Gelation of mixed myofibrillar/wheat gluten proteins treated with microbial transglutaminase

Gluten (Glu) and an acid-extracted protein fraction (AF) from wheat flour were mixed (1:1 ratio) with myofibrillar protein (MP) and treated with microbial transglutaminase (MTGase) to observe the effect on heat-induced gelation. Dynamic rheological properties and thermal denaturation patterns of treated samples were measured, respectively, with an oscillatory rheometer and a differential scanning calorimeter. The storage modulus (G′) of control MP sample (no MTGase), with a value of 533 Pa at end of heating (77 °C), was not affected (P > 0.05) by Glu nor by AF. However, mixed protein samples after the MTGase treatment produced higher gel elasticity values that differed (P < 0.05) between samples (1355, 1700 and 1875 Pa at 77 °C for MP, MP/AF, and MP/Glu, respectively). The MP sample underwent three endothermic transitions (peaking at 61.5, 68.0, and 78.5 °C) during thermal scan. The treatment with MTGase and/or addition of Glu or AF tended to lower the temperature for the first transition but raised the temperature for the third transition, suggesting possible interactions of the muscle with non-muscle proteins.     

The impact of the protein network on the pasting and cooking properties of dry pasta products

Durum wheat semolina gluten and starch as well as processing conditions determine pasta cooking quality. This study investigated whether, for good organoleptic properties, a permanent protein network needs to be formed during pasta drying or can still be formed during cooking. The cooking quality of 16 spaghetti samples was related to the levels of sodium dodecyl sulphate extractable protein (SDSEP), starch gelatinisation temperatures as well as to the swelling properties of milled dry spaghettis. SDSEP levels in dry and cooked products varied between 31% and 56%, and 12% to 21% of total protein contents, respectively. The highest quality spaghettis had relatively higher levels of SDSEP in the dry product, low starch gelatinisation temperatures and swelling powers, and rigid particles. The lowest quality spaghettis had lower levels of SDSEP and higher gelatinisation temperatures. This work implies that high pasta quality results from an optimal degree of protein polymerisation during drying and/or the subsequent cooking.     

Effect of semolina replacement with a raw:popped amaranth flour blend on cooking quality and texture of pasta

The replacement of semolina (SEM) with raw:popped (90:10) amaranth flour blend (AFB) in pasta making at 25, 50, 75, and 100 g/100 g levels (flour basis, 14 g of water/100 g) was carried out to evaluate the effects on cooking quality and texture of the supplemented pasta samples. Significant differences on cooking quality characteristics and texture of the pasta samples were observed. The pasta solid loss increased, weight gain and firmness decreased as the AFB level increased. The semolina pasta showed the lowest solid loss (7 g/100 g) and the highest weight gain (188.3 g/100 g) and firmness (1.49 N), whereas the amaranth blend pasta was the softer (around half of the firmness of semolina pasta) and lost the higher amount of solids (11.5 g/100 g). The raw and popped AFB was suitable for increasing the nutritional quality through dietary fiber and high quality protein and even to obtain gluten-free pasta with acceptable cooking quality (solid loss of 3.5 g/100 g higher than that considered as acceptable for semolina pasta). The amaranth blend used in this study enables the partial or total replacement of wheat semolina in pastas with acceptable cooking quality and texture.     

变性对转谷氨酰胺酶在乳蛋白间交联影响初探

利用SDS-PAGE电泳结合凝胶成像分析技术，比较了在非变性、加入还原剂变性和加热后再加入还原剂变性三种条件下转谷氨酰胺酶对酪蛋白和乳清蛋白之间的交联情况。结果表明：在非变性条件下，酪蛋白质量分数下降96％，乳清蛋白下降15％，酪蛋白和乳清蛋白几乎不能交联。超分子量聚合物是酪蛋白单一聚合物，α-乳白蛋白形成部分低聚体；在加入还原剂时，酪蛋白质量分数下降86％，乳清蛋白下降30％，反应4h后有少量乳清蛋白和酪蛋白中某一组分交联；预热更有助于酪蛋白和乳清蛋白聚合，在第三种条件下，反应24h后乳清蛋白下降60％。     

Effect of rice bran fibre on the quality of rice pasta

This study investigated the effects of rice bran fibre (RBF) on the properties of rice pasta by extrusion processing. As the level of RBF increased, the content of total dietary fibre (TDF), insoluble dietary fibre (IDF) and soluble dietary fibre (SDF) increased, respectively. The difference in the content of ΔIDF between before and after extrusion decreased from 1.01% to 0.69% and that of ΔSDF decreased from 1.06% to 0.55%. Depending on the increasing level of RBF, the water absorption index decreased and water solubility index increased, respectively. The crystallinity of newly formed crystals decreased from 21.43% to 18.66% as the level of RBF increased. Adding RBF darkened the colour of rice pasta and reduced its hardness and chewiness. The cooking loss (CL) increased significantly compared with the control (0% RBF). The results indicate that rice pasta with extra RBF (up to 15%) can provide an acceptable quality product with a satisfactory colour and CL.     

