Transglutaminase Levels Research Articles

Determination of the optimum mixture of transglutaminase, l-ascorbic acid and xylanase for the quality and consumer acceptability of bread using response surface methodology.

The optimum levels of transglutaminase (TGase), l-ascorbic acid (l-AA), and xylanase (Xyl) were determined using response surface methodology to improve quality and consumer acceptability of bread made with wheat flour. A Box-Behnken design with three independent variables (TGase, l-AA, and Xyl) and three levels was used to develop models for the different responses (peak time, mixing tolerance, extensibility, resistance, specific volume, hardness, and consumer acceptability). Overall, l-AA and Xyl improved dough and bread properties, whereas the addition of TGase positively affected to texture and overall acceptability by consumer test. The optimal formulation for dough and bread properties and consumer acceptability were identified and the optimal value was 0.36 g/100 g TGase, 0.026 g/100 g Xyl, and 0.005 g/100 g l-AA. The results demonstrate that the addition of optimum amounts of TGase, Xyl, and l-AA improves the baking quality of the flour by enhancing dough properties and increase the consumer acceptability of the bread.

Effects of Oxidative Stress on the Conjunctiva in Cu, Zn-Superoxide Dismutase-1 (Sod1)–Knockout Mice

A healthy conjunctiva secreting mucins is essential for maintaining the integrity of the ocular surface epithelium. We used Cu, Zn-superoxide dismutase 1-deficient mice (Sod1-/- mice) and investigated the effect of oxidative stress on the tear function, conjunctival phenotype, and ocular surface mucin expression. Fifty-week-old C57/B6 wild-type (WT) and Sod1-/- mice were used for evaluations of the tear film breakup time and periodic acid Schiff staining of the conjunctival specimens to detect goblet cell densities in the conjunctiva. Immunohistochemistry stainings with anti-Muc5AC, anti-Muc1, anti-4-hydroxy-2-nonenal, and anti-8-hydroxy-2'-deoxyguanosine antibodies were also performed. The mRNA expression levels of Muc1, Muc5AC, Spdef, involcurin, and transglutaminase 1 were quantified with real-time RT-PCR. The mean goblet cell density in the aged Sod1-/- mice was significantly lower than the aged WT mice. The mean number of Muc5ac-positive cells was significantly lower in the aged Sod1-/- mice compared with the aged WT mice. The conjunctival epithelium in the aged Sod1-/- mice displayed marked staining with lipid and DNA oxidative stress markers. The mRNA expression of transglutaminase 1 and involcurin in the aged Sod1-/- mice was significantly higher than the aged WT mice. The Spdef mRNA expression in the aged Sod1-/- mice was also significantly lower than the aged WT mice. Elevated oxidative stress status appears to affect the conjunctival differentiation and alter the conjunctival epithelial phenotype with aging in the Sod1-/- mice.

INCREASED TISSUE TRANSGLUTAMINASE LEVELS ARE ASSOCIATED WITH INCREASED EPILEPTIFORM ACTIVITY IN ELECTROENCEPHALOGRAPHY AMONG PATIENTS WITH CELIAC DISEASE.

Celiac disease is an autoimmune systemic disorder in genetically predisposed individuals precipitated by gluten ingestion. In this study, we aimed to determine asymptomatic spike-and-wave findings on electroencephalography in children with celiac disease. A total of 175 children with the diagnosis of celiac disease (study group) and 99 age- and sex-matched healthy children as controls (control group) were included in the study. In order to determine the effects of gluten free diet on laboratory and electroencephalography findings, the celiac group is further subdivided into two as newly-diagnosed and formerly-diagnosed patients. Medical histories of all children and laboratory findings were all recorded and neurologic statuses were evaluated. All patients underwent a sleep and awake electroencephalography. Among 175 celiac disease patients included in the study, 43 were newly diagnosed while 132 were formerly-diagnosed patients. In electroencephalography evaluation of patients the epileptiform activity was determined in 4 (9.3%) of newly diagnosed and in 2 (1.5%) of formerly diagnosed patients; on the other hand the epileptiform activity was present in only 1 (1.0%) of control cases. There was a statistically significant difference between groups in regards to the presence of epileptiform activity in electroencephalography. Pearson correlation analysis revealed that epileptiform activity in both sleep and awake electroencephalography were positively correlated with tissue transglutaminase levels (P=0.014 and P=0.019, respectively). We have determined an increased epileptiform activity frequency among newly-diagnosed celiac disease patients compared with formerly-diagnosed celiac disease patients and control cases. Moreover the tissue transglutaminase levels were also correlated with the presence of epileptiform activity in electroencephalography. Among newly diagnosed celiac disease patients, clinicians should be aware of this association and be alert about any neurological symptoms.

