Impact of zinc salts on heat-induced aggregation of natural actomyosin from yellow stripe trevally

Impact of zinc sulphate (ZnSO₄) and zinc chloride (ZnCl₂) on heat-induced aggregation of natural actomyosin (NAM) extracted from yellow stripe trevally (Selaroides leptolepis) was investigated. In the presence of ZnSO₄ or ZnCl₂, the transition temperature (T_max) of myosin shifted from 47.83 ± 0.30 °C to 46.05 ± 0.36 and 46.49 ± 0.49 °C, with the coincidental decreases in ΔH from 1.07 ± 0.03 J/g to 0.63 ± 0.02 and 0.67 ± 0.04 J/g, respectively (P < 0.05). Additionally, Ca²⁺–ATPase activity of NAM decreased with increasing the concentrations of ZnSO₄ or ZnCl₂ during heating up to 40 °C. During heating from 20 to 75 °C, higher turbidity, surface hydrophobicity and disulphide bond formation were obtained in NAM added with ZnSO₄ or ZnCl₂ at temperatures ranging from 40 to 75 °C, compared with the control. Nevertheless, a higher aggregation was found in NAM added with ZnSO_4, compared with ZnCl_2. Zeta potential (ζ) analysis suggested that the surface of NAM added with ZnSO₄ became less negatively charged, compared with that of ZnCl₂ counterpart. Transmission electron microscopy showed that the structure of NAM was highly interconnected, finer and denser when zinc salts, especially ZnSO₄ were incorporated. Therefore, ZnSO₄ could be used to induce aggregation of fish muscle proteins, thereby improving gelling property of fish mince or surimi.     

Impact of microbial transglutaminase on gelling properties of Indian mackerel fish protein isolates

Impacts of microbial transglutaminase (MTGase) (0–0.6 units/g sample) on gel properties of Indian mackerel unwashed mince, surimi and protein isolates with and without prewashing were studied. Generally, lower myoglobin and lipid contents were found in protein isolate with and without prewashing, compared to those of unwashed mince and surimi (P < 0.05). Protein isolate had the decreased Ca²⁺-ATPase and protein solubility, indicating protein denaturation. When MTGase was incorporated, breaking force and deformation of all gels markedly increased, especially as MTGase levels increased (P < 0.05). At the same MTGase level, gel from protein isolate with prewashing exhibited the highest breaking force and deformation (P < 0.05). The addition of MTGase could lower the expressible moisture content of most gels. No change in whiteness of gel was observed with the addition of MTGase (P > 0.05), but gel from protein isolate gels had decreased whiteness as MTGase at high level was added. The microstructure of protein isolate gels without prewashing showed a similar network to unwashed mince gels, whilst a similar network was observed between surimi gel and gel from protein isolate with prewashing. Nevertheless, a larger void was noticeable in gels from protein isolates. All gels incorporated with MTGase (0.6 units/g) showed a slightly denser network than those without MTGase. Thus, gel with improved properties could be obtained from protein isolate from Indian mackerel with added MTGase.     

Effect of phosphate compounds on gel-forming ability of surimi from bigeye snapper (Priacanthus tayenus)

The properties of surimi gel from bigeye snapper (Priacanthus tayenus) added with various phosphate compounds (sodium pyrophosphate, PP; sodium tripolyphosphate, TPP; and sodium hexametaphosphate, HMP) at different levels (0%, 0.05%, 0.1%, 0.3% and 0.5% w/w) and heated under various conditions were studied. Kamaboko and directly heated gels from bigeye snapper surimi added with 0.05% PP had the increase in breaking force and deformation by 17.35% and 11.52%, and 13.54% and 3.53%, respectively, compared with the control gel (without PP addition). At the same level used (0.05%), TPP had no influence, but HMP exhibited a detrimental effect on kamaboko gel. The addition of PP (0.025%) in combination with 50 mmol CaCl₂/kg increased the breaking force by 38.68% as compared with the control gel (without additives), suggesting that the sufficient amount of CaCl₂ could enhance the setting of the gel. Generally, the marked decrease in breaking force with the coincidental increased expressible moisture was observed when the excessive amount of phosphate compounds was used (p<0.05). Microstructure study revealed that a gel with a fine network was formed with addition of PP. Therefore, the addition of PP in combination with CaCl₂ could increase the gel strength as well as water holding capacity of surimi gel.     

