Application of fish gelatin as a food component in replace of mammalian sources has attracted attentions recently. However, physicochemical properties of fish gelatin might be affected by other food components thus affecting its application. To determine whether and how sugar and salt components in food affect the physicochemical properties of fish gelatin, nanostructure of tilapia fish gelatin was studied by atomic force microscopy (AFM) with the secondary structure investigated by Fourier transform infrared (FTIR) spectroscopy. The results indicated that 1.5% NaCl addition led to a loss in molecular order in secondary structure which was accompanied with reducted gel strength; however, addition of 1.5% sucrose did not affect physicochemical and structural properties of fish gelatin. Fish gelatin possessed heterogeneous nanostructure including spherical aggregates, ring like structure, short and long rods as well as continuous fibre network. Incorporation of NaCl with fish gelatin increased diameter of spherical aggregates to more than two folds of control. These data suggest that addition of NaCl reduced gel strength through inducing large nano-aggregates, which could be at improper alignment that prevented the formation of a rigid gel. Interestingly, the fish skin gelatin studied here showed good storage stability over 30 days of storage at 4 °C. Sodium chloride affects fish gelatin's nanostructure and physicochemical properties more than sucrose at the same concentration.

Fish fillet is easily spoiled during storage. Antimicrobial edible coating of gelatin extracted from fish skins and bones and tea polyphenol (TP) was developed to inhibit the spoilage of fish fillet during cold storage. For coating containing 0.4 % TP and 1.2 % gelatin, the pH only slightly increased from 6.17 at day 0 to 6.32 at day 17 of cold storage, while the pH of control coating increased to 6.87 at day 17. Atomic force spectrometry was used to analyse the nanostructure of myofibril, which is the major component of fish muscle. The results showed that the length of myofibril from 0.4 % TP and 1.2 % gelatin group was greater than 15 μm, while the diameter and height were 3.38 and 0.59 μm, respectively, which exhibited the most intact nanostructure after 17 days of cold storage. Meanwhile, matrix-assisted laser desorption–ionisation–time-of-flight mass spectrometry result showed that TP delayed the degradation of myosin light chain 3 and troponin T in myofibril. Gas chromatography–mass spectrometry of volatile organic compounds (VOCs) also showed that 0.4 % TP and 1.2 % gelatin coating group had minimal production of spoilage markers, such as 1-octen-3-ol, 2-methyl propanoic acid and dimethyl sulfide. The microbial analysis showed that the aerobic mesophilic/psychrotrophic count, yeasts and moulds of 0.4 % TP and 1.2 % gelatin group were significantly lower than the control group. Therefore, 0.4 % TP and 1.2 % gelatin coating showed the best antimicrobial effect and can be used to maintain the nanostructure of fish fillet and prevent the spoilage during cold storage.

Fish gelatin (FG) is more suitable for consumption by religious people than mammalian gelatin. One common modification method of FG is mixing FG with polysaccharides. However, the mechanism is not clear. We found that FG gel containing 0.1 g/100 mL gellan, 20 mmol/L CaCl2 and 6.67 g/100 mL FG (180 Bloom) matched gel strength, hardness, cohesiveness, chewiness as well as gelling temperature (Tg) and melting temperature (Tm) of commercial beef gelatin (BG) (240 Bloom). The modified FG was also observed by the result of helix/coil ratio and spherical aggregates. The modification decreased the diameter of FG's aggregates from 472 to 249 nm, which matched with BG (272 nm, P < 0.05). Co-existence of segregative gellan-gellan fibrous aggregates and associated FG-gellan amorphous structure were also identified at the modified FG by atomic force microscope (AFM). The helix/coil ratio and diameter of spherical aggregates were inversely correlated, the mechanism behind was the strength of gelatin association. The involvement of hydrogen bond and presence of FG-gellan complex have been validated by urea addition and Fourier transform infrared (FTIR) spectroscopy. A schematic model was proposed. As modified FG successfully matched the of texture properties of BG, it is promising to replace BG with FG.

The effect and mechanisms of calcium chloride and citric acid addition on the acid method of processing tilapia protein isolates and surimi gels were studied. The alkaline method shows better gel quality than the acid method with lower yield and high lipid content. The addition of calcium chloride increased the breaking force to 494.56 g and citric acid helped reducing the lipid content by 85.85%, resulting in a higher yield of 75.36%. Gels with calcium maintained low levels of expressible moisture (2.30%), indicating a well-organised gel matrix. The decrease in -SH content and increase in ionic bonds content suggested increased formation of disulphide bonds and ionic bonds. Oscillatory dynamic measurement indicated that more heat resistant bonds were formed. The morphology of myofibril proteins studied by atomic force microscopy (AFM) showed that the height of the proteins in the calcium-added gels decreased 79.4%, which suggested that the protein structure was “suppressed”.

