Structural changes to starch after acid hydrolysis, debranching, autoclaving-cooling cycles, and heat moisture treatment (HMT): A review

Heat-moisture and acid treatments can increase levels of resistant starch in arrowroot starch without adversely affecting its prebiotic activity in human colon microbiota

Carbohydrates are an important macronutrient whose processing and digestive fate can have numerous beneficial or adverse effects on consumer health. This study investigated the impact of heat-moisture treatments (HMT) and citric acid treatments (CAT) on arrowroot starch (ARS) with a focus on its physicochemical properties, digestibility, and influence on gut microbiota. The results revealed that HMT and CAT did not alter the colloidal characteristics of ARS but significantly affected the balance between amorphous and crystalline regions. Changes in thermal properties, morphology, and particle size were also observed. These can influence ARS shelf life and functional properties in various food applications. Furthermore, certain treatments in both processing methods increased the resistant starch (RS) content of ARS, with HMT for 16 hours at 80 °C and CAT with 0.6 M citric acid, resulting in the most pronounced effects. These changes coincided with reductions in rapidly digestible starch (RDS) levels and improvements in the ratio of slowly digestible starch (SDS) to RDS, which could potentially improve glycemic control. This study also examined the impact of processed ARS on colonic microbiota composition. It found that ARS-derived RS formed under HMT and CAT did not negatively affect the prebiotic potential of the RS fraction. Both treatments were associated with lowering the Firmicutes to Bacteroidetes ratio (F/B), a marker of gut health, and decreasing the relative abundance of Proteobacteria, microbes associated with adverse health effects. Additionally, CAT-derived RS showed a significant increase in the relative abundance of Roseburia, a beneficial gut bacterium. In conclusion, processing ARS through HMT and CAT techniques has the potential for enhancing its RS content, improving its glycemic impact, and positively influencing the gut microbiota composition, potentially contributing to gut health and metabolic well-being.

Recrystallization of Cellulose, Chitin and Starch in Their Individual and Native Forms

Semi-crystalline natural polymers are involved in many technological processes. Biopolymers having identical chemical compositions can differ in reactivity in heterogeneous transformations depending on their crystal structure (polymorphic modification). This paper compares the crystal structure recrystallization processes occurring in natural polysaccharides (cellulose, chitin, and starch) in the individual form and as a component of native biomass. Aqueous treatment of pre-amorphized semi-crystalline biopolymers was shown to result in swelling, thus alleviating the kinetic restrictions imposed on the restoration of crystalline regions and phase transition to the thermodynamically more stable polymorphic modification. During recrystallization, cellulose I in the individual form and within plant-based biomass undergoes a transition to the more stable cellulose II. A similar situation was demonstrated for α- and β-chitin, which recrystallize only into the α-polymorphic modification in the case of both individual polymers and native materials. Recrystallization of A-, B-, and C-type starch, both in the individual form and within plant-based flour, during aqueous treatment, results in a phase transition, predominantly to the B-type starch. The recrystallization process depends on the temperature of aqueous treatment; longer treatment duration has almost no effect on the recrystallization degree of polymers, both in the individual form and within native materials.

Effect of different heat-moisture treatment times on the structure, physicochemical properties and in vitro digestibility of japonica starch

Modified starch was prepared from japonica starch (JS) by heat-moisture treatments (HMT). Under the same moisture content and HMT temperature, the effects of various HMT times on the structural, properties of JS and its in vitro digestibility properties were investigated. The results showed that adhesion occurred between the particles of japonica starch after the HMT, and there were depressions on the surface. The size of the JS particles increased, the short-range ordering and relative crystallinity of the HMT-modified starch increased and gradually decreased, reaching a peak of 36.51 % at 6 h, as the HMT time was extended. The pasting indexes of HMT-modified starch decreased and then increased with the increase of the HMT time; compared with JS, the thermal stability of HMT-modified starch increased while the pasting enthalpy decreased. All the HMT-modified starches were weakly gelatinous systems and pseudoplastic fluids. Following HMT, the amount of resistant starch (RS) and slowly digested starch (SDS) grew initially before declining. The amount of RS in HMT-modified starch peaked at 24.28 % when the HMT time was 6 h. The results of this research can serve as a theoretical foundation for the creation of modified japonica starch and its use in the food industry.

