Durum Wheat Lipoxygenase Activity and Other Quality Parameters that Affect Pasta Color

Pasta yellowness is affected by different factors, the most important of which are intrinsic to the quality of semolina (natural carotenoid pigments, protein, ash, and lipoxygenase [LOX] activity) and processing conditions. Because all the parameters involved in pasta color are under the control of varietal and environmental factors, the role of the genotype, environment, and the interaction between genotype and environment on color expression were studied. Although the analysis of variance showed the genotype-by-environment interaction to be significant, a nonorthogonal analysis attributed a higher weight to genotype on parameters directly involved in color expression: β-carotene content, yellow index, and LOX activity. Furthermore, the loss of pigments and yellow index after milling and processing was evaluated and correlated with all the parameters involved in the determination of final pasta color. The phase mainly responsible for pigment loss was pasta processing. A decrease of 16.3% in semolina β-carotene content during pasta processing versus a 7.9% loss during milling was determined. The isoenzymatic forms LOX-2 and LOX-3, active at the pH of dough, were responsible for the loss of color in pasta products. Simple correlations and the linear multiple regression corroborated this finding. Hydroperoxidation activity at pH 6.6, bleaching activity, and ash content were responsible for 87% (R² adjusted) of total variance, with each variable accounting for 57, 61, and 22% of the variation, respectively. This confirms that LOX activity is the main factor involved in the loss of color, while a secondary and lesser role can be seen for ash content. Therefore, a high pigment content, located in the interior of the whole grain, and a lower LOX activity in semolina must be the selection characteristics by which breeding programs obtain a bright yellow pasta.     

A Fast,Simple, and Reliable Method to Predict Pasta Yellowness

Pasta yellowness depends on the semolina carotenoid content, carotenoid degradation by lipoxygenase (LOX), and pasta processing conditions. In breeding programs, early generation lines are selected for high grain yellow pigment content with the intent to improve pasta color. This approach has been successful in increasing the grain yellow pigment of Canadian durum wheat in the last few decades. In recent years, however, a weak relationship between pasta yellowness (b*) as measured by a Minolta spectrophotometer and semolina yellow pigment content (r = 0.19–0.52) was noted in the Canadian durum wheat lines. Thus, total semolina yellow pigment content cannot effectively predict the yellowness of its pasta product. Therefore, a fast and simple method was developed to predict pasta yellowness by measuring semolina dough sheet color at different time intervals after sheeting (0.5, 2.0, and 24 hr). Spaghettis were processed from the semolina samples at two drying temperature cycles (70 and 90°C). There were significant correlations between dough sheet b* values at all three times and spaghetti b* values at both drying temperatures (r = 0.87–0.94). Semolina dough sheet can be easily prepared in 15 min and requires only 30 g of material. Shortly after sheeting (30 min), dough sheet b* values can be used to predict pasta yellowness without producing the end product (involving mixing, extrusion, and drying). In this study, we also found that dough sheet b* values increased significantly with time over the sampling intervals after sheeting for those breeding lines with superior pasta color. DNA analysis revealed that all those lines lacked the Lpx‐B1.1 duplication.     

Yellow Pigment Determination for Single Kernels of Durum Wheat (Triticum durum Desf.)

The carotenoid concentration of durum wheat is a criterion for the assessment of semolina quality, and it is of particular importance in determining the color of pasta. Thus, the development of a rapid screening method for kernel and semolina color has facilitated increasing the yellow color in durum wheat cultivars. However, the distribution of the pigment might vary within the ear of the wheat. The micromethod for the determination of yellow pigment concentration (YPC) of single wheat kernels now allows the discovery of whether this variation is the same for cultivars with different carotenoid concentrations. All of the cultivars investigated showed similar trends in the arrangements of the kernels within the ears, with the central positions of the ears being the most stable for YPC. Indeed, the best combination of higher YPC and larger kernel size is seen for the basal‐central region of the ear, which can be used for the selection during wheat‐breeding programs of cultivars with a more intense yellow color.     

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.     

Changes in Semolina Yellow Pigment Content and Carotenoid Composition During Pasta Processing

Changes in total yellow pigment (TYP) content and carotenoid composition were examined at different stages of pasta processing. Semolina samples were milled from durum genotypes with and without the Lpx‐B1.1 gene deletion and then processed into dry pasta. Significant pigment loss (12.8–15.3%) based on TYP content was observed from semolina to dough in genotypes without the gene deletion. Such loss remained low (2.0–2.8%) for genotypes with the Lpx‐B1.1 gene deletion. Extrusion and drying processes did not result in substantial pigment loss. The overall pigment loss (from semolina to dried pasta) of genotypes with the gene deletion was 9.1–12.8%, in comparison with 19.0–21.7% in genotypes without the deletion. Changes in carotenoids examined by ultra‐performance liquid chromatography showed that lutein decreased gradually from representing 80% of total carotenoids to 70% of total carotenoids during pasta processing. The reduction of lutein was mostly during dough mixing, with a decrease of 16.7% in genotypes with the Lpx‐B1.1 deletion and 27.8% in genotypes without the deletion. Minor carotenoids increased during pasta drying, possibly at the expense of lutein. Results of this study showed that although breeding for elevated yellow pigments is the key, pasta color can be further improved by reducing pigment losses at different stages of pasta processing through selection of genotypes with Lpx‐B1.1 deletion and applying a vacuum during mixing and extrusion processes.     

