Influence of Gluten Proteins and Drying Temperature on the Cooking Quality of Durum Wheat Pasta

It is well known that gluten plays a major role in determining cooking quality in durum wheat pasta. This work is an attempt to systematically elucidate the role of gluten quantity and nature in determining cooking quality as a function of the drying cycle used in the manufacturing process. Gluten and starch were fractionated from two durum wheat cultivars possessing good and poor gluten quality. Either of them were then added back to the original base semolina to alter its protein content and to produce two semolina series with identical protein contents. Semolinas were processed into pasta and dried following three drying programs (low, medium, and high temperature). Cooking quality was determined with sensorial, chemical, and instrumental methods. The results indicate that optimum cooking time is governed by gluten quality. The positive effect on cooking quality of increasing gluten contents and of the application of HT drying is evident in weak gluten samples, but it is not significant in the strong gluten samples.     

Effect of Fusarium Head Blight on Semolina Milling and Pasta-Making Quality of Durum Wheat

Ten durum wheat cultivars harvested in Manitoba in 1995, which were downgraded primarily because of fusarium-damaged (FD) kernels, were subjected to mycological tests and evaluated for semolina milling and pasta-making quality. Fusarium graminearum was the primary fungus infecting kernels. The ratio of FD to deoxynivlaenol (DON) level varied slightly among cultivars but was generally near unity. Retention of DON in semolina was about 50%. FD had a negative impact on kernel weight and test weight, resulting in lower semolina yield. Semolina ash content and bran specks were not affected by FD, but semolina became duller and redder. FD had no effect on protein content, but gluten strength was weaker probably due to a lower proportion of glutenins as shown by reversed-phase high-performance liquid chromatographic analysis of sequentially extracted gluten proteins. The influence of FD on gluten strength was not sufficient to alter pasta texture. FD had a strong adverse effect on pasta color. Even for the least damaged cultivars, which had FD levels near the limit of 2% established for the No. 3 and No. 4 Canadian Western Amber Durum (CWAD) grades, the deterioration in pasta color was readily discernible by eye, confirming that the strict FD tolerances for premium No. 1 CWAD (0.25%) and No. 2 CWAD (0.5%) grades are warranted.     

Fractionation and reconstitution experiments provide insight into the role of gluten and starch interactions in pasta quality

Commercial durum wheat (Triticum durum desf.) semolina was fractionated into starch, gluten, and water extractables. Starch surface proteins and surface lipids were removed, and two starches with manipulated granule size distributions were produced to influence starch properties, affecting its interaction with other semolina components. Reconstituted spaghetti was made with untreated (control) or treated starches. The pasta made from the starting semolina material had lower cooking time and was of lower quality than the samples made from reconstituted material. This was not due to changes in gluten properties as a result of the first step of the fractionation process. For the reconstituted samples, starch interaction behavior was not changed after surface protein or surface lipid removal. Starch surface properties thus do not influence the starch interaction behavior, indicating that starch-gluten interaction in raw (uncooked) pasta is mainly due to physical inclusion. All reconstituted pasta samples also had generally the same cooking quality. It was concluded that the small changes in starch gelatinization behavior, caused by the above-mentioned starch modifications, are of little importance for pasta quality.     

Quality of Spaghetti Made from Full and Partial Waxy Durum Wheat

The waxy character is achieved in durum wheat (Triticum turgidum L. var. durum) when the granule‐bound starch synthase activity is eliminated. The result is a crop that produces kernels with no amylose in the starch. The presence of two Waxy loci in tetraploid wheat permits the production of two partial waxy wheat genotypes. Advanced full and partial waxy durum wheat genotypes were used to study the effect of waxy null alleles on pasta quality. Semolina from full and partial waxy durum wheats was processed into spaghetti with a semicommercial‐scale extruder, and pasta quality was evaluated. Cooked waxy pasta was softer and exhibited more cooking loss than pasta made from traditional durum cultivars. These features were attributed to lower setback of waxy starch as measured with the Rapid Visco Analyser. High cooking loss may be due to the lack of amylose‐protein interaction, preventing the formation of a strong protein network and permitting exudates to escape. Waxy pasta cooked faster but was less resistant to overcooking than normal pasta. Partial waxy pasta properties were similar to results obtained from wild‐type pasta. This indicates that the presence of a single pair of functional waxy genes in durum wheat was sufficient to generate durum grain with normal properties for pasta production. Waxy durum wheat is not suitable for pasta production because of its softening effect. However, this property may offer an advantage in other applications.     

