Genetic variability in yellow pigment components in cultivated and wild tetraploid wheats

Yellow pigment concentration (YPC) in durum wheat is an important criterion in the assessment of semolina quality, particularly in determining the commercial and nutritional quality of end-products. Genetic variability of YPC and carotenoid components was analysed in 102 wild and cultivated tetraploid wheat accessions in two trials. Overall, modern cultivars showed significantly higher values of YPC compared to old cultivars and wild ssp. dicoccum and ssp. dicoccoides accessions. Total carotenoid concentration varied between 1.178 and 4.416 μg/g with an average of 2.460 μg/g. The portion of carotenoids amounted to 33.2% of the YPC in 80 wheat accessions examined in the 2006 trial. Lutein was the main component of carotenoids, followed by zeaxanthin and β-carotene. α-carotene and β-cryptoxanthin were minor components. Pigment concentration was negatively correlated with kernel weight and grain protein concentration. Significant positive correlations were found between b* index and YPC. Knowledge of the carotenoid composition and concentration is useful for wheat breeders in the development of cultivars with high yellow colour and enhanced phytochemical concentrations, and provides valuable information for evaluating contributions to health benefits from the consumption of durum wheat end-products.     

Different mechanisms control lipoxygenase activity in durum wheat kernels

Yellow pigment content (YPC), lipoxygenase (LPX) activity and the polymorphism at the Lpx-B1.1 locus were assessed on an Italian durum wheat germplasm collection and four varieties contrasting for YPC and LPX activity were then characterized in terms of Lpx gene expression, biochemical LPX properties and their performance during pasta processing. The screening of 71 genotypes showed a great genetic variability for YPC (3.68–9.43 μg/g dw) and LPX activity (0.02–7.91 EU/g dw). The Lpx-B1.1 polymorphism was significantly associated with differences in LPX activity. Besides the Lpx-B1.1 deletion, different expression levels of Lpx mRNAs were found associated with differences in LPX activity. The temporal expression of three Lpx genes showed different profiles among the cultivars investigated. Genotypes with high LPX activity showed an anticipated temporal expression for Lpx-1 compared to low LPX activity ones. The LPX activity in the analysed genotypes is most likely due to the contribution of different LPX isoforms observed in the later stage of grain filling.     

A rapid method for the estimation of damaged starch in wheat flours

A new method was developed for determination of damaged starch in wheat flour. The method was based on the idea that the difference between the soluble matter contents of the extracts prepared from the same flour with and without alpha-amylase is mainly due to the action of alpha-amylase on damaged granules. The extraction stage of the method is similar to the AACC method (76-30A). However, after this stage a refractometer was used to measure Brix values of solutions instead of determination of reducing sugars. The sample size and incubation period of the AACC method were optimized for the proposed method using response surface methodology. The damaged starch levels of twenty-five commercial samples were determined by the proposed method as well as the two AACC Methods (No: 76-30A and 76-31). The results of the proposed method are compared with the results of the AACC Methods by using regression analysis. The correlation coefficients between the proposed method and both of the AACC Methods were 0.99. The average absolute differences between the proposed method and the AACC methods were 3.9 and 5.0%, respectively. The proposed method can be completed in 30 min with low number of experimental steps. The results showed that the starch damage values measured by the new method could be viewed with as much confidence as the traditional AACC Method 76-30A.     

Bread-making performances of durum wheat semolina,as affected by ageing

The present study addresses the influence of ageing on the bread-making performances of durum wheat semolina by bread image analysis. Bread loaves were produced from semolina samples stored in 4 different packaging materials for up to 150 days. Sampling and bread-making trials were performed every 15 days. Results showed that ageing does affect durum wheat semolina bread-making performances, highlighting that storage time, rather than the type of packaging material, is the main factor determining quality changes in the final bread samples. In particular, a change in the crust colour parameters and a reduction of the bread slice area and height by 20–35% were observed with increasing semolina storage time, along with a slight increase of crust % area. The change in farinographic parameters of dough suggests that the observed reduction of technological quality might be due to increased stiffness and reduced extensibility of gluten occurring in aged semolina. Unlike common wheat flours, which usually improve their technological features during ageing, durum wheat semolina is negatively affected in its quality by storage. The study highlights the importance of considering bread-making performances among the quality parameters to be taken into account for the shelf life evaluation of durum wheat semolina.     

