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To tailor the properties and enhance the applicability of starch, various ways of starch modification have been practiced. Among them, physical modification methods (micronization, nonthermal plasma, high-pressure, ultrasonication, pulsed electric field, and γ-irradiation) are highly potential for starch modification considering its safety, environmentally friendliness, and cost-effectiveness, without generating chemical wastes. Thus, this article provides an overview of the recent advances in nonthermal physical modification of starch and summarizes the resulting changes in the multi-level structures and physicochemical properties. While the effect of these techniques highly depends on starch type and treatment condition, they generally lead to the destruction of starch granules, the degradation of molecules, decreases in crystallinity, gelatinization temperatures, and viscosity, increases in solubility and swelling power, and an increase or decrease in digestibility, to different extents. The advantages and shortcomings of these techniques in starch processing are compared, and the knowledge gap in this area is commented on.

Background Starches and proteins are two major types of biopolymer components, especially in many flour (starch)-based foods consumed worldwide, which provide energy and nutrition needed by the human body. In many such starch-based matrices (the main structural component of such foods), proteins and their interactions with starches greatly influence the matrix structure and properties. Studying the different roles played by proteins (endogenous and exogenous) in various starch-based food systems can provide a frame of reference for the design and production of improved starch-based food products with tailored properties and desirable nutritional functions. Scope and approach Significant efforts have recently been made to tailor the morphology, structure, and properties of many starch-based food systems, and thus to design various starch-based food products with satisfactory attributes. This review surveys the latest literature on starch-based matrices containing proteins. Discussed are the influences of proteins and their interactions with starches on the morphologies and structures (e.g. short- and long-range orders) of starch-based matrices, as well as on their pasting, thermal, rheological, textural, sensory, and digestive properties. Also, current understandings of structure–property links are presented, along with their implications on the production of various starchy foods (e.g. pastas, breads, cakes, and biscuits), including gluten-free versions. Key findings and conclusions Proteins in many starchy food matrices can encapsulate the starch phase (or be adsorbed on its surfaces) on a micron scale, and thereby interact with starch chains via both non-covalent (e.g. hydrogen bonding, hydrophobic, and electrostatic) and covalent bonds (e.g. via Maillard reactions). These facts and protein features (e.g. hydration and gelation abilities) can play major roles in inhibiting starch retrogradation (the reassembly of cooked starch chains into ordered structures) and in regulating various other properties of such starch-based matrices, including viscosity, transition temperatures, moduli, hardness, sensory, digestibility, and shelf-life. Despite the fact that the current literature presents considerable information on the structure–property relationships of many different starch-based matrices and their applications in the processing of various starchy foods (e.g. pastas, noodles, and biscuits), it is still highly necessary to define more comprehensive correlations among starch–protein interactions, starch–protein matrix structures, and the resulting properties of such food products.

This work concerns how starch-protein interplay affects the multi-scale structures (e.g., short- and long-range orders, nanoscale structure and morphology) of starch undergoing thermal processing (pasting) involving heating and cooling at high water content. An indica rice starch (IRS) and three proteins (whey protein isolate, WPI; soy protein isolate, SPI; casein, CS) were used. By inspecting rheological profiles of mixed systems before and after adding chemicals, IRS-WPI and IRS-CS showed mainly hydrophobic molecular interaction; and IRS-SPI exhibited hydrophobic, hydrogen bonding and electrostatic interactions. The RVA results revealed that, with starch and proteins as controls, starch-globular protein (WPI or SPI) interplay accelerated the swelling of starch granules (faster viscosity increase at initial pasting stage), and reduced the paste stability during heating (higher breakdown) and during cooling (higher setback); however, the starch-casein interactions resulted in opposed effects. Moreover, starch-protein interactions varied the multi-scale chain reassembly of starch into different structures during cooling. Observed could be fewer short- and long-range starch orders, and larger nonperiod structure (or colloidal clusters) on the nanoscale. On even larger scale to micron, IRS-globular protein molecules generated larger grids (with reduced number) in the gel network, and IRS-casein formed a more continuous gel network with less prominent tunnel-like features.

Separation of antioxidant peptides from complex food matrix is labor-intensive and time-consuming. The combination of peptidomics and bioinformatics may shorten this process. In this work, the gast...