GlutoPeak: A Breeding Tool for Screening Dough Properties of Durum Wheat Semolina

A rapid shear‐based test using a GlutoPeak instrument was compared with tests commonly used by durum wheat breeders to assess the potential of this instrument to discriminate between samples. Thirty‐two durum wheat semolina samples were analyzed by mixograph, SDS sedimentation (SDSS), gluten index (GI), and GlutoPeak testing. A subset was also tested for pasta quality. GlutoPeak peak maximum time (PMT) was the best indicator of gluten strength and correlated well with the other tests except SDSS. Samples with higher levels of SDS‐unextractable glutenin (insoluble protein [IP]) had stronger dough and longer PMT, but the GlutoPeak test only correlated with pasta stickiness using a smaller set of samples. The range in mixogram profiles encountered in breeding material was related to the IP content, and the pasta made from the different types was of similar quality, differing more because of protein content rather than mixogram type. The GlutoPeak test is faster than GI and uses less sample, requires little technical skill, and is suitable for evaluating large numbers of breeder's lines. The GlutoPeak test is best suited to discriminating weak from strong dough samples and allows for testing with small samples, thus facilitating quality evaluations at early stages of a breeding program.     

New Insights Into the Role of Gluten on Durum Pasta Quality Using Reconstitution Method

The effects of varying the gluten composition at constant protein, protein content at constant composition, and glutenin‐to‐gliadin (glu/gli) ratio on durum semolina rheological properties and the quality of the spaghetti derived from these doughs was investigated using the reconstitution method. Reconstituted flours were built up from a common durum starch and water‐soluble fraction but with varying gluten types from a range of wheats at both 12 and 9% total protein. A 10‐g mixograph and microextensigraph properties were affected by the source of the gluten, which was related to glutenin composition and polymeric molecular weight distribution. Cooked pasta firmness was highly correlated to mixograph development time (MDDT). Furthermore, varying the protein content (9–20%) showed an increase in mixograph peak resistance (PR) with no effect on extensigraph Rmax. Pasta firmness increased and stickiness decreased with increasing protein content. In another experiment, the glutenin and gliadin fractions isolated from durum wheat were added to the respective base semolina to investigate the effect of varying the glu/gli ratio by 1.3–1.6 fold. Increasing the ratio increased MDDT but had no effect on PR and resistance breakdown. Variable effects were obtained for spaghetti firmness. The information obtained should prove useful to durum breeders by providing further evidence for the importance of protein to pasta quality.     

Breadmaking Quality of Selected Durum Wheat Genotypes and Its Relationship with High Molecular Weight Glutenin Subunits Allelic Variation and Gluten Protein Polymeric Composition

Twenty‐seven durum wheat genotypes originating from different geographical areas, all expressing LMW‐2 at Glu‐B3, and five bread wheats were evaluated for flour mixing properties, dough physical characteristics, and baking performance. Gluten polymeric composition was studied using size‐exclusion HPLC of unreduced flour protein extracts. As a group, durum wheats had poorer baking quality than bread wheats in spite of higher protein and total polymer concentrations. Durum wheats exhibited weaker gluten characteristics, which could generally be attributed to a reduced proportion of SDS‐unextractable polymer, and produced less extensible doughs than did bread wheats. However, substantial variation in breadmaking quality attributes was observed among durum genotypes. Better baking performance was generally associated with greater dough extensibility and protein content, but not with gluten strength related parameters. Extensibility did not correlate with gluten strength or SEHPLC parameters. Genotypes expressing high molecular weight glutenin subunits (HMW‐GS) 6+8 exhibited better overall breadmaking quality compared with those expressing HMW‐GS 7+8 or 20. Whereas differences between genotypes expressing HMW‐GS 6+8 and those carrying HMW‐GS 7+8 could only be attributed to variations in extensibility, the generally inferior baking performance of the HMW‐GS 20 group relative to the HMW‐GS 6+8 group could be attributed to both weaker and less extensible gluten characteristics.     

