Effect of microbial transglutaminase on autolysis and gelation of lizardfish surimi

In the absence of microbial transglutaminase (MTGase), the textural properties of lizardfish surimi (Saurida spp) improved when pre‐incubated at 4 and 25 °C for 24 and 4 h, respectively. MTGase optimally catalyzed incorporation of monodansylcadaverine (MDC) into surimi at 40 °C. Addition of MTGase appeared to reduce autolytic activity at 25 and 40 °C, but had no effect on autolytic activity at 65 °C. Breaking force and deformation of lizardfish surimi significantly improved when 0.1 unit MTGase g^?1 surimi (1.8 g kg^?1) was added and pre‐incubated at either 25 or 40 °C. Textural properties improved concomitant with cross‐linked polymers of myosin heavy chain and tropomyosin, but not actin. Addition of MTGase also improved the storage modulus (G′). The gel network of surimi mixed with MTGase and pre‐incubated at 40 °C readily formed during the pre‐incubation period, while formation of the gel network began at 48.1 °C in the absence of MTGase. Copyright © 2005 Society of Chemical Industry     

谷朊的糖基化及其谷氨酰胺转氨酶脱酰胺改性研究

谷朊富含谷氨酰胺和较多的疏水性氨基酸,具有不溶于水等独特性质。试验采用糖基化和谷氨酰胺转氨酶对谷朊改性,使蛋白质分子带有更多的极性基团,从而使其功能性质得到改善。研究首先在60℃,75%的相对湿度下对谷朊进行糖基化,当谷朊与葡萄糖和葡聚糖的质量比均为10∶1,Maillard反应时间24h,糖基化后的谷朊可利用的ε-NH2分别下降了40%和20%左右。2种糖基化谷朊在底物浓度为5%,谷氨酰胺转氨酶(MTG)浓度为100 U/g谷朊,在pH 6.0,37℃条件下进行脱酰胺改性,MTG作用7 h后,葡萄糖和葡聚糖糖基化谷朊氨释放量分别达到40μM氨/g蛋白和50μM氨/g蛋白,高于非糖基化谷朊的31μM氨/g蛋白,经MTG改性后的糖基化谷朊表面疏水性和溶解性有小幅度的提高,但持水性和持油性有较大提高。     

Low‐salt restructured fish products using microbial transglutaminase as binding agent

Low‐salt restructured silver carp products were obtained using mechanically deboned fish meat from filleting wastes of silver carp (Hypophthalmichthys molitrix). The additives used were NaCl at three levels (0 (control), 10 and 20 g kg^?1) and microbial transglutaminase (MTGase) also at three levels (0 (control), 3 and 6 g kg^?1). The fish meat was massaged with the additives at <15 °C for 1 h. The massaged fish paste was then packed into steel stainless tubes and cooked at 40 °C for 30 min followed by 90 °C for 15 min. Changes in mechanical properties (texture profile analysis and punch test), solubility, electrophoretic profile and expressible water were evaluated. Hardness was in the range from 26.3 to 52.4 N, cohesiveness varied from 0.185 to 0.318 and springiness varied from 0.418 to 0.768. Increasing the amount of both additives improved the mechanical and functional properties of the restructured silver carp products. MTGase activity was associated with a decrease in protein solubility and a decrease in the myosin band (SDS‐PAGE). Increasing NaCl decreased the amount of expressible water. The results indicated that it is feasible to obtain low‐salt restructured silver carp products with improved mechanical and good functional properties using 3 g kg^?1 MTGase and 10 g kg^?1 NaCl. © 2002 Society of Chemical Industry     

Structural analysis of enniatin H,I, and MK1688 and beauvericin by liquid chromatography-tandem mass spectrometry (LC-MS/MS) and their production by Fusarium oxysporum KFCC 11363P