Dual Modification of Cassava Starch Using Physical Treatments for Production of Pickering Stabilizers

Cassava starch nanoparticles (SNP) were produced using the nanoprecipitation method after modification of starch granules using ultrasound (US) or heat-moisture treatment (HMT). To produce SNP, cassava starches were gelatinized (95 °C/30 min) and precipitated after cooling, using absolute ethanol. SNPs were isolated using centrifugation and lyophilized. The nanoparticles produced from native starch and starches modified using US or HMT, named NSNP, USNP and HSNP, respectively, were characterized in terms of their main physical or functional properties. The SNP showed cluster plate formats, which were smooth for particles produced from native starch (NSNP) and rough for particles from starch modified with US (USNP) or HMT (HSNP), with smaller size ranges presented by HSNP (~63-674 nm) than by USNP (~123-1300 nm) or NSNP (~25-1450 nm). SNP had low surface charge values and a V-type crystalline structure. FTIR and thermal analyses confirmed the reduction of crystallinity. The SNP produced after physical pretreatments (US, HMT) showed an improvement in lipophilicity, with their oil absorption capacity in decreasing order being HSNP > USNP > NSNP, which was confirmed by the significant increase in contact angles from ~68.4° (NSNP) to ~76° (USNP; HSNP). A concentration of SNP higher than 4% may be required to produce stability with 20% oil content. The emulsions produced with HSNP showed stability during the storage (7 days at 20 °C), whereas the emulsions prepared with NSNP exhibited phase separation after preparation. The results suggested that dual physical modifications could be used for the production of starch nanoparticles as stabilizers for Pickering emulsions with stable characteristics.

Red rice starch modification - Combination of the non-thermal method with a pulsed electric field (PEF) and enzymatic method using α-amylase

The objective of this study was to investigate the dual modification of red rice starch using pulsed electric field (PEF) and α-amylase, focusing on morpho-structural, thermal, and viscoamylographic properties. Native starch (Control) underwent various treatments: PEF at 30 kV cm-1 (PEF30), α-amylase at 9.0 U mg-1 (AA0), and a combination of both (PEF30 + α and α + PEF30). The PEF30 + α treatment exhibited the highest degree of digestion (10.66 %) and resulted in morphological changes in the starch granules, which became elongated and curved, with an increased average diameter of 50.49 μm compared to the control. The starch was classified as type A, with a maximum reduction in crystallinity of up to 21.17 % for PEF30. The deconvolution of FT-IR bands indicated an increase in the double helix degree (DDH) for PEF30 and AA0, while the degree of order (DO) was reduced for PEF30, AA0, and PEF30 + α. DSC analysis revealed significant modifications in gelatinization temperatures, particularly for PEF30, and these changes were supported by a reduction in gelatinization enthalpy (ΔH) of up to 28.05 % for AA0. These findings indicate that both individual and combined treatments promote a decrease in starch gelatinization and facilitate the process, requiring less energy. Differences were observed between the formulations subjected to single and alternating dual treatments, highlighting the influence of the order of PEF application on the structural characteristics of starch, especially when applied before the enzymatic treatment (PEF + α). Regarding the viscoamylographic parameters, it was observed that AA0 presented higher values than the control, indicating that α-amylase enhances the firmness of the paste. The double modification with PEF + α was more effective in reducing syneresis and starch retrogradation, leading to improvements in paste properties. This study provided significant insights into the modification of red rice starch using an efficient and environmentally friendly approach.

