Carboxyl functionalization of cellulose could enhance its stabilizing ability in Pickering emulsions, though the influences of different carboxylation methods remain largely unknown. In order to fill in this knowledge gap, three typical carboxylated cellulosic materials, TEMPO-oxidized cellulose nanofibrils (TCN), carboxymethylated cellulose nanofibrils (CM-CN) and carboxymethyl cellulose (CMC), have been investigated to stabilize Pickering emulsions. There is a common feature among the three carboxylated cellulosic materials that they were all adsorbed at oil-water interface to form an elastic cellulose particle shell around oil droplets. However, the networks formed in the aqueous phase were quite different. For both TCN and CM-CN, the physical entanglement of the fibers and the interactions between fibers, mainly intramolecular hydrogen bonds, led to strong networks in the aqueous phase, thus contributing to good stability of Pickering emulsions. In contrary, the interaction between the suspended CMC particles was limited, which could not drive them to form a continuous network in the aqueous phase, so that CMC was least effective to stabilize oil droplets as indicated by the clearly observed phase separation even in the freshly prepared Pickering emulsions. Specifically, CM-CN with a larger aspect ratio (length of 499 ± 306 nm and diameter of 7 ± 2 nm), excellent thermal stability and comparatively high three phase contact angle (78.4°) was an effective stabilizer to prepare a super-stable Pickering emulsion, which had best emulsifying index (100%) even after 30-day of storage. This study demonstrated that different carboxyl functionalization would lead to different properties of cellulose, thus affecting their performance in stabilizing Pickering emulsions.

Gelation and gel properties are crucial to surimi-based seafood products, and many factors significantly influence surimi gel quality. Although physical and chemical modifications can improve surimi gel performance, challenges such as high cost, difficulties in industrialization and environmental pollution pose significant barriers to their practicality. Natural additives offer a promising alternative by reinforcing and improving the characteristics of surimi gel through mechanisms such as protein conformational transformation, protein denaturation, and altered chemical forces. By incorporating different substances into surimi gel, it is possible to tune the interaction between the additives and the myofibrillar proteins, thus enhancing the gelation process and achieving the desired textural profiles. This review comprehensively explored the factors influencing the surimi gelation chemistry, with a focus on how the natural additives such as proteins, lipids, polysaccharides, salts, enzymes, and extracts impact the surimi gel properties. It elucidated the reinforcing mechanisms of these additives and proposed a general interaction model between natural substance and myofibrillar proteins. Furthermore, this review well established the interrelation between the performance and mechanism of enhancement effects of typical natural substances on surimi gels and provided new insights on tuning surimi gelation and gel properties by adding natural additives with specific physicochemical properties, thus facilitating the production of high-quality surimi products with satisfactory gel characteristics in food industry.

This study investigated the effect of different reheating treatments on gel properties and flavor changes of surimi products. As the reheating temperature increased from 90 degrees C to 121 degrees C, the heat-induced proteolysis produced more abundant umami and sweet amino acids, which took part in the conversion of IMP to AMP, thus enhancing the taste profiles. Reheating increased the exposure of active -NH2 terminals in proteins, which boosted Maillard and Strecker reactions with carbonyl compounds originated from fatty acid oxidation, thus not only reducing the aldehydes and esters contents but also lowering the whiteness of surimi products. Reheating at 90 degrees C prohibited the production of warmed-over flavor (WOF) and well-preserved the textural characteristics, but high temperatures >= 100 degrees C were prone to generate furan as the major WOF substance and to destroy gel structures. Collectively, this study provides new insights on understanding the role of reheating on sensory properties of surimi products.