The molecular structures of enniatins H, I, and MK1688 and beauvericin were investigated by liquid chromatography-tandem mass spectrometry (LC-MS/MS). MS fragmentation occurred by loss of -CO after opening of the cyclic molecule to carbonyl carbon, and cleavage of the peptide and ester bonds in the molecular structure. Fusarium oxysporum KFCC 11363P was tested for its ability to produce beauvericin and enniatins H, I, and MK1688 on five cereal substrates: rice, barley, maize, wheat, and Indian millet kernels. Furthermore, optimal conditions for the production of the four mycotoxins by the Fusarium isolate were examined on maize at four temperatures (15, 20, 25, and 30°C) and at three moisture contents (10, 20, and 40%). Large amounts of beauvericin and enniatin H were present in maize cultures at 25°C (232.4 and 196.4 µg g^?1, respectively). Enniatins I and MK1688 were maximally formed at 20°C (221.5 and 180.2 µg g^?1, respectively). The optimal moisture contents for the production of enniatins H (196.4 µg g^?1) and MK1688 (165.6 µg g^?1), were 40%.     

Reduction of the polycyclic aromatic hydrocarbon (PAH) content of charcoal smoke during grilling by charcoal preparation using high carbonisation and a preheating step

Charcoal-grilling may lead to contamination of food with carcinogenic polycyclic aromatic hydrocarbons (PAHs) during the grilling process. The objective of this work was to determine the effect of charcoal preparation on 16 USEPA priority PAHs in the smoke produced during the grilling process. Firstly, mangrove charcoal was prepared at carbonisation temperatures of 500, 750 and 1000°C. The charcoal were then preheated by burning at 650°C. This preheating step is usually used to prepare hot charcoal for the grilling process in the food industry. In this study, charcoal was preheated at different burning times at 5, 20 min and 5 h, at which time partial and whole charcoal glowed, and charcoal was completely burnt, respectively. Finally, PAHs in the smoke were collected and determined by GC/MS. The result showed that charcoal prepared at a carbonisation temperature of 500°C had higher levels of PAHs released into the smoke. In contrast, charcoal produced at 750 and 1000°C had lower PAHs released for all burning times. In addition, PAHs released for 5, 20 min and 5 h of burning time were about 19.9, 1.2 and 0.7 µg g^?1 dry charcoal for charcoal produced at 500°C, and about 0.9–1.4, 0.8–1.2 and 0.15–0.3 µg g^?1 dry charcoal for charcoal produced at 750 and 1000°C, respectively. Therefore, this research suggests that food grilled using charcoal carbonised at a high temperature of about 750°C presents a lower risk of PAH contamination. In addition, in the preheating step, whole charcoal should fully glow in order to reduce the PAH content in charcoal before grilling.     

Quality of dried white salted noodles affected by microbial transglutaminase

To examine the potential application of microbial transglutaminase (MTGase) in oriental noodle making, the effects of various MTGase addition levels on the rheological, textural and structural properties of noodles were investigated using good quality (‘Red Bicycle’) and poor quality (‘Sandow’) wheat flours. Addition of MTGase at 5–20 g kg^?1 levels, but not at 1 g kg^?1 level, to the two different wheat flours decreased rapid visco‐analyser (RVA) parameters of hot paste viscosity and final viscosity while increasing breakdown. For fresh white salted noodle dough sheets, the storage modulus (G′) and loss modulus (G″) increased significantly at 1 g kg^?1 MTGase addition for both types of flour, but there was no clear trend with higher levels of MTGase. For dried white salted noodles, textural parameters (tensile force, hardness and gumminess) generally increased, cooking loss was little affected and the yield of the cooked noodle was significantly decreased by MTGase. Color was slightly adversely affected. Scanning electron microscopy (SEM) results indicated that physical properties of dry noodles were improved through the formation of cross‐links [ε‐(γ‐glutamyl)lysine] by MTGase. Copyright © 2005 Society of Chemical Industry     

Separation of bread wheat flours into starch and gluten fractions: effect of water temperature alone or in combination with water to flour ratio

