Kernel vitreousness and protein content: Relationship,interaction and synergistic effects on durum wheat quality

Four sets of durum samples were used in this study to further understand the interrelationships among hard vitreous kernels (HVK), protein content, and pigment concentration, with a focus on the interaction and synergistic effects of protein content and vitreousness on durum quality. HVK level increases with higher protein content in the range of 9.5–12.5%, but this relationship is less evident in durum samples with high protein content (12.5–14.5%). Both protein content and kernel vitreousness can significantly affect durum milling quality. White starchy kernels (WSK) in low protein durum have a very detrimental impact on milling and pasta processing quality, but high protein content can mitigate the adverse impact of WSK on durum quality. Although protein content plays a dominant role, higher HVK might contribute positively to pasta firmness. There was no significant difference in yellow pigment content between HVK and WSK. However, pigment loss from semolina to dough was higher for WSK than HVK. Despite the difference in protein content, HVK and WSK have little difference in gluten strength. The monomeric protein was preferentially accumulated in HVK. The glutenin proteins of HVK and WSK were similar in the ratios of 1Bx/1By and HMW/LMW-GS.     

Identification of sorghum genotypes suitable for specific end uses: Semolina recovery and popping

There has always been an interest in devising breeding programs for designer foods that would benefit both the producer and consumer. The challenge today is transformation of agriculture from “subsistence farming” to “market and income generation oriented” production system for which sorghum with its diverse end uses can assume significant role. Breeding for end-use identity-specific genotypes is needed for increased profitability to the farmers. In the present study, 60 sorghum genotypes were evaluated over two years to identify genotypes suitable for semolina recovery and popping properties, i.e. popping efficiency and pop volume expansion. Semolina recovery ranged from 20.7% to 48.3%, while popping efficiency ranged from 0 to 77.5%. Semolina recovery had positive and significant association with endosperm texture (r = 0.62), grain density (r = 0.49) and grain hardness (r = 0.55) indicating that genotypes with corneous endosperm yield high semolina. Also, semolina recovery had significant positive correlation with popping efficiency (r = 0.49) indicating that genotypes suitable for semolina can also be used for popping. Genetic divergence studies indicated that out of three clusters formed, cluster II having guinea race germplasm lines are suitable for semolina and popping. The information generated and the genotypes identified will help in enhancing the demand for sorghum as an industrial crop.     

Prediction of semolina technological quality by FT-NIR spectroscopy

The feasibility of applying FT-NIR spectroscopy (a rapid and non-destructive method) to evaluate and predict semolina characteristics by means of spectra collected directly from the kernels was investigated. More than 500 samples of durum wheat grains and of the corresponding semolina, representative of the Italian production of 4 different crops (from 2002/2003 to 2005/2006) were analyzed. Pasta-making capability of each semolina sample was assessed by the reference methods, for protein, gluten content, gluten index and alveographic indices. The kernels were also evaluated by a FT-NIR spectrometer, fitted with an integration sphere working in diffuse reflectance. The processed spectra collected on the kernels were correlated with the chemical and rheological parameters obtained by the reference tests performed on semolina. The PLS algorithm was used to develop calibration models from the original spectra datasets. Protein content proved to be well correlated to kernel spectral data: high values for the RPD indicate efficient NIR reflectance predictions for protein content. The models obtained for gluten content, gluten index and alveographic W and P/L parameters were less successful. The results of this work highlighted the feasibility of applying FT-NIR spectroscopy to evaluate and predict the technological properties of semolina, in particular that of the protein content, by collecting the spectra directly from the kernels, without performing further grinding or milling operations.     

婴儿配方奶粉生产中部分应用大豆分离蛋白的研究

通过对人乳和牛乳蛋白质组分的差异比较,利用大豆分离蛋白中的优质氨基酸与乳蛋白混合后的营养互补,提高营养价值.同时与乳糖配合可以达到部分替代脱盐乳清粉D90的目的,进而提升产品营养,做到婴儿配方奶粉的国产化.     

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.     

A deletion at the Lpx-B1 locus is associated with low lipoxygenase activity and improved pasta color in durum wheat (Triticum turgidum ssp. durum)

The concentration of yellow carotenoid pigments in durum wheat grain is an important quality criterion and is determined both by their accumulation and by their degradation by lipoxygenase enzymes (Lpx loci). The existence of a duplication at the Lpx-B1 locus and the allelic variation for a deletion of the Lpx-B1.1 copy is reported. This deletion was associated with a 4.5-fold reduction in lipoxygenase activity and improved pasta color (P<0.0001) but not semolina color, suggesting reduced pigment degradation during pasta processing. A molecular marker for the deletion was mapped on chromosome 4B in a population obtained from the cross between durum line UC1113 and variety Kofa. A second lipoxygenase locus, designated Lpx-A3, was mapped on the homoeologous region on chromosome 4A and was associated with semolina and pasta color (P<0.01) but not with lipoxygenase activity in the mature grain. Selection for both the UC1113 allele for Lpx-A3 and the Kofa Lpx-B1.1 deletion resulted in a 10% increase in yellow scores for dry pasta relative to the opposite allele combination. This result indicates that the markers and the new allelic variants reported here will be useful tools to manipulate the wheat Lpx loci and to improve pasta color.     

Distribution along durum wheat kernel of the components involved in semolina colour

A bright yellow colour of pasta is an important qualitative trait for the durum wheat industry. Final colour is the result of the balance between yellow and brown components in semolina. Carotenoid pigments and lipoxygenase (LOX) enzyme are mainly involved in yellowness, whereas peroxidase (POD) and ash affect brown hue. All these components have a different distribution across the kernel, with varietal differences too. This study aimed to evaluate the distribution pattern of carotenoid pigments, α-tocopherol, linoleic acid, and ash content as well as of LOX and POD activities within the kernel of six durum wheat cultivars characterised by different pigment content and hydroperoxidation activity of LOX in semolina. The results confirmed differences in the distribution of these components across the kernel and among varieties. Additionally, this study identified for some components (POD, pigments and bleaching activity of LOX) a higher effect of genotype whereas for others (ash, α-tocopherol, hydroperoxidation activity) a marked effect of the debranning process. These results suggest that improvement of the final semolina colour could be reached both through breeding activity, enabling an early selection of better lines, and through an appropriate debranning process.