Impact of plasma-activated water on the supramolecular structure and functionality of small and large starch granules

Hydrothermal (HMT) and water agitation (WA) treatments using plasma-activated water (PAW) were employed as sustainable methods to modify the molecular and functional performance of small (rice) and large (potato) starch granules. HMT-PAW and WA-PAW treatments resulted in etched and damaged granular surfaces that rearranged the long and short-range crystallinity of the modified starches. Both treatments seemed to predominantly occur in the amorphous region of the rice starch and the crystalline regions of the potato starch, changing the crystallinity values from 22.9 and 14.8 % to 31.8 and 10.4 %, respectively. Thus, the level of the arrangement of chains reached after PAW treatment decreased the ability of rice starch granules to swell (16 to 9 %) and leach out starch molecules from the granules (4.5 to 1.3 %), decreasing the viscosity and pasting profiles as indicated by n and k values. Opposite behavior was observed in the modified potato starches since starch components leached out to a higher extent (1.7 to 5.4 %). The results showed that HMT and WA treatments using PAW are feasible eco-friendly methods for modifying starch granules without chemical reagents. These modified starches could be suitable as functional ingredients or biopolymeric matrices for the food and packaging industry.

Customizing Starch Properties: A Review of Starch Modifications and Their Applications

Starch has been a convenient, economically important polymer with substantial applications in the food and processing industry. However, native starches present restricted applications, which hinder their industrial usage. Therefore, modification of starch is carried out to augment the positive characteristics and eliminate the limitations of the native starches. Modifications of starch can result in generating novel polymers with numerous functional and value-added properties that suit the needs of the industry. Here, we summarize the possible starch modifications in planta and outside the plant system (physical, chemical, and enzymatic) and their corresponding applications. In addition, this review will highlight the implications of each starch property adjustment.

A Review on Isolation, Characterization, Modification, and Applications of Proso Millet Starch

Proso millet starch (PMS) as an unconventional and underutilized millet starch is becoming increasingly popular worldwide due to its health-promoting properties. This review summarizes research progress in the isolation, characterization, modification, and applications of PMS. PMS can be isolated from proso millet grains by acidic, alkaline, or enzymatic extraction. PMS exhibits typical A-type polymorphic diffraction patterns and shows polygonal and spherical granular structures with a granule size of 0.3-17 µm. PMS is modified by chemical, physical, and biological methods. The native and modified PMS are analyzed for swelling power, solubility, pasting properties, thermal properties, retrogradation, freeze-thaw stability, and in vitro digestibility. The improved physicochemical, structural, and functional properties and digestibility of modified PMS are discussed in terms of their suitability for specific applications. The potential applications of native and modified PMS in food and nonfood products are presented. Future prospects for research and commercial use of PMS in the food industry are also highlighted.

Property improvement of a thermoplastic starch/poly(butylene adipate-co-terephthalate) blown film by the addition of sodium nitrite

Recently, global awareness of the adverse environmental impacts of single-use plastics has risen due to their nonbiodegradability and likelihood of ending up in the ocean. Thermoplastic starch (TPS) is an alternative material employed for manufacturing single-use products because of its high biodegradability, nontoxicity, and low cost. However, TPS is moisture sensitive and has poor mechanical properties and processability. Blending TPS with biodegradable polyesters, including poly(butylene adipate-co-terephthalate) (PBAT), can expand its practical applications. This research aims to improve the performance of TPS/PBAT blends by adding sodium nitrite, a food additive, and considering its effect on the morphological characteristics and properties of TPS/PBAT blends. TPS/PBAT/sodium nitrite (TPS/PBAT/N) blends with a TPS:PBAT weight ratio of 40:60 and sodium nitrite concentrations of 0.5, 1, 1.5, and 2 wt% were prepared by extrusion and then blown into films. The acids generated from the sodium nitrite during extrusion led to the molecular weight reduction of starch and PBAT polymers, causing the increased melt flow ability of the TPS/PBAT/N blends. The incorporation of sodium nitrite improved the blends' homogeneity and the compatibility between the TPS and PBAT phases, resulting in the increased tensile strength, extensibility, impact strength, and oxygen barrier properties of the TPS/PBAT blend film.

