Strategies to reduce fishy odor in aquatic products: Focusing on formation mechanism and mitigation means.

Aquatic products, integral to human diets, often bear a distinct fishy odor that diminishes their appeal. Currently, the formation mechanisms of these odoriferous compounds are not fully understood, complicating their effective control. This review aims to provide a comprehensive overview of key fishy compounds, with a focus on their formation mechanisms and innovative methods for controlling fishy odors. Fishy odors in aquatic products arise not only from the surrounding environment but also from endogenous transformations due to lipid autoxidation, enzymatic reactions, degradation of trimethylamine oxide, and Strecker degradation. Methods such as sensory masking, adsorbent and biomaterial adsorption, nanoliposome encapsulation, heat treatment, vacuum treatment, chemical reactions, and biological metabolic transformations have been developed to control fishy odors. Investigating the formation mechanisms of fishy odors will provide solid foundational knowledge that can inspire creative approaches to controlling these unpleasant odors.

Preparation, stability and controlled release properties of starch-based micelles for oral delivery of hydrophobic bioactive molecules.

Amphiphilic starches incorporating fatty acid ester chains of varying lengths and degrees of substitution (DS) were synthesized to fabricate starch-based micelles for oral delivery of hydrophobic bioactive molecules. The assembly of the amphiphilic starches is influenced by the concentration, temperature, and the chain length and DS of their fatty acid ester chain. Highly acidic environment can hydrolyze the amphiphilic starches, resulting in the formation of small-sized micelles. Conversely, high ionic concentration hinders the self-assembly of amphiphilic starches and the digestive fluids can dilute the amphiphilic starches concentration, leading to the micelle dissociation. However, amphiphilic starches with longer chain length and/or higher DS of the fatty acid ester chain possess greater hydrophobicity, enhancing the stability of starch-based micelles under varying conditions and favouring the protection of Trp-2 peptides during storage. The micelles demonstrate high cell bioaccessibility for Trp-2 peptides, with 59.25 % of Trp-2 peptides being transferred by the intestinal epithelium. These findings suggest a potential starch-based micelle system can be adjusted for the oral delivery of hydrophobic bioactive molecules.

A novel method for obtaining high amylose starch fractions from debranched starch.

High amylose starch shows wide applications in food and non-food-based industries. Traditional complex-precipitation approach for the amylose fractionation required a large volume of organic reagents and was possibly risky for food safety. The object of this work was to establish a novel method to obtain starch fractions rich in amylose from debranch starch through repeated short-term retrogradation and centrifugation. Four starch fractions were obtained with the amylose content of 52.08% (C1), 62.28% (C2), 63.58% (C3), and 64.74% (C4). The thermograms of samples displayed that multiple endothermic peaks were detected in C1 and C2 and only one endothermic peak with melting temperature over 120 °C were observed in C3 and C4, indicating their differences in retrogradation behavior. The chain length distribution results of sample exhibited that C1 and C2 contained more short chains (DP ≤ 24), while C3 and C4 consisted of mainly long chains (DP ≥ 25). Accordingly, the differences in fine structures could provide more choices for these fractionated high amylose starch to utilize in practical applications.

Preparation, multi-scale structures, and functionalities of acetylated starch: An updated review.

Acetylated starch has been widely used as food additives. However, there was limited information available regarding the impact of acetylation on starch structure and functionalities, as well as the advanced acetylation technologies. This review aimed to summarize current methods for starch acetylation and discuss the structure and functionalities of acetylated starch. Innovative techniques, such as milling, microwave, pulsed electric fields, ultrasonic, and extrusion, could be employed for environmental-friendly synthesis of acetylated starch. Acetylation led to the degradation of starch structures and weakening of the interactions between starch molecules, resulting in the disorganization of starch multi-scale ordered structure. The introduction of acetyl groups retarded the self-reassembly behavior of starch, leading to increased solubility, clarity, and softness of starch-based hydrogels. Moreover, the acetyl groups improved water/oil absorption capacity, emulsifiability, film-forming properties, and colonic fermentability of starch, while reduced the susceptibility of starch molecules to enzymes. Importantly, starch functionalities were largely influenced by the decoration of acetyl groups on starch molecules, while the impact of multi-scale ordered structures on starch physicochemical properties was relatively minor. These findings will aid in the design of structured acetylated starch with desirable functionalities.

Multi-responsive starch-based nanocapsules for colon-targeting delivery of peptides: In vitro and in vivo evaluation.