Effects of increasing levels of transglutaminase on cooking quality of bran supplemented spaghetti

This study investigated the possibility of incorporating high levels of bran into spaghetti formulation by using transglutaminase (TG)—catalyzed crosslinking, without deterioration in spaghetti quality. Two durum wheat samples and one bread wheat sample were milled to semolina or farina. Ground mixture of coarse and fine brans of each cultivar was substituted for a portion of semolina or farina obtained from the respective cultivar, at the levels of 15 and 30% and then processed into spaghetti. Bacterial TG was added to the spaghetti formula at the levels of 0.2% and 0.4% (w/w). The results indicated that the TOM values and the sensory characteristics of the spaghetti were generally affected by the cultivar, bran supplementation, and TG addition level. The samples with TG exhibited significantly lower scores for TOM and higher sensory scores for firmness, stickiness, and bulkiness when compared with the respective control sample of each cultivar. As a result, transglutaminase addition had a significant improving effect on spaghetti quality which was more obvious in the weaker cultivar and it was possible to overcome the deteriorative effects of bran on spaghetti quality.     

The use of transglutaminase in dairy products

Modification of proteins by enzymes such as transglutaminase (TG) has recently become of great interest to food scientists. TG (EC 2.3.2.13) catalyses the post-translational modification of proteins by transamidation of available glutamine residues by the formation of covalent cross-links between glutamine and lysine residues in proteins. It is suggested that TG is a useful tool for the production of dairy products. In this review, properties of TG and its possible use in the manufacture of dairy products are discussed. Aspects covered include reactions catalysed by the enzyme and properties of modified proteins of selected milk proteins and products.     

Chemical,technological, and nutritional characteristics of two lines of “farro” (Triticum turgidum ssp. dicoccum)

In recent years, the renewed interest for foods with a natural image has increased the demand for dry pasta produced from “hulled” wheat such as the Triticum turgidum ssp. dicoccum, also known as “farro”. In order to contribute to the general knowledge, two lines of farro were considered in this study. To have a comparison, an old cultivar of Triticum turgidum ssp. durum (Senatore Cappelli) in addition to a commercial semolina were also examined. All semolina samples were used to produce pasta samples. Results showed some differences among pasta samples that seem to be due not to the presence of specific protein subunits but especially to the quantitative ratio between the different subunits. Results also reconfirmed the role played by the drying technology that is able to affect the sensory characteristics of pasta products.     

Sensory and nutritional attributes of fibre-enriched pasta

The objective of this study was to evaluate the impact that the incorporation of resistant starch type II (RSII), resistant starch type IV (RSIV) and oat bran (OB) have on sensory and nutritional quality of pasta. RSII, RSIV and OB were incorporated into recipes in four proportions (w/w): 2.5, 5.0, 7.5, and 10.0 g/100 g. Resistant, digestible and total starch were measured in cooked pasta. An in vitro digestion and sensory analysis of pasta were performed in order to estimate glycemic index. Results showed that both, the type and amount of added fibre influence nutritional quality of pasta. Incorporation of RSII into pasta formulation generates an additional quantity of resistant starch content in cooked pasta. Differences in in vitro digestibility of pasta can be appreciated. RSIV presented the greatest effect on total starch hydrolysis. The lower glycemic index was obtained with addition of RSIV and RSII at 7.5 g/100 g and 10.0 g/100 g. Sensory analysis showed high scores for overall acceptability for Control, RSII and RSIV samples. Results suggest that by using insoluble fibre it is possible to enhance the nutritional quality of pasta, without affecting its sensory properties negatively.     

Improvement of cooking quality of maize pasta products by heat treatment

A new process has been developed to manufacture good pasta products from a blend of durum wheat semolina and maize flour (ratio 33: 66). It consists of submitting, to a high temperature (90 to 120°C) for 90 to 180 min, pasta previously processed and dried under the usual industrial conditions. Colour characteristics (yellowness, brownness and red index) are not affected when the treatment is kept below 100°C; at a higher temperature the red index increases sharply. There is a distinct improvement in cooking quality (cooking losses, surface condition) and this is inversely related to the water content of the pasta before treatment. The viscoelasticity of cooked pasta is dramatically modified when the temperature of treatment is 120°C.     