Whey protein concentrate: Autolysis inhibition and effects on the gel properties of surimi prepared from tropical fish

Effects of whey protein concentrate (WPC) on autolysis inhibition and gel properties of surimi produced from bigeye snapper (Priacanthus tayenus), goatfish (Mulloidichthys vanicolensis), threadfin bream (Nemipterus bleekeri) and lizardfish (Saurida tumbil) were investigated. WPC (0–3%) showed inhibitory activity against autolysis in all surimi at both 60 and 65 °C in a concentration-dependent manner. Myosin heavy chain (MHC) of surimi was more retained in the presence of WPC. Breaking force and deformation of kamaboko gels of all surimi increased as added levels of WPC increased (P < 0.05). This was associated with lower levels of protein degradation, as evidenced by the decrease in trichloroacetic acid-soluble peptide content (P < 0.05). WPC at 3% (w/w) significantly decreased the whiteness of gels. However, water-holding capacity of kamaboko gels was improved with increasing concentration of WPC. The microstructure of surimi gels generally became denser with the addition of WPC.     

大豆分离蛋白、木薯淀粉与转谷氨酰胺酶组合对鲢鱼鱼糜凝胶品质的影响

探究了大豆分离蛋白、木薯淀粉及转谷氨酰胺酶对鲢鱼鱼糜制品的影响并确定最适添加量。结果表明,当大豆分离蛋白添加量6%,木薯淀粉添加量9%以及转谷氨酰胺酶添加量4U/g·蛋白时,能有效增加鱼糜的持水性,降低其蒸煮损失,且不会使鱼糜带有大豆分离蛋白的淡黄色,同时提高了鱼糜的凝胶强度,鲢鱼鱼糜制品各项指标较好。通过低场核磁共振和扫描电镜检测发现,未添加的对照组在6次冻融后凝胶结构完全被破坏,不易移动水峰面积(A_(23))下降了25%,试验组凝胶结构比较致密,A_(23)下降了11%,进一步验证了此配方组合对鱼糜在冻融循环过程中凝胶结构的稳定性具有保护作用。     

Color improvement by titanium dioxide and its effect on gelation and texture of proteins recovered from whole fish using isoelectric solubilization/precipitation

Whiteness is a critical attribute for restructured fish products such as surimi seafood. However, the whiteness of gels made from proteins recovered from fish processing by-products or whole fish using isoelectric solubilization/precipitation is poor. The by-products and whole fish contain bones, scales, skin, etc. that affect gel color. Therefore, whiteness needs to be improved if marketable products are to be developed from recovered proteins. The objectives of this study were to determine effects of titanium dioxide (TiO₂) on: (1) color; (2) texture; and (3) viscoelasticity (G′) of gels made from isolated carp proteins and Alaska pollock surimi. Carp proteins were recovered with isoelectric solubilization/precipitation. TiO₂ was added to carp proteins at 0-0.5 g/100 g. TiO₂ was not added to surimi. Due to much higher (P < 0.05) yellowness (b^∗) and lower (P < 0.05) lightness (L^∗), the whiteness of carp gels without TiO₂ was lower (P < 0.05) than surimi gels. TiO₂ at ≥ 0.2 g/100 g resulted in better (P < 0.05) whiteness of carp gels than surimi gels without chalky and artificially white appearance. TiO₂ did not affect texture or viscoelasticity. This research demonstrates that whiteness of restructured fish products based on proteins recovered from whole fish via isoelectric solubilization/precipitation can be similar to the whiteness of surimi seafood.     

Effect of formaldehyde on protein cross-linking and gel forming ability of surimi from lizardfish induced by microbial transglutaminase

Impact of formaldehyde (FA) at various levels (0–9 μmol/g surimi) on gel properties of surimi from lizardfish added with microbial transglutaminase (MTGase) was studied. During iced storage of 10 days, total and free FA in lizardfish flesh increased continuously (P < 0.05). In the presence of FA, breaking force of gels slightly increased, whilst the deformation decreased (P < 0.05). The addition of MTGase (0.4 units/g surimi) was able to increase gel strength and water holding capacity of resulting gel. Nevertheless, gel strengthening effect of MTGase was lowered when FA at higher level was present. Myosin heavy chain (MHC) dominantly underwent polymerisation to a higher extent when either MTGase or FA was added. The higher reduction in ε-amino group content was observed in natural actomyosin (NAM) when FA at higher levels (0–30 μmol/g protein) was incorporated. Acyl transfer reaction mediated by MTGase was impeded in NAM containing FA, especially at higher levels. Generally, FA had an adverse effect on cross-linking ability towards surimi proteins induced by MTGase. Therefore, cross-linking and gel-forming ability of lizardfish surimi could be maximised by MTGase when surimi contained no FA.     

