatically modified starches and relevant food applications. Overall, structure-digestibility relationships provide opportunities for targeted modification of starch during food production and improving the nutritional profile of starchy foods.

Rheological Analysis of the Structuralisation Kinetics of Starch Gels

Using the method of dynamic–mechanical analysis, the structuralisation kinetics of condensed starch solutions, cooled down to the temperature of 20 °C, was investigated. A close correlation of spatial crosslinking with local processes of macromolecule associations was discovered. It was found that depending on the concentration intervals of starch solutions, equilibrium nodes of the spatial network assume the form of either single or double hexagonal structures made up of bispiral chain associates. The increase of gel crosslinking, together with the passage of time, is the result of increasing the node functionality of the spatial network.

Digestibility of resistant starch type 3 is affected by crystal type, molecular weight and molecular weight distribution

Resistant starch type 3 (RS-3) holds great potential as a prebiotic by supporting gut microbiota following intestinal digestion. However the factors influencing the digestibility of RS-3 are largely unknown. This research aims to reveal how crystal type and molecular weight (distribution) of RS-3 influence its resistance. Narrow and polydisperse α-glucans of degree of polymerization (DP) 14-76, either obtained by enzymatic synthesis or debranching amylopectins from different sources, were crystallized in 12 different A- or B-type crystals and in vitro digested. Crystal type had the largest influence on resistance to digestion (A >>> B), followed by molecular weight (Mw) (high DP >> low DP) and Mw distribution (narrow disperse > polydisperse). B-type crystals escaping digestion changed in Mw and Mw distribution compared to that in the original B-type crystals, whereas A-type crystals were unchanged. This indicates that pancreatic α-amylase binds and acts differently to A- or B-type RS-3 crystals.

Physicochemical properties of pea starch-lauric acid complex modified by maltogenic amylase and pullulanase

An enzymatic method was investigated to initiate a strategy of increasing the branch density of pea starch, thus facilitating the formation of a starch-lipid complex after debranching. When the starch was modified by exposure to maltogenic amylase (MAL) and pullulanase (PUL), lower molecular weight values and higher amylose content resulted compared to the untreated sample. High-performance anion-exchange chromatography results suggested that the average chain length decreased and the branch density increased after the starch received MAL treatment. The diffraction intensities and the total melting enthalpies of the dual-enzyme treated complex were greater than those for other samples when the level of MAL between 4-12 U/g. Fourier transform infrared spectroscopy revealed that more ordered structure was formed in MAL (4/8/12)-PUL-starch-lauric acid (Lau) complexes. Digestive performance analysis indicated that the enzyme resistance of the starch-Lau complex was reinforced by applying the MAL-PUL modification to the starch.

Effects of oligosaccharides on particle structure, pasting and thermal properties of wheat starch granules under different freezing temperatures

The effects of fructooligosaccharides (FOS), galactooligosaccharides (GOS), and xylooligosaccharides (XOS) on gelatinization, retrogradation, thermal properties and particle size of wheat starch at different freezing temperatures were studied. The results showed that the wheat starch porosity, particle size, peak viscosity increased with increasing freezing temperature. With the addition of 16% oligosaccharides to starch, the porosity, particle size, crystallinity, initial gelatinization temperature, peak value, breakdown and retrogradation viscosity of the starch granules significantly decreased in the order of XOS > GOS > FOS. However, the pasting temperature of the granules increased. The addition of oligosaccharides (especially XOS, which has the most significant effect in inhibiting starch retrogradation) can inhibit the formation of starch crystal structures to a certain extent, reduce the damage from ice crystals to starch granules and delay starch retrogradation. Therefore, functional oligosaccharides can be used as a potentially effective additive to increase freezing stability in frozen starch-based foods.

Starch nanoparticles prepared by enzymatic hydrolysis and self-assembly of short-chain glucans

Enzymatic hydrolysis and self-assembly are considered promising methods for preparation of starch nanoparticles (SNPs) because they are environmentally friendly, and time- and cost-effective. These methods are based on the self-assembly of short-chain glucans released from the α-1,6 bonds in amylopectin. Since their discovery, many studies have described the structural and physicochemical properties of self-assembled SNPs. Self-assembled SNPs can be prepared by two methods: using only the soluble portion containing the short-chain glucans, or using the whole hydrolyzate including both insoluble and soluble fractions. Although the structural and physical properties of self-assembled SNPs can be attributed to the composition of the hydrolyzates that participate in self-assembly, this aspect has not yet been discussed. This review focuses on SNPs self-assembled with only soluble short-chain glucans and addresses their characteristics, including formation mechanisms as well as structural and physicochemical properties, compared with SNPs prepared with total hydrolyzates.