Pigment loss from semolina to dough: Rapid measurement and relationship with pasta colour

The yellow colour of pasta is due largely to the presence of carotenoid pigments in semolina. Some of the carotenoids can be degraded during pasta processing through oxidation induced by lipoxygenase (LOX), resulting in pasta colour loss. Measurement of LOX activity is complex and not practical as a screening tool, so there is a need to develop a rapid, cost effective, high throughput method for routine measurement of colour loss in breeding programs and the durum milling and pasta processing industries. After establishing a rapid micro-scale pigment extraction procedure, this study developed a method to quantify pigment loss due to enzymatic degradation in semolina. It can be conducted in parallel with a simple and reliable micro-scale semolina pigment content assay utilizing water saturated 1-butanol extraction. Water (0.15 ml) was added to semolina (200 mg) in a micro centrifuge tube. The mixture was then homogenized to simulate the mixing and kneading processes in pasta-making, and allowed to rest for 1.0 or 2.0 h. Pigments in the resulting dough were extracted by adding 0.85 ml of 1-butanol, followed by homogenization, resting, and centrifugation. Absorption at 435 nm was recorded and converted to yellow pigment concentration. The pigment loss from semolina to dough was found to be genotype dependent. Durum genotypes with low loss (0–3.8%) were characterized by the absence of a LOX gene duplication at the Lpx-B1 locus, which was shown previously to be associated with a strong reduction in LOX activity in semolina. The loss was higher (5.5–21.8%) for genotypes carrying the LOX gene duplication. While the relationship between pigment content in semolina and pasta colour was significant (r² = 0.55–0.61), the relationship between pigment content in dough after oxidative loss and pasta colour was stronger (r² = 0.59–0.90). These results suggest that the method developed in this study could be used as a tool to select for reduced colour loss due to LOX activity.     

四倍体小麦籽粒多组分营养物质含量的QTL定位及相关性分析

为了寻找改良普通栽培小麦营养物质含量的基因资源,以野生二粒小麦G18-16和硬粒小麦Langdon杂交所构建的重组自交系F6代群体为研究材料,种植于黔中地区并对该群体籽粒可溶性蛋白质、总类黄酮、总酚、植酸和黄色素5个营养性状含量进行测定。共检测到6个相关的QTLs,分别分布在染色体2A、3A、4A、6B和7A上。除小麦籽粒总酚性状外,其余四个性状均呈正态分布。网络相关性分析表明,所有营养性状与农艺性状间均呈显著负相关,仅黄色素与农艺性状无显著相关性。主成分分析(Principal component analysis,PCA)也显示总酚和黄色素与其他营养性状有显著差异,并且是造成群体分布差异最主要的因素。因此,小麦总酚和黄色素性状在其生理代谢中可能存在特殊性。另外,PCA还筛选出2组在5个营养性状上存在显著差异的基因池家系各4株,为回交和精细定位提供了较可靠的研究材料。     

Investigation of amber durum wheat for production of yellow alkaline noodles

Samples of Canadian amber durum wheat varieties, of various protein content and a composite of export cargo samples, were milled to yield straight-grade and patent flours by reducing semolina and processed into yellow alkaline noodles (YAN). Samples of Canada Hard White Spring (CWHWS) and Canada Western Red Spring (CWRS) were included for comparative purposes. YAN from durum wheat displayed a colour advantage over CWRS and CWHWS YAN. The durum YAN displayed an approximate 9–20 unit greater b* (yellowness) value than CWRS and CWHWS at 2 and 24 h after preparation. This relates to greater yellow pigment and flavonoid contents in the durum flours. All durum wheat YAN exhibited excellent noodle brightness, which was retained over time due to lower levels of the enzymes polyphenol oxidase (PPO) and peroxidase (POD). Durum noodles displayed significantly fewer specks than CWRS and were comparable to CWHWS. Durum wheat YAN cooking quality was equal to or slightly superior to CWRS and CWHWS. Durum wheat flour refinement imparted no significant effects on cooked noodle texture (maximum cutting stress, recovery, resistance to compression). However, the various texture parameters improved with durum wheat protein content and gluten strength.     