The effects of pH and iron ions on the mechanical properties of pea starch hydrogels

In this study, the network strength of starch hydrogels was improved by adjusting the pH value (3-11.5) and adding iron ions (Fe3+), and the mechanical properties and swelling properties of the hydrogels were improved. The complex modulus of the starch hydrogel with a pH value of 11.5 and containing Fe3+ was above 3400 Pa. SEM showed that the hydrogel structure became more compact with the increase of pH value. In addition, the hardness of the hydrogel increased from 50.29 g at pH 3.0 to 215.1 g at pH 11.5, while the addition of 0.5 mol/L Fe3+ at pH 11.5 promoted a further hardness increase to 301.8 g. Moreover, the swelling rate of the hydrogel decreased from 670.2 % at pH 7.0 to 464.4 % at pH 11.5, and the addition of 0.5 mol/L Fe3+ further decreased the swelling rate to 191.8 %. Overall, the results indicate that the mechanical properties of starch hydrogels can be improved by making simple adjustments to the pH and the iron ion concentrations.

Effect of autoclave-cooling cycles combined pullulanase on the physicochemical and structural properties of resistant starch from black Tartary buckwheat

A starch-rich portion is produced as a by-product of black Tartary buckwheat processing. The effect of enzymatic combined with autoclaving-cooling cycles (one, two, or three times) on the physicochemical and structural properties of black Tartary buckwheat type 3 resistant starch (BRS) was evaluated. The autoclaving-cooling cycles enhanced solubility and reduced swelling, with the BRS content increasing from 14.12% to 25.18%. The high crystallinity of the BRS reflected a high molecular order. However, increasing the number of autoclaving-cooling cycles did not result in higher BRS content. The highest BRS yield in the autoclaved starch samples was 25.18% after double-autoclaving-cooling cycles. Furthermore, the autoclaving-cooling cycles altered the crystalline structure of black Tartary buckwheat, and the subsequent crystallinity changed from 36.33% to 42.05% to 38.27%. Fourier-transform infrared spectroscopy shows that the number of cycles results in more efficient double-helical packing within the crystalline lamella. Principal component analysis showed that the autoclaving-cooling cycle treatment leads to significant changes in the molecular structure of resistant starch (RS). These results indicated that autoclaving-cooling cycles might be a feasible way for producing RS from black Tartary buckwheat starch with better structural stability to expand their application range.

Application of multistage induced electric field for acid hydrolysis of starch in a continuous-flow reactor

Herein, a multistage induced electric field (IEF) combined with a continuous-flow reactor was utilized to assist the acid hydrolysis of corn, potato, and waxy corn starch for avoiding plate corrosion and heavy metal leakage. It was found that adding IEF stages was beneficial to improve the hydrolysis efficiency. Treating potato, corn, and waxy corn starch via continuous-flow IEF increased the reducing sugar contents up to 78.76 %, 57.86 %, and 66.18 %, respectively. The electrical conductivity of starch grew with the reaction stages, while starch yield demonstrated the opposite trend. Treated starch had higher solubility and gelatinization peak temperature than native starch, with the gelatinization enthalpy showing fluctuations. Meanwhile, the swelling power decreased as the number of IEF stages was increased. Observations of Fourier transform infrared spectroscopy, X-ray diffraction, and scanning electron microscopy indicated that the treated starch became more ordered, and crystalline regions were destroyed to various degrees with pores forming on particle surfaces. These variations could be attributed to acid hydrolysis and IEF.