Chemical composition, cooking quality, and consumer acceptance of pasta made with dried amaranth leaves flour

Pasta is a staple food in many countries. Amaranth is a pseudo-cereal being re-discovered because of its nutritional properties. The main objective of this study was to evaluate the potential of the green material of the amaranth plant (leaves) as a component for pasta production and its effect on the pasta quality and consumer acceptance. Dried amaranth (Amaranthus caudatus) leaves and spinach leaves flours were prepared. Pasta samples were manufactured following a small-scale pilot procedure. Amaranth pasta samples were evaluated for its chemical composition, cooking quality, textural, and sensory/consumer acceptance. Results showed that pasta made with dried amaranth leaves had similar chemical composition (protein content: 14.18 g/100 g, Fe content: 9.1 mg/100 g), cooking quality (2.15 pasta weight increase, 4.47% residue loss), textural characteristics (firmness and adhesiveness), and sensory acceptance than green pasta made with dried spinach leaves. Since amaranth leaves have similar nutritional characteristics to spinach leaves and since this biomass in not currently used for food purposes, this study points out that amaranth leaves could be technically used for pasta production and that consumer acceptance of pasta made with amaranth green leaves flour is similar to that of pasta made with spinach.     

Use of natural compounds to improve the microbial stability of Amaranth-based homemade fresh pasta

A study on the use of natural antimicrobial compounds to improve the microbiological stability of refrigerated amaranth-based homemade fresh pasta is presented in this work. In particular, the antimicrobial activity of thymol, lemon extract, chitosan and grapefruit seed extract (GFSE) has been tested against mesophilic and psychrotrophic bacteria, total coliforms, Staphylococcus spp., yeasts and moulds. A sensory analysis on both fresh and cooked pasta was also run. Results suggest that chitosan and GFSE strongly increase the microbial acceptability limit of the investigated spoilage microorganisms, being the former the most effective. Thymol efficiently reduces the growth of mesophilic bacteria, psychrotrophic bacteria and Staphylococcus spp., whereas it does not affect, substantially, the growth cycle of total coliforms. Lemon extract is the less effective in preventing microbial growth. In fact, it is able to delay only total mesophilic and psychrotrophic bacterial evolution. From a sensorial point of view no significant differences were recorded between the control samples and all the types of loaded amaranth-based pasta.     

Studies on the protein composition and baking quality of einkorn lines

White flours from 23 einkorn breeding lines (assortment 1) and wholemeal flours from 24 einkorn lines (assortment 2) were investigated for their qualitative and quantitative protein compositions by means of a combined extraction/HPLC procedure. The HPLC patterns of the gliadin fractions enabled the differentiation of most einkorn samples. The absence of a group of γ-gliadins at the beginning of the γ-gliadin elution region was unique for einkorn compared to all other wheat species. Differences in the patterns of γ-gliadins allowed the classification of einkorns into four groups; a further subdivision of these groups was possible by the number of ω5-gliadins and the different patterns of α-gliadins and low-molecular-weight glutenin subunits. The total gluten protein (gliadins + glutenins) contents of einkorn flours were similar to or even higher than those of common wheat and spelt. Typical for einkorn flours was the extreme excess of gliadins over glutenins with ω5-gliadins being most abundant and high-molecular-weight glutenin subunits being extremely rare. Micro-tests on the mixing properties and baking performance of assortment 2 flours revealed remarkable differences. Dough development time was negatively correlated with the ratio of gliadins to glutenins and positively with the content of glutenins; bread volume was mainly dependent on the content of glutenins. In conclusion, the determination of the quantitative gluten protein compositions offers a reliable indication of the expected baking quality during the early stages of breeding.     

谷氨酰胺转氨酶对挤压糙米粉面团蛋白特性和面条品质的影响

将挤压糙米粉(EBR)与小麦粉以1∶1(m/m)的比例混合制成面条,研究了谷氨酰胺转氨酶(TG)添加量(0.5%、1.0%和1.5%)对面条性质的影响。结果表明,TG添加后,面条中游离巯基含量减少,SDS-PAGE条带显示面条中形成了大分子质量的聚集体。随着TG的添加,面条最佳蒸煮时间增加,干物质损失率降低,吸水率升高。添加量为1.0%时,面条最佳蒸煮时间和吸水率达到最大值,蒸煮损失率达到最小值。TG添加量为0.5%时,面条的硬度、耐咀性、回复性和剪切力最大。扫描电镜结果显示,TG的添加明显增强了面条内部结构的连接与聚合,面条内部变得更加紧实,连续性增强。TG添加量为0.5%~1.0%时,挤压糙米粉面条质构品质和蒸煮品质较好。     