小麦籽粒PPO活性检测方法改良与应用

小麦籽粒多酚氧化酶（polyphenol oxidase,PPO）活性是造成面粉及其制品酶促褐变的最主要原因。为快速、准确地检测小麦籽粒PPO活性,将酶标仪应用于PPO活性测定,对小麦籽粒PPO活性传统检测方法（AACC 22-85.01）进行了改良,并利用改良方法测定了283份国内外小麦品种PPO活性。结果表明,改良方法与传统方法所测PPO活性呈极显著正相关,相关系数达0.982。应用改良方法对144份小麦品种PPO活性进行重复测定,三次重复间的相关系数高达0.993～0.994。283份国内外小麦品种PPO活性变异范围为1.12 U·g^-1·min^-1～10.95 U·g^-1·min^-1,筛选到34份PPO活性较低的品种,可作为亲本材料用于低籽粒PPO活性小麦品种选育。与传统方法相比,改良方法大大减少了工作量,缩短了检测时间,效率提高约12～15倍。因此,本研究中改良的AACC 22-85.01法是一个操作简便、准确可靠、稳定高效的小麦籽粒PPO活性检测方法,可代替传统AACC 22-85.01法用于PPO活性大规模测定,为面制品色泽性状遗传改良提供技术支撑。     

Heat and drought stress on durum wheat: Responses of genotypes,yield, and quality parameters

Heat and/or drought stress during cultivation are likely to affect the processing quality of durum wheat (Triticum turgidum L. ssp. durum). This work examined the effects of drought and heat stress conditions on grain yield and quality parameters of nine durum wheat varieties, grown during two years (2008–09 and 2009–10). Generally, G and E showed main effects on all the parameters whereas the effects of G × E were relatively small. More precipitation in Y09–10 may account for the large differences in parameters observed between crop cycles (Y08–09 and Y09–10). Combined results of the two crop cycles showed that flour protein content (FP) and SDS sedimentation volume (SDSS) increased under both stress conditions, but not significantly. In contrast the gluten strength-related parameters lactic acid retention capacity (LARC) and mixograph peak time (MPT) increased and decreased significantly under drought and heat stress, respectively. Drought and heat stress drastically reduced grain yield (Y) but significantly enhanced flour yellowness (FY). LARC and the swelling index of glutenin (SIG) could be alternative tests to screen for gluten strength. Genotypes and qualtiy parameters performed differently to drought and heat stress, which justifies screening durum wheat for both yield and quality traits under these two abiotic stress conditions.     

Investigation of amber durum wheat for production of yellow alkaline noodles

Samples of Canadian amber durum wheat varieties, of various protein content and a composite of export cargo samples, were milled to yield straight-grade and patent flours by reducing semolina and processed into yellow alkaline noodles (YAN). Samples of Canada Hard White Spring (CWHWS) and Canada Western Red Spring (CWRS) were included for comparative purposes. YAN from durum wheat displayed a colour advantage over CWRS and CWHWS YAN. The durum YAN displayed an approximate 9–20 unit greater b* (yellowness) value than CWRS and CWHWS at 2 and 24 h after preparation. This relates to greater yellow pigment and flavonoid contents in the durum flours. All durum wheat YAN exhibited excellent noodle brightness, which was retained over time due to lower levels of the enzymes polyphenol oxidase (PPO) and peroxidase (POD). Durum noodles displayed significantly fewer specks than CWRS and were comparable to CWHWS. Durum wheat YAN cooking quality was equal to or slightly superior to CWRS and CWHWS. Durum wheat flour refinement imparted no significant effects on cooked noodle texture (maximum cutting stress, recovery, resistance to compression). However, the various texture parameters improved with durum wheat protein content and gluten strength.     

