Modification of potato starch by using superheated steam

Starch hydrolysates, their impurities and the role of membrane-based technologies as a promising sustainable purification method at industrial scale

Starch hydrolysates are syrups obtained through the hydrolysis of starch with a defined carbohydrate composition and concentration. Annual harvest conditions and the availability of raw materials, such as corn, wheat, rice, potato, and certain plant roots, influence their quality. High-quality starch hydrolysate products serve numerous applications, including ingredients in food, textiles, paper, cosmetics, bioplastics, pharmaceuticals and construction. However, impurities such as colour molecules, characteristic flavours, salts, and proteins encountered in the solution along the starch processing steps can compromise product quality. With increasing emphasis on organic and sustainable production, starch hydrolysates must meet higher health and environmental standards. This review provides a comprehensive overview of starch hydrolysates production and purification. It explores the chemical processes leading to the formation of impurities and their impact on the final product composition and specific characteristics. Downstream processing methods for recovery, purification, and concentration are also investigated, comparing traditional techniques with emerging membrane-based technologies. Membrane technologies offer a potential solution for purifying plant-based starch hydrolysates efficiently and sustainably by enhancing purification while reducing energy consumption and waste generation. They operate at lower temperatures, avoiding phase transitions, extra heating, chemicals, and solvent exchanges. Although membrane technologies are widely used in various food industries, minimal research exist on their applications in starch hydrolysate processing, with limited experimental validation available. Addressing this gap, this review compiles established applications and discusses challenges hindering industrial adoption-including membrane fouling, the selection of appropriate membranes, the operational lifespan, and replacement costs,- while also identifying areas requiring further experimental research and development.

Superheated steam processing as a novel strategy for rapid synthesis of millet-starch citrates: Preparation, characterization, and in vitro starch digestibility

This study investigates the potential of superheated steam (SS) as a rapid and sustainable method for synthesising millet starch citrates with improved physicochemical and functional properties. Millet starch was esterified with citric acid (CA) under varying SS conditions (160-180 °C, 15-45 min) to optimise the degree of substitution (DS) and evaluate its influence on starch functionality. A range of DS values (0.023 to 0.121) were achieved, with the highest DS observed at 170 °C for 45 min. Structural analysis using Fourier-transform infrared spectroscopy confirmed successful esterification, with the appearance of a new peak at 1735 cm-1 indicating ester bond formation. X-ray diffraction showed a reduction in crystallinity with increasing DS, while polarised light microscopy and confocal scanning laser microscopy revealed alterations in molecular organisation. Scanning electron microscopy demonstrated minimal disruption to granule morphology. Contact angle measurements indicated increased hydrophobicity, with water contact angles rising from 29.63° in native starch to 71.63° in high DS samples. Additionally, a significant (p < 0.05) reduction in amylose content and paste viscosities was observed, correlating with improved resistance to gelatinisation and retrogradation. In vitro digestibility analysis showed a substantial increase in resistant starch content, from 18.69 % in native starch to 40.11 % in high DS samples. These findings highlight SS as an efficient and eco-friendly technology for producing starch citrates with tailored functionalities, particularly suited for low-glycaemic response and health-promoting food applications.

Exposure of Proso millet starch to superheated steam: Effect on physicochemical, techno-functional, rheological behavior, digestibility, and related mechanism

In the present study, proso millet starch (PMS) was treated with SHS (120-160 °C for 1-5 min) to investigate the molecular interactions and techno-functional, rheological, and digestible properties. Exposure to SHS induced the degradation of helical structure, and longer chains, reducing amylose, blue value, optical density, and relative crystallinity. Meanwhile, SHS treatment might have introduced hydro‑carbonyl groups, eventually increasing water absorption capacity, swelling power, and transparency. As per SEM images, SHS-treated PMS had rough and irregular polygon surfaces with small pinholes. Compared to control, SHS treatment slightly improved the elastic nature of PMS samples. Furthermore, SHS treatment at 140 and 160 °C for 3 and 5 min increased the slowly digestible and resistant starch content. Multivariate analysis suggests that SHS treatment could be performed at 140 °C for 3 min to modify the PMS.