Pickering emulsions stabilized by cellulose nanofibrils (CN) have sparked significant attention, however the fundamental mechanisms underpinning the stabilization process remain insufficiently elucidated. Focusing on an academic debate of surface charge's contribution to stabilization, this study first explored how the varying carboxyl group contents of TEMPO-oxidized CN (TCNs) impacted Pickering emulsions' formation and stability. TCNs with 662 μmol/g carboxyl groups exhibited distinctive attributes, including larger particle sizes (322 nm in length), improved thermal stability (maximum decomposition temperature of 317 °C), and increased viscosity (1.57 Paִִ⋅s) compared to their counterparts with 963–1011 μmol/g charge density. Notably, the former one, with a larger three-phase contact angle (51.5°), higher interfacial tension, and greater detachment energy (21.69 × 10−18 J), resulted in a homogeneous dispersion of spherical oil droplets and super-stable Pickering emulsions with a consistent emulsifying index of 100% over 30 days. These findings clearly clarified that TCNs with a lower charge density exhibit superior emulsifying properties. In addition, for the first time, a distinct oil droplet-decorated fibrillar structure was observed, probably suggesting that TCNs might be able to serve as anchoring matrixes to guide the distribution of oil droplets. These structures seemed to impeded the migration and accumulation of the oil droplets, consequently enhancing the stability of the resulting Pickering emulsions. To sum, this study clearly elucidated the role of surface charge in stabilizing cellulose-based Pickering emulsions and proposed a new model to expound the cellulose-oil interaction mechanisms, thus providing new theoretical and practical insights on utilization of CN as highly effective emulsifier for super-stable food-grade Pickering emulsions.

Three commonly used plant proteins, soy isolate protein (SPI), wheat gluten (WG) and pea protein (PP), were incorporated into surimi gels, and their effects on myofibrillar protein gelation and resultant surimi gel properties have been investigated. Results revealed that addition of any of these plant proteins at 5 g/100 g surimi enhanced the surimi gelation, among which SPI addition resulted in smoother, denser and whiter surimi gels (whiteness of 61.49) with superior textural attributes (hardness of 1994 g), water-holding capacity (85.67%) and structural integrity. Such improvements were attributed to the uniform distribution of SPI solution between adjacent surimi protein molecules, not only aiding in maintaining the matrix's continuity but bridging the interaction between the proteins. SPI with a higher content of charged amino acids (47.17%) exhibited a better ability to interact with the charged N- and C- terminals of surimi proteins. This interaction promoted the complete unfolding of surimi proteins, facilitated the conversion of α-helix to β structures, exposing hydrophobic ends and sulfhydryl groups, and consequently enhanced the formation of hydrophobic interactions and disulfide bonds during gelation. This study demonstrated that plant proteins, especially SPI, are effective gel-reinforcing additives in surimi gels, offering insights for developing plant protein-rich surimi products.

Plant oil body (POB) is a natural oil droplet in micron- or submicron-scale covered by a specific shell composed of proteins and phospholipids, it has arisen numerous research interests in food industry due to its excellent emulsifying ability and great safety as natural product. In this study, POB has been exploited as an effective textural enhancer in surimi-based 3D food printing, and the underpinned mechanisms were investigated. First, POB with great rheological and emulsifying properties was prepared from peanuts, which behaved as a high internal phase emulsion. Second, for the first time, POB was introduced into surimi-based inks, which was able to facilitate the rearrangement of myofibrillar proteins through emulsification, thus ensuring fidelity and stability of 3D-printed surimi structures. The best printing performance was achieved at 2 % POB addition without compromising the surimi gel properties. However, excessive POB addition resulted in decreased viscosity, printing failure, and deteriorated gel characteristics. Third, a new mechanism was proposed to elucidate the interaction between POB and surimi proteins. On the one hand, POB physically filled in the gaps between proteins to increase the continuity and integrity of the surimi inks, thus improving the printability. On the other hand, POB with active surface altered the surimi protein molecular structure to boost the formation of hydrophobic interactions and disulfide bonds, leading to improved gel properties. Overall, this study demonstrated that POB was an effective improver for surimi-based 3D printing, providing new insights on developing new application of POB in food industry.