Using CERES-Wheat to simulate durum wheat production and phenology in Southern Sardinia,Italy

Durum wheat is a crop of great economic relevance for Mediterranean regions, especially in developing countries. A decreasing trend in durum production is expected in the near future because of several factors, in particular environmental constraints due to climate change and variability. The aim of this work was to test the predictive performance of CERES-Wheat model, implemented in DSSAT software systems, under Mediterranean climate condition and soil types of Southern Sardinia, Italy. CERES-Wheat model was calibrated for three durum wheat Italian varieties (Creso, Duilio, and Simeto) using a 30-year data set (1974–2004) and a trial and error iterative procedure. Then, the model was validated and evaluated using several statistics. The model showed a quite good performance in predicting grain yield and anthesis date, with errors comparable with those reported by other studies conducted on bread and durum wheat. Predictions of grain weight and grain number did not match very well observations, confirming the difficulties of CERES-Wheat in estimating grain yield components. The results of this study suggest the need of specific field experiments and further model evaluations and improvements to better understand model simulation results of grain yield components of durum wheat.     

Phytate and mineral elements concentration in a collection of Italian durum wheat cultivars

Mineral deficiencies are prevalent in human populations and the improvement of the mineral content in cereal products represents a possible strategy to increase the human mineral intake. Nevertheless, most of the inorganic phosphorus (P_i) present in mature cereal seeds (40–80%) is stored as phytate, an anti-nutritional factor that forms complexes with minerals such as Ca, Mg, Zn and Fe reducing their bioavailability. The present study was undertaken: (i) to determine the variation in phytate and mineral concentrations in the whole grains of 84 Italian durum wheat (Triticum durum Desf.) cultivars representative of old and modern germplasm; (ii) to estimate the magnitude of genotype × environment interaction effects; and (iii) to examine the interrelationships among mineral concentrations in durum wheat with the final aim to identify superior durum wheat cultivars that possess low phytate content and high concentration of mineral elements in their whole-wheat flour. The cultivars were grown in field trials during 2004–2005 at Foggia, Italy and during 2005–2006 at Foggia and Fiorenzuola d’Arda—Southern and Northern Italy. The phytate content was estimated indirectly by using a microtitre plate assay evaluating the P_i absorbance at 820 nm, while the Cu, Fe, Mn, Ca, K, Mg, Na and Zn mineral contents were determined by ICP/OES. The contents of Zn and Fe across years and locations ranged from 28.5 to 46.3 mg/kg for Zn with an average of 37.4 mg/kg and from 33.6 to 65.6 mg/kg for Fe with an average of 49.6 mg/kg. P_i grain content was between 0.46 and 0.76 mg/g showing a positive correlation with all minerals except Cu and Zn. Although breeding activity for Fe and Zn would be difficult because G × E interaction is prevalent, multi-location evaluation of germplasm collection help to identify superior genotypes to achieve this objective. The results here reported open the possibility of designing a specific breeding program for improving the nutritional value of durum wheat through the identification of parental lines with low-P_i and high minerals concentration in whole grains.     

Quantitative trait loci for yellow pigment concentration and individual carotenoid compounds in durum wheat

A defining factor for the commercial value of durum wheat pasta is its amber colour, which depends on the semolina yellow pigment concentration and on the oxidative enzymatic activity. Among carotenoids controlling yellow colour, the presence of β-carotene is also important as precursors of vitamin A. The aim of the present study was to detect quantitative trait loci (QTL) for yellow pigment concentration, yellow index and individual carotenoid compounds (lutein, zeaxanthin, β-cryptoxanthin, α-carotene and β-carotene) in a durum segregant population. Total carotenoid concentration amounted to 37% of the yellow pigments, indicating unknown colour-producing compounds in the durum extracts. Lutein was the most abundant carotenoid, followed by zeaxanthin, α-carotene and β-carotene, while β-cryptoxanthin was a minor component. Phytoene synthase marker Psy-A1, 150 SSR and EST-SSR markers, and 345 DArT^® markers, were used to construct the linkage map for subsequent QTL analysis. Clusters of QTL for total and/or one or more carotenoid compounds were detected on the same chromosome regions (2A, 3B, 5A and 7A) where QTL for yellow pigment concentration and yellow index were identified. The molecular markers associated to major QTL would be useful for marker-assisted selection programs to facilitate high carotenoid concentration with high nutritional carotenoid compounds in wheat grain.     