Verification of autoclaving-cooling treatment to increase the resistant starch contents in food starches based on meta-analysis result

Autoclaving-cooling is a common starch modification method to increase the resistant starch (RS) content. The effect of this method varies depending on the type of crop and treatment condition used. The objectives of this study were to verify the autoclaving-cooling treatment based on a meta-analysis result and to evaluate the physicochemical properties of modified starches. The meta-analysis study used 10 articles from a total of 1,293 that were retrieved using the PRISMA approach. Meta-analysis showed that the optimal treatments of autoclaving-cooling process that increase the RS content significantly, was in starch samples from the cereal group (corn, oats, rice) (SMD: 19.60; 95% CI: 9.56–29.64; p < 0.001), with water ratio 1:4 (SMD: 13.69; 95% CI: 5.50–21.87; p < 0.001), using two cycles of autoclaving-cooling (SMD: 16.33; 95% CI: 6.98–25.67; p < 0.001) and 30 min of autoclaving heating (SMD: 12.97; 95% CI: 1.97–23.97; p < 0.001) at 121°C (SMD: 12.18; 95% CI: 1.88–22.47; p < 0.001). Verification using corn flour and corn starch showed a significant increase in RS contents from 15.84 to 27.78% and from 15.27 to 32.53%, respectively, and a significant decrease in starch digestibility from 67.02 to 35.74% and from 76.15 to 28.09%, respectively. Treated sample also showed the pasting profile that was stable under heating and stirring.

Acid Hydrolysis and Optimization Techniques for Nanoparticles Preparation: Current Review

Nanostarch is unique in that it is highly soluble, thermally stable, non-toxic and inexpensive. Hence, it is utilized in numerous well-established applications, including drug delivery, cosmetics, textiles, foods, and enhanced oil recovery (EOR). These applications take advantage of the special functions that can be achieved through modifications to the structure and properties of native starch. The most common method for the preparation of nanostarch with a relatively higher crystallinity and stability is acid hydrolysis. Technically, the properties of nanostarch are highly dependent on several factors during the hydrolysis process, such as the acid, concentration of acid, reaction time, reaction temperature, and source of starch. The production of nanostarch with desired properties requires a detailed understanding on each of the factors as they are inevitably affected the physical and chemical properties of nanostarch. Hence, it is vital to incorporate optimization technique into the production process to achieve the full potential of nanostarch. Therefore, the current review comprehensively elaborates on the factors that affect acid hydrolysis as well as the optimization techniques used in the preparation of nanostarch.

An Insight into the Gelatinization Properties Influencing the Modified Starches Used in Food Industry: A review

Native starch is subjected to various forms of modification to improve its structural, mechanical, and thermal properties for wider applications in the food industry. Physical, chemical, and dual modifications have a substantial effect on the gelatinization properties of starch. Consequently, this review explores and compares the different methods of starch modification applicable in the food industry and their effect on the gelatinization properties such as onset temperature (To), peak gelatinization temperature (Tp), end set temperature (Tc), and gelatinization enthalpy (ΔH), studied using differential scanning calorimetry (DSC). Chemical modifications including acetylation and acid hydrolysis decrease the gelatinization temperature of starch whereas cross-linking and oxidation result in increased gelatinization temperatures. Common physical modifications such as heat moisture treatment and annealing also increase the gelatinization temperature. The gelatinization properties of modified starch can be applied for the improvement of food products such as ready-to-eat, easily heated or frozen food, or food products with longer shelf life.

The combined effect of thermal-acid hydrolysis, periodate oxidation, and iodine species removal on the properties of native tapioca (Manihot esculenta Crantz) starch

Through a four-step top-down approach, native tapioca starch (NTS) was thermally acid-hydrolyzed, periodate-oxidized with subsequent removal of iodine species (i.e., IO₄(-), IO₃(-), I(-), and I₂), and dialdehyde tapioca starch (DTS) alcohol-precipitation. The percent yield was ∼91%. Analyses confirmed the presence of aldehydic functionalities (∼71%), effectual iodine species removal (∼98%), and enhanced water-solubility (∼96.57%). Besides, the combined treatment significantly reduced the M_w (∼57.81 kDa) and ameliorated homogeneity as well as thermal stability (T_max ∼ 667.15 °C). Structural-spectral characterization also confirmed the presence of aldehydic functionality, polymorphic transition (C- to A-type), and a higher degree of crystallinity (∼91.77%), the latter further corroborated by thermal analysis. The morphological study revealed that the combined treatment reduced size (∼393.55-nm-diameter and ∼5.22-μm-length) and changed shape into rod-like crystals. DTS showed considerably and significantly low cytotoxicity to HaCaT cells in vitro at the concentrations assayed over the test period (24 h). DTS's conformation was most stable at -289 kcal/mol and -151.7 au heat formation and minimum potential energies, respectively. Overall, these results demonstrated that the combined treatment had no deleterious effects on NTS's properties, thus yielded DTS with ideal properties for multifarious uses.

