Transglutaminase-Induced Chemical and Rheological Properties of Cheese

Ultrasound-Assisted Transglutaminase Catalysis of the Cross-Linking and Microstructure of αs-Casein, β-Casein and κ-Casein

The effects of ultrasonic treatment (UT)-assisted transglutaminase (TGase) catalysis on the physicochemical properties of individual αs-casein (αs-CN), β-casein (β-CN), and κ-casein (κ-CN) were investigated. After 60 min of incubation at 30 °C, αs-CN, β-CN, and κ-CN were cross-linked with TGase (6.0 units/mL), and high molecular weight polymers (>200 kDa) were formed. The use of TGase in conjunction with UT (20 kHz, power of 400 W, and amplitude 20%) led to an increase in the rate of αs-CN, β-CN, and κ-CN polymerization compared to the individual casein that contained TGase but did not undergo UT. SDS-PAGE scrutiny showed that the intensities of αs-CN, β-CN, and κ-CN incubation with regard to TGase and UT at 30 °C for 60 min noticeably decreased to 5.66 ± 0.39, 3.97 ± 0.43, and 26.07 ± 1.18%, respectively (p < 0.05). Particle size analysis results indicated that the molecule size appropriation for the cross-linking of αs-CN, β-CN, and κ-CN ranged from 6000 to 10,000 nm after 60 min incubation with TGase and UT. Transmission electron microscopy investigation showed network structures of cross-linking αs-CN, β-CN, and κ-CN were formed from αs-CN, β-CN, and κ-CN, respectively. As our results show, the comprehensive utilization of TGase and UT will be a superior method for the polymerization of αs-CN, β-CN, and κ-CN.

New insights into food hydrogels with reinforced mechanical properties: A review on innovative strategies

Enhancement on the mechanical properties of hydrogels leads to a wider range of their applications in various fields. Therefore, there has been a great interest recently for developing new strategies to reinforce hydrogels. Moreover, food gels must be edible in terms of both raw materials and production. This paper reviews innovative techniques such as particle/fiber-reinforced hydrogel, double network, dual crosslinking, freeze-thaw cycles, physical conditioning and soaking methods to improve the mechanical properties of hydrogels. Additionally, their fundamental mechanisms, advantages and disadvantages have been discussed. Important biopolymers that have been employed for these strategies and also their potentials in food applications have been summarized. The general mechanism of these strategies is based on increasing the degree of crosslinking between interacting polymers in hydrogels. These links can be formed by adding fillers (oil droplets or fibers in filled gels) or cross-linkers (regarding double network and soaking method) and also by condensation or alignment of the biopolymers (freeze-thaw cycle and physical conditioning) in the gel network. The properties of particle/fiber-reinforced hydrogels extremely depend on the filler, gel matrix and the interaction between them. In freeze-thaw cycles and physical conditioning methods, it is possible to form new links in the gel network without adding any cross-linkers or fillers. It is expected that the utilization of gels will get broader and more varied in food industries by using these strategies.

Characterization of transglutaminase from Bacillus subtilis and its cross-linking function with a bovine serum albumin model

Finding new crosslinking enzymes for enzyme-mediated protein conjugation is a great need in the food industry. In this research, the properties of Bacillus subtilis transglutaminase (BTG) were characterized in detail and its protein crosslinking functions with bovine serum albumin (BSA) as a model were studied. Compared to the commercial transglutaminase from Streptoverticillium mobaraense, BTG was more stable in a broad range of temperatures (30-60 °C) and pH values (pH 5.0-9.0), with its maximum enzymatic activity at 60 °C and pH 8.0. The protein function evaluation results demonstrated that the BTG-modified BSA showed better emulsifying and foaming properties (p < 0.05) compared with the native one. Additionally, significant improvements (p < 0.05) were observed in the rheological properties, water holding capacity, and textural properties of the BTG-treated BSA gels. With good thermal and pH stability and excellent crosslinking effects, BTG would be a potential enzyme for food structure engineering to improve the functional properties of food proteins and expand their applications.

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.

Yield and Textural Characteristics of Panela Cheeses Produced with Dairy-Vegetable Protein (Soybean or Peanut) Blends Supplemented with Transglutaminase

The study evaluated panela cheeses made from dairy-plant protein blends, using soybean or peanut protein isolates, supplemented with transglutaminase (TG). Plant proteins were isolated using an alkaline extraction method followed by acid precipitation, and added to the dairy system in order to increase 50% or 100% the protein concentration. The total protein extraction for peanut and soybean isolates was 30.3% and 54.6%, respectively (based on initial protein content of sources), and no impairment of their essential amino acid profile was detected. Cheeses supplemented with TG and soybean showed the highest moisture and crude yield (>67.8% and 20.7%, respectively), whereas protein content was higher in the peanut isolate--added samples without TG (>67.4%). Cheese solids yield (ratio between final and initial solids) was higher for treatments with TG and 100% of plant protein addition (>50.7%). Regarding texture, 4 parameters were measured: hardness, cohesiveness, chewiness, and springiness. All cheeses containing soybean isolates and TG presented the highest chewiness and cohesiveness values, similar to those of the control treatment. Springiness was similar for all treatments, but hardness was higher in cheeses prepared with the peanut protein isolate added with TG. From these results it can be concluded that panela cheeses can be elaborated following a traditional procedure, but with the addition of soybean or peanut protein to the dairy ingredients. Cheeses containing these protein isolates showed higher protein than the milk control cheese and similar textural characteristics.