Evaluation of microbial transglutaminase and ribose cross-linked soy protein isolate-based microcapsules containing fish oil

Soy protein isolate (SPI)-based microcapsules containing fish oil were prepared using a modified coacervation method followed by cross-linking treatments. The procedure yielded 95–98% microcapsules containing 0.5–0.6 g fish oil/g capsule with a volume mean diameter ranged from ~ 260 to ~ 280 μm. Four types of microcapsules produced were SPI with sucrose (MC-C/S), SPI with ribose (MC-C/R), SPI with sucrose and microbial transglutaminase (MC-MTG/S) and SPI with ribose and MTGase (MC-MTG/R). Protein cross-linking due to ε-(γ-glutamyl)lysine bonds and “Maillard cross-linking” were evidenced in the SDS-PAGE profiles of MC-C/R, MC-MTG/S and MC-MTG/R. Even though the microcapsules prepared with cross-linking treatments had significantly (P < 0.05) lower protein solubility as compared to that of the control, the results of fish oil release in pepsin solution at 37 °C indicated that the core release of all microcapsules prepared with ribose (MC-C/R and MC-MTG/R) was significantly (P < 0.05) lower than other microcapsules. During storage, microcapsules prepared with ribose had longer shelf life as compared to other microcapsules. This may be due to the release of antioxidative Maillard reaction products during heating and storage and a slower rate of gas permeability through the capsules.

Industrial relevance

The use of protein-based wall materials in the food industry for sensitive ingredients is limited because proteins are generally unstable with heating and damaged by organic solvents and the cross-linking agent is usually harmful. Therefore a novel method of combining two familiar cross-linking agents such as the microbial transglutaminase and ribose can convert SPI microcapsules into a stable form. The application of SPI in industry would be increased.     

The use of microbial transglutaminase and soy protein isolate to enhance retention of capsaicin in capsaicin-enriched layered noodles

Specialty layered noodles (LN) were prepared by sandwiching a capsaicin-enriched dough (CED) between two gastro-resistant dough layers made up of wheat flour, soy protein isolate (SPI) and microbial transglutaminase (MTG) at 0.5 (0.5MTG LN), 1.0 (1.0MTG LN) and 1.5 (1.5MYG LN) g/100 g of wheat-SPI flour. The textural, tensile and structural breakdown properties, capsaicin retention, microstructures and the sensory characteristics of cooked LN were evaluated. Compared to other LN, 1.5MTG LN exhibited the highest textural and tensile parameters, highest capsaicin retention, densest structure and was the most difficult to breakdown. The sensory quality of all LN was acceptable, even though it was the Control LN (prepared without SPI and MTG) that scored the highest acceptability. In general, increasing the level of MTG in the sandwiching dough layers of MTG LN reduced the release of capsaicin in simulated mouth, gastric and intestinal conditions, and these results could be due to increased protein cross-linking.     

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。     

Development of a probiotic delivery system from agrowastes, soy protein isolate, and microbial transglutaminase

Abstract: Probiotic delivery system was developed via the use of microbial transglutaminase (MTG) cross‐linked soy protein isolate (SPI) incorporated with agrowastes such as banana peel (BE), banana pulp (BU), and pomelo rind (PR). Inoculums of Lactobacillus bulgaricus FTDC 1511 were added to the cross‐linked protein matrix. The incorporation of agrowastes had significantly (P < 0.05) reduced the strength, pH value, and the lightness of the SPI gel carriers, while sodium dodecyl sulfate‐polyacrylamide gel electrophoresis profiles revealed that the occurring cross‐links within the SPI gel carriers were attributed to the addition of MTG. Scanning electron microscope micrographs illustrated that SPI carriers containing agrowastes have exhibited a less‐dense protein matrix. All the SPI carriers possessed maximum swelling ratio at 4 to 4.5 within 15 min in simulated gastric fluid (SGF), whereas the maximum swelling ratios of SPI/BE, SPI/BU, and SPI/PR were higher compared to that of control in simulated intestinal fluid (SIF). Additionally, SPI carriers in SGF medium did not show degradation of structure, whereas a major collapse of network was observed in SIF medium, indicating controlled‐release in the intestines. The addition of agrowastes into SPI carriers led to a significantly (P < 0.0001) lower release of L. bulgaricus FTDC 1511 in SGF medium and a higher release in SIF medium, compared to that of the control. SPI carriers containing agrowastes may be useful transports for living probiotic cells through the stomach prior to delivery in the lower intestines. Practical Application: Agrowastes could be utilized as a new probiotic carrier for enhanced gastrointestinal transit and during storage. This also reduces the amount of agrowastes accumulated.     