Effects of Carboxymethylcellulose, Yoghurt and Transglutaminase on Textural Properties of Oat Bread

AbstractOat bread was baked with carboxylmethylcellulose (CMC), yoghurt (YG) and transglutaminase (TG) following a 33 Box‐Behnken design consisting of CMC (1, 2 g), YG (10.75, 33.75 g) and TG (0.5, 1.5 g) as independent variables. The dependent variables of interest for the textural properties were hardness, chewiness, gumminess, springiness and specific loaf volume. Increasing CMC (1–2 g) significantly (P < 0.05) increased all the textural parameters of the bread, but not its specific volume (1.49–1.46 mL/g). YG significantly (P < 0.05) decreased the hardness (786.01–593.39 N), chewiness (36.44–20.22 N) and gumminess (2.28–1.21 N), but sightly (P > 0.05) increased the springiness (11.28–11.41 mm) and specific loaf volume (1.51–1.67 mL/g) of the resulting bread. TG significantly (P < 0.05) affected all the textural parameters of oat bread, increased bread hardness (537.85–692.41 N), but decreased other parameters such as gumminess (4.66–2.14 N), springiness (6.47–4.14 mm), and specific loaf volume (1.61–1.54 mL/g) as the level of TG increased from 0.5 to 1.5 g. The objective of the optimization was to establish the amount of CMC, YG and TG required for optimal oat bread production. Hardness, chewiness, gumminess and springiness were used for numerical optimization to estimate the optimal level of ingredients for the production of oat bread. The predicted optimal ingredients for preparing oat bread were: CMC (1 g), yoghurt (33.75 g) and TG (0.98 g) with a desirability of 0.93.Practical ApplicationsThe consumption of oats is increasing worldwide, mainly due to the interest in novel and healthy foods as potential alternative ingredients to wheat flour for breadmaking. However, the absence of gluten development in oat dough leads to bread with a crumbling texture and other postbaking defects. This technological problem has created the need for functional food ingredients such as carboxymethylcellulose (CMC), yoghurt (YG) and transglutaminase (TG) to counteract these undesirable baking and postbaking defects. CMC increased all the textural parameters of bread, except its specific loaf volume. YG decreased the hardness, chewiness and gumminess but increased the resilience (cohesion energy and cohesion force), springiness and specific loaf volume of the resulting bread. TG decreased all the physical and textural parameters of oat bread with exception of hardness which increased. Optimizing the amount of CMC, YG and TG required for oat bread with the most desirable properties is vital because the quality and price of the final product depend on this parameter.

Early response as shown by enhancement of transglutaminase 1 expression after cisplatin-induced acute kidney injury

Acute kidney injury (AKI) is caused by drugs and other stimuli, which limits the use of several therapeutic approaches. The AKI mouse model generated by intraperitoneal administration with cisplatin, one of the most widely used anti-cancer drugs, is generally applied to study on this disease. Transglutaminases are posttranslational modifying enzymes that catalyze irreversible cross-linking reactions between proteins in several biological events such as skin formation and blood coagulation. In this study, we found an increase in the expression level of transglutaminase (TG1) in the kidney of mice which had been injected with cisplatin and underwent progressive nephrotoxicity. Before the appearance of the tentative symptoms of renal failure, which is apparent by morphological damage in the kidney and increases in blood creatinine levels, both the expression level and activity of TG1 rapidly increased mainly at the proximal tubule. On the other hand, the protein expression level of another major isozyme (TG2) remained mostly unaltered. This investigation will provide a possible basal-level biomarker and also information on progression of renal failure from the aspect of the protein-modifying enzyme, transglutaminase.

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

SummaryThe 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.

High rate of spontaneous normalization of celiac serology in a cohort of 446 children with type 1 diabetes: a prospective study.

