In vitro digestibility of rice starch granules modified by β-amylase, transglucosidase and pullulanase

Physiochemical characterization and ameliorative effect of rice resistant starch modified by heat-stable α-amylase and glucoamylase on the gut microbial community in T2DM mice

In the presented study, natural rice containing high resistant starch content was used as a raw material to produce rice resistant starch (RRS) through enzymatic hydrolysis with heat-stable α-amylase and glucoamylase. The chemical composition, structural characteristics and in vitro glycemic index (GI) of RRS were evaluated. The effects of RRS at different doses on the body weight, serum biochemical levels, pathological indexes, production of short-chain fatty acids (SCFAs) in the gut and the intestinal microbial composition in T2DM mice were investigated. The results of physiochemical characterization indicated that, relative to rice flour, RRS mainly comprising resistant starch had higher crystallinity (25.85%) and a more stable structure, which contributed to its lower digestibility and decreased GI in vitro. Compared with the model control group, 1 g per kg BW and 2 g per kg BW oral gavage dosages of RRS effectively enhanced the SCFA productivity in the T2DM mouse gut, as well as alleviating T2DM symptoms, involving an increase in body weight, reduction in fasting blood glucose, total cholesterol, triglyceride, low-density lipoprotein cholesterol, alanine transaminase and aspartate aminotransferase, and an increase in serum insulin and high-density lipoprotein cholesterol. Besides, 1 g per kg BW and 2 g per kg BW dosages of RRS mitigated T2DM-induced pancreas damage. Furthermore, up-regulation in the abundance of probiotics (Lactobacillus, Ruminococcus, etc.) and down-regulation in the number of harmful bacteria (Desulfovibrio, Prevotella, etc.) were observed in all RRS-treated groups. In summary, this work suggested that RRS prepared using heat-stable α-amylase and glucoamylase could be a potential functional component for amelioration of T2DM applied in the fields of food and pharmaceutics.

Two-step modification of pullulanase and transglucosidase: A novel way to improve the gel strength and reduce the digestibility of rice starch

The multiscale structure, gel strength and digestibility of rice starch modified by the two-step modification of pullulanase (PUL) pretreatment and transglucosidase (TG) treatment for 6, 12, 18 and 24 h were investigated. The debranching hydrolysis of PUL produced some linear chains, which rearranged to form stable crystalline structures, reducing the digestible starch content, but weakening the gel strength. TG treatment connected some short chains to longer linear chains via α-1,6-glycosidic bonds, generating the structures of linear chain with fewer branches. The short branches promoted the interaction between starch molecules to form a more compact three-dimensional gel network structure, showing higher hardness and springiness. Moreover, these chains could form more stable crystals, reducing the digestible starch content, and the increase of branching degree inhibited digestive enzyme hydrolysis, reducing the digestion rate. The multiscale structure of starch tended to stabilize after TG treatment for 18 h, which could form a gel with stronger strength and lower digestibility than native starch gel. Therefore, the two-step modification of PUL and TG was an effective way to change the structure of rice starch to improve the gel strength and reduce the digestibility.

Impact of starch chain length distributions on physicochemical properties and digestibility of starches

Changing starch structure at different levels is a promising approach to promote desirable metabolic responses. Chain length distribution (CLD) is among the starch structural characteristics having a potential to determine properties of starch-based products. Therefore, the objective of the current review is to summarize recent findings on CLD and its impact on physicochemical properties and digestion. Investigations undertaken to enhance understanding of starch structure have shown clearly that CLD is a significant determining factor in modulating starch digestibility. Enzymatic modifications and processing treatments alter the CLD of starch, which in turn affects the rate of digestion, but the underlying molecular mechanisms have yet to be fully elucidated. Even though advances have been made in manipulating CLD using different methods and to correlate the changes with various functional properties, in general the area needs further investigations to open new awareness for enhancing healthiness of starchy foods.