Colon-targeting delivery of insulin is surging great interests in revolutionizing diabetes. Herein, insulin-loaded starch-based nanocapsules developed by layer-by-layer self-assembly technology were rationally structured. Interactions between starches and the structural changes of the nanocapsules were unraveled to understand in vitro and in vivo insulin release properties. By increasing the deposition layers of starches, the structural compactness of nanocapsules increased and in turn retarded insulin release in the upper gastrointestinal tract. Spherical nanocapsules deposited at least five layers of starches could deliver insulin to the colon in a high efficiency according to the in vitro and in vivo insulin release performance. The underlying mechanism of the insulin colon-targeting release should ascribe to the suitable changes in compactness of the nanocapsules and the interactions between deposited starches after multi-response to the changes in pH, time and enzymes in gastrointestinal tract. Starch molecules interacted with each other much stronger at the intestine than that at the colon, which guaranteed a compact structure in the intestine but a loose structure in the colon for the colon-targeting nanocapsules. It suggested that rather than controlling the deposition layer of the nanocapsules, controlling the interaction between starches could also regulate the structures of the nanocapsules for colon-targeting delivery system.

Starch intrinsic crystals affected the changes of starch structures and digestibility during microwave heat-moisture treatment.

The structural and functional changes of starch during hydrothermal treatment are influenced by its intrinsic properties. However, how the intrinsic crystalline structures of starch affect changes in structure and digestibility during microwave heat-moisture treatment (MHMT) has not been well understood. In this study, we prepared starch samples with varying moisture content (10 %, 20 %, and 30 %) and A-type crystal content (4.13 %, 6.81 %, and 16.35 %) and investigated the changes in their structures and digestibility during MHMT. Results showed that starch with a high A-type crystal content (16.35 %) and moisture levels of 10 % to 30 % exhibited less ordered structures after MHMT, while starches with lower A-type crystal content (4.13 % to 6.18 %) and moisture content of 10 % to 20 % showed more ordered structures after treatment; but less ordered structures when the moisture content was 30 %. All starch samples had lower digestibility after MHMT and cooking; however, starches with lower A-type crystal content (4.13 % to 6.18 %) and moisture content of 10 % to 20 % displayed significantly lower digestibility after treatment compared to modified starches. Accordingly, starches contained content of A-type crystals of 4.13 %-6.18 % and moisture of 10 %-20 % potentially had better reassembly behaviors during the MHMT to slow starch digestibility in a larger magnitude.

A novel very small granular starch from Chlorella sp. MBFJNU-17.

Novel resources of very small granular starch are of great interests to food scientists. We previously found Chlorella sp. MBFJNU-17 contained small granular starch but whether the MBFJNU-17 was a novel resource of very small granular starch remained unresolved. This study isolated and characterized the starch from MBFJNU-17 in comparison with quinoa starch (a typical very small granular starch), and discussed whether the MBFJNU-17 could be a resource of very small granular starch. Results showed that chlorella starch displayed a smaller size (1024 nm) than quinoa starch did (1107 nm), suggesting MBFJNU-17 was a good resource of very small granular starch. Additionally, chlorella starch had less amylose, higher proportion of long amylopectin branches, more ordered structures, thinner amorphous lamellae, better paste thermostability, and slower enzymatic digestion than quinoa starch did. These findings indicated that Chlorella sp. MBFJNU-17 was a novel resource of very small granular starch with desirable thermostability and nutritional attributes.

Dietary compounds slow starch enzymatic digestion: A review.

Dietary compounds significantly affected starch enzymatic digestion. However, effects of dietary compounds on starch digestion and their underlying mechanisms have been not systematically discussed yet. This review summarized the effects of dietary compounds including cell walls, proteins, lipids, non-starchy polysaccharides, and polyphenols on starch enzymatic digestion. Cell walls, proteins, and non-starchy polysaccharides restricted starch disruption during hydrothermal treatment and the retained ordered structures limited enzymatic binding. Moreover, they encapsulated starch granules and formed physical barriers for enzyme accessibility. Proteins, non-starchy polysaccharides along with lipids and polyphenols interacted with starch and formed ordered assemblies. Furthermore, non-starchy polysaccharides and polyphenols showed robust abilities to reduce activities of α-amylase and α-glucosidase. Accordingly, it can be concluded that dietary compounds lowered starch digestion mainly by three modes: (i) prevented ordered structures from disruption and formed ordered assemblies chaperoned with these dietary compounds; (ii) formed physical barriers and prevented enzymes from accessing/binding to starch; (iii) reduced enzymes activities. Dietary compounds showed great potentials in lowering starch enzymatic digestion, thereby modulating postprandial glucose response to food and preventing or treating type II diabetes disease.