Quality of fish sausages can be compromised due to fatty acid oxidation. The effects of tocopherol nanoemulsions (NEs) and coarse emulsions (CEs) on the physicochemical properties and lipid oxidation of fish sausages were assessed during 16-day storage at 4 °C. The addition of 250 and 500 mg/kg tocopherol NEs not only improved fish sausages' quality during cold storage but also effectively retarded lipid oxidation, as evidenced by the significantly lower peroxide value and higher polyunsaturated fatty acid content. Omega-6 fatty acids of tocopherol NEs added sausages were maintained at 31.01% for NE250 and 29.59% for NE500 on day 16. However, CEs did not exert significant antioxidant activity. The particle size of the tocopherol NEs remained below 500 nm when stored at 4 °C for 16 days while the particle size of tocopherol CEs increased from 4 to 6 μm. The smaller particle size, even distribution, and stability of tocopherol NEs might explain the better antioxidant activity of them in fish sausages. Interestingly, NEs encapsulated with 250 mg/kg tocopherol are effective to delay the lipid oxidation and improve the fish sausages quality without altering their texture properties during cold storage.

The gelation of iota carrageenan (IC) with different ethanol concentrations (0–40 mL/100 mL) was investigated in terms of rheology, chemical structure, and microstructure. Ethanol facilitated IC gel formation with predictable increasing gelling temperature (52.6–62.6 °C) and critical gelling points (50.8–61.3 °C). The ethanol –OH moiety was responsible for Kirkwood-Buff theory through exclusion effects and direct binding with IC. Fourier transform infrared (FTIR) confirmed the binding with the chemical shifts on both sulphated groups (G4S from 850 to 854 cm−1 and DA2S from 805 to 808 cm−1). The gel strength decreased at < 10 mL/100 mL ethanol and increased up to 40 mL/100 mL ethanol. From Winter-Chambon equation, 40 mL/100 mL ethanol provided a significantly lower fractal dimension df (2.09). Confocal laser scanning microscopy (CLSM) and field emission scanning electron microscopy (FESEM) also showed a less complex network. These results indicated that a small amount of ethanol stabilised IC gelation and that the increased gel strength was more significant at high ethanol concentrations (>10 mL/100 mL), which improved the design of IC-ethanol systems.

The impact of Eucheuma on water loss and status in sponge cakes was measured and analyzed in this study. Eucheuma was used to replace 0%, 10%, and 20% of wheat flour to make sponge cakes, coded as the control, EP10, and EP20, respectively. The initial water content of batters showed no significant differences (around 57.0%, dry basis), whereas the final EP10 and EP20 products had higher water content. Three stages were found during baking in control sample and these three stages were fitted by linear, linear, and exponential models with root mean squared error (RMSE) of 0.016, 0.018, and 0.133, respectively. Eucheuma addition decreased the water loss rate and changed the water loss stages, which were fitted by linear, linear, and linear models in EP20 sample (RMSE = 0.027, 0.047, and 0.108, respectively). The crust formation and crumb structure analysis showed that the formation of cracks and the disappearance of pore structures hindered the water evaporation. The low‐field proton nuclear magnetic resonance and magnetic resonance imaging results showed that the water status in the final EP20 products was not as tightly as that in the control samples. A proposed schematic diagram was developed based on the qualitative analysis of the transfer mechanisms to explain the total effect of Eucheuma on the water loss rate and status. These results aid our understanding of the water loss process of sponge cakes and promote the potential application of Eucheuma in bakery products.

The inhibiting effect of chitosan coating (2%) on the softening and sodium carbonate-soluble pectin (SSP) evolution of sweet cherries during non-isothermal storage was investigated. Chitosan coating significantly extend the softening (6.4% greater than the control group), maintained the SSP content (6.6% greater than the control group), and reduced the degradation of SSP by inhibiting the expression of the paPME1–5 genes, which regulating pectin methylesterase activity of sweet cherries under temperature variation. In addition, the results of methylation and monosaccharide composition indicated that the chitosan coating reduced demethylation of SSP and the loss of RG-I main and side chain neutral sugars. Atomic force microscopy images revealed that the coated sweet cherries contained more linked, branched, and long SSP chains and maintained the width of the pectin backbone (>140 nm). These results indicated that a chitosan coating is feasible to preserve postharvest fruit under non-isothermal conditions.;Highlights•Temperature variation accelerated sweet cherry softening and pectin degradation.•Chitosan coating extended sweet cherry firmness loss in non-isothermal conditions.•Chitosan coating reduced the expression of pectin methylesterase-related genes.•Chitosan coating alleviated nanostructure degradation of pectin in sweet cherry.

