How Does Starch Structure Impact Amylolysis? Review of Current Strategies for Starch Digestibility Study

Influence of mulberry, pectin, rutin, and their combinations on α-amylase activity and glucose absorption during starch digestion

Most studies have primarily focused on the effects of individual sources of pectin or polyphenols on starch digestibility. However, the interactions between pectin and polyphenols in digestive fluids may influence their inhibitory capacity against starch digestion by modulating α-amylase activity (αAA), a relationship that remains poorly understood. This study aims to clarify how pectin affects starch digestion when combined with mulberry fruit powder (MFP), mulberry polyphenol extract (MPE), and rutin (the main phenolic compound in MPE). Results showed that the combination of pectin and MFP initially inhibited αAA but later enhanced it. The combination of pectin and MPE consistently showed stronger inhibition of αAA than MPE alone throughout digestion; similar results were observed for the pectin-rutin combination, though the pectin-MPE pairing exhibited greater inhibition than the latter. Pectin's enhanced inhibitory effect on starch digestion may arise from its interactions with α-amylase, starch, and polyphenols through hydrophobic interactions, hydrogen bonding, and non-covalent forces.

Loss-of-function of SSIIa and SSIIIa confers high resistant starch content in rice endosperm

Rice (Oryza sativa L.) endosperm accumulates huge amounts of starch. Rice starch is highly digestible, potentially enhancing the occurrence of blood sugar- and intestine-related diseases such as type 2 diabetes. Resistant starch (RS) is hardly digestible in small intestine but can be converted into beneficial short-chain fatty acids in large intestine, potentially reducing the incidence of these diseases. However, it is still difficult to produce a high RS rice variety. Here, we report that simultaneous deficiency of soluble starch synthases IIa and IIIa confers high RS content in rice endosperm. The ssIIa ssIIIa exhibited higher RS content than did the ssIIIa ssIIIb, a mutant reported currently to have remarkably higher RS content than parental ssIIIa, under our experimental conditions. Loss-of-function of SSIIa and SSIIIa significantly elevated the activity of granule-bound starch synthase I and thus content of amylose. Furthermore, total lipid content increased in mutant seeds, implying that intermediate metabolites spilled out from starch biosynthesis into lipid biosynthesis. The increased amylose content and improved lipid synthesis coordinately contributed to high RS content in mutant seeds. These results further reveal the molecular mechanism of RS occurrence in rice endosperm and provide a critical genetic resource for breeding higher RS rice cultivars.

Understanding the Impact of Extrusion Treatment on Cereals: Insights from Alterations in Starch Physicochemical Properties and In Vitro Digestion Kinetics

In this study, three samples were randomly selected from corn, wheat, and broken rice before and after extrusion for electron microscope scanning, Fourier transform infrared spectral analysis, and in vitro digestion to investigate the impact of extrusion on physicochemical characteristics and starch digestion kinetics of cereals. The cereals used for extrusion were sourced identically before and after the process, with each analysis conducted in triplicate. The results showed that the extrusion compromised the physical structure of cereal, resulting in loose structure arrangement, and the ratio of Fourier transform infrared spectral absorbance at wavelength 1047 cm-1 and 1022 cm-1, which characterized the short-range order of starch, was significantly reduced (p < 0.05). In addition, the proportion of rapidly digestible starch (RDS), the velocity parameter k of digestive kinetics and the predicted glycemic index of cereals were significantly increased by extrusion (p < 0.05). Digestibility kinetics showed a total increase of 10.7%, 7.3%, and 5.4% for cereals, along with a sharp rise in digestion rate within the first 15 minutes. The findings revealed that the compromising of starch's structural integrity and the increase in proportion of RDS not only enhanced overall starch digestibility, but also significantly accelerated its digestion, particularly during the initial 15 min of intestinal digestion.

Evaluation of extruded starch foam for glucose-supplying biomaterials

The survival rate of mesenchymal stem cells (MSC), a crucial factor in tissue engineering, is highly dependent on glucose supply. The purpose of this paper is to study the potential of starch foams as glucose suppliers. It is investigated through in vitro hydrolysis by amyloglucosidase in conditions that respect physiological constraints (37 °C and pH 7.4), including a duration of 21 days, and no stirring. Nine extruded starch foams with amylose contents ranging from 0 to 74 %, with various cell wall thicknesses (50 to 300 μm), and different crystallinities (0-30 %) were hydrolysed. These kinetics were fitted by a model which shows that the maximum rate of hydrolysis varies from 7 to 100 %, and which allows the rate of hydrolysis at 21 days to be calculated precisely. The results reveal the major role of amylose in glucose delivery kinetics, and the secondary roles of crystallinity and cell wall thickness of the foams. Additional hydrolysis of starch films revealed that thickness positively influences the amylose chain reorganisation during hydrolysis, which, in slows down and limits glucose delivery. A simple glucose delivery kinetics analysis procedure is proposed to select samples for testing as MSC glucose suppliers.

The multifactorial phenomenon of enzymatic hydrolysis resistance in unripe banana flour and its starch: A concise review

Unripe banana flour starch possesses a high degree of resistance to enzymatic hydrolysis, a unique and desirable property that could be exploited in the development of functional food products to regulate blood sugar levels and promote digestive health. However, due to a multifactorial phenomenon in the banana flour matrix-from the molecular to the micro level-there is no consensus regarding the complex mechanisms behind the slow enzymatic hydrolysis of unripe banana flour starch. This work therefore explores factors that influence the enzymatic hydrolysis resistance of raw and modified banana flour and its starch including the proportion and distribution of the amorphous and crystalline phases of the starch granules; granule morphology; amylose-amylopectin ratio; as well as the presence of nonstarch components such as proteins, lipids, and phenolic compounds. Our findings revealed that the relative contributions of these factors to banana starch hydrolytic resistance are apparently dependent on the native or processed state of the starch as well as the cultivar type. The interrelatability of these factors in ensuring amylolytic resistance of unripe banana flour starch was further highlighted as another reason for the multifactorial phenomenon. Knowledge of these factors and their contributions to enzymatic hydrolysis resistance individually and interconnectedly will provide insights into enhanced ways of extraction, processing, and utilization of unripe banana flour and its starch.