Influence of Durum Genotype on Whole Wheat and Traditional Spaghetti Qualities

This research was conducted to determine if genotypes selected for their superior traditional semolina pasta quality would also make the best whole wheat pasta. Results from 19 durum wheat cultivars and 17 breeding lines grown at 19 different environments in North Dakota showed that physical and cooking qualities varied differently for whole wheat and traditional spaghettis, respectively. Ward's clustering segregated the 36 genotypes into five groups based on whole wheat spaghetti quality. Groups 1 and 2 (21 genotypes) produced good to high‐quality whole wheat pasta that displayed high mean values for cooked firmness (4.3 and 4.1 g·cm), mechanical strength (31.3 and 31.0 g), and color (brightness, 34.92 and 34.54), respectively. Groups 4 and 5 produced poor quality whole wheat pasta that had low cooked firmness (both 3.5 g·cm) and high cooking loss (10.1 and 10.4%). Grain protein content (≥13.9%) was found with high quality of whole wheat spaghetti. Of the 36 genotypes evaluated, 21 and 3 genotypes produced good and poor qualities, respectively, of whole wheat and traditional spaghettis, and 12 other genotypes produced good traditional spaghetti but produced poor quality whole wheat spaghetti. These data indicate the need to select genotypes specifically for their whole wheat pasta quality.     

Fractionation and reconstitution experiments provide insight into the role of starch gelatinization and pasting properties in pasta quality

Commercial durum wheat semolina was fractionated into protein, starch, water-extractable, and sludge fractions. The starch fraction was hydroxypropylated, annealed, or cross-linked to change its gelatinization and pasting properties. Spaghettis were made by reconstitution of the fractions, and their quality was assessed. Hydroxypropylated starches were detrimental for cooked pasta quality. Cross-linked starches made the reconstituted pasta firmer and even brittle when the degree of cross-linking was too high. These results indicate that starch properties play a role in pasta quality, although the gluten remains very important as an ultrastructure agent. It was concluded that, given a certain gluten ultrastructure, starch water uptake and gel properties and/or its interference with or breakdown of the continuous gluten network during cooking determine pasta quality.     

Effects of Salinity and Drought Stress on Grain Quality of Durum Wheat

This work aimed to assess the influences of soil salinity and drought stresses on grain quality characteristics of selected salt-tolerant genotypes differing in salinity tolerance in durum wheat. This study was conducted under control, drought, and saline field conditions in separate experiments during 2 years. A randomized complete block design with three replications was used for each experiment. The results showed significant effects of genotype and environmental conditions on all grain-quality related traits. Salt and drought stress caused the significant increment of grain protein content, wet and dry gluten contents, and sodium dodecyl sulfate (SDS) sedimentation volume. Thousand-grain weight, grain protein yield, and test weight reduced significantly under both salinity and drought stress conditions. Protein content showed positive correlation with wet gluten, dry gluten, SDS sedimentation, and volume and strong negative correlation with other traits. It is concluded that influence of salinity stress was greater than drought stress on grain protein yield and some other grain-quality-related traits.     