Effect of Superheated Steam Treatment on Rice Quality, Structure, and Physicochemical Properties of Starch

This study aimed to investigate the effect of superheated steam treatment on the cooking and eating quality of rice, and further explore the effect of superheated steam treatment on the structure, gel properties, and rheological behavior of rice starch. After superheated steam treatment, the optimal cooking time of rice was effectively reduced by 26.9%, and the taste value of rice was significantly improved, from 78.45 to 84.20, when treated at 155 °C for 10 s. Superheated steam treatment significantly reduced the amylose and protein content, and increased the average particle size of rice starch. Compared with the control, the enthalpy change (ΔH) in the superheated steam treatment rice starch decreased notably from 6.53 to 5.28 after treatment, the relative crystallinity of the starch was significantly reduced from 21.20 to 10.89, and the short-term order of the starch was enhanced owing to the rearrangement of starch molecules after gelatinization. The starch structure was more compact and orderly after the superheated steam treatment, which significantly improved the hardness, viscoelasticity, and strength of the gel. These results indicate that superheated steam treatment improves the quality of rice by changing the structure of rice starch.

Impact of waxy protein deletions on the crystalline structure and physicochemical properties of wheat V-type resistant starch (RS5)

This study investigated the effects of waxy (Wx) protein on wheat V-type resistant starch (RS5) formation, molecular structure, and physicochemical properties. We discovered that waxy protein deletions led to a rise in B- and C-type starch granules, while reducing A-type starch granules, amylose, and slowly digestible starch contents. Further, dodecyl gallate (DG) addition significantly increased RS5 content, and molecular dynamics simulations indicated that amylose and DG can form stable complexes. Molecular docking indicated that DG could potentially aid in protecting wheat starch from digestion by human α-glucosidase. RS5 content was significantly reduced by waxy protein deletions. X-ray powder diffraction, Fourier-transform infrared spectroscopy, and laser confocal microscopy-Raman analyses revealed that waxy protein deletions decreased long-range crystalline structures and relative crystallinity and increased short-range crystalline structures，and full width at half maximum at 480 cm-1 of RS5. Pearson correlation analysis showed that RS5 content was highly correlated with its crystal structure, functional characteristics, and digestive characteristics. Principal component analysis revealed that five parameters (amylopectin, long-range crystalline structures, amylose, relative crystallinity, and RS5 content) had significant effect on the crystalline structure and functionality of RS5.

Effects of different heat treatment methods on physicochemical characteristics and in vitro digestibility of sweet potato flour and its application in meal replacement flour

This study examined the effects of various heat treatments on physicochemical properties, functionality, and starch digestibility of sweet potato flour. Heat treatments darkened the color but did not change the chemical structure. Solubility decreased and swelling power increased (17.3%-18.3%) with baking, frying, and microwaving, while extrusion and steaming had opposite effects. Rapidly digestible starch content increased (8.96%-41.91%) in all treatments except steaming, which reduced slowly digestible starch (61.81%-28.97%). Based on the analysis of these studies, using low-temperature baked and extruded sweet potato flour as the main raw material, combined with the concept of complete nutrition, supplemented by nutritious ingredients such as quinoa, oats, and whey protein, we have successfully developed two sweet potato meal replacement flours (SP-1 and SP-2) and found they had good brewing properties and showed shear-thinning behavior. This study provided theoretical basis for sweet potato deep processing and functional product development. PRACTICAL APPLICATION: This paper studied the effects of different heat treatments on sweet potato flour, and developed two meal replacement flour based on this, to provide a theoretical basis for the application of the sweet potato industry.

Effect of superheated steam treatment on enzyme inactivation, morphostructural, physicochemical and digestion properties of sand rice (Agriophyllum squarrosum) flour

The lipase (LA) and peroxidase (POD) activities, as well as morphological structure, physicochemical and digestion properties of sand rice flour (SRF) treated with superheated steam (SS), were investigated. SS treatment at 165 °C completely deactivated LA and resulted in a 98% deactivation of POD activities in SRF. This treatment also intensified gelatinization, induced noticeable color alterations, and decreased pasting viscosities. Furthermore, there was a moderate reduction in crystal structure, lamellar structure, and short-range ordered structure, with a pronounced reduction at temperatures exceeding 170 °C. These alterations significantly impacted SRF digestibility, leading to increased levels of rapidly digestible starch (RDS) and resistant starch (RS), with the highest RS content achieved at 165 °C. The effectiveness of SS treatment depends on temperature, with 165 °C being able to stabilize SRF with moderate changes in color and structure. These findings will provide a scientific foundation for SS applicated in SRF stabilization and modification.