Evaluation of heat damage, sugars, amylases and colour in breads from einkorn, durum and bread wheat flours

To limit nutritional losses and optimise bread processing, heat damage indices (furosine, glucosylisomaltol, hydroxymethylfurfural), sugars, α-amylase, β-amylase and colour were monitored during bread manufacturing from refined flour of three einkorn, three bread and one durum wheat samples. The heat damage indices increased only during the baking step. Furosine was significantly lower in einkorn (on average, 9.3 ± 5.33 and 25.3 ± 10.70 mg/100 g protein in crumb and crust, respectively) than in bread wheat (31.6 ± 3.05 and 115.6 ± 13.53) and durum wheat (36.2 ± 2.82 and 165.0 ± 3.17). Glucosylisomaltol and hydroxymethylfurfural were detected only in the crust, with lower levels in einkorn (on average, 2.3 ± 1.78 and 10.0 ± 7.79 mg/kg DM, respectively) than in bread wheat (13.1 ± 5.57 and 42.8 ± 10.64) and durum wheat (18.9 ± 1.11 and 57.2 ± 0.80). The different behaviour of einkorn was probably related to its moderate β-amylase activity, and thus the low maltose content of its dough. Colour was correlated with heat damage, as einkorn breads were lighter than the others.The results show that einkorn bread undergoes lower heat damage than analogous products from durum and bread wheat, thus probably better preserving its nutritional value.     

Study of the microstructure of durum wheat endosperm using X-ray micro-computed tomography

Durum wheat grains are used for producing food, such as pasta or couscous. The grain mechanical properties which are linked to its internal micro-structure (i.e. endosperm porosity) are known to determine its ability to produce semolina during milling. The proportion of grains having porous endosperm in a batch appears therefore as a critical quality factor for the durum wheat value chain. Our objective was to investigate the ability of X-ray micro-tomography (μCT) method to describe the porous or vitreous counterpart structures in the endosperm of durum wheat grains. We selected two different durum wheat samples displaying vitreous or partially porous endosperms. The grains were analyzed using μCT at two pixel sizes (1 μm or 7 μm). The μCT data collected at 7 μm pixel size were used for qualitative classification of grains according to apparent distribution curve of the porosity parameters. Analysis of μCT images at 1 μm pixel size allowed us to propose pore size classification in the vitreous and porous parts of the endosperm in three durum wheat grain. Results are used to better describe the durum-wheat endosperm microstructure, but requires long scanning periods.     

Effects of gamma-irradiation of wheat on gluten proteins

The effects of ⁶⁰Co gamma-irradiation treatments (2·5, 5·0, 10·0 and 20·0 kGy) on the gluten proteins of two bread wheats and one durum wheat cultivar were investigated. Dough rheological properties of the flour processed from the irradiated wheat were also determined using a computerised micromixograph. Irradiation caused a significant deteriorating effect on all mixogram parameters. There was no observable effect of irradiation on gliadin proteins analysed by polyacrylamide gel electrophoresis. The 50% 1-propanol-insoluble (50 PI) glutenin fraction was highly affected by irradiation. By sodium dodecyl sulfate polyacrylamide gel electrophoresis, reduced 50 PI glutenin showed a noticeable reduction in band intensities of both high (HMW) and low molecular weight (LMW) glutenin subunits (GS) with increasing irradiation dosage greater than 5 kGy. The irradiation effect on 50 PI glutenin was further studied and quantified by reversed-phase high-performance liquid chromatography of glutenin subunits; there was a progressive decrease in the quantity of subunits with increasing irradiation dose level. Compared to non-irradiated wheat, the relative decline in total insoluble glutenin at the 20 kGy dosage level ranged from 34–49% depending on cultivar. Increasing levels of irradiation also progressively reduced the ratio of HMW:LMW-GS up to 13–15% at 20 kGy indicating that irradiation had a greater effect on the largest polymers of glutenin. The observed weakening of dough mixing properties and concomitant decline in the quantity of 50 PI glutenin with increasing levels of gamma-irradiation are consistent with a degradation of glutenin to a lower average molecular size by depolymerisation and/or disaggregation.     

