Effect of transglutaminase-treated milk powders on the properties of skim milk yoghurt

Optimizing Skim Milk Yogurt Properties: Combined Impact of Trans-glutaminase and Protein-Glutaminase

The lack of fat in yogurt can lead to alterations in taste and whey separation, reducing consumer acceptance. In this study, the feasibility of enhancing the quality of skim milk yogurt through a combination of transglutaminase (TG) and protein-glutaminase (PG) was investigated. The combination of TG and PG resulted in simultaneous cross-linking and deamidated of casein micelles, with PG deamidation taking priority over TG cross-linking, leading to higher solubility and lower turbidity of milk proteins compared with TG alone. When 0.06 U/mL TG and 0.03 U/mL PG were added, firmness and viscosity indexes significantly increased by 38.26 and 78.59%, respectively as compared with the control. Microscopic images revealed increased cross-linking with casein and filling of cavities by smaller sub-micelles in the combination of TG and PG treatment. Furthermore, the combination of TG and PG resolved issues of rough taste and whey separation, leading to improved overall liking. This study highlights the benefits of using both enzymes in dairy production and has important implication for future research.

Transglutaminase in Foods and Biotechnology

Stabilization and reusability of enzyme transglutaminase (TGM) are important goals for the enzymatic process since immobilizing TGM plays an important role in different technologies and industries. TGM can be used in many applications. In the food industry, it plays a role as a protein-modifying enzyme, while, in biotechnology and pharmaceutical applications, it is used in mediated bioconjugation due to its extraordinary crosslinking ability. TGMs (EC 2.3.2.13) are enzymes that catalyze the formation of a covalent bond between a free amino group of protein-bound or peptide-bound lysine, which acts as an acyl acceptor, and the γ-carboxamide group of protein-bound or peptide-bound glutamine, which acts as an acyl donor. This results in the modification of proteins through either intramolecular or intermolecular crosslinking, which improves the use of the respective proteins significantly.

Assessment of angiotensin converting enzyme inhibitory activity and quality attributes of yoghurt enriched with Cinnamomum verum, Elettaria cardamomum, Beta vulgaris and Brassica oleracea

The new concept of functional foods has led to the varieties in the production of foods that provide not only basic nutrition, but can also warrant good health and longevity. This study deals with the production and evaluation of fortified yogurts' with Cinnamomum verum, Elettaria cardamomum, Beta vulgaris and Brassica oleracea. The qualitative and quantitative phytochemical analysis of above mentioned plant extracts before using them into the preparation of functional yoghurt was carried out. The sensory evaluation of enriched yogurts with plant extracts carried out using 9 point hedonic scale. Comparative analysis between enriched yogurts and plain yogurt was carried. The results indicated increase in ash contents, water holding capacity, titratable acidity, total soluble solids, total phenolic content, tannin content, and total flavonoid content in fortified yogurt as compared to plain yogurt. In addition to this fortified yogurts showed greater antioxidant and antibacterial activity in contrast to plain yogurt. However, moisture contents, pH and susceptibility to syneresis of yogurt decreases with the addition of plant extracts. Shelf life of plain and fortified yogurt was determined both at room and refrigerated temperature. The results revealed that shelf life of fortified yogurt was greater as compared to plain yogurt. In silico analysis was carried out by using the galaxy web software. The results indicated that bioactive compounds including ascorbic acid, sinapinic acid, cinnamaldehyde and linalool acetate present in the flavored yogurts binds with angiotensin converting enzyme. All enriched yogurts showed higher anti-Angiotensin converting enzyme activity as compared to plain-yogurt.

Functional and physiochemical properties of the yoghurt modified by heat lactosylation and microbial transglutaminase cross-linking of milk proteins

This study aimed to recognize the effect of Maillard reaction (MR) on the functional properties of milk proteins and the physiochemical, textural, and sensory properties of yoghurt. Heating at 100°C for 2 h increased the carbohydrate ratio in caseins, whey proteins, and total milk proteins from 2.83%, 1.93%, and 1.8% to 4.15%, 3.58%, and 5.32%, respectively. Solubility of the lactosylated caseins, whey proteins, and total milk proteins is increased at low pH values compared to that of the control caseins, whey proteins, and total milk proteins. Lactosylation at 70 and 100°C increased the emulsion activity index (EAI) of caseins at all pH values, especially at pH below 6, and this increment was higher for casein samples treated at 100°C. Foam volume of whey proteins and total milk proteins also increased for samples lactosylated at 100°C compared to control samples. The combination of heating and microbial transglutaminase (MTGase) had a synergistic and enhancing effect on the pH values of yoghurt samples, especially in yoghurt samples produced by whole milk protein compared to control samples. Viscosity and hardness of yoghurt samples were enhanced by heat lactosylation, MTGase treatment, and also storage for 21 days at 7 ± 1°C.