Human Salivary α-Amylase and Starch Digestion: A Simple and Inexpensive At-Home Laboratory Experience in Times of the COVID-19 Pandemic

The first case of coronavirus disease 2019 in Colombia was detected on March 6, 2020. Subsequently, schools, colleges, and universities were closed on March 26, which forced a massive migration to virtual education and impacted laboratory-based teaching courses. The teaching of biochemistry requires an experimental component that virtual laboratories cannot emulate. To address this concern, the article describes an at-home biochemistry laboratory experience that explores the hydrolysis of starch by α-amylase as a function of enzyme concentration, reaction time, and pH. The general success of the experience was assessed through the quality of information submitted through laboratory reports and feedback from students. A total of 19 laboratory reports were reviewed, and 50 students were surveyed. The analysis indicated that approximately 90% of students expressed favorable opinions about the experience. They understood the objective of the practice, identified the function of each material, and explained the relationship between the obtained results and concepts of enzyme activity presented in theoretical classes. Finally, the study concluded that the at-home laboratory experience is inexpensive and easy to perform outside the traditional laboratory. Furthermore, it enables a genuine practical experience with observations, data collection, analysis, and discussion of results, which meets the expectations for pharmaceutical chemistry students at the Universidad El Bosque in Bogotá, Colombia.

Methods for characterizing the structure of starch in relation to its applications: a comprehensive review

Starch is a major part of the human diet and an important material for industrial utilization. The structure of starch granules is the subject of intensive research because it determines functionality, and hence suitability for specific applications. Starch granules are made up of a hierarchy of complex structural elements, from lamellae and amorphous regions to blocklets, growth rings and granules, which increase in scale from nanometers to microns. The complexity of these native structures changes with the processing of starch-rich ingredients into foods and other products. This review aims to provide a comprehensive review of analytical methods developed to characterize structure of starch granules, and their applications in analyzing the changes in starch structure as a result of processing, with particular consideration of the poorly understood short-range ordered structures in amorphous regions of granules.

Physical modification of starch by heat-moisture treatment and annealing and their applications: A review

Heat-moisture treatment (HMT) and annealing are hydrothermal starch modifications. HMT is performed using high temperature and low moisture content range, whereas annealing uses excess of water, a long period of time, and temperature above the glass transition and below the gelatinization temperature. This review focuses on: research advances; the effect of HMT and annealing on starch structure and most important properties; combined modifications; and HMT-starch and annealed-starch applications. Annealing and HMT can be performed together or combined with other modifications. These combinations contribute to new applications in different areas. The annealed and HMT-starches can be used for pasta, candy, bakery products, films, nanocrystals, and nanoparticles. HMT has been studied on starch digestibility and promising data have been reported, due to increased content of slowly digestible and resistant starches. The starch industry is in constant expansion, and modification processes increase its versatility, adapting it for different purposes in food industries.