Relationship between gluten strength and pasta firmness in Indian durum wheats

Selected Indian durum wheats including five newly released varieties and seven landraces were studied for their grain quality, gluten strength (sodium dodecyl sulphate‐sedimentation and mixograph) and pasta making properties. Landraces were found to have good grain size, protein content, and gluten strength but they had lower test weight and semolina yield than released varieties. As protein composition affects gluten strength, landraces having combination of low molecular weight (LMW‐GS) with 5, 12, 15 and 19 linked to Gli‐B1 43.5 and high molecular weight (HMW‐GS) 2*, 14 + 15 provide a dough strength comparable with the 7 + 8 and LMW‐GS 2, 4, 6, 12, 15 and 19 (caa) allelic pattern, typically associated with good gluten strength. Landraces have rare combinations of glutenins and gliadins, which are not seen in commercial Indian durums, and in some cases, these rare alleles seem to favour good gluten strength and pasta firmness. Introduction of these alleles through breeding should improve the gluten strength and pasta making properties of Indian durum cultivars.     

Effect of pasta drying temperature on gastrointestinal digestibility and allergenicity of durum wheat proteins

The effects of different drying temperatures (20, 60, 85, 110 and 180 °C) on digestibility and potential allergenicity of durum wheat proteins were studied in model pasta samples, cooked in boiling water (MPSs). Increasing the drying temperature resulted in increased protein denaturation and aggregation. In vitro treatment of MPSs with pepsin and pancreatin showed similar protein degradability up to a drying temperature of 110 °C, resulting in the disappearance of the main prolamin components. In contrast, the MPS treated at 180 °C was much less digestible, due to the presence of Maillard-type protein aggregates.     

Effect of microbial transglutaminase on spaghetti quality

ABSTRACT:  To examine the potential application of microbial transglutaminase (MTG) on semolina dough properties and quality of raw and cooked spaghetti, the effects of various MTG addition levels on the solubility of proteins, SDS-PAGE pattern of semolina dough proteins, and textural and structural properties of raw and cooked spaghetti were investigated using semolina from a high-protein good variety (MACS 1967) and a low-protein poor variety (PDW 274) durum wheat. To increase the concentration of lysyl residues and possibly enhance the extent of cross-linking of protein matrix by MTG, a commercial soy protein isolate (SPI) was added at a level of 3% (w/w) in combination with MTG, and its effect on semolina dough properties and spaghetti quality was investigated. The addition of MTG significantly decreased the solubility of semolina dough proteins. SDS-PAGE results showed that with increasing levels of MTG, a progressive decrease in the intensity of the bands corresponding to molecular weight of around 66 kDa was observed. Protein cross-linking reaction catalyzed by MTG resulted in changes in dough properties, dry spaghetti quality, cooking quality characteristics, and microstructure of cooked spaghetti. However, the quality improvements were more evident in spaghetti from the poor variety PDW 274 than from the good variety MACS 1967. The results also showed the ability of MTG in the formation of heterologous polymers between SPI and durum wheat proteins to improve the quality of spaghetti samples.     

Purification and characterisation of transglutaminase from four fish species: Effect of added transglutaminase on the viscoelastic behaviour of fish mince

The transglutaminase (TGase) enzyme from four different fish species, namely bigeye snapper, Indian oil sardine, tilapia and common carp have been isolated and characterised. The specific activity of the enzyme was higher in tilapia followed by oil sardine, common carp and bigeye snapper. The molecular weight of pure TGase was found to be in the range of 73–95 kD for four different fish species. The temperature optima for maximum activity of TGase varied amongst four species studied. The effect of activator (calcium chloride) and inhibitors (ethylenediaminetetraacetic acid (EDTA), ammonium chloride and free lysine–hydrochloride) at different concentrations on the TGase enzyme activity have been evaluated. The addition of isolated TGase to fish mince from Cynoglossus sp. was attempted in order to evaluate the setting and gelling ability. The setting and gelling ability of fish mince in presence of TGase improved considerably as revealed by small strain and large strain test.     

Improvement of canola protein gelation properties through enzymatic modification with transglutaminase

Enzymatic modification with transglutaminase (TG) was used to enhance the gelation of canola protein isolate (CPI) and thus improve its potential as a food ingredient. The effects of CPI concentration, TG concentration, treatment temperature and treatment time on CPI gelation properties were evaluated. A texture analyzer, sodium dodecyl sulfate polyacrylamide gel electrophoresis (SDS-PAGE) and scanning electron microscopy were used to characterize the resulting networks. The protein concentration, amount of TG, and treatment temperature were found to significantly impact gel strength. It was found that gelation can be improved by increasing the amounts of protein and TG and by keeping the treatment temperature close to 40 °C. SDS-PAGE showed that cross-linking of subunits occurred through TG treatment thus helping to explain the increase in gel strength observed during texture analysis. Micrographs further corroborated the trends noted during rheological studies.