Enhancement of gel strength of bigeye snapper (Priacanthus tayenus) surimi using oxidised phenolic compounds

Effects of different oxidised phenolic compounds (ferulic acid, OFA; tannic acid, OTA; catechin, OCT and caffeic acid, OCF) at different levels (0–0.25% of protein content) on the properties of gels from bigeye snapper (Priacanthus tayenus) surimi were investigated. Breaking force and deformation of surimi gel varied with types and amounts of oxidised phenolic compounds. Gels added with 0.20% OFA, 0.05% OTA, 0.15% OCF and 0.05% OCT exhibited the marked increases in both breaking force and deformation, compared with the control (P < 0.05). Those increases were associated with lower expressible moisture content. No increases in both breaking force and deformation were observed when ferulic acid without oxygenation at alkaline pH was added, regardless of amount added (P > 0.05). No changes in the whiteness of gel were found with addition of OFA (P > 0.05), but the decreases in whiteness were noticeable as other oxidised phenolics were incorporated (P < 0.05). Different microstructures were obtained among gels with different oxidised phenolics. The physicochemical properties of natural actomyosin suggest that oxidised phenolics could induce conformational changes and the cross-linking through amino groups or the induction of disulphide bond formation. Therefore, the addition of oxidised phenolic compounds at the optimum level could increase the gel strength of surimi gel.     

Physico-chemical properties of whey protein isolate films containing oregano oil and their antimicrobial action against spoilage flora of fresh beef

Antimicrobial films were prepared by incorporating different levels of oregano oil (0.5%, 1.0%, and 1.5% w/w in the film forming solution) into sorbitol-plasticized whey protein isolate (WPI) films. The moisture uptake behavior and the water vapor permeability (WVP) were not affected by the addition of oregano oil at any of the concentrations used. A reduction of the glass transition temperature (∼10–20 °C), as determined by dynamic mechanical thermal analysis (DMTA), was caused by addition of oil into the protein matrix. A decrease of Young modulus (E) and maximum tensile strength (σ_max) accompanied with an increase in elongation at break (%EB) was observed with increasing oil concentration up to a level of 1.0% (w/w). Wrapping of beef cuts with the antimicrobial films resulted in smaller changes in total color difference (ΔΕ) and saturation difference (Δ_chroma) during refrigeration (5 °C, 12 days). The maximum specific growth rate (μ_max) of total flora (total viable count, TVC) and pseudomonads were significantly reduced (P < 0.05) by a factor of two with the use of antimicrobial films (1.5% w/w oil in the film forming solution), while the growth of lactic acid bacteria was completely inhibited. These results pointed to the effectiveness of oregano oil containing whey protein films to increase the shelf life of fresh beef.     

Protein cross-linking ability of sarcoplasmic proteins extracted from threadfin bream

Sarcoplasmic proteins extracted from threadfin bream (TB, Nemipterus sp.) contained transglutaminase (TGase) activity exhibiting a pH optima at 7.5. Activity increased with CaCl₂ and reached the maximum at 5 mmol/L, showing the Ca²⁺-dependent characteristic. TGase activity staining on native-polyacrylamide gel electrophoresis (native-PAGE) showed two fluorescent bands catalyzing incorporation of monodansylcadavarine (MDC) into di-methylated casein (DMC). However, both fluorescent bands showed only one major protein band with a molecular weight of about 66 kDa on sodium dodecylsulfate-PAGE (SDS-PAGE), suggesting the presence of isozymes. The TB sarcoplasmic protein (TBSP) concentrated using a 30-kDa ultrafiltration membrane induced cross-linkings of bovine serum albumin when incubated at 25 °C for 6 h. Addition of the concentrated TBSP at 1.6 g protein/100 g along with 0.1 g CaCl₂/100 g resulted in a 1.8-fold increase in the breaking force of the proteinase-laden lizardfish surimi pre-incubated at 37 °C for 20 min. TBSP effectively minimized proteolysis of lizardfish surimi at 37 °C. TBSP could be a promising protein additive that improves textural properties of proteinase-laden surimi.     