Pork gelatin is not suitable for halal and kosher application; however, fish gelatin (FG) can be modified for use as a pork gelatin (PG) mimetic. Herein, low-acyl gellan (GE), κ-carrageenan (KC), and salts (CaCl2 or KCl) were combined with a 180 Bloom tilapia FG. A formulation comprising 5.925% (w/v) FG + 0.025% (w/v) GE + 3mM CaCl2 best matched the physicochemical properties of PG. The modification increased the FG gel strength from 115 ± 2 to 149 ± 2 g (matching the 148 ± 2 of PG), while the Tm increased from 27.9 ± 1.0 to 32.4 ± 0.8 °C (matching the 33.1 ± 0.3 °C of PG). Nanoaggregates (diameter between 150 and 300 nm) could be an important structural factor affecting the physicochemical properties, as both PG and GE-modified FG showed a similar frequency distribution in this size group (57.4 ± 1.6% (PG) compared with 56.3 ± 2.2% (modified FG)). To further explore the differences between KC and GE in modifying of FG's structure, the FG-KC and FG-GE gels were compared. The zeta potential and Fourier transform infrared (FTIR) spectroscopy results for the FG-KC gel supported an associative interaction with complex formation, as indicated from the large aggregates and amorphous phase under atomic force microscopy (AFM). Contrastingly, a segregative FG-GE interaction took place in presence of CaCl2 . These structures and interaction differences between FG-GE and FG-KC influenced the macro-properties of FG, possibly explaining the differences in the modification of the melting temperature of FG. A diagram representing the interaction-structure-physicochemical properties was proposed to explain the differences between the FG-GE and FG-KC gels.

An enzymatic method to tenderise golden pomfret (GP, Trachinotus blochii ) flesh by marinating with bromelain (BML) solution was developed to produce GP fish balls with a texture similar to those of yellowtail fusilier (YF, Caesio cuning ). Treatment with BML reduced the hardness, chewiness and gel strength significantly but increased the resilience of GP fish balls. As a result, 0.4% (enzyme-substrate ratio, w / w ) BML-treated GP fish balls had the same texture properties as YF fish balls. Meanwhile, changes in myofibrillar proteins in the fish balls were determined using sodium dodecyl sulphate polyacrylamide gel electrophoresis, matrix-assisted laser desorption/ionisation time-of-flight mass spectrometry and atomic force microscopy. The results indicated that BML degraded myosin light chain and troponin T effectively, without affecting actin. BML treatment generated protein fragments with significantly smaller sizes, thereby improving the tenderness of the flesh. The length, width and height of the myofibrils from 0.4% BML-treated fish ball were 6.42, 1.52 and 1.48 μm, respectively, which were not significantly different from the myofibrils of YF fish balls, indicating that the similar nanostructure determined the comparable texture properties. Gas chromatography-mass spectrometry analysis showed that 0.4% BML decreased the amount of hexanal, hexadecane, 1-octen-3-ol and 2,6,10,14-tetramethylpentadecane but increased the ratio of heptadecane from 18.14 to 38.23% in the treated fish balls, making the flavour of 0.4% BML-treated GP fish balls similar to that of YF balls. Overall, the results suggest that 0.4% BML-tenderised GP could be a promising alternative to YF to produce quality fish balls.

Cakes are important confectionery and are enjoyed socially within groups. Eggs are important components of cakes, providing emulsification, flavour, colour, and many other properties. However, because of various health concerns and religious beliefs, some consumers cannot enjoy traditional cakes made with eggs. In the current study, isolated pea protein (PPI), xanthan gum (XN), and emulsifier mixtures were investigated to prepare eggless cakes and their roles were determined. The physicochemical properties of the batter and final cake products, the microstructure of the final cakes, and structural properties of starches and glutens at the meso-scale were characterised. The eggless cake recipe containing PPI, 0.1% XN and 1% soy lecithin (SL) was found to be close to the control traditional cakes in terms of specific gravity (1.01 vs. 1.03), crumb colour (a* at 0.09 vs. −0.04), and crumb pore properties (average pore area both 0.20 mm2). Cakes with formulation R4 were most similar to the control cakes with respect to the 1047/1022 relative intensity of the IR spectra of starches (both 0.55) and the nanostructures of glutenins. Therefore, formulation PPI+0.1% XN+ 1% SL was considered as a potential candidate recipe for substituting eggs in cakes.;Graphical abstract [Display omitted] ;Highlights•Natural ingredients were screened to develop egg substitutes.•Image analysis detected the relative differences between different cakes.•FTIR and AFM analyses revealed structural differences among cakes.•PPI + 0.1% XN + 1% SL was promising as an egg substitute in cakes.

