Structural and functional characterizations of α-amylase-treated porous popcorn starch

Mechanism analysis for the differences in multi-level structure, enzyme accessibility and pasting properties of starch granules caused by different hydrolysis pathways of maltogenic α-amylase

The effect of pores distribution on the multi-scale structure, enzyme accessibility, and pasting properties of the waxy maize starch granules with the same degree of hydrolysis were examined. Increased maltogenic α-amylase (MA) dosage obviously increased the shallow pores number and the roughness, whereas extended time increased the holes depth. Despite achieving the same hydrolysis degree and specific surface area, samples with numerous shallow holes exhibited a higher mass fractal dimension, a lower, peak viscosity, final viscosity and setback. Besides, increased dosage prompted a sustained decrease in the number of short chains with DP 10-17; whereas prolonging time encouraged the continuous catalyzation in the same chains. Enzymatic probe profiles showed MA was more accessible to the amorphous region on the periphery of starch granules, rather than the inside. This finding provides a more valuable understanding of the catalytic mechanism for MA in heterogeneous systems and an accurate guidance for the industrial production.

Preparation and characterization of porous corn starch-based antibacterial sustained-release intelligent film

A novel porous corn starch-based antibacterial sustained-release intelligent film was prepared with the porous corn starch as the substrate, purple corn cob anthocyanin (PCA) as the indicator, and tangerine peel essential oil as the antibacterial agent, and its properties were studied. The results showed that the porous corn starch-based antimicrobial sustained-release indicator film had good mechanical strength, surface hydrophobicity and light transmittance. The tensile strength of the sustained-release indicator film (PLSt-12) prepared by porous corn starch with an enzymatic hydrolysis time of 12 h was 14.35 MPa and the elongation at break was 6.55 %. The water contact angle was 89.10°, and the water vapor transmittance was 6.62 × 10-4 g·mm2·s-1·Pa-1. The PLSt-12 was brown at pH 10 and had a sensitive color response. The PLSt-12 reduced the release rate of anthocyanins by 25.01 %, and the sustained-release mechanism was non-Fick diffusion. It showed a significant color change when the pork quality deteriorated, which can be used to monitor the freshness of the pork. This type of antibacterial sustained-release intelligent film had considerable application potential in indicating food freshness.

Sub-high amylose maize starch: an ideal substrate to generate starch with lower digestibility by fermentation of Qu

BACKGROUND

The fermentation of Qu (FQ) is a novel method to modify the properties of starch to expand its application and especially to increase the resistant starch (RS) content. Using waxy maize starch (WMS) as a fermentation substrate can increase the RS content significantly but it may be time consuming and not cost effective due to the almost negligible RS content of WMS. To solve this problem, we hypothesized that sub-high amylose starch (s-HAMS), with an amylose content close to 50% could be an ideal substrate for FQ.

RESULTS

The results showed that FQ did not change the shape and the particle size of starch granules, the gelatinization peak (Tp), or the conclusion temperature (Tc), but the slowly digested starch content declined. Rapidly digested starch content fluctuated during FQ and the amylose content decreased within 36 h and then increased. Within 24h, FQ significanlty increased these values: the RS content, relative crystallinity (RC), the ratio of FTIR absorbances at 1047/1022cm-1, the diffraction peak at 19.8° in X-ray diffraction (XRD), and the gelatinization onset temperature (To) increased significantly, within 24 h of FQ. However, after 24 h of fermentation, the RS content, RC, the ratio of FTIR absorbances at 1047/1022 cm-1, and gelatinization enthalpy (ΔH) decreased significantly.

CONCLUSION

Sub-high amylose starch is more suitable for FQ to produce low digestibility starch, and the increase in RS may be due to the formation of 'amylose-lipid' complexes (RS5). © 2024 Society of Chemical Industry.