Spelt (Triticum spelta L.) Pasta Quality: Combined Effect of Flour Properties and Drying Conditions

Three spelt genotypes (Rouquin, Redoute, and HGQ Rouquin= Rouquin improved for gluten quality), each characterized by either high or low protein content, were processed to manufacture spaghetti, which was dried at both low (60°C) and high temperature (90°C) to assess the effects of flour properties and drying conditions on spelt pasta quality. Protein content in the spelt flour was considered low at ≈11.4% db and high at ≈13.5% db. Gluten properties, assessed by SDS sedimentation and gluten index values and by alveograph and farinograph parameters varied widely, ranging from poor for Redoute to very good for HGQ Rouquin. Pasta quality was assessed by determining color (L*, a*, and b* values), furosine, and cooking quality (stickiness, bulkiness, firmness, and total organic matter [TOM]). Furosine and color (a* and b* values) were significantly influenced by the intensity of the drying process. TOM and organoleptic judgement (OJ) showed that spelt pastas dried at low temperature, independent of their protein levels, were very poor (TOM ≥ 2.7 g/100 g of dry pasta, OJ ≤ 40), except for HGQ Rouquin which was characterized by good gluten strength. On the other hand, the cooking quality of spelt pastas dried at high temperature showed good values (TOM ≤ 1.8 g/100 g of dry pasta, OJ ≥ 53). The combination of high protein content (≥13.5% db) and high‐temperature drying resulted in the production of satisfactory cooking quality pastas from spelt wheats (TOM ≤ 1.2 g/100 g of dry pasta, OJ ≥ 67).     

Variation and Correlation of Protein Molecular Weight Distribution and Semolina Quality Parameters for Durum Genotypes Grown in North Dakota

This research assessed variation of protein molecular weight distribution (MWD) parameters and their correlations with quality characteristics of semolina samples that were obtained from durum genotypes grown in North Dakota. Sodium dodecyl sulfate buffer extractable and unextractable proteins in semolina were analyzed for MWD by size‐exclusion HPLC with a microbore column. ANOVA indicated that quantitative variations of all the HPLC protein fractions were significantly (P < 0.001) influenced by growing environments. The extractable and unextractable gluten proteins correlated differently with semolina gluten characteristics. Both gluten index and mixograph classification showed positive correlations (P < 0.05) with unextractable polymeric proteins and negative correlations (P < 0.05) with extractable gliadins and polymeric proteins. Quantitative variations of gluten proteins greatly influenced spaghetti cooking characteristics. Specifically, cooked spaghetti firmness (CSF) had high and positive simple linear correlations (P < 0.001) with quantity of gluten proteins in both extractable and unextractable fractions. However, a qualitative MWD parameter, percentage of the extractable gliadins in total protein, had a negative genotypic correlation with CSF (r = –0.81, P < 0.01), whereas percentage of the unextractable polymeric proteins had a positive genotypic correlation (r = 0.75, P < 0.01). Those two MWD parameters also showed significant (P < 0.05) variations for genotypes, indicating that they might be useful for screening durum genotypes for pasta cooking quality.     

Characterization of Durum Wheat Semolina by Means of a Rapid Shear‐Based Method

A rapid shear‐based test (the GlutoPeak test, recently proposed by Brabender) was used to investigate gluten aggregation properties of durum wheat semolina and to relate them to pasta cooking behavior. Thirty semolina samples were characterized by means of the conventional approaches used for pasta‐quality prediction (protein content, gluten index, and alveographic indices). All samples were also analyzed by the GlutoPeak test, obtaining three parameters: maximum peak torque, maximum peak time, and area under the peak. The GlutoPeak indices were significantly correlated with protein content, gluten index, and W alveographic parameter. The cooking quality of pasta obtained from the 30 semolina samples was evaluated by sensory analysis in terms of stickiness, bulkiness, firmness, and overall quality. The GlutoPeak indices were significantly correlated with the sensorial parameters. In comparison with the alveographic test, which is presently the most used rheological approach for semolina characterization, GlutoPeak analysis presents some advantages represented by a smaller amount of sample (9 g), a shorter time (less than 5 min), and the possibility that untrained analysts can carry it out. In addition, following testing with larger sample numbers, the GlutoPeak test has the potential to be used instead of the gluten index as a rapid and reliable approach for medium‐quality semolina characterization.     