Hot-water soluble fraction of starch as particle-stabilizers of oil-in-water emulsions: Effect of dry heat modification

Dry heat treatment (DHT) ranging from 130 to 190 °C was employed to modify corn starch. The hot-water soluble fraction (HWS) of the DHT-modified starch was isolated, and its capacity and mechanism for stabilizing O/W emulsions were investigated. Corn starch underwent a significant structural transformation by DHT at 190 °C, characterized by a 7.3 % reduction in relative crystallinity, a tenfold decrease in weight-average molecular weight from 95.21 to 8.11 × 106 g/mol, and a degradation of over one-third of the extra-long chains of amylopectin (DP > 36) into short chains (DP 6-12). These structural modifications resulted in a substantial formation of soluble amylopectin, leading to a sharp increase in the HWS content of corn starch from 3.16 % to 85.06 %. This augmented HWS content surpassed the critical macromolecule concentration, prompting the formation of HWS nanoaggregates. These nanoaggregates, with an average particle size of 33 nm, functioned as particle stabilizers, ensuring the stability of the O/W emulsion through the Pickering mechanism. The O/W emulsion stabilized by HWS nanoaggregates exhibited noteworthy centrifugal and storage stability, with rheological properties remaining nearly unchanged over a storage period of 180 days. Given its straightforward preparation process, the HWS of DHT-modified starch could be a promising natural emulsifier.

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.

Effects of cooking methods on the physical properties and in vitro digestibility of starch isolated from Chinese yam

The objective of this study was to compare the structural and functional attributes of Chinese yam starches obtained via different domestic cooking methods. Cooking changed the crystalline type from the C type to the CB type, and disrupted the short- and long-range molecular order of Chinese yam starch. The average chain length of amylopectin in BOS (boiling starch) was the smallest at 22.78, while RWS had the longest average chain length, reaching 24.24. These alterations in molecular structure resulted in variations in functional properties such as solubility, swelling power (SP), pasting characteristics, and rheological properties. Among these alterations, boiling was the most effective method for increasing the water-binding capacity and SP of starch. Specifically, its water holding capacity was 2.12 times that of RWS. In vitro digestion experiments indicated that BOS has a higher digestion rate (k = 0.0272 min-1) and lower RDS (rapidly digestible starch), which may be related to its amylopectin chain length distribution. This study can guide us to utilize yam starch through suitable cooking methods, which is relevant for the processing and application of Chinese yam starch.

The properties of the rice resistant starch processing and its application in skimmed yogurt

Extrusion is typically employed to prepare resistant starch (RS). However, the process is complicated. In this study, the effects of twin-screw extrusion on the crystallinity, thermal properties, and functional properties of starch formed in different extrusion zones were investigated. The effects of this process on the rheological properties and microstructure of RS-added skimmed yogurt were also studied. According to the results, the RS content increased from 7.40 % in the raw material to 33.79 % in the extrudate. The A-type crystal structure of the starch was not observed. The dissociation temperature of the extruded starch ranged from 87.76 °C to 100.94 °C. The glycemic index (GI) of skimmed yogurt fortified with 0.4 % RS was 48.7, and the viscosity was also improved. The microstructure exhibited a uniform network of the starch-protein structure. The findings may serve as a theoretical basis for the application of RS in the food industry.