Assessment of commercial milling potential of hard wheat by measurement of the rheological properties of whole grain

The single-kernel characterisation system (SKCS) 4100 instrument has previously been shown to provide in situ measurements of the rheological properties of the bran and endosperm layers of wheat, otherwise only possible following their isolation by dissection or machining. The current study has confirmed that endosperm maximum stress (endosperm strength (ES) as measured using the SKCS 4100 correlates highly (r=0.898$r=0.898$) with compressive strength (maximum stress, σ_max) measurements performed on specimens of endosperm tissues of known dimensions, isolated from different subsamples of the same bulk wheat samples. This provides a means of scaling the stress axis of the crush–response profile plots to the Instron scale (MPa) so that the SKCS endosperm stress/strain curves for hard wheat, soft wheat and durum can be compared with Instron results presented in the literature. In addition, a simple method for the measurement of ES and stiffness, using the SKCS 4100, has been developed. The method has been shown to rank wheat samples according to their performance when processed on a 650 kg/h pilot mill. The criterion against which the SKCS-derived rankings were compared was the Milling Quality Index, which uses both the percentage flour extraction and Branscan speck count measurements.     

Influence of the addition of buckwheat flour and durum wheat bran on spaghetti quality

The quality of nine spaghetti typologies, produced by using wheat durum semolina as a base plus the addition of buckwheat and durum wheat bran, was investigated. The quality of the produced spaghetti was compared with that of spaghetti made only of durum semolina (CTRL). Tests were run on the samples to determine breakage susceptibility and colour of dry spaghetti, the cooking resistance, instrumental stickiness at optimal cooking time (OCT) and overcooking, the cooking loss and sensorial attributes at the optimal cooking time. Results suggest that the breakage susceptibility decreases with the addition of 15% and 20% bran, the spaghetti dry colour changes with the addition of buckwheat flour and bran compared to the spaghetti made only of durum semolina, while the cooking resistance, instrumental stickiness and the cooking loss, in general, were equal to that of the CTRL. However, the addition of buckwheat flour and bran affected the sensorial attributes differently.     

Variability in dehydrodiferulic acid composition of durum wheat (Triticum durum Desf.) and distribution in milling fractions

The dehydrodiferulic acid content of different common and durum wheat grains and milling fractions was determined by an HPLC procedure. The 8-O-4′, 5–8′ benzofuran, 5–8′ and 5-5′ dehydrodimers were identified in all samples studied and occurred in decreasing relative amounts, respectively. Durum wheats were twice as concentrated in dimers as common wheats. An important genetic variation for dehydrodiferulic acid content was shown within durum wheat grains, whereas the agronomic conditions had no effect. There was 10 to 20 times more dehydrodiferulic acids in external layers (aleurone, bran) than in the starchy endosperm of durum wheat grains. The content and composition in dimers of the inner endosperm did not vary according to genotypes and cultivation conditions. The ratio of dehydrodimers to monomers of ferulic acid which represented an index of dimerisation, was 1·6 times higher in the external layers of the grain than in the endosperm. No relation was found, however, between the degree of ferulic acid dimerisation and the milling behaviour of durum wheat grains.     

Effect of genotype,environment and genotype-by-environment interaction on metabolite profiling in durum wheat (Triticum durum Desf.) grain

The aim of this study was to assess the relative roles of genotype, environment and genotype-by-environment interactions in determining the metabolite profile of durum wheat grain. Four durum wheat cultivars were grown under conventional and organic farming systems over three consecutive years. The use of a high-throughput gas chromatography–mass spectrometry platform allowed the analysis of sets of different polar and non-polar compounds, including amino acids, sugars, organic acids, fatty acids (saturated and unsaturated), and sterols. Statistical analysis of the data showed a small impact of genotype and large effects of both year and genotype-by-environment interaction on the metabolite composition and quality of the wheat grain. Overall, the data from this study highlight the potential role of metabolic profiling in the analysis of durum wheat quality and production.