Proteomic analysis by two-dimensional gel electrophoresis and starch characterization of Triticum turgidum L. var. durum cultivars for pasta making

Criteria for durum wheat quality are continuously evolving in response to market pressure and consumer's preference. Specific attributes of durum wheat for different end products require more rapid and objective means to grade and classify wheat parcels based on processing potential. A total of 10 durum wheat cultivars were compared for compositional, protein, and starch characteristics. Mean values for the gross composition differed for total protein, gluten, and starch. Two-dimensional electrophoresis (2DE) analysis showed the proteome diversity among the cultivars. As shown by the principal component analysis (PCA) applied to 2DE data of gliadin and glutenin fractions, cultivars differed mainly from the number of proteins and levels of protein expression. As determined by the rapid viscoanalyzer (RVA), swelling power, starch damage, amylose content, and starch pasting properties of 10 cultivars differed significantly. 2DE fingerprinting and amylose content seemed to distinguish specific cultivars being useful tools for selecting suitable durum wheat cultivars for pasta making.     

Protein and Starch Properties of Some Tetraploid Wheats

The tetraploid relatives (subspecies) of commercial durum wheat (Triticum turgidum L. subsp. turgidum conv. durum (Desf.) MacKey) offer a source of economically useful genes for the genetic improvement of durum cultivars. Thirty‐two accessions, representing five different subspecies: var. durum (13 accessions), polonicum (7), persicum (3), turanicum (5), and turgidum (4) were grown at Tamworth, Australia, in 1997 and 1999. These accessions were compared with three durum cultivars: Wollaroi and Kamilaroi (in both years) and Yallaroi (in 1998 only). In this study, the glutenin subunit composition and molecular weight distribution, together with starch properties of these accessions, were studied. A much wider range in both the glutenin subunit composition and the starch RVA paste viscosities and gelatinization profiles were found in the accessions compared with the cultivated durum wheats. Most of the accessions had lower gluten strength and the presence of poor quality LMW alleles, and low proportions of unextractable polymeric protein could explain this. For starch, RVA peak viscosity correlated strongly with cooking loss of pasta, the only significant correlation between starch properties and measured aspects of pasta quality.     

Relationship of Creep-Recovery and Dynamic Oscillatory Measurements to Durum Wheat Physical Dough Properties

Durum wheat gluten strength is important in determining extrusion properties and pasta cooking quality. Durum wheats varying in strength were tested using an alveograph and a 2-g micro-mixograph, both widely accepted techniques for determination of physical dough properties. Doughs from the 2-g micro-mixograph were characterized by dynamic oscillatory and large deformation creep tests using a controlled stress rheometer. Mechanical properties obtained from both testing regimes were strongly correlated with many of the parameters provided by the alveograph and micro-mixograph. Maximum strain attained after 5 min creep ranged from <5% for the strongest least extensible cultivar to >25% for the weakest cultivar, with a coefficient of variation among replicates of <10%. Storage modulus (G′) at 2 Hz ranged from ≈7,000 Pa for the weakest cultivar to >16,000 Pa for the strongest, least extensible cultivars, with a coefficient of variation of <6%. Tan δ (G″/G′) values were ≈0.4 for the strongest versus >0.5 for the weakest cultivars, indicating the larger contribution of the elastic component in the strong cultivars. The rheometer allows discrimination of durum wheat cultivars of varying gluten strength while requiring less sample than traditional physical dough testing techniques.     

Grain Quality Characteristics and Milling Performance of Full and Partial Waxy Durum Lines

Mutation of the gene coding for the granule bound starch synthase (waxy protein) leads to reduced amylose content in cereal endosperm. Durum wheat (Triticum turgidum L. var. durum) has one waxy locus in each of its two genomes. Full waxy durum wheat is produced when both genomes carry the waxy null alleles. When only one locus is mutated, partial waxy durum wheat is obtained. Partial and full waxy near‐isogenic lines of durum wheat developed by a breeding program were analyzed as to their quality characteristics. Amylose was largely eliminated in full waxy lines; however, no reduction in amylose content was detected in partial waxy lines. The waxy mutation did not affect grain yield, kernel size, or kernel hardness. Full waxy durum lines had higher kernel ash content, α‐amylase activity, and a unique nonvitreous kernel appearance. Protein quality, as evaluated by SDS microsedimentation value, gluten index, and wet gluten was slightly lower in the full waxy lines than in the other genotypes. However, comparisons with current cultivars indicated that protein quality of all derived lines remained in the range of strong gluten cultivars. Semolina yield was lowered by the waxy mutations due to lower friability that resulted in less complete separation of the endosperm from the bran. Waxy semolina was more sensitive to mechanical damage during milling, but modified tempering and milling conditions may limit the damage. Overall, quality characteristics of waxy durum grain were satisfactory and suitable for application testing.     