Nowadays, resulting from disordered glucose and lipid metabolism, metabolic diseases (e.g., hyperglycemia, type 2 diabetes, and obesity) are among the most serious health issues facing humans worldwide. Increasing evidence has confirmed that dietary intervention (with healthy foods) is effective at regulating the metabolic syndrome. Whole grain rice (WGR) rich in dietary fiber and many bioactive compounds (e.g., γ-amino butyric acid, γ-oryzanol, and polyphenols) can not only inhibit starch digestion and prevent rapid increase in the blood glucose level, but also reduce oxidative stress and damage to the liver, thereby regulating glucose and lipid metabolism. The rate of starch digestion is directly related to the blood glucose level in the organism after WGR intake. Therefore, the effects of different factors (e.g., additives, cooking, germination, and physical treatments) on WGR starch digestibility are examined in this review. In addition, the mechanisms from human and animal experiments regarding the correlation between the intake of WGR or its products and the lowered blood glucose and lipid levels and the reduced incidence of diabetes and obesity are discussed. Moreover, information on developing WGR products with the health benefits is provided.

Colored brown rice shows better health benefits than polished rice, and there is great interest in the design of demanded cooking manners for brown rice. This investigation concerns how the change of cooking mode can slow starch digestion of colored brown rice by inspecting mainly starch structural changes during cooking. Compared to cooking Mode 1, the soaking of Mode 2, at higher temperature, probably enhanced water diffusion into rice matrices, thus strengthening starch lamellae without apparently altering rice morphology and ordered structures such as starch polymorphs and helices. The followed heating of Mode 2, with reduced time, more sufficiently disrupted rice structures, causing less prominent nonperiodic molecular organizations. At the final cooking stage, the braising of Mode 2, having faster temperature reduction for prolonged time, leading to similar rice morphology, reduced molecular orders (e.g., helices) and probably denser amorphous regions of nonperiodic organizations. Such features tended to increase packing density of molecular chains (mainly starch) in rice matrices, thus slowing the enzyme diffusion in rice matrices and associated binding and catalysis events. In this way, a reduced starch digestion rate and increased resistant starch (RS) and slowly digestible starch (SDS) were seen for the rice following Mode 2 cooking.

This work investigated the multiscale structure and gelatinization properties of different oil-modified crosslinked starches and their relationship with the texture and microstructure of surimi/starch composite gels. The results showed clusters were formed by the agglomeration of starch, with oil on the surface of granules. Oil modification did not damage the long-range crystalline structure but impaired the short-range ordered structure. A high oil modification degree was shown to weaken starch structure, in contrast to an adverse effect for a high crosslinking level. Furthermore, compared with crosslinked starches, Oil-CTS had lower pasting temperature and gelatinization enthalpy, a higher viscosity, and better gel-reinforcing effect. Correlation analysis revealed the texture of surimi/starch composite gels was negatively correlated with the helical structure and pasting temperature of starch, and positively correlated with final and setback viscosity of starch and the swollen size of starch granules in surimi gel.

This work investigated the structure and physicochemical properties of cross-linked tapioca starch (CTS), acetylated tapioca starch (ATS) and their counterparts (Oil-CTS and Oil-ATS). The results showed oil on the interface of starch granules promoted granule agglomeration after oil modification. Besides, oil modification could increase granule size and destroy the crystalline structure but did not affect the molecular structure of starch. Meanwhile, oil-modified starches did not form the V-type structure like amylose-fatty acid complex, suggesting that oil could not enter the helical cavity of amylose to form complex. Furthermore, compared with CTS and ATS, oil-modified starches had higher shear resistance, lower viscosity and gelatinization enthalpy. Notably, Oil-CTS possessed excellent emulsion stability, with the potential application as an emulsion stabilizer. This study revealed oil modification as an innovative method to endow starch with high shear resistance, low gelatinization enthalpy and excellent emulsion stability to meet the demands of food industries.

Cold-chain cooked rice is a widely-consumed instant food. While the quality of cooked rice as affected by processing has been widely studied, it remains largely unexplored how concurrent cold-chain conditions (e.g., refrigeration time with specific water contents) tailor the structure and starch digestibility of cooked rice. Here, as shown by combined techniques (e.g., scanning electron microscopy and small angle X-ray scattering), the cold storage (1 to 3 days) of cooked rice at 1.1:1 w/w water-to-rice ratio increased the uniformity of the rice matrix, strengthened the nonperiodic structure, and allowed more B-type starch crystallites and short-range orders. This induced an increase in the slowly digestible starch (SDS) content (from ca. 33.7% to 38.5%) as the refrigeration time rose. In contrast, for cooked rice with 1.5:1 w/w water-to-rice ratio, the cold storage (mainly 1 day) strengthened the matrix uniformity and the nonperiodic structure, and eventually increased the resistant starch (RS) content from ca. 10.3% to 17.7%. The present data could facilitate the design of cold-chain cooked rice with tailored starch digestibility.