Conjugation of soy protein isolate (SPI) with pectin: effects of structural modification of the grafting polysaccharide.

Recently, there has been a great interest in enhancing the emulsifying properties of soy protein isolate (SPI) by Maillard reaction. As a commonly-used grafting polysaccharide, pectin has proved useful in modifying proteins. However, effects of its structural characteristics on conjugation are still not fully understood. To address this problem, we employed alkaline or/and enzymatic treatments to modify pectin and obtained three modified samples. Structural characteristics of pectin, including the molecular weight, degree of methoxylation and acetylation, and monosaccharide compositions were measured. When conjugated with SPI, pectin with lower molecular weight and less main chains induced higher conjugate yield. Fluorescence intensity and surface hydrophobicity of all conjugates markedly reduced compared to the original SPI, suggesting a more loosened protein structure after Maillard reaction. In this study, the enzymolysis pectin proved an optimum grafting polysaccharide considering the simple preparation procedures and the highest emulsifying properties of its resulting conjugates.

Starch crystal seed tailors starch recrystallization for slowing starch digestion.

Crystal seed significantly affected polymers homogeneous or heterogeneous crystallization. However, how starch crystal seed affected recrystallization of gelatinized starch and in turn digestibility were not clearly understood. Herein, effects of endogenous crystal seed on starch recrystallization and digestibility were herein investigated. Structures of retrograded starches characterized by Fourier transform infrared spectroscopy and X-ray diffraction indicated that endogenous A-type crystal seed significantly promoted starch reassociation to form well-defined crystalline structure. Notably, starch crystal seed-mediated retrograded starch contained more compact structures after cooking in comparison with that of retrograded starch mediation without the crystal seed, and therefore the crystal seed-mediated retrograded starch exhibited a lower digestibility. This study preliminarily indicated starch endogenous crystal seed significantly modulate starch retrogradation and digestibility, nevertheless, how recrystallization temperature, the content and crystalline structure of the crystal seed affect recrystallization behaviors of crystal seed-containing starch are part of future work.

Understanding how starch constituent in frozen dough following freezing-thawing treatment affected quality of steamed bread.

Understanding how starch constituent in frozen dough affected bread quality would be valuable for contributing to the frozen products with better quality. To elucidate the underlying mechanism, starch was fractionated from multiple freezing-thawing (F/T) treated dough and reconstituted with gluten. Results showed that F/T treatment destructed the molecular and supramolecular structures of starch, which were more severe as the F/T cycle increasing. These structural disorganizations made water molecules easier to permeate into the interior of starch granules and form hydrogen bonds with starch molecular chains, which elevated the peak, breakdown, setback and final viscosity of starch paste. In addition, F/T treatment resulted in decreased specific volume (from 1.54 to 0.90 × 103 m3/Kg) and increased hardness (from 42.98 to 52.31 N) for steamed bread. We propose the strengthened water absorption ability and accelerated intra- and inter-molecular rearrangement of starch molecules and weak stability of "starch-gluten matrices" would allow interpreting deteriorated bread quality.

Development of pullulan/carboxylated cellulose nanocrystal/tea polyphenol bionanocomposite films for active food packaging.

In this study, novel active films based on pullulan and carboxylated cellulose nanocrystal (C-CNC) incorporated with tea polyphenol (TP) was prepared by solution casting method. The effect of TP addition on the microstructural, mechanical, barrier, optical, functional properties of the resultant pullulan/C-CNC/TP (PC-TP) bionanocomposite films was systematically evaluated. Scanning electron microscopy showed that an appropriate TP adding was well distributed within the PC-TP bionanocomposite matrix. Fourier-transform infrared further revealed that new hydrogen bond was formed among the pullulan, C-CNC, TP. Addition of TP at an appropriate level (3%, w/w, on a dry basis of the weight of pullulan and C-CNC) led to stronger intermolecular interactions and more compact microstructure, and thus enhanced the water barrier properties, thermal stability and tensile strength of the resultant bionanocomposite films. Nevertheless, overloading of TP in the bionanocomposite films might produce some aggregations and thus have negative effects on their performance. In addition, the incorporation of TP significantly improved the UV-barrier properties, antioxidant activity and antimicrobial activity of PC-TP bionanocomposite films, while induced a decrease in the transmittance. These results revealed that PC-TP bionanocomposite films with TP at appropriate levels had potential to be used as active food packaging.

New insights into how starch structure synergistically affects the starch digestibility, texture, and flavor quality of rice noodles.