In children with type 1 diabetes mellitus (T1DM), elevated levels of antitissue transglutaminase (anti-tTG) antibody may spontaneously normalize, despite continued consumption of gluten. We aimed to investigate the prevalence of spontaneous normalization of anti-tTG levels and the existence of factors predictive for this outcome. All children referred from 2002 to 2012 were screened for celiac disease (CD) at diabetes onset and at specific intervals. In the presence of a high anti-tTG titer or clinical symptoms, children were offered endoscopy, and asymptomatic patients with a low anti-tTG titer were invited to a second serological test after 6 months of eating a gluten-containing diet. The study included 446 children. Of these, 65 (14.5%) became positive for celiac serology: 38 (58%) had a persistently elevated anti-tTG titer and 27 (41%) fluctuating anti-tTG titer; 18 (28%) became negative. The prevalence of positive CD autoimmunity and overt CD was 14.3% (95% CI 11-17) and 8.5% (95% CI 5-10), 15- and 8-times higher than the general pediatric population, respectively. Asymptomatic children older than 9.1 years at T1DM onset had the lowest risk to develop CD. Serum anti-tTG levels decreased spontaneously in 40% of children with T1DM and became negative in 20%, despite gluten consumption. This finding supports the hypothesis of a state of temporary positivity of celiac serology in children with diabetes. In absence of clinical symptoms or signs of CD, histological confirmation of the disease and the gluten-free diet should be postponed to avoid unnecessary procedures and reduce an additional psychological burden.

Growth Trajectories and Bone Mineral Density in Anti-Tissue Transglutaminase Antibody–positive Children: The Generation R Study

Increased levels of anti-tissue transglutaminase (tTG) have been associated with reduced weight and bone mineral density (BMD) in symptomatic patients with celiac disease. Little is known about the effects of these antibodies in patients with subclinical or other forms of celiac disease. We examined associations between anti-tTG positivity and growth and BMD. In a population-based prospective cohort study, serum samples were collected from children (median age, 6 years; n = 4442) and analyzed for anti-tTG. All children were born between April 2002 and January 2006 and were not previously diagnosed with celiac disease. Children were categorized as anti-tTG negative (<7 U/mL, n = 4249) or anti-tTG positive (≥7 U/mL, n = 57). Children's levels of anti-tTG were further categorized on the basis of ≥10 times upper limit of normal (70 U/mL). Height, weight, and body mass index (BMI) age- and sex-adjusted standard deviation scores (SDS) ([observed value - mean]/SD) were obtained by using Dutch reference growth charts. BMD was measured by dual-energy x-ray absorptiometry. Multivariable linear regression and linear mixed models were performed. Children who tested positive for anti-tTG had reduced growth in weight SDS/year (reduction of 0.05; 95% CI, reductions of 0.09-0.01) and BMI SDS/year (reduction of 0.10; 95% CI, reductions of 0.18-0.01) from 6 months until 6 years, compared with children without anti-tTG; they also tended to have reduced growth in height from 6 months until 6 years (reduction of 0.02 SDS/year; 95% CI, reductions of 0.06-0.02). Children who tested positive for anti-tTG were shorter (0.29 SDS shorter; 95% CI, reductions of 0.55-0.04 SDS), weighed less (0.38 SDS less; 95% CI, reductions of 0.64-0.12), and had lower BMIs (0.26 SDS less; 95% CI, reductions of 0.49-0.03) and BMDs (0.26 SDS less; 95% CI, reductions of 0.45-0.08) at 6 years of age than anti-tTG negative children. Anti-tTG positive children without gastrointestinal symptoms have lower BMDs and reduced growth trajectories until they are 6 years old. This suggests that subclinical or potential celiac disease can affect BMD and growth.

Optimization of Gluten-Free Cake Prepared from Chestnut Flour and Transglutaminase: Response Surface Methodology Approach

Abstract In this study, the possible usage of chestnut flour in gluten-free cake formulation was investigated. Response surface methodology was used to evaluate the effects of water, xanthan and guar gum mixture and potato starch. Crust and crumb attributes, sensory and textural properties of the cake samples were investigated. Considering all cake properties, better results were obtained by increasing xanthan gum in the gum blend. Increasing the amount of potato starch in the chestnut flour–potato starch blend decreased the batter density, consistency, hardness and chewiness, but increased the specific volume, cohesiveness and scores of the interior and exterior attributes. Optimum concentration of gum mixture was found as 0.225% xanthan gum, 0.075% guar gum and ratio of chestnut flour to potato starch was 7:3. Then, four different levels of transglutaminase were added to control and optimized gluten-free cake formula. The highest desirability value was obtained in gluten-free formula containing 0.25% transglutaminase. According to the results of the sensory analyses, no significant difference was observed between control and gluten-free cake.