小麦蛋白对TGase酶交联改性大豆蛋白凝胶特性的影响及机制

为探讨TGase酶对大豆与小麦混合蛋白凝胶性质的影响,本文研究了小麦蛋白的加入前后混合蛋白凝胶功能性质的变化规律。通过研究TGase酶添加量、反应温度、反应pH对混合蛋白凝胶特性的影响可知:蛋白浓度为11%（11 g/100 mL）保持不变,TGase酶添加量为30 U/g,反应温度为40℃,反应pH为7.0时,TGase酶对混合蛋白凝胶特性改善效果最强。对比小麦蛋白加入前后蛋白凝胶的性质,发现小麦蛋白的添加使得蛋白结构的β-折叠含量升高,游离巯基含量减少,凝胶弹性模量（G’）增强,形成了更为多空且紧密有序的三维网络结构,使得混合蛋白的凝胶性能显著增强（p<0.05）。      

Evaluation of red bean protein [Vigna angularis] isolate on rheological properties of pork myofibrillar protein gels induced by microbial transglutaminase

The effects of 1% red bean protein isolate (RBPI) on the gel properties of myofibrillar protein (MP) in various levels of microbial transglutaminase (MTG: 0%, 0.1%, 0.5%, & 1%) were evaluated. The cooking yield (CY) of the MP gels decreased with increasing MTG level, while the addition of RBPI improved the CY of the MP gels. Gel strength (GS) was also improved when RBPI was incorporated into the MP gels containing higher than 0.5% of MTG. The addition of MTG and RBPI was slightly changed the endothermic peak temperatures. Scanning electron microscopy (SEM) showed that the three‐dimensional structure of MP with RBPI alone or in combined with MTG was compacted as compared to the control. Based on the results, RBPI could be functioned as a substrate for MTG (0.5–1.0%) and a water binder of meat protein gel mediated by MTG.     

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.     

Computed microtomography and mechanical property analysis of soy protein porous hydrogel prepared by homogenizing and microbial transglutaminase cross-linking

A novel, safe and rapid method for preparing soy protein-based porous hydrogel was described in this work. The porous hydrogel was synthesized by high speed homogenizing in the presence of microbial transglutaminase (MTGase) that catalyzed the cross-linking of the proteins. Computed microtomography (μCT) was used to characterize the porous structure of the formed gels. The extent of cross-linking and mechanical properties of the hydrogel were also evaluated. The influence of MTGase addition, homogenizing speed and soy protein isolates (SPI) dispersion pre-heating temperature on the porosity and mechanical properties of the hydrogel was investigated. The amount of MTGase, which determined the degree of cross-linking, gelation time and gel strength, played a critical role in preparation. With this method, soy protein porous hydrogel with controllable porous architecture was able to be prepared in a fast and simple way. This porous structure provided a special texture and some potential applications such as nutrients and flavors carrier for the hydrogel.     

Effects of red lentil protein addition on textural quality and starch digestibility of brown rice noodles

In this study, the additions of red lentil, rice protein and lentil protein on the quality of brown rice (BR) noodles were investigated, aiming to develop nutritionally fortified noodles with both desirable textural quality and lower starch digestibility. The results showed that the additives reduced the hardness, cohesiveness and chewiness, and increased cooking loss and turbidity of rice noodles. The addition of lentil protein had less effect on the texture quality of rice noodles when compared with the red lentil and rice protein. Lentil protein decreased the starch digestibility of BR noodles, thereby reducing the estimated glycemic index (eGI) from 70.48 to 65.33. XRD and FTIR revealed that lentil protein increased the relative crystallinity and 1047/1022 cm⁻¹ ratio. Ordered structure could effectively limit the interaction between amylase and starch, and reduce its digestibility. Therefore, lentil protein was more suitable to be added in BR noodles to reduce starch digestibility.     

柠檬酸钙和大豆分离蛋白对大米淀粉质构分级的影响

目的 探究柠檬酸钙和大豆分离蛋白对大米淀粉液体食品质构分级的影响。方法 本研究通过国际吞咽障碍饮食标准(International Dysphagia Diet Standardisation Initiative, IDDSI)质构测试、物性分析、快速黏度分析及扫描电镜等技术方法分析柠檬酸钙(0.1%、0.2%和0.3%)和大豆分离蛋白(5%、10%和15%)对大米淀粉质构分级的影响。结果 IDDSI质构测试结果表明,柠檬酸钙使大米淀粉质构等级呈上升趋势(添加量为0.3%时,质构等级由2级变为3级),而大豆分离蛋白使大米淀粉质构等级呈下降趋势。物性分析(A/BE模式)结果表明,添加比例为0.3%的柠檬酸钙的淀粉样品黏度升高51.4%,添加比例为15%的大豆分离蛋白的淀粉样品黏度下降19.4%。快速黏度分析淀粉样品的终值黏度结果与物性分析的黏度结果趋势一致。粒径分析结果表明,柠檬酸钙提高了淀粉颗粒的尺寸,促进了淀粉颗粒的膨胀。大豆分离蛋白减小了淀粉颗粒的尺寸,抑制了淀粉颗粒的膨胀。红外光谱分析表明,钙盐和蛋白的添加量越大,淀粉分子之间的氢键数量减少的越明显。此外,通过扫描电镜观察到柠檬...     