Possible inhibitory effect of microbial transglutaminase on the formation of biogenic amines during Trappist cheese ripening

Trappist cheese (semi-hard, rennet-coagulated cheese with round eyes) was manufactured and matured for 4 weeks at 12 ± 1°C, 85% relative humidity (RH). The effect of microbial transglutaminase (MTGase) was followed by measuring the levels of free amino acids (FAAs) and biogenic amines (BAs) every 2 weeks during 4 weeks of cheese ripening. Results show that MTGase can decrease the cadaverine production by 30%, but only at the initial stage of ripening. Application of MTGase results in 49% less putrescine, 12% less tyramine production at the end of 4 weeks ripening time, and can decrease histamine levels by 8% after 2 weeks of ripening time in the examined semi-hard cheese type.

Influence of Transglutaminase Crosslinking on Casein Protein Fractionation during Low Temperature Microfiltration

Low temperature microfiltration (MF) is applied in dairy processing to achieve higher protein and microbiological quality ingredients and to support ingredient innovation; however, low temperature reduces hydrophobic interactions between casein proteins and increases the solubility of colloidal calcium phosphate, promoting reversible dissociation of micellar β-casein into the serum phase, and thus into permeate, during MF. Crosslinking of casein proteins using transglutaminase was studied as an approach to reduce the permeation of casein monomers, which typically results in reduced yield of protein in the retentate fraction. Two treatments (a) 5 °C/24 h (TA) and (b) 40 °C/90 min (TB), were applied to the feed before filtration at 5 °C, with a 0.1 µm membrane. Flux was high for TA treatment possibly due to the stabilising effect of transglutaminase on casein micelles. It is likely that formation of isopeptide bonds within and on the surface of micelles results in the micelles being less readily available for protein-protein and protein–membrane interactions, resulting in less resistance to membrane pores and flow passage, thereby conferring higher permeate flux. The results also showed that permeation of casein monomers into the permeate was significantly reduced after both enzymatic treatments as compared to control feed due to the reduced molecular mobility of soluble casein, mainly β-casein, caused by transglutaminase crosslinking.

The Effect of Microbial Transglutaminase on the Viscosity and Protein Network of Kefir Made from Cow, Goat, or Donkey Milk

In this study, we aim to decrease the fermentation time and to produce low-fat set-type kefir with adequate textural properties using microbial transglutaminase without inactivation. In addition, we reveal the effect of microbial transglutaminase, during and after fermentation, on kefir made with cow, goat, or donkey milk, which is a novel approach. Fermentation is followed by continuous pH and viscosity measurements; the final product is characterized by dry matter content, whey separation, protein pattern, and viscosity parameters, as well as gel firmness. The results show that already 0.5 U/g protein dosage of MTGase decreases pH levels independent of milk type, but MTGase does not influence the kinetics of fermentation. Apparent viscosity could be measured from different stages of fermentation depending on milk type (cow milk, 6 h; goat milk, 8 h; and donkey milk, 9 h). The final product characteristics show that the higher the casein ratio of the applied milk, the better the viscosity and gel firmness of the kefir due to the high reaction affinity of MTGase.

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.

Property changes of caseinate in response to its dityrosine formation induced by horseradish peroxidase, glucose oxidase and d-glucose

BACKGROUND

A ternary system containing horseradish peroxidase (HRP), glucose oxidase and d-glucose using one- or two-step treatment was evidently able to cross-link proteins via dityrosine formation and thus was assessed for its possible impact on several properties of a protein ingredient caseinate.

RESULTS

HRP, glucose oxidase and d-glucose were used at 200 U, 6 U and 0.05 mmol g^-1 protein to treat caseinate by one- and two-step methods, producing two cross-linked caseinates named CLCN-I and CLCN-II, respectively. In response to the conducted cross-linking, both CLCN-I and CLCN-II gained slightly reduced dispersibility at pH 5-10, enlarged hydrodynamic radius (particle size distribution, 266.37 and 258.33 versus 226.67 nm) and negative zeta-potential (-26.60 and -22.27 versus -14.30 mV) in dispersions, increased water-binding (3.70 and 3.09 versus 2.68 kg kg^-1 protein), decreased oil-binding (1.75 and 2.74 versus 2.87 kg kg^-1 protein) and emulsifying activity (76.2 and 82.3 versus 94.3 m² g^-1 protein), increased emulsion stability (84.3% and 82.5% versus 78.6%), and enhanced thermal stability with lower mass loss (58.5% and 59.6% versus 64.3%) or higher decomposition temperatures (331.2 °C and 328.7 °C versus 327.6 °C) upon heating at 105-450 °C. In addition, CLCN-I and CLCN-II had decreased gelling temperatures and shortened gelling times when forming acid-induced gels, and the gels were endowed with increased values in four textural indices and finer microstructure. Moreover, CLCN-I with a higher cross-linking extent showed greater property changes than CLCN-II.