Mild steam treatment: Enhancing the rehydration performance of instant rice noodles by changing the physicochemical properties and gel structure of rice starch

The "instant" quality of instant rice noodles is significantly affected by slow rehydration during cooking. This happens as a result of the native rice starch's low ability to gelatinize as well as the high shear and pressure utilized in industries during the widely used extrusion molding process. In order to address this issue, the rice flour was pretreated with mild steam (MS) technology. The results revealed that the rehydration qualities of the rice noodles that were extruded from the steam-treated flour significantly improved. There was a reduction of 25.5% in the rehydration time, from 443 to 330 s. The MS-treated rice starch's peak viscosity increased to 4503 from 4044 mPa/s. Decreases in gelatinization enthalpy (ΔH) and short-range ordering also suggest a reduction in difficulty in accomplishing starch gelatinization. Scanning electron microscopy studies showed particle aggregation increased as the treatment duration lasted longer. In conclusion, our findings indicate that we successfully addressed the issue of slow rehydration in instant rice noodles while presenting a novel approach for their manufacturing in the manufacturing sector.

Effects of different high-temperature conduction modes on the ovalbumin-glucose model: AGEs production and regulation of glycated ovalbumin on gut microbiota

Food high-temperature processing frequently induces the production of advanced glycation end products (AGEs) in the food industry. In this study, the effects of three high-temperature conduction modes on the AGEs production derived from ovalbumin (OVA)-glucose model and the regulation of glycated OVA on gut microbiota were investigated. The peak time of OVA shifted maximally from 13.72 to 13.57 due to the rise in molecular weight, confirming successful coupling between OVA and glucose. The inhibition of superheated steam (SS) on AGEs was observed, with the sample treated by SS showing the lowest content among glycated OVA groups. The analysis revealed an increase in AGEs during digestion and a decrease in fermentation, suggesting the release during digestion and the availability by intestinal flora. Furthermore, an expansion of Bifidobacterium and Lactobacillus, and the inhibition of Desulfovibrio and Escherichia-Shigella were observed, indicating the prebiotic activity of glycated OVA and its potential to improve intestinal health. These results provide valuable information for controlling high-temperature processing to inhibit AGEs formation and highlight the positive effects of glycated proteins on intestinal health.

Comparison of ovalbumin glycation induced by high-temperature steaming and high-temperature baking: A study combining conventional spectroscopy with high-resolution mass spectrometry

High-temperature steaming (HTS) and high-temperature baking (HTB)-induced ovalbumin (OVA)-glucose glycation (140 °C, 1-3 min) were compared, and the different mechanisms were evaluated by changes in protein conformation, glycation sites and average degree of substitution per peptide molecule (DSP) values as well as the antioxidant activity of glycated OVA. Conventional spectroscopic results suggested that in comparison with HTB, HTS promoted protein expansion, increased β-sheet content and made OVA structure more orderly. Liquid chromatography-high resolution mass spectrometry (LC-HRMS) analysis showed that 10 glycation sites were found under HTB, while 4 new glycation sites R111, R200, R219 and K323 appeared under HTS, and 2 of them (R219 and K323) were located in internal β-sheet chains. The antioxidant activities of glycated OVA increased with increasing treatment time, and HTS showed stronger enhancement effect than HTB. Furthermore, the DSP values were generally higher under HTS than HTB. Compared with HTB, HTS with high penetrability could enhance the change of OVA primary structure and spatial conformation, making the protein structure more unfolded and stable, leading to more protein-sugar collisions occurred in inner OVA molecular and significantly promoted glycation. In conclusion, HTS is a promising method for high-temperature short-time glycation reaction, with drastically increasing the protein antioxidant activities.

Comparison of milling methods on the properties of common buckwheat flour and the quality of wantuan, a traditional Chinese buckwheat food

The microstructural and techno-functional properties of buckwheat flour and its processability for making wantuan, as affected by different milling methods, were investigated. Results showed that the particle sizes (d(0.5)) of the flours made by stone-milling (SM), hammer-milling (HM), laboratory grinding with steaming pretreatment for 5 min (LG-5) and 10 min (LG-10) were 95.5, 111.5, 35.4 and 41.1 μm, respectively. Moreover, SM and HM flours had less liberated starch granules and 20.84%-24.32% higher relative crystallinity than LG-10 flour. Slurries of laboratory-grinded flours showed excellent suspension stability. LG-10 flour had lowest pasting viscosities but greatest storage modulus and loss modulus. Color differences among the wantuan made from different flours were not visibly perceived (ΔE < 5). Wantuan made from LG-5 flour exhibited highest textual quality due to its greatest resilience (0.376), good springiness (0.933) and accepted chewiness (1093.31). Concluding, steaming prior to grinding could improve the qualities of buckwheat flour for wantuan making.