Effects of ultrasound on structural and physical properties of soy protein isolate (SPI) dispersions

The effects of low-frequency (20 kHz) ultrasonication at varying power (200, 400 or 600 W) and time (15 or 30 min) on functional and structural properties of reconstituted soy protein isolate (SPI) dispersions were examined. Ultrasonic treatments reduced both the storage modulus and loss modulus of SPI dispersions and formed more viscous SPI dispersions (fluid character). Moreover, ultrasound treatment significantly decreased the consistency coefficients and increased the flow behaviour index of SPI dispersions. Scanning electron microscopy of lyophilized ultrasonicated SPI showed different microstructure with larger aggregates compared to non-treated SPI. No significant change was observed in the protein electrophoretic patterns by SDS-PAGE. However, free sulfhydryl content, surface hydrophobicity and protein solubility of SPI dispersions were all increased with ultrasonic treatment. Differences in solubility profiles in the presence versus absence of denaturing (0.5% sodium dodecyl sulphate and 6 M urea) and reducing (mercaptoethanol) agents suggested a decrease in non-covalent interactions of SPI in dispersion after ultrasonic treatment. Secondary structure analysis by circular dichroism indicated lower α-helix and random coil in SPI treated at lower power, in contrast to higher α-helix and lower β-sheet in SPI treated with higher power (600 W). In conclusion, under the conditions investigated in this study, ultrasonic treatment resulted in partial unfolding and reduction of intermolecular interactions as demonstrated by increases in free sulfhydryl groups and surface hydrophobicity, leading to improved solubility and fluid character of SPI dispersions, while larger aggregates of ultrasonic-treated SPI in the dry state were formed after lyophilization.     

微生物谷氨酰胺转移酶对大豆分离蛋白凝胶性能的影响

研究了底物浓度、pH、酶浓度、温度、时间、离子浓度和二巯基苏糖醇(DTT)的添加对微生物谷氨酰胺转移酶(MTGase)诱导的大豆分离蛋白(SPI)凝胶强度的影响。结果表明,在SPI溶液中加入MTGase,可以使体系在低温下形成凝胶;SPI低于8%不能形成凝胶;pH7.0,酶量为30U/g蛋白,50℃水浴加热1h,NaCl为0.6N时,均可获得最高的凝胶强度;添加DTT,对体系无影响。     

Effect of adding zein,soy protein isolate and whey protein isolate on the physicochemical and in vitro digestion of proso millet starch

Mixtures of proso millet starch with zein (15%, w/v), soy protein isolate (SPI, 15%, w/v) and whey protein isolate (WPI, 10%, w/v) as starch–protein composites were prepared through heat–moisture treatment, and the effects of protein addition on the physicochemical, structural and digestibility properties of starch were investigated. Rapid Visco Analysis showed that the addition of zein, SPI and WPI gave significantly decreased setback values to 240.7cp, 192.0cp and 83.0cp, respectively, and setback values decreased reflected the excellent cold paste properties. Thermal analysis showed that each protein reduced the enthalpy, but especially WPI (reduced by 94.7%), suggesting that the double helices of the starch granules were decreased. X-ray diffraction showed that starch crystallinity was decreased after protein addition. The digestibility studies revealed that the addition of zein, SPI and WPI decreased the content of rapidly digestible starch and increased the resistant starch content to 8.4%, 14.6% and 17.5%, respectively. The whey protein displayed a more obvious impact on the digestibility of proso millet starch. These results will help guide the production and processing of starchy foods with desirable properties.     

Effects of soy protein isolate,acid-hydrolysed vegetable protein and glucose on the volatile components of extruded wheat starch