Effect of spray-drying and extrusion on physicochemical characteristics of sweet potato starch

This study aimed to understand the physicochemical characteristics of sweet potato starch following spray-drying and extrusion processes for desirable applications. Spray-dried starch showed formation of agglomerates and decreased in average granular size from 16.5 μm of the native starch granules to 14.1 μm. Spray-drying reduced the percentage crystallinity from 25.3 to 22.6% and showed a slight decrease in the molecular weight of amylopectin from 3.1 to 2.6 × 10⁸ g mol^-1. In addition, changes in the pasting and gelatinization properties, higher final viscosity (454.4 RVU), and less enthalpy change (8.73 J g^-1) were reported after spray-drying. Thus, spray-drying resulted in partially gelatinized starch, which can be selected for making more viscous products. Extruded sweet potato starch displayed an amorphous structure, showed total loss of crystallinity, and significant reduction in molecular weight of amylopectin to 0.41 × 10⁸ g mol^-1, reflecting complete gelatinization of starch granules during extrusion. Extruded starch showed significant changes in pasting properties, including a display cold viscosity (9.4 RVU). Therefore, extruded starch was suitable for products that require quick solubility and a low final viscosity. Thus, the spray-drying and extrusion processes produce sweet potato starches with particular characteristics that can be used for different and potential applications in industries.

Comparison of structural features and in vitro digestibility of purple yam (Dioscorea alata L.) resistant starches by autoclaving and multi-enzyme hydrolysis

Resistant starches (RS) were prepared from purple yam by dual autoclaving-retrogradation (DAS), and pullulanase debranching treatment (PDS). DAS and PDS were then hydrolyzed by α-amylase and amyloglucosidase to obtain DAS.H and PDS.H. Differences in structural characteristics and in vitro digestibility among the four samples were investigated. The results showed that granules of RS had a rough surface and irregular shape. DAS had the lowest amylose content (29.52%), whereas PDS.H had the highest amylose content (41.96%). The order of crystallinity of the RS was: PDS.H (31.23%) > DAS.H (30.16%) > PDS (21.23%) > DAS (15.30%). Analysis by in vitro digestibility indicated a decreased hydrolysis index and glycemic index due to lower swelling power and water-binding capacity, and a well-ordered double helix structure and more crystallization in PDS.H than in the other RS samples. These results suggest that pullulanase debranching combined with α-amylase and amyloglucosidase hydrolysis may produce better RS with improved crystalline structure and higher digestion resistibility.

Moisture content during extrusion of oats impacts the initial fermentation metabolites and probiotic bacteria during extended fermentation by human fecal microbiota

Extrusion exposes flour components to high pressure and shear during processing, which may affect the dietary fiber fermentability by human fecal microbiota. The objective of this study was to determine the effect of flour moisture content during extrusion on in vitro fermentation properties of whole grain oats. Extrudates were processed at three moisture levels (15%, 18%, and 21%) at fixed screw speed (300rpm) and temperature (130°C). The extrudates were then subjected to in vitro digestion and fermentation. Extrusion moisture significantly affected water-extractable β-glucan (WE-BG) in the extrudates, with samples processed at 15% moisture (lowest) and 21% moisture (highest) having the highest concentration of WE-BG. After the first 8h of fermentation, more WE-BG remained in fermentation media in samples processed at 15% moisture compared with the other conditions. Also, extrusion moisture significantly affected the production of acetate, butyrate, and total SCFA by the microbiota during the first 8h of fermentation. Microbiota grown on extrudates processed at 18% moisture had the highest production of acetate and total SCFA, whereas bacteria grown on extrudates processed at 15% and 18% moisture had the highest butyrate production. After 24h of fermentation, samples processed at 15% moisture supported lower Bifidobacterium counts than those produced at other conditions, but had among the highest Lactobacillus counts. Thus, moisture content during extrusion significantly affects production of fermentation metabolites by the gut microbiota during the initial stages of fermentation, while also affecting probiotic bacteria counts during extended fermentation.