The art and science of porous starch: understanding the preparation method and structure-function relationship

Porous starch (PS), a modified form of starch with unique properties, is attracting substantial attention for its diverse advantages and applications. Its intricate porous structure, crystalline and amorphous characteristics, and hydrophilic-hydrophobic properties stem from pore formation via physical, chemical, enzymatic, and combined synergistic methods. Porous starch offers benefits like improved gelatinization temperature, water absorption, increased surface area, tunable crystallinity, and enhanced functional properties, making it appealing for diverse food industry applications. To optimize its properties, determining the parameters governing porous structure formation is crucial. Factors such as processing conditions, starch source, and modification methods substantially impact porosity and the overall characteristics of the material. Understanding and controlling these parameters allows customization for specific applications, from pharmaceutical drug delivery systems to enhancing texture and moisture retention in food products. To date, studies shedding light on how porosity formation can be fine-tuned for specific applications are fewer. This review critically assesses the existing reports on porous starch, focusing on how preparation methods affect porosity formation, thereby influencing the product's crystallinity/hydrophilic-hydrophobic nature and overall applicability.

Formation, influencing factors, and applications of internal channels in starch: A review

Starch, a natural polymer, has a complex internal structure. Some starches, such as corn and wheat starches, have well-developed surface pores and internal channels. These channel structures are considered crucial in connecting surface stomata and internal cavities and have adequate space for loading guest molecules. After processing or modification, the starch-containing channel structures can be used for food and drug encapsulation and delivery. This article reviews the formation and determination of starch internal channels, and the influence of different factors (such as starch species and processing conditions) on the channel structure. It also discusses relevant starch preparation methods (physical, chemical, enzymatic, and synergistic), and the encapsulation effect of starch containing internal channels on different substances. In addition, the role of internal channels in regulating the starch digestion rate and other aspects is also discussed here. This review highlights the significant multifunctional applications of starch with a channel structure.

Insights into starch-based gels: Selection, fabrication, and application

Starch a natural polymer, has made significant advancements in recent decades, offering superior performance and versatility compared to synthetic materials. This review discusses up-to-date diverse applications of starch gels, their fabrication techniques, and their advantages over synthetic materials. Starch gels renewability, biocompatibility, biodegradability, scalability, and affordability make them attractive. Also, advanced theoretical foundations and emerging industrial technologies could further expand their scope and functions inspiring new applications.

Bioactive delivery systems based on starch and its derivatives: Assembly and application at different structural levels

Starch and modified starch, spanning various structural levels, are comprehensively reviewed, with a special emphasis on the advancement of starch and its derivative-based delivery systems for bioactive substances. The pivotal aspect highlighted is the controlled release of active ingredients by starch-based delivery systems with distinct hierarchical structures. At the molecular level, diverse categories of starch degradation products, such as dextrin and highly branched starch, serve as versatile amphiphilic carriers for encapsulating active ingredients. At the level of helical structure, the distinctive configuration of the starch-guest complex partly determines the mechanism of controlled release for diverse active components. At the crystal and particle structural level, starch assumes the role of a carrier, effectively modulating the release of active substances, and enhances the innate physiological activity of different active components. As a natural polymer molecule, starch can also generate hydrogel materials in polymer form, expanding its utility in the fields of food, materials, and even medicine.

Expanded porous-starch matrix as an alternative to porous starch granule: Present status, challenges, and future prospects

Exposing the hydrated-soft-starch matrix of intact grain or reconstituted flour dough to a high-temperature-short-time (HTST) leads to rapid vapor generation that facilitates high-pressure build-up in its elastic matrix linked to large deformation and expansion. The expanded starch matrix at high temperatures dries up quickly by flash vaporization of water, which causes loss of its structural flexibility and imparts a porous and rigid structure of the expanded porous starch matrix (EPSM). EPSM, with abundant pores in its construction, offers adsorptive effectiveness, solubility, swelling ability, mechanical strength, and thermal stability. It can be a sustainable and easy-to-construct alternative to porous starch (PS) in food and pharmaceutical applications. This review is a comparative study of PS and EPSM on their preparation methods, structure, and physicochemical properties, finding compatibility and addressing challenges in recommending EPSM as an alternative to PS in adsorbing, dispersing, stabilizing, and delivering active ingredients in a controlled and efficient way.