The volatile components produced in wheat starch containing 1% soy protein isolate (SPI), and wheat starch/1% SPI combined with 1% glucose, 1% acid-hydrolysed vegetable protein (aHVP), or 1% glucose and 1% aHVP, extruded under different processing conditions (temperatures of 150 or 180 °C and moisture content of 16% or 20%), were identified by gas chromatography–mass spectrometry (GC–MS). Gas chromatography olfactometry (GCO) was used to assess the odour intensity of volatile components present in the starch/glucose/SPI and starch/glucose/SPI/aHVP extrudates obtained at 180 °C. In total, 94 compounds were identified in the eight extrudates. The smallest number (31) was found in the extrudate of the starch/glucose/SPI feedstock processed at 150 °C and the largest (64) in the extrudate of the starch/SPI feedstock processed at 180 °C. Lipid degradation products, such as alkanals, 2-alkanones, 2-alkenals and 2,4-alkadienals, were present in all extrudates in significant quantities. Strecker aldehydes were also present in all extrudates; however, in those extrudates containing aHVP, these compounds were quantitatively the dominant components. Maillard reaction products, such as pyrroles, pyrazines and oxazoles, were mainly found in extrudates containing aHVP whereas sulphur-containing aliphatic compounds were found in all extrudates. The production of the Maillard reaction products and sulphur-containing compounds was favoured by extrusion at 180 °C. Sensory analyses showed that each of the eight extrudates had different odours, and that the extrudates containing both glucose and aHVP possessed the highest overall odour intensity. In addition, SPI was found to have a modifying effect on the volatile content and odour of extrudates also containing glucose and aHVP.     

Physical properties and chemical forces of extruded corn starch fortified with soy protein isolate

The effect of soy protein addition on physical properties of extruded corn starch was studied. The correlations between the chemical bonds in proteins and the physical properties of extrudates were analysed. Increasing soy protein isolate content resulted in higher expansion ratio (ER) but lower bulk density (BD), hardness, water solubility index (WSI), degree of starch gelatinisation (DSG), content of sulphydryl (SH) groups and protein solubility in phosphate buffer. In the other hand, increasing the processing temperature resulted in higher ER, water absorption index, DSG, contents of the SH group and disulphide (SS) bond but in lower specific mechanical energy, BD, hardness and WSI. The results indicated that changes in the chemical bonds in proteins had a significant effect on the apparent physical properties of extrudates. More protein–protein and protein–starch cross‐linking reactions occurred through new chemical linkages, such as the nondisulphide covalent bonds and hydrogen bonds, which are beneficial to the expansion of starch‐based products.     

谷氨酰胺转氨酶对大豆分离蛋白溶解性和乳化性的影响

以谷氨酰胺转氨酶(Transglutaminase,TG)为交联剂,与大豆分离蛋白(soybean protein isolate,SPI)发生交联反应,通过单因素试验研究热处理温度、TG浓度、交联温度、交联时间、SPI浓度和交联pH值对SPI溶解性和乳化性的影响。结果表明,4%的SPI溶液在70℃下热处理30 min,按照2 U/g SPI的剂量添加TG,在45℃、pH 6.5条件下交联1 h,此时SPI的溶解性、乳化活性和乳化稳定性分别为0.037 g/mL、328.868 cm-1、0.951。与未经处理的4%SPI相比,TG交联SPI的乳化活性和乳化稳定性显著提高,但溶解性显著下降。     

Antioxidant activities and functional properties of soy protein isolate hydrolysates obtained using microbial proteases

Soy protein isolate (SPI) hydrolysates were prepared using microbial proteases to produce peptides with antioxidant activity. The process parameters (substrate and enzyme concentrations), hydrolysis time, functional properties and the effects of ultrafiltration were further investigated. The results showed that the soy protein isolate exhibited a 7.0‐fold increase in antioxidant activity after hydrolysis. The hydrolysis parameters, defined by the experimental design, were a substrate concentration of 90 mg mL^?1 and the addition of 70.0 U of protease per mL of reaction. The maximum antioxidant activities were observed between 120 and 180 min of hydrolysis, where the degree of hydrolysis was approximately 20.0%. The hydrolysis increased solubility of the soy protein isolate; however, the hydrolysates exhibited a tendency to decrease in the interfacial activities and the heat stability. The SPI hydrolysates fractions obtained by ultrafiltration showed that the enzymatic hydrolysis resulted in samples with homogenous size and strong antioxidant activity.     

Effect of high pressure treatment on aggregation and structural properties of soy protein isolate

The aggregation and structural properties of soy protein isolate (SPI), induced by high pressure (HP) treatment at 200-600 MPa were investigated by size-exclusion chromatography combined with multi-angle laser scattering (SEC-MALLS) and fourier transform infrared (FTIR) spectroscopy. HP treatment at lower pressure level (e.g., 200 MPa) resulted in formation of marked insoluble aggregate of SPI, while the treatment at higher pressure level (e.g., 600 MPa) led to transformation of insoluble aggregate to soluble one. The soluble aggregate formed at 400 or 600 MPa had much less mean molecular weight (MW) (about 5.2 × 10⁶ g/mol) than that at 200 MPa (about 1.6 × 10⁷ g/mol), and was also much more homogenous in MW distribution. FTIR analyses confirmed changes in secondary and tertiary structures, induced by HP treatment. These results can provide direct evidence or explanation for HP-induced modification of soy proteins.