Two different commercial bread wheat flours (BF‐I, 65% extraction and BF‐V, 86% extraction) were separated into gluten and starch milk by making a dough, allowing some time for maturation, dispersing the dough in water and wet sieving/washing. The effect of using of warm water (20–45 °C) for dough making and washing on separation was studied for BF‐I flour at 640 g kg^?1 water to flour ratio of and 300 s maturation time, and the separation was found to improve with increase in temperature. The combined effects of water temperature (20–50 °C) and water to flour ratio (640–780 g kg^?1 for BF‐I and 620–870 g kg^?1 for BF‐V) were studied at 600 s maturation time. The quantities and dry matter contents of the gluten fraction and starch milk were measured; a sample of starch milk was centrifuged to obtain decantate, tailing and prime starch fractions, and the dry matter contents of each were determined. All the dried samples were also analysed for protein content, and the fractional recoveries of dry matter and protein in the gluten fraction, prime starch, tailings and decantate were calculated. The results indicated the optimum point for BF‐I flour to be the combination of optimum farinograph water absorption and 40 °C. BF‐V showed very poor separation behaviour within the ranges studied. At the optimum farinograph water absorption the use of warm water for dough making and 20 °C water for washing steps was also tried, but no significant improvement over the 20 °C results was obtained. © 2002 Society of Chemical Industry     

A new testing method for vital gluten swelling index

Vital gluten is a kind of functional protein, but currently its quality indices are mostly focused on the outer character rather than the inner content. The objective of this study was to develop an improved testing method for the measurement of vital gluten, reported here as the vital gluten swelling index (VGSI). The procedures were optimized using the vital gluten water absorption ratio and the wheat flour protein fraction content. The following procedure is recommended: use 0.9 mL distilled water to hydrate 20 mg vital gluten for 10 min, and then add 0.9 mL of 0.03 g kg^?1 sodium dodecyl sulfate–lactic acid solution and mix for another 30 min. Finally, centrifuge the mixture at 5000 × g and measure the residue weight. The quality of vital gluten can be simply classified by its swelling index value. A VGSI of ≥ 28% indicates vital gluten of superior grade, between 24% and 28% is a good grade, while ≤24% is an inferior grade. Compared with the laborious method of vital gluten water absorption (VGWA), which takes a relatively long time to test one sample, VGSI requires only 47 min to test 24 samples. Further, the VGSI method is more accurate, reliable and repeatable. The coefficient of variation of VGWA of the vital gluten samples is 2.09, while the corresponding value for VGSI was 14.83. The correlation coefficients between VGSI and other vital gluten indices were significant. The research indicates that the method developed is the best to evaluate vital gluten. Copyright © 2007 Society of Chemical Industry     

Effect of oil oxidation on aggregation of wheat gluten–peanut oil complexes during extrusion

To better understand the aggregation mechanism of wheat gluten–peanut oil complex (WPE), the oxidation properties of peanut oil and wheat gluten at different extrusion temperatures were investigated. With the increase in extrusion temperature from 100 to 180 °C, the total oxidation value of peanut oil in WPE increased from 5.04 ± 0.26 to 10.01 ± 0.87, and the carbonyls content of gluten increased from 21.73 ± 0.62 to 31.43 ± 0.58 nmol mg⁻¹. The results of surface hydrophobicity and carbonyls content indicated that peanut oil could induce gluten oxidation in WPE. The morphology of the extrudates showed that the addition of peanut oil promoted the aggregation of gluten protein. These results enhance our understanding of the interactions between peanut oil and gluten in extrudates and provide a theoretical basis for gluten-based extrudates with favourable textural properties.     

Fate of aflatoxin B(1) in contaminated corn gluten during acid hydrolysis

BACKGROUND: Aflatoxins are a group of mycotoxins that cause serious chronic disease outbreaks and contaminate several food products such as corn and its by‐product, corn gluten. The aim of the current study was to evaluate the effect of hydrochloric acid (HCl) on aflatoxin B₁ (AFB₁) degradation in contaminated corn gluten under different HCl concentrations, hydrolysis temperatures and hydrolysis times. RESULTS: During the wet milling process the highest AFB₁ level (45.68 µg kg^?1) (37.86%) was found in corn gluten fraction. Treatment with 1 mol L^?1 HCL at 110 °C resulted in degradation of AFB₁ by 27.6% (33.07 µg kg^?1) after 4 h and reached 42.5% (26.26 µg kg^?1) after 8 h. Increasing HCl concentration from 1 to 3 mol L^?1 HCl resulted in increased degradation of AFB₁, while complete degradation occurred in the presence of 5 mol L^?1 HCl after 4 h at 110 °C. Meanwhile, half‐life time of AFB₁ was recorded after 2 h at 100 °C and was < 2 h at 110 °C in the presence of 3 mol L^?1 HCl. CONCLUSION: It could be demonstrated that the manufacture of hydrolyzed vegetable protein is a suitable method for decontamination of aflatoxin in highly contaminated grains, especially gluten fractions. The hydrolysis reaction could be considered in terms of first‐order reaction kinetics of AFB₁ degradation. Copyright © 2010 Society of Chemical Industry     