CONCLUSION

This ternary system could be used in caseinate cross-linking to improve properties such as aggregation, emulsification, gelation and thermal stability. © 2020 Society of Chemical Industry.

The functionality of laccase- or peroxidase-treated potato flour: Role of interactions between protein and protein/starch

Potato flour is used in bakery products, extruded products and snacks. However, it displays weaker gel strengths and thus the wholesome utility is curtailed significantly. To improve viscoelastic properties and stability of potato gels, herein potato flour was treated with laccase and peroxidase to create a protein network structure leading to stable gels. The results revealed that the secondary structure of potato proteins altered upon the enzyme treatment. The gels of peroxidase-treated potato flour (PPF) and laccase-treated potato flour (LPF) displayed larger anti-shear ability, thermal stability and stronger three-dimensional network structure compared to the native potato gel. The PPF and LPF gels exhibited stronger viscoelastic properties and structural stability compared to peroxidase-treated potato protein and laccase-treated potato protein gels. The outcome serves as a theoretical basis to improve the properties of potato gels and to promote the designing and the development of novel potato flour based functional food.

The effect of the addition of microbial transglutaminase before the fermentation process on the quality characteristics of three types of yogurt

The effect of the addition of microbial TGase to milk on selected physical properties of the final product and the viability of lactic acid bacteria cultures during storage at 6 °C for 56 days was studied. Three types of set-style yogurt were made with varying parameters. Weekly analyses included the determination of syneresis and water-holding capacity, texture, pH, and the lactic acid bacteria population. Our research has confirmed that mTGase may be used to stabilize yogurts, although the syneresis, the water-holding capacity of yogurts, and the textural features of yogurts were dependent on the step in the production process at which mTGase was added to milk. The presence of mTGase had no relevance with regard to the acidity of yogurts stored under refrigerated conditions. The addition of mTGase had no effect on lactobacilli, but had a variable effect on Streptococcus thermophilus, depending on the duration of enzymatic activity.

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.

Influence of milk protein cross-linking by transglutaminase on the rennet coagulation time and the gel properties

BACKGROUND

Transglutaminase (TGase) modifies milk proteins by cross-linking of caseins, with increased cheese yield being the main technological benefit. In the present work the influence of TGase addition in different concentrations (0, 1, 2 and 3 U g(-1) protein in the system) and under different incubation conditions (0 h, 40 °C/2 h, 25 °C/4 h and 5 °C/16 h) on the rennet coagulation time (RCT) and the comprehensive rennet gel properties were investigated.

RESULTS

Modification of milk proteins by TGase in a concentration-dependent manner caused longer RCT and lower gel firmness. The highest TGase concentration and incubation at 40 °C for 2 h resulted in the longest RCT and the lowest gel firmness. Rennet gels obtained from TGase modified milk were characterised by significantly lower values of texture parameters, lower syneresis and were composed of smaller casein micelles, thinner chains and smaller clusters than those obtained from the control milk. The content of whey proteins in the gel from modified milk was higher and the content of individual casein fractions in the milk samples and rennet gels decreased upon TGase modification.

CONCLUSION

Rennet cheese with modified textural and nutritional properties and improved yield can be obtained upon TGase modification but simultaneous addition of rennet and TGase is recommended. © 2015 Society of Chemical Industry.

Caseinate-gelatin and caseinate-hydrolyzed gelatin composites formed via transglutaminase: chemical and functional properties

BACKGROUND

Treatment of food proteins by enzymatic crosslinking and other reactions can confer modified properties on the treated proteins. Bovine gelatin and hydrolyzed bovine gelatin were used to generate two caseinate-based composites via transglutaminase, and potential useful properties to food processing were investigated for both composites.

RESULTS

Caseinate-gelatin and caseinate-hydrolyzed gelatin composites contained 33.4 and 10.3 g kg(-1) protein of 4-hydroxyproline, respectively. Caseinate conjugation with gelatin and hydrolyzed gelatin resulted in two composites with stronger absorption at five wavenumbers during Fourier transform-infrared analysis, demonstrating that they were rich in hydroxyl and carboxyl groups. Both composites exhibited higher viscosity values in aqueous dispersions, lower thermal stability (i.e. higher mass loss) during thermogravimetric analysis and worse emulsifying properties than original caseinate, owing to conjugation and crosslinking via transglutaminase. However, confocal laser scanning microscopy (CLSM) analysis revealed that both composites actually had better emulsion stability after 2 weeks of storage.

CONCLUSION

The composites generated were different in chemical characteristics and better in viscosity and emulsion stability than original caseinate. They might have potential as protein thickeners and emulsifiers. CLSM is a better technique to assess emulsion stability of food proteins than the classic turbidity method.