Optimization of Heat-Moisture Treatment Conditions for High-Amylose Starch and Its Application in High-Resistant Starch Triticale Noodles

Heat-moisture treatment (HMT) is a widely used method for modifying starch properties with the potential to reduce the digestibility of high-amylose starch (HAS). This study aimed to optimize the HMT conditions for HAS and apply the resulting HMT-HAS to triticale noodles to develop low-glycemic-index products. HMT significantly increased the resistant starch (RS) content and decreased the rapidly digestible starch (RDS) content of HAS. The treatment conditions-temperature, heating time, and moisture content-were found to significantly influence the starch composition. Optimal HMT conditions were determined using response surface methodology: a temperature of 108 °C, a heating time of 5.8 h, and a moisture content of 25.50%. Under these conditions, the RS content of HMT-HAS was 60.23%, nearly double that of the untreated sample. Increasing the level of HMT-HAS in triticale noodles led to significant decreases in short-range order, relative crystallinity, and viscosities, while the RS content increased from 12.08% to 34.41%. These findings suggest that incorporating HMT-HAS into triticale noodles effectively enhances starch digestive resistance, supporting the development of functional, low-glycemic-index triticale-based foods.

Exploring a novel GH13_5 α-amylase from Jeotgalibacillus malaysiensis D5T for raw starch hydrolysis

α-Amylase plays a crucial role in the industrial degradation of starch. The genus Jeotgalibacillus of the underexplored marine bacteria family Caryophanaceae has not been investigated in terms of α-amylase production. Herein, we report the comprehensive analysis of an α-amylase (AmyJM) from Jeotgalibacillus malaysiensis D5T (= DSM28777T = KCTC33550T). Protein phylogenetic analysis indicated that AmyJM belongs to glycoside hydrolase family 13 subfamily 5 (GH13_5) and exhibits low sequence identity with known α-amylases, with its closest counterpart being the GH13_5 α-amylase from Bacillus sp. KSM-K38 (51.05% identity). Purified AmyJM (molecular mass of 70 kDa) is stable at a pH range of 5.5-9.0 and optimally active at pH 7.5. The optimum temperature for AmyJM is 40 °C, where the enzyme is reasonably stable at this temperature. Similar to other α-amylases, the presence of CaCl2 enhanced both the activity and stability of AmyJM. AmyJM exhibited activity toward raw and gelatinized forms of starches and related α-glucans, generating a mixture of reducing sugars, such as glucose, maltose, maltotriose, maltotetraose, and maltopentaose. In raw starch hydrolysis, AmyJM exhibited its highest efficiency (51.10% degradation) in hydrolyzing raw wheat starch after 3-h incubation at 40 °C. Under the same conditions, AmyJM also hydrolyzed tapioca, sago, potato, rice, and corn raw starches, yielding 16.01-30.05%. These findings highlight the potential of AmyJM as a biocatalyst for the saccharification of raw starches, particularly those derived from wheat.

Structural, rheological, and gelling characteristics of starch-based materials in context to 3D food printing applications in precision nutrition

Starch-based materials have viscoelasticity, viscous film-forming, dough pseudoplasticity, and rheological properties, which possess the structural characteristics (crystal structure, double helix structure, and layered structure) suitable for three-dimensional (3D) food printing inks. 3D food printing technology has significant advantages in customizing personalized and precise nutrition, expanding the range of ingredients, designing unique food appearances, and simplifying the food supply chain. Precision nutrition aims to consider individual nutritional needs and individual differences, which include special food product design and personalized precise nutrition, thus expanding future food resources, then simplifying the food supply chain, and attracting extensive attention in food industry. Different types of starch-based materials with different structures and rheological properties meet different 3D food printing technology requirements. Starch-based materials suitable for 3D food printing technology can accurately deliver and release active substances or drugs. These active substances or drugs have certain regulatory effects on the gut microbiome and diabetes, so as to maintain personalized and accurate nutrition.

Determining whether granule structural or surface features govern the wheat starch digestion, a kinetic analysis

Deciphering the determinants of starch digestion from multiple interrelated properties is a challenge that can benefit from multifactorial data analysis. The present study investigated the digestion kinetic parameters (rate, final extent) of size-fractions from four commercial wheat starches with different amylose contents. Each size-fraction was isolated and characterized comprehensively using a large range of analytic techniques (FACE, XRD, CP-MAS NMR, time-domain NMR, DSC…). A statistical clustering analysis applied on the results revealed that the mobility of water and starch protons measured by time-domain NMR was consistently related to the macromolecular composition of the glucan chains and to the ultrastructure of the granule. The final extent of starch digestion was determined by the granule structural features. The digestion rate coefficient dependencies, on the other hand, changed significantly with the range of granule size, i.e. the accessible surface for initial binding of α-amylase. The study particularly showed the molecular order and the chains mobility predominantly limiting or accelerating the digestion rate depending on the accessible surface. This result confirmed the need to differentiate between the surface and the inner-granule related mechanisms in starch digestion studies.