Effect of Thermal Pretreatments on Phosphorylation of Corypha umbraculifera L. Stem Pith Starch: A Comparative Study Using Dry-Heat, Heat-Moisture and Autoclave Treatments

Talipot starch, a non-conventional starch source with a high yield (76%) from the stem pith of talipot palm (Corypha umbraculifera L.) was subjected to three different thermal treatments (dry-heat, heat-moisture and autoclave treatments) prior to phosphorylation. Upon dual modification of starch with thermal treatments and phosphorylation, the phosphorous content and degree of crosslinking significantly increased (p ≤ 0.05) and was confirmed by the increased peak intensity of P=O and P-O-C stretching vibrations compared to phosphorylated talipot starch in the FT-IR spectrum. The highest degree of crosslinking (0.00418) was observed in the autoclave pretreated phosphorylated talipot starch sample. Thermal pretreatment remarkably changed the granule morphology by creating fissures and grooves. The amylose content and relative crystallinity of all phosphorylated talipot starches significantly decreased (p ≤ 0.05) due to crosslinking by the formation of phosphodiester bonds, reducing the swelling power of dual-modified starches. Among all modified starches, dry-heat pretreated phosphorylated starch gel showed an improved light transmittance value of 28.4%, indicating reduced retrogradation tendency. Pasting and rheological properties represented that the thermal pretreated phosphorylated starch formed stronger gels that improved thermal and shear resistance. Autoclave treatment before phosphorylation of talipot starch showed the highest resistant starch content of 48.08%.

Highland barley starch (Qingke): Structures, properties, modifications, and applications

Highland barley (HB) is mainly composed of starch, which may account for up to 65% of the dry weight to the kernel. HB possesses unique physical and chemical properties and has good industrial application potential. It has also been identified as a minor grain crop with excellent nutritional and health functions. Highland barley starch (HBS) features a number of structural and functional properties that render it a useful material for numerous food and non-food applications. This review summarizes the current status of research on the extraction processes, chemical composition, molecular fine structures, granular morphology, physicochemical properties, digestibility, chemical and physical modifications, and potential uses of HBS. The findings provide a comprehensive reference for further research on HBS and its applications in various food and non-food industries.

Microbial starch debranching enzymes: Developments and applications

Starch debranching enzymes (SDBEs) hydrolyze the α-1,6 glycosidic bonds in polysaccharides such as starch, amylopectin, pullulan and glycogen. SDBEs are also important enzymes for the preparation of sugar syrup, resistant starch and cyclodextrin. As the synergistic catalysis of SDBEs and other starch-acting hydrolases can effectively improve the raw material utilization and production efficiency during starch processing steps such as saccharification and modification, they have attracted substantial research interest in the past decades. The substrate specificities of the two major members of SDBEs, pullulanases and isoamylases, are quite different. Pullulanases generally require at least two α-1,4 linked glucose units existing on both sugar chains linked by the α-1,6 bond, while isoamylases require at least three units of α-1,4 linked glucose. SDBEs mainly belong to glycoside hydrolase (GH) family 13 and 57. Except for GH57 type II pullulanse, GH13 pullulanases and isoamylases share plenty of similarities in sequence and structure of the core catalytic domains. However, the N-terminal domains, which might be one of the determinants contributing to the substrate binding of SDBEs, are distinct in different enzymes. In order to overcome the current defects of SDBEs in catalytic efficiency, thermostability and expression level, great efforts have been made to develop effective enzyme engineering and fermentation strategies. Herein, the diverse biochemical properties and distinct features in the sequence and structure of pullulanase and isoamylase from different sources are summarized. Up-to-date developments in the enzyme engineering, heterologous production and industrial applications of SDBEs is also reviewed. Finally, research perspective which could help understanding and broadening the applications of SDBEs are provided.

Effects of heat-moisture treatment on the thermal, functional properties and composition of cereal, legume and tuber starches-a review

Several methods are currently employed in the modification of starch obtained from different botanical sources. Starch in its native form is limited in application due to retrogradation, syneresis, inability to withstand shear stress as well as its unstable nature at varying temperatures and pH environment. Modification of starch is therefore needed to enhance its food and industrial application. A primary and safe means of modifying starch for food and industrial use is through hydrothermal methods which involves heat-moisture treatment and annealing. Heat-moisture treatment (HMT) is a physical modification technique that improves the functional and physicochemical properties of starch without changing its molecular composition. Upon modification through HMT, starches from cereals, legumes and tuber crops serve as important ingredients in diverse food, pharmaceutical and industrial processes. Although changes in starch initiated by HMT have been studied in starches of different plant origin, this work further provides insight on the composition, thermal and functional properties of heat-moisture treated starch obtained from cereals, legumes and tuber crops.