Salt substitute has been widely used to prepare low-salt foods due to potential health benefits, though the role of CaCl2 in salt substitute and its unique impacts on food quality have been rarely investigated. In this study, comprehensive research has been conducted to elucidate the effects of replacing NaCl with varying concentrations of CaCl2 on the surimi gel characteristics. The introduction of CaCl2 interacted with surimi proteins differently from NaCl, thus leading to difference in protein aggregation behaviors and surimi gel properties. It has been found that a proper proportion of CaCl2 for NaCl substitution could create salt bridges between surimi proteins more effectively, resulting in an ordered, smooth and dense gel network with an increased water holding capacity (WHC) and improved gel strength. Furthermore, TGase activated by Ca2+ boosted the formation of epsilon-(gamma-glutamyl) lysine bonds, which cross-linked surimi proteins to form a firm gel with a better three-dimensional structure. However, replacing NaCl with excessive amount of CaCl2 as divalent salts induced more serious protein aggregation, leading to water loss and gel properties deterioration. More specially, replacing NaCl with CaCl2 at 50% showed the best performance, as evidenced by the most abundant disulfide bonds and hydrophobic interactions, highest hardness and chewiness, and greatest storage modulus. This study provided new insights on developing high-quality surimi gels with significantly reduced salt concentration and improved gel characteristics.

Surimi products have unsatisfactory gel properties. Hence, this study evaluates the effect of collagen-adding on surimi gel properties and provides the first observation results regarding collagen type influence. With higher water solubility and more charged amino acids than type II, collagen type I intertwines with surimi myofibrillar proteins better to induce higher exposure of protein functional domains, more sufficient conformational changes of myosin and greater formation of chemical forces among proteins. These enhancements accelerate the gelation rate, leading to a well-stabilized surimi gel. The collagen I-containing surimi gels show more compact structures with uniformly distributed smaller pores than those containing collagen II, thereby providing the final products with higher water holding capacity and better textural profiles. As such, the surimi gel fortification performance of collagen I and the well-elucidated collagen-myofibrillar protein interaction mechanism will guide the further exploitation of collagen as an effective additive in the food industry.

For the first time, two common marine-derived dietary fibres (MDFs), fucoidan (FU) and oligochitosan (OCS), were introduced as textural and nutritional enhancers in hairtail surimi gels. The MDFs could assist with inhabiting the endogenous proteolytic enzyme activity, unfolding the myosin to expose more reactive domains, inducing favorable protein conformational transition, and thus, promoting gelation. The highly hydrophilic MDFs rich in -OH groups can bind water molecules via strong hydrogen bonds, facilitating water redistribution within the gel network. Driven by the enhanced chemical forces, a stable protein-FU-OCS gel is obtained, which improves the hardness by almost 100% and the water holding capacity from 86.25% to 92.25%. Collectively, this study demonstrates that MDFs are a group of effective additives to improve gel characteristics and nutritional profiles of surimi-based seafood products. The proposed MDF-protein interaction model would guide the application of MDFs as novel additives in the food industry.

Nanocelluloses and cellulose nanomaterials derived from natural resources are a group of ideal platform materials for advanced applications. However, their synthesis through sustainable and facile processes to achieve the required properties are still challenging. Here, we prepare the nanocellulose oxalate (n-COX) from cotton with outstanding physicochemical properties by defining the optimal oxalic acid pretreatment conditions. Thus-obtained n-COX with unique 1D nanofiber shape as a platform material is further processed to various high-performance multidimensional bio-nanomaterials through several simple yet effective strategies. First, 2D n-COX films prepared through a casting-drying method show comparable or even better transparency and tensile strength than those made from other types of nanocelluloses. Second, 3D n-COX hydrogels/aerogels fabricated by a molding-crosslinking approach demonstrate good shape stability, well-preserved nanoporous networks, and qualified mechanical properties. Third, n-COX-derived bioinks display improved printability and fidelity, resulting in better size-preserving and shape-control of the 3D-bioprinted scaffolds. We expect this work could offer new insights on engineering natural cellulose and using n-COX as a platform material for further advanced fabrication, and thus, open up application potentials of this new nanocellulose.