Different characterization methods spanning length scales from molecular to micron scale were applied to inspect the microstructures and mechanical/hydrophilic features of agar/konjac glucomannan (KGM) films prepared under different drying temperatures (40 and 60 °C). Note that the lower preparation temperature (40 °C) could increase the strength and elongation of agar/KGM films at high KGM levels (18:82

The practical features (e.g., sol-gel, mechanical and hydrophobic) of biopolymer systems are crucial for their materials applications. This work reveals how polyvinyl alcohol (PVA) inclusion affects the practical features of agar/konjac glucomannan (KGM) system. From rheological analysis, incorporating PVA (especially 6%) enhanced the chain entanglements of resulted ternary solution (A70K24P6) with stabilized sol-gel transition point. Such effect not only increased the zero-shear viscosity (ca. 1.5 times that of agar/KGM counterpart) and structural recovery degree of A70K24P6 solution, but also caused reduced crystallites and simultaneously increased tensile strength, elongation at break and hydrophobicity for A70K24P6 film from solution dehydration. This ternary film exhibited a tensile strength of ca. 105 MPa, an elongation at break of ca. 20%, and a water contact angle of ca. 97.6°. Additionally, incorporating PVA almost unaffected the morphology of film fracture surface. These results are valuable for the design of agar/KGM systems with improved practical features.

This study explored how microwave reheating (to about 73 °C at different power levels) affects the microstructure and digestion characteristics of cooked rice with different water contents (1.1 and 1.5 times that of rice in weight). Irrespective of water content, mainly the V-type crystallites remained after microwaving reheating, with slight changes in other multi-scale structural features. Only at a relatively high water content (1.5) and with a power level high enough could short-range order be reduced. Such microwave reheating increased the digestion resistance of cooked rice. At a water content of 1.1 times, increasing the microwave power led to a decreased rapid digestible starch (RDS) content and an increased resistant starch (RS) content. With a higher water content (1.5), the enhancement of digestion resistance with higher microwave power was less significant but still, a reduced slowly digestible starch (SDS) content and a higher RS content were observed.

The gelatinization and retrogradation behaviors of crosslinked/acetylated tapioca starches (CA-TS) as affected by crosslinking and acetylation degrees were studied. Likewise, the influence of gelatinization and retrogradation of CA-TS on the gel properties of fish myofibrillar protein (MP) was investigated at the weight concentrations of 6.0% MP and 0.3% CA-TS. Highly-crosslinked TS had a higher pasting temperature and heat-stability, and lower gelling capacity than other CA-TS, while highly-acetylated TS had a lower pasting temperature and higher peak viscosity. X-ray diffraction (XRD) results showed the characteristic diffraction peaks of native CA-TS disappeared after gelatinization and did not reappear after retrogradation. However, polarized light micrographs showed bright spots in the retrograded MP/CA-TS gels. Additionally, high level of crosslinking delayed the water-absorption, swelling and rupture of starch granules, further inhibiting their concentrating and filling effects within the MP network. But high level of acetylation enabled the starch gelatinization to occur before the complete gelation of MP, thus interfering with the formation of MP gel network. Meanwhile, low-crosslinked/acetylated TS exhibited a suitable pasting temperature (>61 °C), relatively high peak viscosity and gelling capacity, which can significantly enhance the storage modulus G′ and textural properties of MP. Furthermore, the rapid increase in the G′ of MP/CA-TS composites during cooling (90 → 20 °C) indicated that the partial crystal CA-TS might act as a semi-rigid filler that enhanced the MP gel strength. SEM photographs showed the formation of an extremely homogeneous and compact MP network in presence of low-acetylated TS in contrast to a loose network in presence of highly-acetylated TS.

Cellulose nanofibers (CNFs) were isolated from lettuce peel using specific chemical treatments, i.e., NaOH alkali solution treatment, NaClO2 bleaching and sulfuric acid hydrolysis. Both cellulose and cellulose nanofibers were characterized by Fourier transform infrared spectroscopy (FTIR) and X-ray diffraction (XRD). Morphological features and particle size distribution of cellulose and nanostructures were explored using transmission electron microscopy (TEM), scanning electron microscope (SEM) and the Malvern laser particle size analyzer. Results showed that particle diameters of the majority of morphological nanofibrillated cellulose were in the range of 10 to 20 nm, and length between 190 to 460 nm. The crystallinity index reached 41.57%, which increased by 117.3% compared with the raw material. The crystalline type of lettuce peel nanofibers belongs to cellulose type I. Moreover，thermal degradation temperature of CNFs is 271.7 °C which is 47.3 °C higher than that of the untreated peel. The CNFs obtained from these treatments can be used as additional biocomposites in reinforced polymer manufacturing processes or the food industry.