Human hair shaft proteomic profiling: individual differences, site specificity and cuticle analysis.

Hair from different individuals can be distinguished by physical properties. Although some data exist on other species, examination of the individual molecular differences within the human hair shaft has not been thoroughly investigated. Shotgun proteomic analysis revealed considerable variation in profile among samples from Caucasian, African–American, Kenyan and Korean subjects. Within these ethnic groups, prominent keratin proteins served to distinguish individual profiles. Differences between ethnic groups, less marked, relied to a large extent on levels of keratin associated proteins. In samples from Caucasian subjects, hair shafts from axillary, beard, pubic and scalp regions exhibited distinguishable profiles, with the last being most different from the others. Finally, the profile of isolated hair cuticle cells was distinguished from that of total hair shaft by levels of more than 20 proteins, the majority of which were prominent keratins. The cuticle also exhibited relatively high levels of epidermal transglutaminase (TGM3), accounting for its observed low degree of protein extraction by denaturants. In addition to providing insight into hair structure, present findings may lead to improvements in differentiating hair from various ethnic origins and offer an approach to extending use of hair in crime scene evidence for distinguishing among individuals.

The Evaluation of The Effects of Paternal And Maternal Silent Coeliac Disease on Birthweight and Gestational Age in Newborns.

Coeliac disease is a chronic disease and is common all over the world. It has many other associated systemic side effects. This study investigated the effect of paternal and maternal silent coeliac disease on birthweight and gestational age in newborns. The study group consisted of 81 newborns who were hospitalized for prematurity or term-intrauterine growth retardation. The parents of premature and/or small for gestational age babies born with coeliac disease-specific antigens were investigated. The differences were not statistically significant in fathers' tissue transglutaminase levels between premature appropriate gestational age, premature small gestational age and term small gestational age infants (p > 0.05), but statistically significant in mothers (p < 0.05). Silent coeliac disease may occur in parents, especially in mothers of preterm and small for gestational age infants, even in the absence of apparent clinical indications.

Effects of low molecular weight soybean peptide on mRNA and protein expression levels of differentiation markers in normal human epidermal keratinocytes.

Low molecular weight soybean peptide (LSP) was applied to normal human epidermal keratinocytes, and the results showed a significant increase in the gene expression levels of involucrin, transglutaminase, and profilaggrin. Filaggrin protein levels were also significantly higher. It is possible that LSP has an epidermal cell differentiation-promoting effect and may be able to regulate metabolism of the epidermis.

Effect of transglutaminase on quality characteristics of a value-added product tilapia wastes.

The aim of this work was to evaluate the physico-chemical, instrumental color and texture, and sensory qualities of restructured tilapia steaks elaborated with small sized (non-commercial) tilapia fillets and different levels of microbial transglutaminase (MTG). Four concentrations of MTG were used: CON (0% MTG), T1 (0.1% MTG), T2 (0.5% MTG), and T3 (0.8% MTG). In addition, bacterial content and pH shifts were also evaluated during 90days of frozen storage. The different levels of MTG did not affect (P > 0.05) either the proximate composition of the restructured tilapia steaks or the bacterial growth during the frozen storage. MTG improved (P < 0.05) cooking yield and instrumental hardness and chewiness as well as sensory (salty taste, succulence and tenderness) attributes; strongly contributing to greater overall acceptance. Therefore, restructured tilapia steaks manufactured with MTG are potentially valued-added products with good consumer acceptance and better purchase-intention than steaks formulated with 0% MTG.

The 55 kDa tissue transglutaminase cross-linking active isoform TG induces cell death

Transamidations are calcium-dependent reactions catalyzed by transglutaminase enzymes. Tissue transglutaminase (TG2 or TGC) is a multifunctional protein with a controversial role in apoptosis. The cross-linking function of transglutaminase enzymes has been shown to play a role in cell death. Human breast cancer cell lines (MCF7 and T47D), which express low endogenous levels of transglutaminase, were transiently transfected with the cross-linking 55 kDa active TG isoform or its precursor the 80 kDa full-length TGC. The increased frequency of apoptosis correlated with the increase in transglutaminase expression and the highest rates of apoptosis were found in cells transfected with the potent TG isoform as compared to the full length TGC. The calcium ionophores A231827 and maitotoxin, which are known to induce transamidation, were found to promote apoptosis, whereas cystamine, an active transglutaminase inhibitor, blocked apoptosis due to the over-expression of the active TG isoform. This is the first time that TG has been used in cellular transfections and the results presented show that TG is a potent inducer of cell death. This finding may help to clarify the conflicting functions of TG in the induction of cell death. The TG-dependent irreversible cross-linking of intracellular proteins, a function previously assigned to TGC, represents an important biochemical event in the induction of the structural changes present in cells during apoptosis.