Application of a polymerase chain reaction (PCR) method as a complementary tool to microscopic analysis for the detection of bones and other animal tissues in home‐made animal meals

A polymerase chain reaction (PCR) method was compared with a variation of the official microscopic technique (Directive 98/88/EC) for the detection in animal meals of cereals (wheat and corn) and animal parts (bone, feathers, meat, liver, fat and blood). Microscopy successfully detected animal bones in raw feeds with a sensitivity of 1 g kg^?1, while the sensitivity of the PCR method was in the range of 5–10 g kg^?1. Microscopy also allowed the detection of animal bones and feathers in feeds processed at 115 and 133 °C but failed to detect other animal materials. The PCR method successfully detected cereals (wheat and corn) as well as meat, bone, liver, fat and feathers after processing at 115 °C for 20 min. Heating at 133 °C under overpressure (autoclave) conditions resulted in more intense DNA fragmentation and lower DNA extractability. Nevertheless, bone and liver, as well as wheat and corn in home‐made animal meals, were successfully detected even after heating at 133 °C for 20 min. Copyright © 2004 Society of Chemical Industry     

A comparison of biochemical changes in cod (Gadus morhua) and haddock (Melanogrammus aeglefinus) fillets during frozen storage

Changes in the muscle proteins of frozen cod fillets, which produce significant amounts of formaldehyde, and frozen haddock fillets, which produce negligible formaldehyde, were compared. Protein extractability and hydrophobicity and the amino acid contents of soluble and insoluble proteins, as well as formaldehyde formation, were investigated in matching pairs of cod and haddock fillets stored at ?10 and ?30 °C (control). Formaldehyde production in cod was much higher (845 and 1065 nmol g^?1 at 20 and 30 weeks respectively) than in haddock (93 and 101 nmol g^?1 after 20 and 30 weeks respectively) at ?10 °C. However, a rapid decrease in solubility of proteins, increase in hydrophobicity and decrease in the amino acid content of salt‐soluble proteins at ?10 compared with ?30 °C were observed in both species. The results showed that there were no significant differences in the nature of the protein changes between these two species, thus indicating that factors other than formaldehyde were involved in the denaturation of proteins and the formation of aggregates during frozen storage of cod and haddock fillets, especially at ?10 °C. © 2001 Society of Chemical Industry     

Preparation and characterization of high‐quality rice bran proteins

Rice bran contains 120–200 g kg^?1 protein in addition to a large amount of fat, carbohydrate, and phytic acid. Rice bran protein (RBP) fractions were refined by a two‐step preparation to eliminate residual carbohydrate. The first step involved the sequential extraction of defatted rice bran into RBP fractions using their distinct solubility to give 37 g kg^?1 of albumin, 31 g kg^?1 of globulin, 27 g kg^?1 of glutelin, and 2 g kg^?1 of prolamin. In the second step, carried out by dissolving in respective solvent and isoelectric precipitation, the protein content of each fraction increased from 69% to 97% for albumin, from 71% to 90% for globulin, from 74% to 83% for glutelin, and from 18% to 20% for prolamin. The low protein content in the prolamin fraction might be due to its low solubility in the protein assay. Emulsifying stability index and surface hydrophobicity increased in the second‐step preparation of albumin and globulin, but not of glutelin. Emulsifying properties of RBPs were lower than that of a soybean protein isolate. Denaturation temperatures and enthalpy values of denaturation for albumin, globulin, glutelin, and prolamin were 50.1 °C/1.2 J g^?1, 79.0 °C/1.8 J g^?1, 74.5 °C/3.0 J g^?1, and 78.5 °C/8.1 J g^?1, respectively. No significant differences in the denaturation temperatures and enthalpy values of denaturation of RBP fractions were obtained with these two‐step preparations (P < 0.05). Copyright © 2007 Society of Chemical Industry     

Optimising the extraction of tea polyphenols, (−)‐epigallocatechin gallate and theanine from summer green tea by using response surface methodology