Changes in physiochemical properties and in vitro digestion of corn starch prepared with heat-moisture treatment

To investigate the effect of heat-moisture treatment (HMT) on the physiochemical properties and in vitro digestibility of corn starch, the pasting behavior, viscoelasticity, thermal properties, long/short range structure, morphology and in vitro digestion of corn starch treated with different HMT conditions (HMT-20, 25, 30, 35 and 40 %) were characterized. Results indicated that after HMT, the pasting and disintegration behaviors of corn starch were affected and correlated with the moisture content. The dynamic viscoelasticity of corn starch was changed, and when glassy conditions were reached, the elastic properties decreased with increasing moisture while the viscous properties increased, especially for the HMT-40 %. The thermal stability of starch was improved by HMT, although the enthalpy of pasting (ΔH) was reduced. Additionally, the HMT processing also promoted the conversion of RDS to SDS and/or RS (SDS and RS increased to 39.80 % and 31.68 % for HMT-40 %, respectively), which might attribute to the rearrangement of free starch molecules. The present work provides a potential approach to make functional starches with healthy properties.

Starch Modification with Molecular Transformation, Physicochemical Characteristics, and Industrial Usability: A State-of-the-Art Review

Starch is a readily available and abundant source of biological raw materials and is widely used in the food, medical, and textile industries. However, native starch with insufficient functionality limits its utilization in the above applications; therefore, it is modified through various physical, chemical, enzymatic, genetic and multiple modifications. This review summarized the relationship between structural changes and functional properties of starch subjected to different modified methods, including hydrothermal treatment, microwave, pre-gelatinization, ball milling, ultrasonication, radiation, high hydrostatic pressure, supercritical CO₂, oxidation, etherification, esterification, acid hydrolysis, enzymatic modification, genetic modification, and their combined modifications. A better understanding of these features has the potential to lead to starch-based products with targeted structures and optimized properties for specific applications.

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.

Combined ultrasound and germination treatment on the fine structure of highland barley starch

Highland barley is a grain crop grown in Tibet, China. This study investigated the structure of highland barley starch using ultrasound (40 kHz, 40 min, 165.5 W) and germination treatments (30℃ with 80% relative humidity). The macroscopic morphology and the barley's fine and molecular structure were evaluated. After sequential ultrasound pretreatment and germination, a significant difference in moisture content and surface roughness was noted between highland barley and the other groups. All test groups showed an increased particle size distribution range with increasing germination time. FTIR results also indicated that after sequential ultrasound pretreatment and germination, the absorption intensity of the intramolecular hydroxyl (-OH) group of starch increased, and hydrogen bonding was stronger compared to the untreated germinated sample. In addition, XRD analysis revealed that starch crystallinity increased following sequential ultrasound treatment and germination, but a-type of crystallinity remained after sonication. Further, the Mw of sequential ultrasound pretreatment and germination at any time is higher than that of sequential germination and ultrasound. As a result of sequential ultrasound pretreatment and germination, changes in the content of chain length of barley starch were consistent with germination alone. At the same time, the average degree of polymerisation (DP) fluctuated slightly. Lastly, the starch was modified during the sonication process, either prior to or following sonication. Pretreatment with ultrasound illustrated a more profound effect on barley starch than sequential germination and ultrasound treatment. In conclusion, these results indicate that sequential ultrasound pretreatment and germination improve the fine structure of highland barley starch.

Influences of high hydrostatic pressure on structures and properties of mung bean starch and quality of cationic starch

It is difficult to improve the quality of chemical-modified starch by traditional technology. Hence, in this study, mung bean starch with poor chemical activity was used as raw material, the native starch was treated and the cationic starch was prepared under high hydrostatic pressure (HHP) at 500 MPa and 40 °C. By studying the changes in the structure and properties of native starch after HHP treatment, the influence mechanism of HHP on improving the quality of cationic starch was analyzed. Results showed high pressure could make water and etherifying agent enter the starch granules through pores, and HHP made the structure of starch undergone three stages similar to mechanochemical effect. After HHP treated for 5 and 20 min, the degree of substitution, reaction efficiency and other qualities of cationic starch increased remarkably. Hence, proper HHP treatment could help to improve the chemical activity of starch and quality of cationic starch.