Effect of yeast β-glucan (YG) at different contents on gel properties, spatial structure and sensory characteristics of silver carp surimi was investigated by texture analysis, magnetic resonance imaging (MRI), light microscopy with eosin staining and sensory evaluation. The 2%YG addition dramatically improved the water-holding capacity (WHC), hardness, springiness, chewiness and gel strength of surimi gel. According to stress relaxation fitted by three-element model, YG addition shortened relaxation time (τ) and increased equilibrium and decay elastic coefficient (E0 and E1) of surimi gel, suggesting an increasing hardness and elasticity and a decreasing viscosity. When YG added, a part of free water transferred into immobile water and the gel surface had more water than the intermediate portion. In surimi/YG gels, YG formed approximately circular voids and uniformly dispersed in continuous network of surimi matrix. As YG increased (0–2%), YG competed with surimi for water, which caused effective concentration of surimi protein increased and gel-forming ability enhanced. Next, the water-absorbing and swelling YG exerted pressure on surimi matrix and caused the matrix more compact and firm. Besides, YG as semi-rigid fillers filled the interspace between protein network to reinforce its structure. However, with a further increase in YG (3–5%), the number and size of voids formed by YG drastically increased, and excess YG instead of surimi could not compensate for the decrease in surimi gel-forming ability, but hinder cross-linking of proteins in surimi to weaken, even disrupt continuous network of surimi matrix. Additionally, YG reduced off-odor from freshwater fish and remained fish delicious taste.

Herein, we concern the multi-scale structure and properties (digestibility and pasting) of highland barley starch following heat moisture treatment (HMT). With the moisture content (MC) rose, HMT reduced the molecular weight (molar mass) but increased the amylose content and the V-type polymorph. When the MC was lower than 25%, a higher MC resulted in increases in the long- (crystallites) and short-range orders (double helices, etc.); nonetheless, a further elevated MC (i.e., 30%) tended to reduce the amounts of these ordered structures. Also, the SAXS results reveal that the lamellar structure could be gradually vanished by the increased MC. These structural changes on multiple scales transformed part of rapidly digestible starch into the slowly digestible and/or resistant forms, accompanied by higher pasting temperature and lower paste viscosity. Hence, highland barley starch following HMT can serve as a food ingredient with reduced digestion rate and paste viscosity.

With screening of Lactobacillus fermentum M9 and Candida santamariae Y11 from a natural fermentation broth (Jinjian) for rice noodle production, this work concerns how fermentation with M9:Y11 suspensions of different volume ratios affects the texture and sensory features of rice noodles. The M9:Y11 strains regulated rice structures and thus the physicochemical features of rice noodles. In particular, 5:5 and 8:2 v/v M9:Y11 strains endowed rice noodles with better texture and sensory performance than did Jinjian. The underlying mechanism regarding evolutions in rice noodle properties was discussed from a rice structural view. Specifically, the fermentation disrupted rice ordered structures (e.g., starch crystallites) and broke starch granules, which was preferable for the swelling and molecule leaching of rice noodle matrixes with enhanced molecule interactions. Such noodle matrixes were robust to resist imposed force, thus exhibiting increased hardness, chewiness and mouthfeel. More interestingly, the 5:5 and 8:2 v/v M9:Y11 strains less prominently altered starch granule integrity, contributing to increasing hardness, chewiness and mouthfeel of rice noodles associated with robustness of swollen granule shell within rice gel matrixes. These two ratios of M9:Y11 strains also improved the color, aroma and taste for rice noodles.