In this study, response surface methodology was applied to determine the optimal conditions for the extraction of tea polyphenols, EGCG and theanine from summer green tea. As results, the optimal extraction conditions were determined to be temperature 96 °C, time 40 min and ratio of water to raw material 16 mL g^?1. Under these optimal conditions, the experimental values for tea polyphenols, EGCG, theanine and IC₅₀ for DPPH free radical scavenging activity were 133.41 ± 3.12 mg gallic acid g^?1, 30.23 ± 1.22, 3.99 ± 1.13 mg g^?1 and 724.95 ± 15.12 μg mL^?1, respectively. There was no statistical difference at significant level of 0.05 between the experimental and predicted values. The results suggested that the regression models were accurate and adequate for the bioactives extraction from summer green tea.     

Effect of initial aflatoxin concentration,heating time and roasting temperature on aflatoxin reduction in contaminated peanuts and process optimisation using response surface modelling

Response surface methodology was applied to optimise the aflatoxin reduction in both naturally and artificially contaminated samples using dry oven. The effect of initial aflatoxin concentration (0–400 ng g^?1), heating time (30–120 min) and temperature (90–150 °C) was evaluated. The maximum reduction of AFB1 (78.4%) and AFB2 (57.3%) of artificially contaminated samples with initial aflatoxin concentration of 237 and 68 ng g^?1, and those of AFG1 (73.9%) and AFG2 (75.2%) with initial aflatoxin concentration of 215 and 75 ng g^?1 was obtained at 150 °C. The maximum reduction of AFB1 (80.2%) and AFB2 (69.7%) of naturally contaminated samples with initial aflatoxin concentration of 174 and 25 ng g^?1 was obtained at 150 °C and 130 °C, respectively.     

Technological Assessment of Chestnut Flour Doughs Regarding to Doughs from Other Commercial Flours and Formulations

The technological assessment of chestnut flour doughs was studied using Mixolab® apparatus, establishing a comparison with gluten (soft, hard and whole wheat) and gluten-free (rice and yellow corn) flour doughs as well as corn starch pastrymaking and breadmaking formulations. This equipment measures the torque in function of temperature and time, firstly at 30 °C (mixing curve) and secondly the mixing during heating (4 °C/min up to 90 °C) and cooling (4 °C/min up to 50 °C) steps (complete curve). Different hydrations of doughs ranging from 41.4% to 68.5% (flour basis) were necessary to reach the torque of 1.10?±?0.07 Nm. Parameters of mixing such as water absorption, development time, stability and mixing tolerance index were obtained. Parameters of heating and cooling cycle related to weakening of proteins, gelatinization starch, amylase activity and starch retrogradation as well as range of gelatinization temperatures were also determined. Chestnut flour showed suitable parameters in the mixing stage such as arrival time (1.93?±?0.1 min), stability (12.1?±?0.4 min) and departure time (14.0?±?0.3 min). In the heating cycle, chestnut flour exhibited close behaviour to soft wheat flour with cooking stability of 1.12?±?0.01 min and seems to be suitable for pastrymaking products. Finally, in the cooling cycle the behaviour revealed that products of this flour can present problems of staling and crumbs firmness due to high values (2.88 Nm) of C5 parameter.     

Study of two different cold restructuring processes using two different qualities of hake (Merluccius capensis) muscle,with addition of microbial transglutaminase

BACKGROUND: Microbial transglutaminase (MTGase) can improve the mechanical and functional properties of restructured fish products without the need of thermal gelation. The present study seeks to determine whether, for different setting times, MTGase activity in restructured hake muscle made with pieces or with homogenised muscle can be affected by the quality of the protein in the raw materials. RESULTS: As regards mechanical properties, samples of both qualities subjected to the two different processes attained a suitable consistency after setting for 24 h at 5 °C. The quality of the protein in the sample is important when pieces are used for restructuring, but not when sample is homogenised. Also, there were strong correlations between residual MTGase activity up to 12 h and mechanical properties and electrophoretic band density. Water binding capacity (WBC) was not significantly altered by MTGase addition. CONCLUSION: The experimental combination of 10 g kg^?1 of MTGase, 15 g kg^?1 of sodium chloride and 7.5 g kg^?1 of sodium caseinate was suitable for the production of minimally processed raw restructured fish products made with two different qualities of fish protein and two different restructuring processes. In the restructured products made with pieces, the protein quality significantly affected final properties, but in finely homogenised product the protein quality was less important. Copyright © 2009 Society of Chemical Industry     