Kernel Properties and Pasta-Making Quality of Five European Spelt Wheat (Triticum spelta L.) Cultivars

The kernel characteristics and composition, milling performance, protein quality, and alveograph parameters of five spelt cultivars grown in European countries were determined in relation of their utilization in pasta products. Long pasta was manufactured and chemically characterized, and its quality was assessed by sensory and chemical tests. Protein and fat contents were high in the grains (15.7 and 4.4% db, mean value, respectively). Total fiber varied from 10.5 to 14.9% db. The average β-glucan content was 1.2% db. The milling performance as determined by yield, damaged starch, ash, and particle-size distribution in the flour was uniform among the five cultivars. The results of the SDS sedimentation and gluten index tests indicated that spelt gluten strength was low, and this was confirmed by the alveograph test. Sensory and chemical evaluations of the pastas, however, indicated that spelt is suitable for obtaining good-quality pasta. The combination of the high protein content and the high-temperature drying cycle adopted in pasta production could be responsible for these good results.     

Interactions of Genotype and Glutenin Subunit Composition on Breadmaking Quality of Durum 1AS•1AL‐1DL Translocation Lines

Dual‐purpose durum (Triticum turgidum L. subsp. durum) wheat, having both good pasta and breadmaking quality, would be an advantage in the market. In this study, we evaluated the effects of genotype and varying HMW and LMW glutenin subunit composition on durum breadmaking quality. Genotypes included five near‐isogenic backgrounds that also differed by variability at the Glu‐D1d (HMW subunits 1Dx5+1Dy10), Glu‐B1 (presence or absence of subunit 1By8), and Glu‐B3 (LMWI or LMWII pattern) loci. Quality tests were conducted on genotypes grown at five North Dakota locations. Genotype had a stronger influence on free asparagine content than glutenin subunit composition. Genotypes carrying Glu‐D1d had higher glutenin content than lines that did not carry Glu‐D1d. Among Rugby translocation genotypes, lines carrying LMWI had higher gliadin content and better loaf volume than genotypes carrying LMWII. Absence of 1By8 produced major reductions in loaf volume in nontranslocation lines regardless of whether LMWI or LMWII was present. In contrast, the presence of Glu‐D1d compensated well for the absence of 1By8 regardless of which LMW pattern was present. The durum genotypes did not have loaf volumes equal to bread wheat cultivars, and results suggest that improved extensibility is needed to improve durum breadmaking quality.     

Textural Images Analysis of Pasta Protein Networks to Determine Influence of Technological Processes

The structure of pasta is largely governed by the presence of a structured protein network. This work analyzed the protein network textures of various cooked pasta products through textural image analysis. Six different pasta types were investigated: reference pasta made from durum semolina; pasta enriched with gluten proteins from soft wheat flour at 10 and 20%; autoclaved pasta; soft wheat flour pasta; and pasta made from reconstituted flour fractions. Pasta samples were sectioned, and each crosssection consisted of three distinct zones (central, intermediate, and external) based on the state of swelling of starch granules for each pasta product. Digital images of the protein network in each zone were acquired using confocal laser scanning microscopy. Textural image analysis was then performed. Similarities and differences in protein network texture were assessed by principal component, stepwise discriminant, and variance analyses. With the exception of autoclaved pasta, protein network structure differed greatly with the position in the pasta. Furthermore the effect of technological treatments was greatly influenced by the position in pasta. The most significant differences in protein network structure were obtained with the autoclaved and 20% protein-enriched samples.