This study investigated the texture properties, water mobility and microstructure of surimi gel added with crosslinked tapioca starch (CTS) and acetylated tapioca starch (ATS), and their counterparts modified with oil (Oil-CTS and Oil-ATS, respectively). Both Oil-CTS and Oil-ATS could improve the breaking force, deformation and elasticity of surimi gel, especially Oil-CTS. Additionally, oil-modified starches could increase the water-holding capacity of surimi gels and prompt the transformation of free water to bound water, resulting in the decrease of water mobility. The difference between oil-modified starches and their counterparts in gel-enhancing effect is due to the swelling ability and different microstructure of surimi/starch gels. Namely, oil-modified starches prompted the formation of a more homogeneous and compact gel network, endowing the surimi/Oil-CTS gel with tiny pores due to its restricted swelling property, while others were opposite. Raman spectral results further unveiled that the addition of oil-modified starches promoted the protein conformational transition from α-helix to β-sheet and β-turn, as well as a decrease of ionic bonds and an increase of hydrogen bonds and hydrophobic interactions of surimi gel, which were beneficial to form firm and compact gel structure. The overall results indicated the new oil-modified starches (especially Oil-CTS) have great potential to improve the quality of surimi-based products.

To date, how the pH conditions of thermal processing tailor the structure and digestibility of resulting starch-based complexes remains largely unclear. Here, indica rice starch (IRS), stearic acid (SA), and a whey protein isolate (WPI) were used as materials. Increasing the pH value from 4 to 8 during thermal processing (pasting) mainly suppressed the starch digestion of starch-WPI-SA complexes rather than starch-SA counterparts. The starch-SA complexes showed moderate structural changes as the pH value rose, and there was less rapidly digestible starch (RDS) only at pH 8. For the starch-WPI-SA complexes, an increased pH value allowed larger nonperiodic structures and more V-type starch crystallites, with almost unchanged short-range orders but apparently collapsed networks at pH 8. Such ternary complexes displayed more resistant starch (RS) as the pH value rose. The ternary sample at pH 8 contained ca. 29.87% of the RS fractions.

While the changes in starch physicochemical properties resulting from typical dry ball milling (usually requiring hours) have been widely studied, there has been limited knowledge regarding how wet ball milling (with liquid media) affects starch structure and properties. This work was to investigate the effect of wet ball milling on the multiscale structures and pasting behavior of indica rice starch. For this starch, increasing ball-milling time resulted in decreases in particle size, crystallinity, and double-helix content and increases in single-helix and amorphous contents. Only 15 min of ball milling effectively destroyed the semicrystalline lamellar structure and resulted in the cleavage of long chains from amylose and amylopectin backbones and marked decreases in pasting temperature and viscosity, while ball milling for an even longer duration did not cause significant changes in these aspects. Thus, this work shows the high efficacy of wet ball milling for modifying rice starch structure and properties.

Starch/agar systems are highly potential for versatile applications such as packaging and biomedical materials. Here, how combined factors affect the features of a starch/agar binary system were explored. An increase of starch amylose/amylopectin ratio from 0/100 to 50/50 increased the sol-gel transition temperature and gel hardness of the aqueous starch/agar mixture. An increased agar content (mainly from 30% to 70%) allowed increases in both the tensile strength (reaching 50–60 MPa) and elongation at break of the starch/agar binary films. This phenomenon should be related to the strengthened crystalline structure and the weakened hydrogen bonding between starch chains (reflected by infrared spectroscopy). Furthermore, a higher relative humidity (from 30% to 70%) allowed enhanced chain interactions and probably nanoscale molecular order but weakened the crystalline structure, leading to reduced tensile strength and increased elongation at break. This work could facilitate the design of starch/agar binary systems with improved sol-gel and mechanical performance.

This work evaluated the effect of micro- and nano-starch (MS and NS) on the gel properties of fish myofibrillar protein (MP). Both MS and NS could enhance MP gel performance in terms of breaking force, elasticity and water holding capacity (p 0.05), with more significant effect from NS than MS. The difference between NS and MS in enhancement effect on MP gel is due to nano-size effect and different microstructures of MP/MS and MP/NS gels, with NS rather than MS contributing to the continuity of MP network. Synchrotron FTIR micro-spectroscopic images further verified that NS with large specific surface had good compatibility with MP, while MS was embedded in MP matrix with evident phase separation. Additionally, β-sheet still dominated the secondary structure of all gels, although adding both MS and NS could change molecular interactions, such as weakening ionic bonds and hydrogen bonds, and strengthening hydrophobic interactions.