The functionalities of gluten-free rice noodles are significantly affected by starch hierarchical structures. Identifying the structures that synergistically determine noodle integrated functionalities is vital to designing health-promoting starchy foods with desirable consumer sensory and nutritional qualities. This study reports on the changes in starch structures and functionalities (starch digestibility, texture, and flavor) of rice noodles during household cooking processes (steaming, boiling, and stir-frying), and describes an underlying structure-functionality relationship. Results show that all the cooking processes examined increased starch reassembled ordered structures, especially short-range ordered structures, helical and crystalline structures, and ordered aggregate structures. Steaming and boiling led to a decrease in rapidly digestible starch (RDS) and an increase in slowly digestible starch, while stir-frying yielded a reduction in RDS content and an increase in resistant starch in rice noodles. Steaming and boiling decreased while stir-frying increased the flavor variety of noodles. All cooking processes examined altered noodle textures, with a significant increase in hardness, gumminess, and chewiness. Structure-functionality relationships suggested short-range ordered structures, crystalline structures, and the ordered molecular and aggregate structures of noodles synergistically determined starch digestion, texture, and flavor. By structuring such key structures, the digestion, texture, and flavor of rice noodles can thus be reasonably controlled.

Digestibility and structure changes of rice starch following co-fermentation of yeast and Lactobacillus strains.

Rice is sometimes fermented with microorganisms to develop health-promoting foods, but the contribution of a short-term fermentation (a necessary step for fermented rice cake-preparation) to properties of rice starch is not resolved yet. The effects of microorganism fermentation with different amount of starter cultures on multi-scale structures and digestibility of rice starch were investigated. The amount of starter cultures significantly affected structures and digestibility of fermented starch. The fermentation with a lower amount of starter cultures induced starch degradation (corrosion of starch granules, reduction of lamellar orders and compactness, decrease in crystallinity, double helix, short ranger-ordered structures, and molar mass) and a slightly reassembly, which increased the content of slowly digestible starch (SDS). While, the fermentation produced more starch fractions with Mw between 0.60 × 107 g/mol and 1.50 × 107 g/mol as the amount of starter cultures increased, and these starch molecules tended to reassemble and form more ordered multi-scale structures including double helical and short range-ordered structures, starch lamellar orders and compactness, which elevated SDS content. The SDS content of fermented starchy foods could be improved via controlling starch reassembly and multi-scale ordered structures through modulating the amount of starter cultures during fermentation.

Tailoring assembly behavior of starches to control insulin release from layer-by-layer assembled colloidal particles.

Self-assembly behavior of charged-starches significantly influenced core-shell structures of layer-by-layer assembled particles. In this study, insulin (IN)-loaded nanoparticles with structured shell features were fabricated to investigate how the interactions of carboxymethyl starch (CMS) with spermine-modified starch (SS) influenced IN release properties of the particles (IN/CMS/SS/CMS) within the gastrointestinal tract (GIT). Results indicated that the assembly action of CMS and SS could be controlled by simply tailoring the ratio of CMS/SS content. An intermediate CMS/SS ratio (1:4) was required to construct nanoparticles with compact shell structure and desirable IN release properties in the colon (74.23%). However, a higher CMS/SS ratio (1:2) yielded particles with loose shell structure and an excessive IN release in the upper GIT (58.89%), and a lower CMS/SS ratio (1:8) rather resulted in particles with higher compactness shell structure along with limited IN release in the colon (29.01%). The interactions between CMS and SS should be the key factor influencing core-shell structures and in turn the IN-release properties of the carrier. The shell structure and release properties of layer-by-layer assembled particles could be tailored by controlling the interactions between starches.

Further insights into the evolution of starch assembly during retrogradation using SAXS.

A new and effective method for evaluating the reassembly of starch molecules at large scale (>2 nm) during retrogradation has been developed based on the small angle X-ray scattering (SAXS) technique. The SAXS curves fitted by the Cauchy plus Power-law functions are decomposed into peak- and non-peak-derived sub-patterns. The peak-derived patterns are used for calculating (i) the size of ordered aggregate structures (d) using Lorentz correction and (ii) the proportion of ordered structures within starch samples (Rpeak) by estimating the ratio of the area under the peak-derived sub-pattern (Speak) to the total area under SAXS curve. The Imax and fractal-like dimension (α) of the scattering aggregates (the fitted parameters of SAXS curve), d, Speak, Snon-peak (the area under the non-peak-derived sub-pattern) and Rpeak change as a function of retrogradation time. Importantly, the Snon-peak interrogates the continuous reduction of amorphous starch molecules during the aging, SAXS parameters including α and d describe starch ordered aggregate structures with larger scale than 2 nm are fitted well with pseudo Avrami equation. The SAXS in this study can be used to unravel the evolution of both amorphous starch structures and ordered aggregates with larger scale during retrogradation.