Improvement of in vitro digestibility and thermostability of debranched waxy maize starch by sequential ethanol fractionation

This study aimed to improve the in vitro digestibility and thermostability of debranched waxy maize starch (DWMS) by sequential fractionation. Waxy maize starch was debranched by pullulanase, followed by sequential precipitation through controlling the ratio of starch supernatants to ethanol at 1:0.5, 1:1, and 1:1.5 (v/v). Subsequently the structural, thermal, in vitro digestive properties of DWMS were investigated. In vitro digestion results showed that the secondary ethanol fractionation of 1:1 on the basis of the initial fractionation (1:0.5) induced a significant higher amount of slowly digestive starch (SDS, 30.0 %) and resistant starch (RS, 58.6 %) amongst all three fractions, along with the highest peak temperature (Tp, 106.4 °C) and the highest decomposition value (Td, 310.0 °C) in calorimetric (DSC) and thermogravimetry (TGA) measurements. Chain length distribution, surface morphology, and laser confocal micro-Raman spectroscopy (LCM-Raman) analyses revealed that medium (degree of polymerization, DP 13- 36) and long chains (DP ≥37) respectively constituting 72.0 % and 10.2 % of DWMS resulted in the formation of spheroidal crystallites with higher homogeneity and more ordered short-range structures. Overall, this work confirmed that ethanol fractionation is an efficient method for improving the in vitro digestibility and heat stability of waxy maize starch.

Impact of a retrograded starch ingredient obtained from Negro Jamapa beans (Phaseolus vulgaris L. Negro Jamapa) on glucose metabolism and oxidative stress in induced diabetic lab rats model

A retrograded starch ingredient obtained from Negro Jampa beans (Phaseolus vulgaris L. Negro Jamapa), applying a debranching process (18 U/g for 12 h) and retrogradation (2 °C for 3 days), was evaluated as a potential functional ingredient to improve glucose homeostasis in a diabetic animal model. The obtained ingredient was reduced in rapid digestible starch amount compared to its related isolated native starch (34.1 % and 53.6 %, respectively) and resistant (33.4 % and 22.3 %, respectively). Therefore, a reduced total digestibility was determined for the obtained ingredient compared to native starch (51.5 % and 79 %, respectively). As consequence, diabetic animals fed with functional ingredient replacement (30 %) showed a lower and attenuated postprandial glucose levels, reducing the hyperglycaemic condition, compared with the non-treated animals (r2 = 0.9775; p ≤ 0.05), reducing the glucose serum levels 73 % compared (17.21 vs 23.6 mmol/L, respectively). Also, significant improvement on weight gain (49.75 ± 34.1 g) compared to non-treated (18.14 ± 45.52 g), as well as lower insulin resistance index and improved oxidative stress status was determined for the treated group. These results highlight the potential of retrograded starch obtained from Negro Jamapa beans as a functional ingredient focus on the improvement of the glucose homeostasis and diabetic condition.

Structural and Physicochemical Properties of a Chinese Yam Starch-Tea Polyphenol Complex Prepared Using Autoclave-Assisted Pullulanase Treatment

Interactions between food components have a positive impact in the field of food science. In this study, the effects of tea polyphenol on the structural and physicochemical properties of Chinese yam starch using autoclave-assisted pullulanase treatment were investigated. X-ray diffraction, Fourier transform infrared spectroscopy, scanning electron microscopy, rapid visco analysis, differential scanning calorimetry, and the 3,5-dinitrosalicylic acid method were applied in this study. The results showed that the Chinese yam starch-tea polyphenol complex formed a structural domain with higher thermal stability along with lower pasting viscosities than native starch. The in vitro digestibility of Chinese yam starch decreased with the addition of the tea polyphenol, and the amount of resistant starch content in the complex was 56.25 ± 1.37%, significantly higher than that of native starch (p < 0.05). In addition, the complex showed a B+V-type crystalline structure, which confirmed that the interaction modes between the starch and tea polyphenol include hydrogen bonding and hydrophobic interactions. Moreover, the appearance of an irregular sponge network structure of the complex further supported the interactions between the starch and tea polyphenol. This study provides a theoretical basis for the development of functional foods using Chinese yam starch.