Natural biopolymers, which are renewable, widely available, biodegradable, and biocompatible, have attracted huge interest in the development of biocomposite materials. Herein, formulation–property relationships for starch/agar composite films were investigated. First, rapid visco analysis was used to confirm the conditions needed for their gelation and to prepare filmogenic solutions. All the original crystalline and/or lamellar structures of starch and agar were destroyed, and films with cohesive and compact structures were formed, as shown by SEM, XRD, and SAXS. All the plasticized films were predominantly amorphous, and the polymorphs of the composite films were closer to that of the agar-only film. FTIR results suggest that the incorporation of agar restricted starch chain interaction and rearrangement. The addition of agar to starch increased both tensile strength and elongation at break, but the improvements were insignificant after the agar content was over 50 wt.%. Contact angle results indicate that compared with the other samples, the 4:6 (wt./wt.) starch/agar film was less hydrophilic. Thus, this work shows that agar dominates the structure and properties of starch/agar composites, and the best properties can be obtained with a certain starch/agar ratio. Such composite polysaccharide films with tailored mechanical properties and surface hydrophilicity could be useful in biodegradable packaging and biomedical applications (wound dressing and tissue scaffolding).

While the cooking of rice into porridge or similar foods is widely practiced, how microwave treatment, a rapid heating technology, changes the structure of rice starch with excess water remains largely unexplored. This work describes the multiscale structural changes of indica rice starch (IRS) with high water contents (70, 80, and 90 wt %, wet basis) subjected to microwave treatment for 1–3 min. Microwave treatment destructed crystalline lamellae, changed the crystalline type from A to B+V, and decreased crystallinity and double-helix content. While these changes depend on both water content and treatment time, the former had a stronger effect due to combined effects of water and heat for starch gelatinization. Interestingly, a highly porous material can be obtained simply upon microwave treatment of IRS for 3 min at a water content of 90 wt %. Thus, this work presents a simple method for creating such material promising for encapsulation and delivery applications.\ud \ud

This work aims to understand the relation between multi-scale structural changes and in vitro digestion of tapioca starch modified by wet-media milling. The native starch granules were smooth and difficult to digest due to the hindrance of enzymes entry into the granules by the concentric shell architecture. However, 1-min milling could break the smooth surface of starch granules, weakening shell architecture and increasing k

Core-shell structural capsules can encapsulate various food ingredients (e.g., nutrients), thus being highly potential for the design of many food products. This work reports how the gum (xanthan, locust bean or gellan) inclusion tailors the practical features of agar/konjac glucomannan (KGM) system for fabricating the core-shell structural capsules. The rheological and textural analyses revealed that xanthan gum inclusion could simultaneously increase the sol-gel transition point and gel strength (ca. 1.6 times higher) of agar/KGM system. The composite gels were dehydrated to generate shell materials. The materials including xanthan or locust bean gum showed stronger chain interactions than did that including gellan gum, accompanied by weakened crystalline features for the different shell materials. Again, compared to the agar/KGM counterpart, the shell materials including xanthan gum could display a similar tensile strength (close to 50 MPa) but an evidently increased elongation at break (ca. 2.5 times higher). Then, these agar/KGM based systems were used to prepare core-shell structural capsules. The capsules based on agar/KGM/xanthan gum materials exhibited the highest roundness and breaking stress. Regarding this, the increased sol-gel point reduced the time required for droplet hardening (to generate core-shell gel balls); such fact, together with the higher gel strength, weakened the deformation of gel balls and thus increased the roundness and breaking stress of capsules (resulting from drying of gel balls).

Background A decreasing freshness occurrs in Ctenopharyngodon (C.) idellus during post-mortem storage. In the present study, chitosan-glucose Maillard reaction products (CG-MRPs) were prepared by heating chitosan and glucose at different reaction temperatures and then used for preserving the freshness and quality of C. idellus fillets during cold storage (4 °C). Results High temperature enhanced the chitosan-glucose Maillard reaction and promoted the accumulation of melanoidins and intermediate compounds. The reducing power of CG-MRPs increased with an increasing reaction temperature. CG-MRPs inhibited the microbial growth rate and retarded the oxidation of proteins, lipids and nucleotides in C. idellus fillets by suppressing total bacterial count, total volatile basic nitrogen, thiobarbituric acid reactive substances and K values during cold storage. Furthermore, CG-MRPs prolonged shelf-life. The fillets treated with the CG-MRPs prepared at 120 °C showed an especially longer shelf-life (7 days). The preservative effect of CG-MRPs on fillets was the result of antibacterial components (melanoidins, reductone and furfural) in CG-MRPs and a reducing power against the oxidative degradation of proteins, nucleotides and lipids in C. idellus fillets. Conclusion The present study demonstrates that, for C. idellus fillets, treatment with CG-MRPs prepared at 120 °C for 40 min could be a feasible approach for maintaining the freshness of C. idellus fillets and prolonging shelf-life during cold storage. © 2018 Society of Chemical Industry.