Physical, Chemical and Biochemical Modification Approaches of Potato (Peel) Constituents for Bio-Based Food Packaging Concepts: A Review

Potatoes are grown in large quantities and are mainly used as food or animal feed. Potato processing generates a large amount of side streams, which are currently low value by-products of the potato processing industry. The utilization of the potato peel side stream and other potato residues is also becoming increasingly important from a sustainability point of view. Individual constituents of potato peel or complete potato tubers can for instance be used for application in other products such as bio-based food packaging. Prior using constituents for specific applications, their properties and characteristics need to be known and understood. This article extensively reviews the scientific literature about physical, chemical, and biochemical modification of potato constituents. Besides short explanations about the modification techniques, extensive summaries of the results from scientific articles are outlined focusing on the main constituents of potatoes, namely potato starch and potato protein. The effects of the different modification techniques are qualitatively interpreted in tables to obtain a condensed overview about the influence of different modification techniques on the potato constituents. Overall, this article provides an up-to-date and comprehensive overview of the possibilities and implications of modifying potato components for potential further valorization in, e.g., bio-based food packaging.

Prevents kudzu starch from agglomeration during rapid pasting with hot water by a non-destructive superheated steam treatment

Superheated steam (SST) at different moisture contents (10% ∼ 30%) was used to prevent the agglomeration of kudzu starch during rapid pasting with hot water. Changes in pasting-related properties and multi-scale structures were investigated. At moisture content of 20%, SST dramatically reduced the agglomeration rate from 42.20% to 2.97% without destroying the microstructure of kudzu starch or deteriorating the rheological properties of kudzu starch paste, which was superior to the conventional pre-gelatinization treatment. The agglomeration was prevented mainly by decreasing the swelling power and increasing the pasting temperature of kudzu starch. The slight disruption of multi-scale structures may facilitate faster water absorption by kudzu starch, but it was not the primary prevention mechanism. Moreover, the solubility of kudzu starch was not related to the agglomeration, since it was significantly decreased by SST. Our findings could provide new insights into the rapid pasting of starchy powders or flours with hot water.

Pickering emulsion stabilized by hydrolyzed starch: Effect of the molecular weight

HYPOTHESIS

The emulsifying ability of starch is influenced by its molecular weight. Reducing the molecular weight of starch is expected to influence interfacial adsorption and membrane elasticities, thereby affecting its emulsifying ability through Pickering effects. Hence, it should be possible to tailor the emulsifying ability of starch by adjusting its molecular weight.

EXPERIMENTS

Waxy corn starch (CS) and rice starch (RS) were hydrolyzed with pullulanase to obtain high (HM) and low molecular weight (LM) fractions. After the molecular weight was determined by size exclusion chromatography, the fractions were used to prepare model oil-in-water emulsions. The stability, microscopy, and particle size of the emulsions were characterized, and the underlying emulsification mechanism was subsequently studied through dynamic laser scattering, surface tension analysis, interfacial rheology, and Pearson's correlation calculations.

FINDINGS

In the molecular weight range obtained in this study, the smaller the molecular weight of starch, the stronger its emulsifying ability. The decrease in molecular weight resulted in considerable different adsorption and interfacial elasticities with smaller fractions occupying less area on the interface and forming interfaces with higher elasticities, resulting in higher stabilities through Pickering effects. Results thus suggest that the emulsifying ability of starch may be tailored by adjusting its molecular weight.