Effect of porcine plasma protein and setting on gel properties of surimi produced from fish caught in Thailand

Effects of porcine plasma protein (PPP) and high temperature setting on gel properties of surimi from bigeye snapper, bigeye croaker, threadfin bream and barracuda were investigated. PPP was effective in increasing breaking force and deformation of kamaboko gels set at 40°C for 30 min and heated at 90°C for 20 min. The optimum levels of PPP were 0.5, 0.5, 1.5 and 1.5 g/100 g and the optimum setting times were 2, 1.5, 1.5 and 2 h for bigeye snapper, bigeye croaker, threadfin bream and barracuda surimi, respectively. However, the addition of PPP significantly decreased whiteness (P<0.05). An increase in gel-forming ability of surimi with PPP coincided with a decrease in solubility in mixture of SDS, urea and β-mercaptoethanol, indicating the formation of nondisulfide covalent bond induced by both endogenous and plasma transglutaminase. The results supported that PPP improve the gelation of surimi in combination with setting.     

The effect of sodium lactate,potassium lactate,carrageenan, whey protein concentrate,yeast extract and fungal proteinases on the cook yield and tenderness of bovine chuck muscles

This study evaluated the efficacy of injection with enhancement solutions containing sodium lactate (NaLac), potassium lactate (KLac), carrageenan, whey protein concentrate (WPC), yeast extract or fungal proteinases alone or in combination with NaCl at increasing the tenderness and cook yield of bovine M.supraspinatus and M. tricepsbrachii caput longum. Muscle sections (400 g) were injected with enhancement solutions at an injection rate of 110% to give specific residual concentrations as follows: 0.5% NaCl; 2% NaLac; 2% KLac; 0.5% NaCl + 1 or 2% NaLac; 0.5% NaCl + 1% KLac; 0.5% NaCl + 0.4% sodium tripolyphosphate (STPP) + 2% NaLac; 0.5% NaCl + 0.4% STPP, 1.5% WPC ± 0.5% NaCl, 1.0% carrageenan ± 0.5% NaCl, 0.5% yeast extract or 0.0005% and 0.001% fungal enzymes. Injection with solutions containing sodium or potassium lactates (alone or in combination with NaCl and STPP), WPC, carrageenan and yeast extract significantly (P < 0.05) decreased WBSF values and increased sensory tenderness ratings, compared to non-injected controls. All of these ingredients in water also significantly (P < 0.05) increased cook yield with the exception of yeast extract which had no significant effect. The fungal enzymes in a water carrier acted as effective tenderising agents in both muscles but when used at the higher level resulted in a significant decrease in percentage cook yield. Injection of the chuck muscles with these ingredients and water represents an effective method of improving their tenderness and in most cases also increasing percentage cook yield.     

Isolation of cathepsin B from the muscle of silver carp (Hypophthalmichthys molitrix) and comparison of cathepsins B and L actions on surimi gel softening

Cathepsin B from silver carp muscle was purified to 263-fold by acid treatment, ammonium sulfate fractionation, followed by a series of chromatographic separations. The molecular mass of the purified enzyme was 29 kDa as determined by SDS-PAGE and immunoblotting. The purified enzyme was activated by dithiothreitol and cysteine while it was substantially inhibited by E-64, suggesting the purified enzyme belongs to the cysteine proteinase family. Optimal pH and temperature were 5.5 and 35 °C, respectively. The enzyme catalyzed the hydrolysis of Z-Arg-Arg-MCA with a parameter of K_m (90 μM) and K_cat (20.3 s⁻¹), but hardly hydrolyzed Arg-MCA. Analysis of surimi gel strength and microstructure showed that cathepsins B and L were capable of destroying the network structure of silver carp surimi gels, consequently causing gel softening. Cathepsin L might play an important role in the modori effect.     