Evaluation of the use of transglutaminase in dairy drinks made from goat milk

The aim of this study was to evaluate the use of transglutaminase in dairy drinks made from with goat milk with 45% of serum, and the physical, chemical, microbiological and sensory characteristics of these drinks within the expiration date of the product. In the first phase, five different levels of transglutaminase (0, 0.2, 0.3, 0.4, 0.5 U/g) were evaluated. In the second phase, the drink that had the best sensory acceptability was evaluated for 30 days. It was observed that the dairy drink treated with 0.5 U/g transglutaminase showed higher sensory acceptability in relation to the 7.18 overall impression. The color values of the dairy drink treated with 0.5 U/g showed no significant difference (p&lt;0.05). The values of lactic acid bacteria are established according to the legislation. Results show the feasibility of the use of transglutaminase in dairy drinks.

A trichobezoar in a child with undiagnosed celiac disease: A case report

Celiac disease is a chronic, immune-mediated enteropathy caused by a permanent sensitivity to ingested gluten cereals that develops in genetically susceptible individuals. The classic presentation of celiac disease includes symptoms of malabsorption but has long been associated with cognitive, emotional, and behavioral disorders. We describe an 8-year-old patient with non-scarring alopecia and diagnosed with trichotillomania. Furthermore, she presented with a 3-year history of poor appetite and two or three annual episodes of mushy, fatty stools. Laboratory investigations showed a normal hemoglobin concentration and a low ferritin level. Serologic studies showed an elevated tissue immunoglobulin G anti-tissue transglutaminase level. A duodenal biopsy showed subtotal villous atrophy and crypt hyperplasia, and a large gastric trichobezoar was found in the stomach. Immediately after beginning a gluten-free diet, complete relief of trichotillomania and trichophagia was achieved. In this report, we describe a behavioral disorder as a primary phenomenon of celiac disease, irrespective of nutritional status.

Tissue Transglutaminase Contributes to the Pathogenesis of Preeclampsia and Stabilizes Placental Angiotensin Receptor Type 1 by Ubiquitination-Preventing Isopeptide Modification

Preeclampsia is a life-threatening pregnancy disorder that is widely thought to be triggered by impaired placental development. However, the placenta-related pathogenic factors are not fully identified, and their underlying mechanisms in disease development remain unclear. Here, we report that the protein level and enzyme activity of tissue transglutaminase (TG2 or tTG), the most ubiquitous member of a family of enzymes that conducts post-translational modification of proteins by forming ε-(γ-glutamyl)-lysine isopeptide bonds, are significantly elevated in placentas of preeclamptic women. TG2 is localized in the placental syncytiotrophoblasts of patients with preeclampsia where it catalyzes the isopeptide modification of the angiotensin receptor type 1 (AT1). To determine the role of elevated TG2 in preeclampsia, we used a mouse model of preeclampsia based on injection of AT1-agonistic autoantibody. A pathogenic role for TG2 in preeclampsia is suggested by in vivo experiments in which cystamine, a potent transglutaminase inhibitor, or small interfering RNA-mediated TG2 knockdown significantly attenuated autoantibody-induced hypertension and proteinuria in pregnant mice. Cystamine treatment also prevented isopeptide modification of placental AT1 receptors in preeclamptic mice. Mechanistically, we revealed that AT1-agonistic autoantibody stimulation enhances the interaction between AT1 receptor and TG2 and results in increased AT1 receptor stabilization via transglutaminase-mediated isopeptide modification in trophoblasts. Mutagenesis studies further demonstrated that TG2-mediated isopeptide modification of AT1 receptors prevents ubiquitination-dependent receptor degradation. Taken together, our studies not only identify a novel pathogenic involvement of TG2 in preeclampsia but also suggest a previously unrecognized role of TG2 in the regulation of G protein-coupled receptor stabilization by inhibiting ubiquitination-dependent degradation.