This work concerns the multi-scale supramolecular structures and physicochemical properties of two small adlay seed starches (Q-2 and P-6) and a big adlay seed starch (BW). Among the three starches, P-6 exhibited unique hierarchical structures and thus thermal and pasting properties. The underlying mechanism on starch property differences was discussed from a hierarchical (multi-scale) structural view. Specifically, P-6 possessed the lowest granule size, the intermediate lamellar thickness and compactness, and the highest contents of helices and crystallites with a relatively high flaw degree. These multi-scale structures were most susceptible to hydrothermal effects, eventually showing the lowest thermal transition and pasting temperatures. Also, this sample had the highest paste viscosities related to the swelling degree of starch granules and the water-holding ability of starch molecules. The shell of the fully swelled granules (granule ghosts) for P-6 were most robust under shearing and heating, resulting in the lowest breakdown viscosity (i.e., the highest paste stability during heating). The strongest assembly capacity for the starch chains of P-6, as indicated by its highest content of orders in untreated granules, induced a prominent increase in the paste viscosity during cooling. The results here indicate that P-6 may serve as functional agents such as thickeners with low pasting temperature as well as high viscosity and high paste stability under shearing and heating.

Using combined analytical techniques, this work discloses how citric acid (CA) treatment affects the pasting features of starch from a view of multi-scale structural evolutions. The treatment induced disruption events in starch multi-level structures and thus modulated the pasting behaviors. A structure-property relationship was proposed to rationalize CA effects on starch pasting properties. Specifically, CA disrupted starch structures from molecular scale to micron scale, eventually reducing pasting temperature and paste viscosities. Interestingly, unlike previous findings that acid hydrolysis normally reduces the breakdown viscosity, the CA here resulted in regulated breakdown viscosity (paste stability under shearing and heating) related to concurrent effects from granule surface corrosion and molecule degradation. Moreover, the molecule degradation of starch weakened its chain rearrangement tendency, allowing increased paste stability during cooling. Also, simply altering CA concentration effectively regulated starch structural and pasting features. Hence, compared to untreated counterpart, the CA-treated starch may serve as food agents with reduced paste viscosity, regulated paste stability under heating and increased paste stability during cooling.

The surface hydrophobicity of starch-based films could be regulated using a two-step surface modification method. Such modification was realized by grafting with alkanols of different chain lengths (hexanol, dodecanol and octadecanol) on the surface of starch-based films. The grafting of alkanol increased the mobility of glycerol as the plasticizer within the film surface. Also, this grafting increased the mass ratio of carbon to oxygen on the film surface but reduced the mass ratio of carbon to nitrogen. Under the same reaction conditions, there were fewer dodecyl chains grafted onto the film surface than hexyl or octadecyl chains. Furthermore, the results revealed that the surface hydrophobicity of starch-based films could be enhanced by simply increasing the alkyl chain length. Also, fewer alkyl chains tended to reduce the surface hydrophobicity of the films. These results are valuable for the rational design of starch-based materials with demanded hydrophobic properties.

The impacts of transglutaminase (TG) and glucose oxidase (GOX) on the protein polymerization in whole-wheat dough (WWD) were investigated. The addition levels were 0.5, 1.5, 3.0, and 6.0 U/g (flour), respectively. Both TG and GOX enhanced dough strength by increasing the development time, stability, and resistance of WWD. A more continuous and compact dough structure was produced by the enzymes, and GOX resulted in thicker and stronger gluten strands than TG as indicated in dough microstructure graphs. GOX was more effective in promoting protein polymerization by showing more enhanced bands in protein electrophoresis patterns. Moreover, increased α-helix and β-sheet conformation by TG and GOX confirmed more polymerized gluten and stable secondary structure formed in WWD. By reducing free water, both enzymes increased the population of less-tightly bound water, indicating enhanced water availability to gluten. The results suggest that TG and GOX could enhance protein polymerization and gluten development in WWD; GOX was more efficient in inducing strengthened gluten network and increasing dough strength than TG.

This work discloses the multi-level structure and thermal behaviors of hydrophobic, propionylated starch-based films as affected by the amylose contents of starch materials used. Scanning electron microscopy results showed that amylose promoted the formation of more compact structure within the film matrices. Also, small and wide angle X-ray scattering analysis revealed that higher amylose content was preferable for the formation of new orders on nanoscale and crystallites. With these structural changes, the viscoelasticity of amorphous short chains was enhanced and the glass transition temperature was reduced by the increased amylose content; but the depolymerization of macromolecules and the decomposition of molecular bonds were postponed, since the increase in starch crystallites restricted the motion of adjacent amorphous regions. Hence, this work provides valuable information for rational design of hydrophobic starch-based films with desired thermal features by simply regulating the amylose content of starch raw materials.

