Soy protein isolate (SPI) gels were produced using single cross-linking agents (SCLA) of microbial transglutaminase (MTG) via incubation for 5 or 24 h (SCLA-MTG). When powdered SCLA-MTG gels were heated for 2 h with ribose (R2) (2 g/100 mL), dark brown gels were formed, and these were designated as combined cross-linking agent (CCLA) gels: MTG5(R2) and MTG24(R2). The results showed that the levels of Maillard-derived browning and cross-links of MTG5(R2) and MTG24(R2) gels were significantly (P < 0.05) lower than a control gel produced without MTG (SCLA-R2) even though the percentage of ribose remaining after heating of these gels was similar, indicating that a similar amount of ribose was consumed during heating. epsilon-(gamma-glutamyl)lysine bonds formed during incubation of SPI with MTG may have reduced the free amino group of SPI to take part in the Maillard reaction; nevertheless, ribose took part in the Maillard reaction and initiated the Maillard cross-linkings within the CCLA gels.
Nine formulations were processed into bologna with different ratios of soy protein isolate (SPI):sodium caseinate (SCA), i.e. 1:1, 1:2.5, 1:5, 5:1, 5:2.5, 5:5, 10:1, 10:2.5 and 10:5. The products were evaluated for yields, emulsion stability, physical measurements (shearforce-kgf and folding test) and taste panel evaluation. Formulations with 5:1 and 5:5 SPI:SCA had lower liquid loss resulting in higher yields while the others had poor emulsion stability and high liquid loss. Firmer texture was exhibited by formulations 1:1, 5:1 and 10:1 SPI:SCA but formulation with 1:1 SPI:SCA showed better gelation followed by 1:2.5, 1:5, 5:1, and 5:2.5. The other formulations had poor gelation and binding properties, especially formulation with 10:5 SPI:SCA. Sensory evaluation was carried out using 30 untrained panelists. Attributes evaluated were aroma, texture, chewiness, juiciness, saltiness, chicken taste and overall acceptance. Formulation with 5:1 SPI:SCA was more acceptable for texture, chicken taste and overall acceptance while formulation with 1:1 SPI:SCA was more acceptable for the chewiness, juiciness and saltiness attributes. There was no significant difference (P > 0.05) in aroma attribute, for all formulations.
A process for enhancing textural and cooking properties of fresh rice flour-soy protein isolate noodles (RNS) to match those of yellow alkaline noodles (YAN) was developed by incorporating microbial transglutaminase (RNS-MTG), glucono-δ-lactone (RNS-GDL), and both MTG and GDL into the RNS noodles (RNS-COM). The formation of γ-glutamyl-lysine bonds in RNS-COM and RNS-MTG was shown by sodium dodecyl sulfate polyacrylamide gel electrophoresis. Scanning electron microscope showed that compared to others, the structure of RNS-COM was denser, smoother with extensive apparent interconnectivity of aggregates. The optimum cooking time was in the order: YAN > RNS-COM > RNS-MTG > RNS-GDL > RN (rice flour noodles); tensile strength was in the order: YAN > RNS-COM > RNS-MTG > RNS-GDL > RN; and elasticity were in the order: YAN > RNS-COM > RNS-MTG, RNS-GDL > RN. Overall, RNS-COM showed similar textural and structural breakdown parameters as compared to those of YAN. Changes in microstructures and improvement of RNS-COM in certain properties were likely due to enhanced crosslinking of proteins attributed to MTG- and GDL-induced cold gelation of proteins at reduced pH value. It is possible to use the combination of MTG and GDL to improve textural and mechanical properties of RNS comparable to those of YAN. PRACTICAL APPLICATION: Combined MTG and GDL yield rice flour noodles with improved textural properties. The restructured rice flour noodles have the potential to replace yellow alkaline noodles.
The present study aims to design a milk fat globule membrane (MFGM)-inspired structured membrane (phospholipid- and protein-rich) for microencapsulation of docosahexaenoic acid (DHA) oil. DHA-enriched oil emulsions were prepared using different ratios of sunflower phospholipid (SPL), proteins [whey protein concentrate (WPC), soy protein isolate (SPI), and sodium caseinate (SC)], and maltodextrin and spray-dried to obtain DHA microcapsules. The prepared DHA oil emulsions have nanosized particles. SPLs were found to affect the secondary structure of WPC, which resulted in increased exposure of the protein hydrophobic site and emulsion stability. SPL also reduced the surface tension and viscosity of the DHA oil emulsions. In vitro digestion of the spray-dried DHA microcapsules showed that they were able to effectively resist gastric proteolysis and protect their bioactivity en route to the intestine. The DHA microcapsules have a high lipid digestibility in the small intestine with a high DHA hydrolysis efficiency (74.3%), which is higher than that of commercial DHA microcapsules.
Cross-linked soy protein isolate (SPI) gels were produced via single-treatment of SPI with microbial transglutaminase (MTG) for 5 h or 24 h, or with ribose for 2 h, or via combined-treatments of SPI with MTG followed by heating with ribose. Assessment of gel strength and solubility concluded that measures which increased protein cross-links resulted in improved gel strength; however, in most cases the digestibility and amino acid content of the gels were reduced. The combined treated gel of SPI/MTG for 24 h/ribose was more easily digested by digestive enzymes and retained higher amounts of amino acids compared with the control Maillard gels of SPI with ribose. MTG consumed lysine and glutamine and reduced the availability of amino acids for the Maillard reaction with ribose. MTG was able to preserve the nutritional value of SPI against the destructive effect of the Maillard reaction and cross-links.
In this study, four different selected wall materials (namely gelatin, soy protein isolate, maltodextrin and Arabic gum) were applied for blueberry anthocyanin extract encapsulation. The effect of these wall material types on the release and degradation of anthocyanin and the modulation of gut microbiota during in vitro simulated gastrointestinal digestion and colonic fermentation were investigated. It was found that the encapsulation of anthocyanin extract using appropriate wall material could significantly enhance the colonic accessibility of anthocyanins. Soy protein isolate and gelatin delayed the release of anthocyanins, whereas the other two wall materials displayed no significant effect on the release time of anthocyanins. Gut microbiota mainly metabolized some phenolic compounds such as 4-hydroxycinnamic acid and chlorogenic acid. Meanwhile, different fermented anthocyanin extract microcapsule broth could significantly decrease the composition and abundance of Firmicutes and increase that of Bacteroidetes. Furthermore, the presence of anthocyanin extract microcapsules, especially those encapsulated with soy protein isolate, promoted the biosynthesis of short-chain fatty acids by gut microbiota. It is concluded that, amongst the wall materials studied, soy protein isolate appeared to be a functional and suitable candidate to delay anthocyanin release and prevent disease through the promotion of gut health.
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.