Celiac Disease Patients Presenting With Anemia Have More Severe Disease Than Those Presenting With Diarrhea

Anemia is considered to be an atypical or silent presentation of celiac disease, compared with the classic presentation with diarrhea. However, little information is available about how these groups compare in terms of disease severity. We compared the severity of celiac disease between patients who present with anemia vs those who present with diarrhea. The study cohort was selected from a database of patients with celiac disease who were evaluated at a tertiary referral center between 1990 and 2011. Severity of celiac disease was assessed by the degree of villous atrophy and clinical and serologic parameters. Patients were compared according to mode of presentation and sex. Multivariable analyses, adjusting for age and sex, were conducted to assess the association between the mode of celiac disease presentation and cholesterol level, bone density, severity of villous atrophy, erythrocyte sedimentation rate, and level of anti-tissue transglutaminase. Of 727 patients, 77% presented with diarrhea and 23% with anemia (92% iron deficient). On multiple regression analysis, presentation with anemia was associated with lower levels of total cholesterol (P= .02) and high-density lipoprotein (P= .002) and a higher erythrocyte sedimentation rate (P= .001) and level of anti-tissue transglutaminase (P= .01). Presentation with anemia was associated with lower level of cholesterol only in women. Anemic patients were more than 2-fold more likely to have severe villous atrophy and a low bone mass density at the time they were diagnosed with celiac disease than patients who presented with diarrhea. Celiac disease patients who present with anemia have more severe disease than those who present with diarrhea. There also appear to be sex-specific differences with regard to the association between anemia and the different features of celiac disease.

Scalloping is a reliable endoscopic marker for celiac disease

Scalloping of duodenal folds noted on esophagogastroduodenoscopy (EGD) has been associated with various illnesses including celiac disease (CD). The aim of the present study was to examine the frequency of scalloping in pediatric patients undergoing EGD and to assess its significance in the diagnosis of CD. We also evaluated the association of scalloping with the histopathology and celiac serology in the subgroup of celiac patients. All children (0-18 years) who underwent EGD at Shaare Zedek Medical Center for any reason during a 2.5-year period were retrospectively included, yielding a consecutive cohort without selection bias. Relevant data were obtained from the patient files. During the study period, 623 children underwent EGD of whom 149 (24%) were eventually diagnosed with CD. In 74/623children (12%), scalloping was seen and had a sensitivity of 48% (95% CI 0.40-0.57), specificity of 99% (0.98-0.99) and positive predictive value of 97% (0.9-0.99) to diagnose CD. The prevalence of scalloping increased with advancing stage of the Marsh classification from 33% (7/21) in Marsh 1 to 63% (34/54) in Marsh 3c (P < 0.001). Scalloping was associated with a significantly higher median tissue transglutaminase level (153 [IQR 98-168] versus 49 [IQR 11-143]; P = 0.011). The results suggest that the diagnosis of CD is almost certain if isolated scalloping is observed during EGD done to rule out CD. Thus, attention to this finding may serve as an additional tool in the diagnosis of CD.

IMPACT OF ENZYMATIC PROTEIN CROSS-LINKING ON GELATION KINETICS AND MICROSTRUCTURE OF RENNET-INDUCED LOW-FAT MILK GEL

A high potential for modifying the texture properties of casein based dairy products through protein cross-linking by microbial transglutaminase (TG) has recently attracted considerable attention. Hereby, the impacts of different levels of TG and heat treatment of milk on the rennet gelation kinetics and microstructure properties of low-fat milk gel (~70% fat reduction) were investigated. The rheological analysis was measured by a dynamic rheometer and by a formagraph. In order to obtain complementary insights into the protein network formed, the gel microstructure was measured using confocal laser scanning microscopy. The results show that the influence of TG on the rennet coagulation properties appears more intense in the secondary phase measurable by; marked increase in curd yield percentages, intensive reduction in curd firmness, declined rigidity rate of casein network and markedly reduction in gel strength, than in the rennet primary phase represented in prolongation of the coagulation times. A denser and more homogeneous systematic protein aggregate network accompanied by finer, smaller and evenly distributed pores, were observed in TG-treated gels. These effects on gelation kinetics and microstructure were more pronounced for higher TG concentrations and higher heat treatment of milk. A highly significant (P<0.001) and strong correlations were obtained among all formagraph and rheometer parameters. In sum, TG cross-linking intensely altered the functional properties of the resulting low-fat milk gel that might allow manifold applications and enhancement of low-fat cheese quality attributes.