The fish oil microcapsules were prepared via spray drying using octenyl succinic anhydride–linked starch (OSA-S) and maltodextrin (MD) as wall materials. The storage stability and in vitro release of entrapped oil were investigated in different storage temperatures and pH (3, 4, 5, 6, and 7). The structural properties of microcapsules were analyzed with scanning electron microscope. Results showed that the oxidation of fish oil microcapsule stored at 60 °C were more serious than 4 °C and 25 °C. Moreover, higher oxidation deterioration was found at pH 3, 4, and 5. For reconstituted emulsions (RCE) of microcapsule, 25 °C and pH 7 contributed to the physical stability, comparing to 60 °C and pH 3–6. Finally, higher release rate (83.73%) of encapsulated fish oil within simulated gastric fluid indicated that the wall materials complex was conducive to the bioavailability of core material under intestinal condition. Herein, the results of this investigation will enrich the comprehensive understanding of the appropriateness of the combination of octenyl succinic anhydride-linked starch and maltodextrin as encapsulation materials.

Encapsulation systems have gained significant interest in designing innovative foods, as they allow for the protection and delivery of food ingredients that have health benefits but are unstable during processing, storage and in the upper gastrointestinal tract. Starch is widely available, cheap, biodegradable, edible, and easy to be modified, thus highly suitable for the development of encapsulants. Much efforts have been made to fabricate various types of porous starch and starch particles using different techniques (e.g. enzymatic hydrolysis, aggregation, emulsification, electrohydrodynamic process, supercritical fluid process, and post-processing drying). Such starch-based systems can load, protect, and deliver various food ingredients (e.g. fatty acids, phenolic compounds, carotenoids, flavors, essential oils, irons, vitamins, probiotics, bacteriocins, co-enzymes, and caffeine), exhibiting great potentials in developing foods with tailored flavor, nutrition, sensory properties, and shelf-life. This review surveys recent advances in different aspects of starch-based encapsulation systems including their forms, manufacturing techniques, and applications in foods.

The multi-scale structures and pasting properties of starch in WWF were investigated after superfine grinding. Five particle size distributions of WWF and their corresponding starch were obtained. The grinding process reduced the particle size of WWF and starch. However, a slight increase of fragments from starch granules was observed with enhanced grinding strength because of the small decrease in starch particle size and the existence of other WWF components that undertook some of shearing force and friction during grinding. A prominent reduction in starch crystallinity was resulted due to the destruction of crystalline structure by grinding. Small-angle X-ray scattering analyses indicated the disordering in starch semi-crystalline lamellae with thinner lamellae thickness. Additionally, the 13C Nuclear Magnetic Resonance spectra demonstrated the alterations in starch chain conformation by varying peak areas of starch carbons (C1 and C4). Along with these structural changes, Starch pasting characteristics showed substantial variations, indicating decreased viscosities and higher pasting stability. The results suggest that the grinding treatments influenced the structures and pasting properties of starch even at a non-separated state, the changes in starch structures were related to the variations in starch gelatinization characteristics.

The influences of bran particle size distribution on the protein polymerization and water mobility in whole-wheat dough (WWD) were investigated. Four bran particle size distributions were obtained by fine-grinding treatments and the mean particle sizes of reconstituted whole-wheat flour (WWF) were 242, 160, 114, and 45 μm, respectively. Mixolab parameters showed that WWF water absorption was increased with reduced bran particle size, and the 160 μm group exhibited a higher stability than any other WWF group. A more continuous gluten matrix and a more compact structure were observed in the 160 μm group due to its moderate bran particle size. Protein secondary structure analyses indicated the increased β-sheet conformation and reduced β-turns structure in the 160 μm group, demonstrating a more polymerized and stable gluten network formed. Additionally, 1H NMR measurements showed larger populations of tightly bound water in WWD due to the presence of arabinoxylan, and confirmed the strengthened gluten strength in the 160 μm group by indicating increased water availability to gluten proteins. The results suggest that modifying bran particle size is a potential method for protein polymerization enhancement and gluten formation improvement in WWD, but appropriate bran particle size is needed to strengthen gluten network.