Effect of transglutaminase on rheological properties and microstructure of chemically acidified sodium caseinate gels

Functional Properties of Casein and Caseinate Produced by Electrodialysis with Bipolar Membrane Coupled to an Ultrafiltration Module

Electrodialysis with a bipolar membrane coupled to an ultrafiltration module (EDBM-UF) is a hybrid technology recently developed as an ecofriendly alternative to chemical acidification to produce casein and caseinate from skim milk. In this study, the composition and functional properties of casein and caseinate obtained by chemical acidification/basification and by the EDBM-UF method from winter and summer milks were analyzed and compared. Results show that the emulsifying properties, solubility, water holding, and gelling capacities are equivalent between casein and caseinate from both methods. However, the foaming properties of EDBM-UF ingredients were improved, and casein was less hygroscopic. Additionally, the season of milk influenced certain functional properties, such as water-holding capacity and hygroscopicity. Therefore, these results allow concluding that EDBM-UF ingredients have equivalent or higher functionality than chemically produced ingredients, and that the EDBM-UF process would be a more eco-efficient alternative to the chemical one.

Size Modulation of Enzymatically Cross-Linked Sodium Caseinate Nanoparticles via Ionic Strength Variation Affects the Properties of Acid-Induced Gels

Enzymatic cross-linking by microbial transglutaminase is a prominent approach to modify the structure and techno-functional properties of food proteins such as casein. However, some of the factors that influence structure-function-interrelations are still unknown. In this study, the size of cross-linked sodium caseinate nanoparticles was modulated by varying the ionic milieu during incubation with the enzyme. As was revealed by size exclusion chromatography, cross-linking at higher ionic strength resulted in larger casein particles. These formed acid-induced gels with higher stiffness and lower susceptibility to forced syneresis compared to those where the same number of ions was added after the cross-linking process. The results show that variations of the ionic milieu during enzymatic cross-linking of casein can be helpful to obtain specific modifications of its molecular structure and certain techno-functional properties. Such knowledge is crucial for the design of protein ingredients with targeted structure and techno-functionality.

Structural characterization of nanoemulsions stabilized with sodium caseinate and of the hydrogels prepared from them by acid-induced gelation

Hydrogels obtained by acidification with glucono-δ-lactone (GDL), starting from nanoemulsions formulated with different concentrations of sodium caseinate (1-4 wt%) or 4 wt% sodium caseinate and sucrose (2-8 wt%), were prepared with the aim of quantifying structural parameters of both, initial nanoemulsions and hydrogels after 2.5 h of GDL addition, using the Guinier-Porod (GP) or the generalized GP models. Gelation process was followed by performing in situ temperature-controlled X-ray small angle scattering experiments (SAXS) using synchrotron radiation. In nanoemulsions, the calculated radius of gyration for oil nanodroplets (Rg _oil ) decreased with increasing protein concentration and for the 4 wt% protein nanoemulsion, with increasing sucrose content. Calculated values of Rg _oil were validated correlating them with experimental Z-average values as measured by dynamic light scattering (DLS). For hydrogels, radii of gyration for the sphere equivalent to the hydrogel scattering object (R _gsph ) were close to 3 nm while correlation distances among building blocks (R _g2 ) were dependent on formulation. They increased with increasing contents of sodium caseinate and sucrose. R _g2 parameter linearly correlated with hydrogel strength (G' _∞ ): a more connected nanostructure led to a stronger hydrogel.

Comparison of the Effects of the Alcalase-Hydrolysates of Caseinate, and of Fish and Bovine Gelatins on the Acidification and Textural Features of Set-Style Skimmed Yogurt-Type Products

Commercial caseinate and two gelatins from bovine and fish skin were hydrolyzed by alcalase, and used at 2 g/kg in skimmed bovine milk that was then fermented with a commercial direct vat set starter, to clarify different effects of these hydrolysates on acidification and textural attributes of set-style yogurt samples. Compared with the fermentation of the yogurt sample without hydrolysate addition, the two gelatin hydrolysates in the yogurt samples endowed lower titratable acidity but higher pH values and thus delayed yogurt fermentation, while the caseinate hydrolysate showed an effect opposite to the two gelatin hydrolysates. The two gelatin hydrolysates induced worse quality attributes for the resultant yogurt samples, including higher syneresis extent, smaller hysteresis loop areas, and lower values in these textural indices like hardness, adhesiveness, apparent viscosity, elastic and viscous moduli. However, the caseinate hydrolysate led to improved quality attributes. Moreover, bovine gelatin hydrolysate always had a greater negative effect than fish gelatin hydrolysate on yogurt acidification and texture. It is concluded that these gelatin hydrolysates could confer the yogurt with intended bio-activities of gelatin hydrolysates but negatively impact yogurt acidification and texture, while the caseinate hydrolysate might be helpful for yogurt processing by shortening fermentation time and improving yogurt texture.

Physicochemical evaluation of low-fat yoghurt produced with microbial transglutaminase

BACKGROUND

Currently consumers demand low-fat or non-fat yoghurt but their physical properties are less attractive than those of full-fat yoghurt. It was reported that microbial transglutaminase (TG) can be used in the production of low-fat yoghurt. The aim of this work was to evaluate the effect of TG on low-fat yoghurt to improve their physicochemical and textural properties to approach to those of full-fat yoghurt. Two TG application methods (addition before fermentation or simultaneous addition with the starter), three dose levels and TG origin were evaluated. Results were compared with commercial low-fat and full-fat yoghurts.