Oil structuring from porous starch to powdered oil: Role of multi-scale structure in the oil adsorption and distribution

Oil structuring from porous starch is a potential alternative for the industrial production of powdered oil, but their relationship between starch multi-scale structure and oil adsorption characteristics was not clear. This study compared the role of multi-scale structure of porous starch (PS) prepared by normal and waxy maize starch in the oil adsorption. Waxy maize porous starch exhibited higher oil adsorption capacity (32.43 %-98.71 %) and more oil distributed on the surface of granules than normal maize porous starch, resulting from the more pores, larger specific surface area (1.01-1.53 m2/g), and pore size (8.45-9.32 nm). The enzymolysis time of native starch dominated oil distribution, leading to different granule adhesion and aggregation state. Pearson correlation analysis further showed oil adsorption capacity was negatively correlated with particle size, but positively correlated with enzymolysis rate and specific surface area of PS. The formation of powdered oil was mainly through the physical adsorption, including surface adsorption and pore adsorption. These findings could provide a promising route for the preparation of powdered oil with controlled multi-scale structure of PS.

Fabrication and study on dually modified starch embedded in alginate hydrogel as an encapsulation system for Satureja essential oil

This study aimed to investigate how the types and order of modifications influence the structure and physicochemical characteristics of modified porous starch. The work focuses on the encapsulation of essential oil in hydrophobic microcapsules embedded in sodium alginate hydrogels. FTIR spectra indicated successful esterification of starch with OSA. 1047:1022 cm-1 and 1022:995 cm-1 band ratios of FTIR spectra revealed increased crystallinity due to enzymatic modification, supported by XRD patterns. Porous-OSA (PO) starch had 1.5 times higher degree of substitution (DS) than OSA-porous (OP) starch, confirmed by the intense peak at 0.85 ppm in 1H NMR spectra. SEM images displayed larger particles and smaller pore diameter in OP compared to PO and porous starch, indicating amylolytic enzyme inhibition by OSA. Loading efficiency (LE) showed no significant difference between OP and PO microcapsules (≈70 %), both significantly higher other starch microcapsules. OP and PO microcapsules exhibited sustained release, with enhanced antibacterial activity. Alginate hydrogels preserved about 60 % antioxidant and 90 % antibacterial activities of SEO against 2 h of UV radiation. These findings suggest that the order of modification could not affect the functional properties of final microcapsules. Additionally, the importance of alginate hydrogels as the protective and second wall material was disclosed.

The effect of thiolation process with l-cysteine on amylolysis efficiency of starch-cysteine conjugate by α-amylase

l-Cysteine (l-Cys) pre-treatment at two concentrations (150 mg/kg; PC1 and 300 mg/kg; PC2) on potato starch was conducted to produce starch-cysteine conjugates. Afterward, the effect of α-amylase on starch digestibility of potato native (PE) and starch-cysteine conjugates (PC1E and PC2E) were examined. Thiolation not only damaged starch according to the formation of pore and blister-like spots on the surface of starch granules, but also provided the functional group to immobilize α-amylase. Starch-cysteine conjugates showed a significantly greater degree of hydrolysis 24.1 % (PC1E) and 36.5 % (PC2E) in comparison with (16.8 %; PE). Destroying the granules integrity were accompanied with decreased crystallinity from 37.7 % to 33.1 % (PC1), 31.1 % (PC2), 27.6 % (PC1E) and 22.4 % (PC2E) with increasing thiol content (%) on surface from 2.3 %; PC1 to 3.4 %; PC2. The ratio of 1047/1022 cm^{- 1} reduced from 1.112 (native potato starch) to 0.974 (PC1E) and 0.867 (PC2E) after being subjected to α-amylase. Additionally, substantially low pasting viscosities (determined by RVA) along with the thermal properties (determined by DSC) of starch-cysteine conjugates treated with α-amylase could confirm the degradation of molecular structures containing low swelling power.