Insights on the structure and digestibility of sweet potato starch: Effect of postharvest storage of sweet potato roots.

To unravel changes in the structures and digestibility of sweet potato starch in the roots during postharvest storage (0 to 20 days), starches are isolated and characterized in terms of amylose content, polyphenols amount, molecular molar mass (Mw), molecular reassociation and multi-scale reassociated structures after cooking. Results reveal that starch digestibility decreases with a concomitant increase on resistant starch (RS) fraction during the first 10 days. These changes are associated with an increase of ordered structures, amylose and polyphenols content as well as the starch fractions with molecular weight of (2.0-2.5) × 107 g/mol. However these trends get reversed at higher postharvesting periods. Correlation matrices reveal that the short-range ordered structures and starch molecular reassociation behavior of starch paste and polyphenol content are the key factors in determining the RS content. Besides, the short-range ordered structures, specific starch molecular weight distribution and amylose of starch paste can be tailored for modulating the digestibility by controlling the postharvest storage time. This study opens a promising pathway to tailor starch digestibility via simply controlling the postharvest storage time of starch-containing crops.

How to calculate starch lamellar features with improved accuracy by small angle X-ray scattering.

Starch lamellar structures unraveled by small angle X-ray scattering (SAXS) have been critically correlated with its functionalities. However, the lamellar features calculated by the classical linear correlation function based on SAXS data are not well convincingly analyzed, because the thickness of amorphous lamellae calculated by previous studies is smaller than the smallest detectable size extrapolated from the selected data. The main reason causes this unconvincing result is the unsuitable data used. Appropriate data are selected in this study for better portraying the linear correlation function profile and then suitable principles are proposed to convincingly analyze starch lamellar features. For verifying the validity of selected data and calculated results, two criterions are established, i.e., (i) the thickness of amorphous lamellae evaluated from the correlation profiles should be larger than the smallest detectable size extrapolated from the selected data according to the Woolf-Bragg's equation and (ii) the value of the thickness of semi-crystalline lamellae calculated from the linear correlation function profile should close to that obtained from the original SAXS curve. Accordingly, the data of 0.10-2.75 nm-1 are optionally selected for calculating starch lamellar parameters. The results of this study provide a promising pathway to unravel starch lamellar features with improved accuracy.

Understanding the structural and digestion changes of starch in heat-moisture treated polished rice grains with varying amylose content.

Although the effects of heat-moisture treatment on starch structures and digestibility have been evaluated, the changes in structures and digestion of starches in heat-moisture treated starch-based food systems with varying amylose contents are not well understood. In the present study, starches isolated from heat-moisture treated polished rice grains were characterized with multi-scale structures and digestibility to reveal the effect of amylose in rice grains on structures and digestibility of starch subjected to heat-moisture treatment. Results indicated that heat-moisture treatment contributed to the partial gelatinization of starch granules, but also significantly reinforced the molecular interactions between starch molecules and thus increased starch resistance to hydrothermal treatment and enzymes attack. The higher amylose content of the native starch was, the greater reduction in digestion was observed for heat-moisture treated starch. Pearson's correlation matrix showed that the amylose content highly correlated with the changes in structural features (e.g., molar mass, short-range ordered structure, crystalline structure, and lamellar structure) of starches followed by heat-moisture treatment. The amylose promoted the reinforcement of interactions between starch chains during heat-moisture treatment and then significantly contributed to the reduction in starch digestibility.

Dry heating and annealing treatment synergistically modulate starch structure and digestibility.

To modulate starch digestibility, dry heating combined with annealing treatment was employed to synergistically modulate structure and digestibility of normal maize starch (NMS) and potato starch (PS). Dry heating decreased starch molecular weight and created small molecular fractions with suitable chain length, resulting in starch better rearrangement during annealing treatment. Accordingly, after dry heating combined with annealing treatment starches had the highest pasting temperature, the thinnest and the thickest of crystalline lamellae for NMS and PS, respectively, and the highest ordered structures of cooked-starch compared with single dry heating or annealing modified starches. The results revealed that the synergistic modification altered starch lamellar thickness and increased double helices orders. Thereby, dry heating combined with annealing treated starches exhibited the lowest enzymatic digestibility with increased ca. 7.90% of slowly digestible starch for NMS or elevated ca. 5.04% of resistant starch for PS. The differential changes caused by dry heating combined with annealing treatment between NMS and PS were comprehensively discussed and the difference should result from the different starch crystalline structure and average chain length. This study provides a promising pathway for modulating starch structures and enzymatic digestibility.