Microcapsules with slow-release characteristics prepared by soluble small molecular starch fractions through the spray drying method

The utilization of starch in the food and medical industry can be facilitated by using new non-chemical methods to make starch the only wall material to encapsulate microcapsules. In this study, soluble small molecular fraction obtained from corn starch by gelatinization and centrifugation methods and commercial soluble starch were used independently to encapsulate oil under the condition that wall material and core material were 2:1. Molecular weight of these starch fractions was measured firstly. The peak molecular weight of the soluble small molecular fraction of corn starch and commercial soluble starch was 3.537 × 105 Da and 2.720 × 104 Da, respectively. Basic physicochemical characteristics and application characteristics of the microcapsules were then characterized and compared. The soluble small molecular fraction of corn starch encapsulated microcapsule and the commercial soluble starch encapsulated microcapsule had high encapsulation efficiency (higher than 88%), high boiling water solubility (higher than 74%), high rehydration stability (higher than 2 h). Most importantly, the encapsulated oil of these microcapsules could be slowly released under the action of α-amylase and amyloglucosidase. Overall, both the soluble small molecular fraction of corn starch and commercial soluble starch could be used as microcapsule wall materials and might have great application potential in food and medicine.

Gluten-Free Bread and Bakery Products Technology

Gluten, a protein fraction from wheat, rye, barley, oats, their hybrids and derivatives, is very important in baking technology. The number of people suffering from gluten intolerance is growing worldwide, and at the same time, the need for foods suitable for a gluten-free diet is increasing. Bread and bakery products are an essential part of the daily diet. Therefore, new naturally gluten-free baking ingredients and new methods of processing traditional ingredients are sought. The study discusses the use of additives to replace gluten and ensure the stability and elasticity of the dough, to improve the nutritional quality and sensory properties of gluten-free bread. The current task is to extend the shelf life of gluten-free bread and bakery products and thus extend the possibility of its distribution in a fresh state. This work is also focused on various technological possibilities of gluten-free bread and the preparation of bakery products.

Effects of Superheated Steam Treatment on the Allergenicity and Structure of Chicken Egg Ovomucoid

The aim of this study was to explore the effects of an emerging and efficient heating technology, superheated steam (SS), on the allergenicity and molecular structure of ovomucoid (OVM). OVM was treated with 120–200 °C of SS for 2 to 10 min. The allergenicity (IgG/IgE binding abilities and cell degranulation assay) and molecular structure (main functional groups and amino acids modification) changes were investigated. The IgG-binding ability of OVM decreased and the releases of β-hex and TNF-γ were inhibited after SS treatment, indicating that the protein allergenicity was reduced. Significant increases in oxidation degree, free SH content and surface hydrophobicity were observed in SS-treated OVM. The protein dimer and trimer appeared after SS treatment. Meanwhile, obvious changes occurred in the primary structure. Specifically, serine can be readily modified by obtaining functional groups from other modification sites during SS treatment. Moreover, the natural OVM structure which showed resistance to trypsin digestion was disrupted, leading to increased protein digestibility. In conclusion, SS-induced OVM aggregation, functional groups and amino acids modifications as well as protein structure alteration led to reduced allergenicity and increased digestibility.

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.

Physical modification on the in vitro digestibility of Tartary buckwheat starch: Repeated retrogradation under isothermal and non-isothermal conditions

The effects of repeated retrogradation (RR, range from 1 to 3 times) at different temperatures (4 °C; 4/25 °C, with a 24 h interval; 25 °C) on the in vitro digestibility and structures of Tartary buckwheat starch (TS) were investigated in this study. Results demonstrated that TS treated by RR for 1 time under 4/25 °C contained the maximum content of slowly digestible starch (SDS, 35.25%); TS treated by RR for 3 times under 25 °C contained the maximum content of resistant starch (RS, 54.92%). As the increase of RR cycle times, the value of relative crystallinity, the ratios of 1047/1022 cm^-1 and 995/1022 cm^-1 increased, the starch pore wall thickened, and more smooth fragments appeared (observed by scanning electron microscope), while the value of melting temperature range trended to decrease. The crystallization type of TS changed from type "A" to a mixture of "B + V" after retrogradation treatment. Pearson correlation analysis revealed that the content of rapidly digestible starch (RDS) was negatively correlated with the ratio of 995/1022 cm^-1, transition temperatures, and enthalpy (P < 0.05). These results would supply a potential method for the preparation of starch with slow-digesting properties, also improve the utilization and expand the application of TS.