RESULTS

No significant differences between application methods were observed. Simultaneous addition of TG was preferred because additional time-consuming steps are not required. The best dose was 1 U TG g^-1 of protein that allowed a firmness higher (4.25 N) than that of commercial low-fat (3.05 N) and full-fat (4.43 N) yoghurts to be achieved. This implies that intermediate values of TG will permit the same firmness as commercial yoghurts to be obtained. It was observed some differences by the TG origin may be due to excipients.

CONCLUSION

TG may be used to replace stabilizers in the production of low-fat yoghurt as it improves texture and avoids initial syneresis. © 2018 Society of Chemical Industry.

Transglutaminase Applications in Dairy Technology

Consumers' expectations from a dairy product have changed dramatically during the last two decades. People are now more eager to purchase more nutritious dairy foods with improved sensory characteristics. Dairy industry has made many efforts to meet such expectations and numerious production strategies and alternatives have been developed over the years including non-thermal processing, membrane applications, enzymatic modifications of milk components, and so on. Among these novel approaches, transglutaminase (TG)-mediated modifications of milk proteins have become fairly popular and such modifications in dairy proteins offer many advantages to the dairy industry. Since late 1980s, a great number of researches have been done on TG applications in milk and dairy products. Especially, milk proteins-based edible films and gels from milk treated with TG have found many application fields at industrial level. This chapter reviews the characteristics of microbial-origin TG as well as its mode of action and recent developments in TG applications in dairy technology.

A sensitive HPLC-MS/MS method for the simultaneous detection of microbial transglutaminase, and bovine and porcine fibrinogen/thrombin in restructured meat

A sensitive HPLC-MS/MS method for the simultaneous detection of microbial transglutaminase (TG) from Streptomyces mobaraensis, and bovine and porcine fibrinogen/thrombin in restructured meat was developed using tryptic marker peptides of TG (five markers), and bovine and porcine fibrinogen (six markers each). Meat binding experiments with beef and pork were performed using a technical TG mixture (Activa, Ajinomoto), and bovine and porcine plasmapowder FG (PPFG; Sonac B.V.). The method developed allows the simultaneous detection of the use of these cold-set binders in raw and heated samples. The peak areas of the fibrinogen marker peptides were increased by a factor of about 100, compared to blank values originating from the occurrence of residual blood in meat, using a concentration of 0.6% bovine and porcine PPFG. A differentiation between the use of blood plasma powder and PPFG using the ratios of fibrinogen to serotransferrin peptide peak areas seems to be possible.

A sensitive high performance liquid chromatography-tandem mass spectrometry method for the detection of microbial transglutaminase in different types of restructured meat

A sensitive HPLC-MS/MS-method for the detection of microbial transglutaminase (TG) from Streptomyces mobaraensis in different types of restructured meat (pork, beef, chicken, and turkey) was developed using six tryptic marker peptides (8-11 amino acids). Meat binding experiments were performed with two technical TG mixtures with and without caseinate. After optimization of the conditions of extraction and tryptic digestion, restructured meat and blank values (total samples: 62) were analyzed in a raw and heated state. By investigation of samples pre-treated with oil marinade, emulsion marinade, seasoning salt as well as breadcrumbs, only very little effects of the type of pre-treatment on the detectability of TG were found. Using four marker peptides, no false-positive or false-negative results were obtained. The limit of detection (LOD) was about a factor of 10 below the recommended amount of transglutaminase for raw as well as heated restructured meat.

Porous protein-based scaffolds prepared through freezing as potential scaffolds for tissue engineering

Successful tissue engineering with the aid of a polymer scaffold offers the possibility to produce a larger construct and to mould the shape after the defect. We investigated the use of cryogelation to form protein-based scaffolds through different types of formation mechanisms; enzymatic crosslinking, chemical crosslinking, and non-covalent interactions. Casein was found to best suited for enzymatic crosslinking, gelatin for chemical crosslinking, and ovalbumin for non-covalent interactions. Fibroblasts and myoblasts were used to evaluate the cryogels for tissue engineering purposes. The stability of the cryogels over time in culture differed depending on formation mechanism. Casein cryogels showed best potential to be used in skeletal tissue engineering, whereas gelatin cryogels would be more suitable for compliable soft tissues even though it also seemed to support a myogenic phenotype. Ovalbumin cryogels would be better suited for elastic tissues with faster regeneration properties due to its faster degradation time. Overall, the cryogelation technique offers a fast, cheap and reproducible way of creating porous scaffolds from proteins without the use of toxic compounds.

Quality indices of the set-yoghurt prepared from bovine milk treated with horseradish peroxidase

Horseradish peroxidase (HRP, EC 1.11.1.7) was applied to treat whole bovine milk in the presence or absence of ferulic acid (FA). The treated milk exhibited different rheological properties from the control milk, and was used to prepare set-yoghurt with commercial direct vat set starter. Some chemical, textural and rheological properties of the yoghurt prepared were measured and compared. Compared to that prepared with the control milk, the yoghurt prepared with the HRP- or HRP and FA-treated bovine milk exhibited an increased hardness and adhesiveness, lower syneresis extent, higher apparent viscosity, and higher storage modulus and viscous modulus. Observation of the microstructure of the yoghurt samples under scanning electron microscopy illustrated that HRP treatment of bovine milk led to the prepared yoghurt a more compact and uniform structure. The results in the present work stated that treatment of bovine milk with HRP in the presence of ferulic acid could be applied to improve the quality of set-yoghurt.