Highlights•The potentiality of using soy protein as egg replacers for cakes was evaluated.•Baking additives improved the physical quality of batter and eggless cakes.•Porous nanostructures in glutenin were important to the final quality of cakes.•Soy protein is a promising egg replacer with the aid of 1% mono, diglycerides.;AbstractTo evaluate the feasibility of substituting eggs in yellow cake by a mixture of soybean proteins, plant polysaccharides, and emulsifiers, the batter properties, including specific gravity and viscosity; cake properties, including specific volume, texture, colour, moisture, microstructures, and structural properties of starch and glutens of the replaced cake and traditional cake containing egg, were evaluated. Replacing eggs with a soy protein isolate and 1% mono-, di-glycerides yielded a similar specific volume, specific gravity, firmness and moisture content (1.92 vs. 2.08cm3/g, 0.95 vs. 1.03, 319.8 vs. 376.1g, and 28.03% vs. 29.01%, respectively) compared with the traditional cakes baked with eggs. Structurally, this formulation comprised dominant gliadin aggregates in the size range of 100–200nm and glutenin networking structures containing fewer but larger porosities. The results suggest that a mixture of soybean proteins and emulsifier is a promising substitute for eggs in cakes.

The effects of vacuum impregnation (VI) with 2% calcium lactate treatment on the VI properties (obtained from hydrodynamic mechanism and deformation–relaxation phenomena models), firmness, and pectin of Kyoho grapes were investigated. Fruit pectin was analysed by atomic force microscopy (AFM). VI was applied for 10–35 min at 25–45 °C and 5 kPa. The maximum values of effective porosity, εe (0.606%), and volume fraction, X (0.588%), occurred at 35 °C when the VI time was 15 min. No change was observed in the volumetric deformation (γ ≈ 0) of the grapes after the impregnation. The firmness significantly increased at 35 °C VI (from 12.93 to 14.47 N). According to the AFM results, calcium mainly inhibited the degradation of chelate-soluble pectin and sodium carbonate-soluble pectin short branches during the VI. Under the studied conditions, the validity of VI to incorporate calcium into fruit to improve the quality of grapes was verified, and a final corresponding product was obtained by VI.

The sanitising effect of low concentration neutralised electrolysed water (LCNEW, pH: 7.0, free available chlorine (FAC): 4 mg/L) combined with ultrasound (37 kHz, 80 W) on food contact surface was evaluated. Stainless steel coupon was chosen as attachment surface for Escherichia coli ATCC 25922, Pichia pastoris GS115 and Aureobasidium pullulans 2012, representing bacteria, yeast and mold, respectively. The results showed that although LCNEW itself could effectively reduce survival population of E. coli ATCC 25922, P. pastoris GS115 and low concentration A. pullulans 2012 in planktonic status, LCNEW combined with ultrasound showed more sanitising efficacy for air-dried cells on coupons, with swift drops: 2.2 and 3.1 log CFU/coupon reductions within 0.2 min for E. coli ATCC 25922 and P. pastoris GS115, respectively and 1.0 log CFU/coupon reductions within 0.1 min for A. pullulans 2012. Air-dried cells after treatment were studied by atomic force microscopy (AFM)/optical microscopy (OM) and protein leakage analyses further. All three strains showed visible cell damage after LCNEW and LCNEW combined with ultrasound treatment and 1.41 and 1.73 μg/mL of protein leakage were observed for E. coli ATCC 25922 and P. pastoris GS115, respectively after 3 min combination treatment, while 6.22 μg/mL of protein leakage for A. pullulans 2012 after 2 min combination treatment. For biofilms, LCNEW combined with ultrasound also significantly reduced the survival cells both on coupons and in suspension for all three strains. The results suggest that LCNEW combined with ultrasound is a promising approach to sanitise food equipment.