Structural, physicochemical and digestive properties of rice starch modified by preheating and pullulanase treatments

The structural, physicochemical and digestive properties of rice starch modified by the combination of different temperature (60, 70, 80, 90 and 100 °C) preheating and pullulanase (PUL60, PUL70, PUL80, PUL90 and PUL100) treatments were investigated. The PUL60 treatment mainly modified the surface layer of starch granules, which increased the amylose content and damaged some ordered structures, resulting in slight decreases of gel strength and estimated glycemic index (eGI). With the increase of preheating temperature, PUL could act on more enzymatic sites to release a large amount of linear chains, reduce the ordered degree, and transform the A-type crystalline structure into B-type. The low molecule interaction strength between linear chains weakened the gel network structure, and some stable crystal structures formed by longer chains resisted the enzyme digestion. The gel strength and eGI value of PUL70 starch decreased significantly, and the properties of PUL80-100 starches tended to be stable, showing a further significant decrease of gel strength and a slight reduction of eGI value. Therefore, the preheating treatments at 60, 70 and 80 °C were suitable for the PUL modification of rice starch to obtain strong, medium and weak gel strength respectively, and the digestibility decreased with increasing preheating temperature.

The relationship between molecular structure and film-forming properties of thermoplastic starches from different botanical sources

To illustrate the correlations between molecular structures and the film-forming properties of thermoplastic starch from various botanical sources, starches from cereal, tuber and legume were modified by thermoplastic extrusion and the corresponding thermoplastic starch films were prepared including thermoplastic corn starch (TCS), thermoplastic rice starch (TRS), thermoplastic sweet potato starch (TSPS), thermoplastic cassava starch (TCAS) and thermoplastic pea starch (TPES) films. TPES film displayed a higher tensile strength (6.28 MPa) and stronger water resistance, such as lower water solubility (15.70 %), water absorption (42.35 %), and water vapor permeability (0.285 g·mm·h-1·m-2·kPa-1) due to higher contents of amylose and B1 chains. TCAS showed a smoother and more amorphous film due to higher amylopectin content, resulting higher elongation at break and larger opacity. TCS film was the most transparent due to a compacter network and more ordered crystallinity structure, which was suit for the packaging of fresh vegetables and aquatic products, whereas TCAS film was the opaquest, which protected package foods from light such as meat products, etc. The outcome would provide an innovative theory to regulate accurately the functional properties of thermoplastic starch films for different food needs.

Starch fine molecular structures: The basis for designer rice with slower digestibility and desirable texture properties

Development of whole rice with low glycaemic index has been achieved, however, these rices are frequently associated with a poor texture property. Recent advances in terms of understanding the importance of starch fine molecular structures on the starch digestibility/texture of cooked whole rice have shed new insights on mechanisms of starch digestibility and texture from molecular levels. With an extensive discussion on the correlative and causal relationships among starch molecular structure, texture and starch digestibility of cooked whole rice, this review identified desirable starch fine molecular structures contributing to both slow starch digestibility and preferable textures. For instance, the selection of rice variety having more amylopectin intermediate chains while less amylopectin long chains might help develop cooked whole rice with both slower starch digestibility and softer texture. The information could help rice industry transform cooked whole rice into a healthier food product with slow starch digestibility and desirable texture.

Pasting, Rheological, and Tribological Properties of Rice Starch and Oat Flour Mixtures at Different Proportions

Rice starch (RS) and oat flour (OF) were mixed in different proportions, and the pasting properties, particle size, rheology, and tribological properties of the mixed system were analyzed. According to the RVA results, OF inhibited the starch pasting, and the pasting temperature and peak viscosity of the mixed system increased. The particle size shifted toward the small particle size after the mixing of RS and OF components, and the RS/OF 9/1 particle size is the smallest. All samples exhibited shear dilution behavior and the viscosity of the system could be significantly increased at a 10 wt% RS content. At sliding speeds of >1 mm/s, the friction of the mixture is usually between the two individual components, which also confirmed the association or interaction between the two polymers.