Importance of Inactivation Methodology in Enzymatic Processing of Raw Potato Starch: NaOCl as Efficient α-Amylase Inactivation Agent

Efficient inactivation of microbial α-amylases (EC 3.2.1.1) can be a challenge in starch systems as the presence of starch has been shown to enhance the stability of the enzymes. In this study, commonly used inactivation methods, including multistep washing and pH adjustment, were assessed for their efficiency in inactivating different α-amylases in presence of raw potato starch. Furthermore, an effective approach for irreversible α-amylase inactivation using sodium hypochlorite (NaOCl) is demonstrated. Regarding inactivation by extreme pH, the activity of five different α-amylases was either eliminated or significantly reduced at pH 1.5 and 12. However, treatment at extreme pH for 5 min, followed by incubation at pH 6.5, resulted in hydrolysis yields of 42–816% relative to controls that had not been subjected to extreme pH. “Inactivation” by multistep washing with water, ethanol, and acetone followed by gelatinization as preparation for analysis gave significant starch hydrolysis compared to samples inactivated with NaOCl before the wash. This indicates that the further starch degradation observed in samples subjected to washing only took place during the subsequent gelatinization. The current study demonstrates the importance of inactivation methodology in α-amylase-mediated raw starch depolymerization and provides a method for efficient α-amylase inactivation in starch systems.

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.

The effects of fermentation of Qu on the digestibility and structure of waxy maize starch

The fermentation of Qu (FQ) could efficiently produce enzymatically modified starch at a low cost. However, it is poorly understood that how FQ influences the waxy maize starch (WMS) structure and the digestion behavior. In this study, WMS was fermented by Qu at different time and starches were isolated at each time point, and its physico-chemical properties and structural parameters were determined. Results showed that the resistant starch (RS), amylose content (AC), the average particle size [D(4,3)] the ratio of peaks at 1,022/995 cm-1, and the onset temperature of gelatinization (T o ) were increased significantly after 36 h. Conversely, the crystallinity, the values of peak viscosity (PV), breakdown (BD), gelatinization enthalpy (ΔH), and the phase transition temperature range (ΔT) were declined significantly after 36 h. It is noteworthy that smaller starch granules were appeared at 36 h, with wrinkles on the surface, and the particle size distribution was also changed from one sharp peak to bimodal. We suggested that the formation of smaller rearranged starch granules was the main reason for the pronounced increase of RS during the FQ process.

Corn starch modification during endogenous malt amylases: The impact of synergistic hydrolysis time of α-amylase and β-amylase and limit dextrinase

To expand the utility of barley malts and decrease the cost of enzyme-modified starch production, the structural and physicochemical characteristics of corn starch modified with fresh barley malts at different hydrolysis time were investigated. The results indicated that compared to native starch, A chain (DP 6-12) of the enzyme-treated starches increased at hydrolysis time (≤12 h), but it decreased at hydrolysis time (>12 h). Inversely, B chains (DP > 13) decreased at hydrolysis time (≤12 h) and they generally increased at hydrolysis time (>12 h). The relative crystallinity decreased from 25.63% to 21.38% and 1047 cm^-1/1022 cm^-1 reduced from 1.042 to 0.942 after endogenous malt amylases at hydrolysis time from 0 to 72 h, and the thermal degradation temperatures decreased from 323.19 to 295.94 °C, whereas the gelatinization temperatures slightly increased. The gel strength decreased at hydrolysis time less than 12 h, but it increased at hydrolysis time more than 12 h. The outcomings would provide a theoretical and applicative basis about how endogenous malt amylases with lower price modify starches to obtain desirable starch derivatives and industrial production.

Structural features of five types of maize starch granule subgroups sorted by flow cytometry

Subgroups of starch granules from five maize phenotypes including waxy-, normal-, popcorn-, sweet corn- and high-amylose maize were sorted by flow cytometry (FC) utilizing the side scatter channel (SSC) and forward scatter channel (FSC). SSC and FSC mainly reflecting internal object complexity, and object size, respectively. Subgroups with higher FSC signal always showed higher SSC signal, indicating larger granules exhibited higher internal structural complexity. Wide-angle and small-angle X-ray scattering analysis showed that the subgroups showing high SSC signal intensity also had high lamellar scattering intensity, and low crystallinity. Vibrational transitions of bonds analyzed by Fourier Transform Infrared Spectroscopy (FT-IR) showed that the subgroups of maize starches, except sweet corn starch, with high SSC signal had high intensities at 1045 and 1022 cm^-1. Hence, our data demonstrate that the structural complexity detected by the SSC signal is mainly associated with lamellar and crystalline features of starch granules.