Effects of ozone exposure on the xerophilic fungus, Eurotium amstelodami IS-SAB-01, isolated from naan bread

Xerophilic moulds cause contamination and spoilage of low moisture foods. This study examined the effect of ozone fumigation on growth of a Eurotium species isolated from naan bread. Two ozone treatments were used — a low-level long-term exposure (0.4 μmol/mol for 21 days) and high-level short-term exposure (300 μmol/mol for 5 to 120 min). For the low level exposure the combination of different media sucrose concentrations (0, 5, 10 and 20% w/v) with ozone treatment was also assessed. The growth of the isolate was found to be sensitive to low-level ozone fumigation depending on the media sucrose concentration and duration of the exposure. Low-level ozone exposure significantly (p < 0.05) reduced the number of asexual spores formed in media with no added sucrose, an effect not observed in media with higher sucrose levels. Electron microscope observations of colonies indicated that ozone exposed cultures produced lower numbers of cleistothecia. High-level ozone exposure for short durations reduced spore viability although 100% reduction in viability was achieved only after 120 min exposure. This work demonstrates that ozone may be used to reduce spore production in Eurotium but that the ozone effect can be mediated by sucrose levels in the growth medium.     

Inhibitory effect of wheat bran feruloyl oligosaccharides on oxidative DNA damage in human lymphocytes

The present work assessed the protective effect of feruloyl oligosaccharides (FOs), the ferulic acid ester of oligosaccharides from wheat bran, against oxidative DNA damage in normal human peripheral blood lymphocytes induced by hydrogen peroxide (H₂O₂). The DNA damage was measured by using the single cell gel electrophoresis assay (comet assay). Lymphocytes were subjected to DNA damage by exposure to a range of H₂O₂ concentrations (10–200 μmol/l). H₂O₂, at a concentration of 200 μmol/l, resulted in nearly all cells being highly damaged. FOs showed no cytotoxicity and genotoxicity to normal human lymphocytes at the tested concentrations (10–500 μmol/l). In addition, DNA damage in human lymphocytes induced by 100 μmol/l H₂O₂ was inhibited by FOs in a concentration-dependent fashion with 91.1% inhibition of lymphocyte DNA damage at 500 μmol/l as compared with the control. The results suggest that water-soluble FOs from wheat bran are able to enhance the ability of human lymphocytes to resist H₂O₂ induced oxidative damage.     

Characterization of fish gelatin from surimi processing wastes: Thermal analysis and effect of transglutaminase on gel properties

Fish gelatin extraction from wastes of fish Herring species (Tenualosa ilisha) was carried out by a series of pretreatment with 0.2 M Ca(OH)₂ followed by 0.1 M citric acid and final water extraction at 50 °C for 3 h. The resulting fish gelatin preparation was evaluated for its dynamic viscoelastic properties, gelling and melting temperatures and gel strength. The gelling and melting temperatures of gelatin samples (at 6.67%, w/v) were obtained from differential scanning calorimetry and rheological studies. The melting temperature of extracted fish gelatin (EFG) obtained ranged from 16.2 to 16.7 °C compared to that of commercial fish gelatin gel (CFG), from 23.7 to 25.6 °C and halal bovine gelatin (HBG), from 26.5 to 28.7 °C. On the other hand, gelling temperatures of EFG, CFG and HBG ranged from 5.1 to 5.2 °C, 11.9 to 17.46 °C, and 12.6 to 19.33 °C, respectively. EFG gave gels with a considerably lower G′ values than CFG and HBG. The bloom strength of EFG gels at 6.67% (w/v) was 69.03 g which was much lower than HBG (336.2 g) and CFG (435.9 g). Enzyme transglutaminase was added in the amounts of 0.5, 1.0, 3.0 and 5.0 mg/g gelatin to modify the gel properties of the extracted fish gelatin. The modified EFG gels obtained had higher gel strengths of 101.1 g and 90.56 g with added transglutaminase of 1.0 and 3.0 mg/g, respectively. However with addition of 5.0 mg/g enzyme the gel strength increased only up to 75.06 g. SDS-PAGE of extracted gelatin gel showed protein band intensities for α1-chains and 53 kDa but in gels added with higher concentration of transglutaminase, these protein band intensities seemed to disappear.     