Structural, physicochemical and long-term retrogradation properties of wheat starch treated using transglucosidase

To reduce the wheat-flour-based food texture and flavor deterioration caused by starch retrogradation, herein wheat starch, the most ingredient in wheat flour, was modified by transglucosidase to delay long-term retrogradation of wheat starch. The study proposed promising data of transglucosidase-treated starch about structure, crystallinity and retrogradation kinetics. Structural properties showed that transglucosidase treatment shortened the average chain length from 19.49 to 16.10 and induced the dominance of amorphous state. Moreover, branching degree increased from 14.11% to 17.97% after transglucosidase treatment, resulting in higher water mobility. Amylose content increased from 25.33% to 59.00% due to the hydrolysis ability of transglucosidase. Relative crystallinity of the retrograded starches decreased from 24.33% to 14.50%. Furthermore, the Avrami parameters demonstrated that transglucosidase treatment significantly retarded the retrogradation rate of wheat starch due to the decrease of re-crystalline rate. The outcoming would supply a solid theory foundation for exploring the wheat staple foods with higher qualities.

The relationship between linear chain length distributions of amylopectin and the functional properties of the debranched starch-based films

The relationship between linear chain length distributions and the functional properties of the starch-based films after pullulanase debranching treatment of corn (CS), rice (RS) and wheat (WS) were investigated. The results indicated that the film thickness was negatively correlated with A chains content (r = -0.939) and apparent amylose content (r = -0.926), and was positively correlated with B3 chains content (r = 0.847). The tensile strength of the debranched starch-based films were positively correlated with apparent amylose content (r = 0.813), and the elongation at break were inversely proportional to B3 chains content (r = -0.817). The hydrophobicity of the starch-based films was positively and negatively correlated with the proportions of linear chains with DP 6-12 (r = 0.892) and DP 25-36 (r = -0.863), respectively. On the contrary, no significant correlation was noticed between chain length distribution of amylopectin and transparency and thermal stability.

Pullulanase modification of granular sweet potato starch: Assistant effect of dielectric barrier discharge plasma on multi-scale structure, physicochemical properties

This study explored the potential application of physical combined enzyme treatment to modify starch granules. Starch was modified by exposure to cold plasma (CP) for 1, 3, and 9 min and to pullulanase (PUL) for 12, 24, and 36 h. Individual treatments with CP and PUL somewhat modified starch structure and physicochemical properties. Nevertheless, compared with native starch and individual treatments, CP-PUL combined treatment significantly (p < 0.05) promoted the subsequent structural modification, increased the short-chain ratio and the amylose content, reduce the molecular weight and the relative crystallinity, and disturb the short-range order. CP also improved the properties of PUL-modified starch, including enhanced solubility, thermal properties and resistance to enzymatic hydrolysis but worsened swelling power and peak viscosity properties. This research provides a new perspective for the rational application of CP-PUL co-treated starch in the food industry.

Isolation, modification, and characterization of rice starch with emphasis on functional properties and industrial application: a review

Starch is one of the organic compounds after cellulose found most abundantly in nature. Starch significantly varies in their different properties like physical, chemical, thermal, morphological and functional. Therefore, starch is modified to increase the beneficial characteristics and remove the shortcomings issues of native starches. The modification methods can change the extremely flexible polymer of starch with their modified physical and chemical properties. These altered structural attributes are of great technological values which have a wide industrial potential in food and non-food. Among them, the production of novel starches is mainly one that evolves with new value-added and functional properties is on high industrial demands. This paper provides an overview of the rice starch components and their effect on the technological and physicochemical properties of obtained starch. Besides, the tuned techno-functional properties of the modified starches through chemical modification means are highlighted.HighlightsNative and modified starches varies largely in physicochemical and functional traits.Modified physical and chemical properties of starch can change the extremely flexible polymer of starch.Techno-functional properties of the modified starches through chemical modification means are highlighted.Dual modification improves the starch functionality and increases the industrial applications.Production of novel starches is on high industrial demands because it mainly evolves with new value added and functional properties.