Effect of semolina and absorption level on extrusion of spaghetti containing non‐traditional ingredients

Specific mechanical energy (SME), mechanical energy, extrusion rate and temperature of extruded spaghetti were monitored to determine the effects of semolina, hydration level and non‐traditional ingredients on pasta extrusion using a semi‐commercial pasta press with a fixed screw speed of 25 rpm. SME transferred to the dough during extrusion and the temperature of extruded spaghetti were greater with strong than with weak gluten semolina and at low than at high absorption levels. When compared with semolina hydrated to 300 g kg^?1 absorption, SME transferred to the dough was 13 kJ kg^?1 lower for semolina mixed with buckwheat (Fagopyrum esculentum Moench.) bran flour, 47 kJ kg^?1 lower for semolina mixed with flaxseed (Linum usitativissimum L.) flour and 7 kJ kg^?1 lower for semolina mixed with wheat (Triticum turgidum var. durum L.) bran. Weak gluten semolina, high absorption levels and non‐traditional ingredients reduced the mechanical energy required for extrusion more than they reduced extrusion rate. The target temperature for extruded spaghetti was 45 °C. The temperature of extruded spaghetti containing flaxseed flour was below 45 °C whereas the temperature of spaghetti containing wheat bran was above 45 °C, regardless of semolina type or absorption level. Copyright © 2006 Society of Chemical Industry     

Xylitol bioproduction from wheat straw: hemicellulose hydrolysis and hydrolyzate fermentation

A 2² central composite design with five center points was performed to estimate the effects of temperature (120, 130 and 140 °C) and acid loading (100, 150 and 200 mg g^?1) on the yield of monomeric xylose recovery from wheat straw hemicellulose (Y_S/RM). Under the best hydrolysis condition (140 °C and 200 mg g^?1), a Y_S/RM of 0.26 g g^?1 was achieved. After vacuum concentration and detoxification by pH alteration and active charcoal adsorption, the hydrolyzate was used as source of xylose for xylitol bioproduction in a stirred tank reactor. A xylitol production of 30.8 g L^?1 was achieved after 54 h^?1 of fermentation, resulting in a productivity (Q_P) of 0.57 g L^?1 h^?1 and bioconversion yield (Y_P/S) of 0.88 g g^?1. The maximum specific rates of xylose consumption and xylitol production were 0.19 and 0.15 g g^?1 h^?1, respectively. Copyright © 2006 Society of Chemical Industry     

Effects of Bambara Groundnut Protein Isolates and Microbial Transglutaminase on Textural and Sensorial Properties of Surmi Gel from Sardine (Sardinella albella)

Effects of different bambara groundnut protein isolates (BGPIs) at a level of 6 % (w/w) in combination with microbial transglutaminase (MTGase) at a concentration of 0.6 U g^?1 surimi on gel properties of sardine (Sardinella albella) surimi were investigated. In the absence of MTGase, all BGPIs showed the adverse effect on gel-forming properties of surimi, as evidenced by the decreases in breaking force and deformation (P?<?0.05). When MTGase was incorporated, the increases in breaking force and deformation were found for all BGPIs used. Water-holding capacity of all gels was improved when BGPIs were added in combination with MTGase (P?<?0.05). Whiteness of gels slightly decreased with the addition of BGPIs; however, MTGase had no impact on whiteness (P?>?0.05). Surimi gel added with BGPI prepared from defatted flour with heat treatment in the presence of ethylenediaminetetraacetic acid (DF-BGPI-HE) and MTGase showed well-ordered network and exhibited the lowest peroxide value and thiobarbituric acid-reactive substances than those containing other BGPIs. Gel containing DF-BGPI-HE had negligible beany flavour. Additionally, DF-BGPI-HE had the lower amount of volatile compounds after storage of 30 days at room temperature than other BGPIs. Thus, the addition of DF-BGPI-HE and MTGase was an effective means to render sardine surimi gel with improved gel property and caused no beany flavour in resulting gel.