Mechanism of gliadin–glutenin cross-linking during hydrothermal treatment

The gluten proteins, gliadin and glutenin, are important for wheat flour functionality and they undergo changes during heat treatment involving sulfhydryl (SH) groups. To change the level of SH-groups during hydrothermal treatment, the oxidant, potassium iodate (2.1 μmol/g protein) and the reducing agent dithiothreitol (DTT, 6.1 μmol/g protein) were added to 20% (w/w) gluten-in-water suspensions at room temperature, at 90 °C and after 15 min at 95 °C, and the viscosity was measured by the Rapid Visco Analyser (RVA). Protein extractabilities after hydrothermal treatment were determined by size-exclusion and reversed-phase HPLC. DTT decreased maximal RVA viscosity and the levels of extractable α- and γ-gliadin and this decrease was independent of the time of addition during hydrothermal treatment. In contrast, potassium iodate increased the levels of extractable α- and γ-gliadin. Its impact was less when added at later times during RVA analysis. A SH-blocking agent (N-ethylmaleimide, 8.0 μmol/g protein), added at room temperature to the gluten suspension, decreased RVA viscosity at 95 °C and increased the extractabilities of glutenin and α- and γ-gliadin after hydrothermal treatment. Subsequent addition, at 90 °C, of a reducing agent (glutathione, 3.1 and 6.2 μmol/g protein) recovered the control RVA profile and restored the control protein extractabilities after RVA analysis. This shows the importance of heat-induced gliadin–glutenin reactions for gluten viscosity and of the presence of free SH-groups for the polymerization of gluten proteins. A model explaining gliadin–glutenin polymerization through a sulfhydryl-disulfide exchange mechanism and demonstrating the effects of redox agents is put forward.     

Gel properties of croaker–mackerel surimi blend

Gel properties of croaker surimi blended with three types of mackerel surimi at different ratios were evaluated. The gel strength of the croaker–mackerel surimi blend was higher than that of the original mackerel surimi (p < 0.05). The presence of croaker surimi in the blend resulted in the increase in myosin heavy chain (MHC) band intensity. No differences in deformation of gels were observed in croaker surimi and croaker-short-bodied mackerel blend at all ratios (p > 0.05). The addition of short-bodied mackerel surimi into croaker surimi up to a ratio of 1:2 had no effect on whiteness and metmyoglobin content of the gel (p > 0.05). Marked decrease in expressible drip and TCA-soluble peptide of gel was noticeable in croaker–frigate mackerel surimi blend (p < 0.05). Therefore, the gel properties of croaker–mackerel surimi blend were governed by the type and content of mackerel surimi used.     

Rheological properties and stability of low-in-fat dressings prepared with high-pressure homogenized yeast

The aim of present study was to investigate the feasibility of application high-pressure homogenized (HPH) yeast aqueous dispersions with low nucleic acid content for the formulation of low-in-fat dressings. The HPH treatment (1500 bar, 3 passes) in alkaline medium improved the protein dispersibility (>50%). Emulsions were prepared using sunflower oil (12.0% or 25% w/w oil), xhantan/guar gums (0.5% w/w), modified starch (0–4.0% w/w), salt, sucrose, acidulants, EDTA, and antimicrobial agents. All emulsions (pH 3.97 ± 0.27; a_w = 0.97 ± 0.01), whatever the starch content, behaved clearly as pseudoplastic fluids in steady flow measurements. Moreover, as the frequency sweep measurements were made they also exhibited a weak gel behavior. Although the presence of starch produced an increase of mean particle size (D_3,2 values), the rheological parameters (consistency index, proportionality coefficient and coordination number) also increased, so that the starch contributes to reinforce the three-dimensional network formed by oil droplets, protein aggregates and other polysaccharides. Yeast dressings were stable to coalescence after 28 days of quiescent storage (7.0 ± 0.5 °C) and only the highest starch concentration at 25% w/w oil was sufficient to maintain the stability of network.     

Transglutaminase treatment of pea proteins: Effect on physicochemical and rheological properties of heat-induced protein gels

Rheological properties of heat-induced pea protein isolate (PPI) gels with added microbial transglutaminase (MTGase) were studied under various reaction conditions. A positive linear relationship was observed between level of MTGase used (0 to 0.7% w/w) and shear stress and shear strain of heat-set commercial pea protein isolate (PPIc) gels at 92 °C following incubation at 50 °C. Use of MTGase allowed for preparation of PPIc gels of similar strength and elasticity as commercial soy protein isolate gels and commercial meat bologna. MTGase treatment did not alter thermal properties of PPI gels. The shear stress and strain of PPIc gels were also improved following low temperature (4 °C) incubation of PPI with MTGase. Enhancement of shear strain or gel elasticity of heat-induced PPI gels with MTGase has not been reported before and provides opportunities for extending the properties of pea proteins when developing new food products.