Effects of freeze-thaw treatment and pullulanase debranching on the structural properties and digestibility of lotus seed starch-glycerin monostearin complexes

The effects of multiple cycles of freeze-thaw treatment, combined with pullulanase debranching, on the structural properties and digestibility of lotus seed starch-glycerin monostearin complexes were investigated. The formation and melting of ice crystals during freeze-thaw treatment disrupted the crystalline structure of the starch granules, creating pores which facilitated access of pullulanase to the interior of the granules. Pullulanase debranching increased the free amylose content of the starch, which promoted the formation of starch-lipid complexes, which, in turn, increased the proportion of resistant starch and the overall resistance of the starch to digestive enzyme action. These effects increased with the number of freeze-thaw cycles, because more cycles increased both the disruption of the granule structure and the extent of pullulanase debranching. These findings provide a basis for the preparation of functional foods with low glycemic indices, which have strong potential for management of type II diabetes.

Development of pullulanase mutants to enhance starch substrate utilization for efficient production of β-CD

The inhibitory effect of β-CD on pullulanase which hydrolyzes α-1,6 glycosidic bond in starch to release more available linear substrates, limited substrate utilization thus influencing the yield of β-CD. Here, an aspartic acid residue (D465) which interacted with cyclodextrin ligand by hydrogen bond, was mutated to explore its contribution to bind inhibitors and obtain mutants with lower affinity to β-CD. Enzyme activity results showed that mutants D465E and D465N retained higher activity than wild-type pullulanase in presence of 10 mM β-CD. Circular dichroism spectra and fluorescence spectra results showed that D465 was related to structure stability. Chain length distribution results confirmed the improvement of substrate utilization by the addition of D465E. The conversion rate from potato starch, cassava starch, and corn starch into β-CD, increased to 56.9%, 55.4% and 54.7%, respectively, when synchronous using β-CGTase and D465E in the production process.

Physicochemical Properties, Antioxidant and Antidiabetic Activities of Polysaccharides from Quinoa (Chenopodium quinoa Willd.) Seeds

Quinoa is known for its rich nutrients and bioactive compounds. In order to elucidate the preliminary structural characteristics and biological activity of polysaccharides from quinoa (QPs), five crude polysaccharides (QPE50, QPE60, QPE70, QPE80 and QPE90) were successively fractionated by gradient ethanol, and their physicochemical properties, antioxidant and antidiabetic activities were analyzed. The results implied that their total sugar contents were 52.82%, 63.69%, 67.15%, 44.56%, and 41.01%, and their weight-average molecular weights were 13,785 Da, 6489 Da, 4732 Da, 3318 Da, and 1960 Da, respectively. Glucose was a predominantly monosaccharide in these QPs, which together in QPE50, QPE60, QPE70, QPE80, and QPE90, respectively, made up 94.37%, 87.92%, 92.21%, 100%, and 100% of the total polysaccharide. Congo red test showed that all five QPs contained triple-helix structure. The Fourier transform-infrared spectroscopy (FT-IR) and X-ray diffractometry (XRD) results suggest that the QPs form a semi-crystalline polymer constituted typical functional groups of polysaccharide including CO, CH and OH. The thermogravimetric analysis (TGA) of QPs showed that weight loss was at about 200 °C and 320 °C. The observation from scanning electron microscope (SEM) and atomic force microscope (AFM) image indicated that the morphology of QPs exhibited spherical shape. Antioxidant and antidiabetic assay exhibited that all five QPs samples had certain antioxidant and antidiabetic activities, and QPE90 showed the best antioxidant and antidiabetic activity. Overall, QPs present a promising natural source of food antioxidants and antidiabetic agents.

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.