Polysaccharides: bowel health and gut microbiota

Polysaccharides that contain many sugar monomers include starch and non-starch polysaccharides (NSPs) together with resistant starch (RS). Dietary polysaccharides are well known to have a wide range of biological benefits for bowel health. Gut microbiota and their fermentative products, short chain fatty acids (SCFA), which have recently been highlighted as metabolic regulators, are thought to mediate the function of dietary complex carbohydrates and bowel health. We discuss the influence of various polysaccharides on human bowel health and the mechanisms underlying these effects. We also describe their biological effects on intestinal health and the mechanisms underlying their activity; the polysaccharides were divided into three categories: dietary, microbial, and host-derived polysaccharides. Physiological impacts of non-starch polysaccharides (NSPs) and resistant starch (RS), both of which pass through the small intestine nearly intact and can be fermented by gut microbiota in the large intestine, are similar to each other. They exert a wide range of beneficial effects including anti-inflammation, gut epithelial barrier protection, and immune modulation through both microbiota-dependent and -independent mechanisms. Bacterial polysaccharides usually found in the cell wall generally act as immune modulators, and host-derived polysaccharides not only protect host cells from pathogenic microbial neighbors but also affect overall intestinal health via interactions with gut microbes. Considering these observations, further studies on polysaccharides will be important for bowel health.

Characteristics of pasting properties and morphology changes of rice starch and flour under different heating modes

The pasting behavior of rice starch and its relationship with cooking properties of rice have been extensively studied. However, the viscosity changes of rice starch and flour under conventional cooking mode and high temperature and high pressure (HTHP) mode remain unknown. In this study, three typical rice starches and seven rice flours of different types and varieties were used to evaluate the effect of cooking modes on their pasting behaviors. A detailed discussion about the relationships among chemical composition, thermal properties, and crystallinity were conducted to explain the different pasting behaviors of the rice samples. The pasting behavior of rice starch was found to be similar with rice flour under standard and conventional heating modes, while remarkably different when treated at different HTHP levels, especially for sticky rice flour. The morphological changes of rice samples at 95 °C and 120 °C confirmed that high temperature long time heating caused extending of molecules, which exhibited layered structure at 120 °C. The rice flour samples showed different morphologies after heating at different modes due to varied amylose content and crystallinity, which contributed to different pasting behavior. These results provide useful information for developing strategies to control rice cooking and improve eating quality.

Effects of heat-moisture and acid treatments on the structural, physicochemical, and in vitro digestibility properties of lily starch

Starch extracted from lily bulb (Lilium brownii var. Viridulum Baker) was modified via heat-moisture treatment (HMT) at different moisture levels (15-35%) and acid treatment (AT) with hydrochloric acid at five different concentrations (0.25-2.0 M). The effects of HMT and AT on the physicochemical properties and in vitro digestibility of lily starch were investigated. HMT and AT led to the clustering of the starch granules, whose surface became rougher, thereby increasing the particle size. X-ray diffraction results showed that HMT increased the relative crystallinity and transformed the crystalline structure from B- to A-type. The relative crystallinity and X-ray patterns of the AT starch significantly increased. The swelling power of HMT and AT starch was significantly reduced, whereas the solubility of HMT starch decreased. The solubility of AT starch was significantly higher than that of native starch (NS) (p < 0.05). Differential scanning calorimetry revealed that the gelatinization temperature of lily starch was higher than that of NS after two modifications, whereas the gelatinization enthalpy of the NS was lower than that of the modified samples. The starch with HMT at 25% showed the highest resistant starch content of 44.15% in cooked samples.

Digestion behavior and gastrointestinal fate of oil-in-water emulsions stabilized by different modified rice starches

This study highlights how starch modification and the concentration of resistant starch may alter the lipid digestion behavior in oil-in-water emulsions.