Quality of Fiber‐Enriched Spaghetti Containing Microbial Transglutaminase

The effects of transglutaminase (TG) on the properties of semolina dough and pasta cooking properties in durum‐only and fiber‐enriched pasta were investigated. TG was blended at levels 0, 0.05, 0.1, 0.25, 0.5, and 1% of semolina weight with semolina and semolina‐pollard (60% w/w) and semolina‐guar gum (15%) mixtures. The addition of TG increased dough maximal resistance, making the dough inextensible at >1%. Optimum effects on dough strength were obtained at 0.5% TG; this dough gave the firmest and least sticky pasta. A more extensive and thicker protein matrix was observed in the TG pasta by confocal scanning laser microscopy, indicating more cross‐links were formed, a finding supported by measuring percentage of unextracted polymeric protein. TG was unable to overcome the negative effect of 60% pollard on cooking loss or 15% guar gum on stickiness. Gluten was generally more effective than TG in restoring the properties of pastas with added fiber.     

Small‐Scale Reconstitution of Durum Semolina Components

Pasta prepared by extrusion from 25 g of semolina has been compared with that made from a standard laboratory extruder and found to have similar quality. Durum semolina was fractionated into its starch, gluten, water soluble, and residue fractions. The freeze‐dried components were reconstituted and the properties of the reconstituted semolina (ReSem) have been measured. Examination using a 2 g‐mixograph and micro‐extension tester has shown that ReSem behaves similarly to the original semolina. ReSem and semolina were made into pasta using a small‐scale pasta extruder and were of comparable cooking quality. The fractionation and reconstitution of durum semolina on this scale is a useful technique to evaluate the contribution of semolina components to pasta quality.     

Estimation of color of durum wheat. Comparison of WSB, HPLC, and reflectance colorimeter measurements

Color is an important parameter involved in the definition of semolina and pasta quality. This character is mainly due to natural pigments (carotenoids) that are present at different levels in cereals and cereal products, due to botanical origin, growing conditions, distribution in the kernel, and technological processes. In food industries, color measurements are usually performed by means of automatic instruments that are rapid and safe, as alternatives to the chemical extraction methods. In this study, automatic measurements (CIE, color-space system L, a, b), water-saturated butanol (WSB), and HPLC determinations have been applied to evaluate the carotenoid content in whole meals and respective semolina samples produced from wheat cultivated in the years 2001 and 2002. In whole meals, total carotenoids, determined by HPLC, were about 3.0 microg/g (2001) and 3.5 microg/g (2002) calculated on dry weight (dw) and about 3.0 and 3.2 microg/g dw in corresponding semolina samples. The b values for the same period were 19.78 and 15.75, respectively, in raw materials and 20.03-21.67 in semolina. Results have confirmed lutein and beta-carotene as the main components mainly responsible for the yellow color in wheat grains. The ability of the index b to express natural dyeing was dependent on sample characteristics as demonstrated by the relationships found between this index and pigments, although the best correlation resulted between HPLC and WSB.     

Effects of Physicochemical Characteristics and Lipid Distribution in Algerian Durum Wheat Semolinas on the Technological Quality of Couscous

Semolinas milled from 18 Algerian durum wheat cultivars cropped over a two‐year period (1999‐2000) were used for making couscous. This study was designed to determine the impact of lipid components of durum wheat semolina on the quality of the couscous end product. Lipids were extracted from semolina by various techniques and classified as free or bound lipids, polar or apolar lipids, and glycolipids or phospholipids. An analysis of the overall results clearly revealed that the cooking quality of couscous made from different durum wheat semolinas was partially dependent on the semolina free lipid content and composition. We have shown that this is mainly a varietal characteristic (53.4%). The surface state of the couscous, i.e., caking index (r = ‐0.48) and cooking loss (r = ‐0.54), thus depends on the apolar lipid content. Polar lipids, and especially glycolipids, affect couscous texture in terms of firmness (r = 0.57 and r = 0.63, respectively). Polar bound lipids also contribute to couscous swelling (r = 0.53) and caking index (r = 0.70). Moreover, we obtained no correlation between cooked couscous quality and the semolina total lipid content (r < 0.3). We also showed that couscous characteristics were not significantly related to the semolina protein and dry gluten contents or gluten index (r < 0.3).     

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.     

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.     

A Practical Spectrophotometric Approach for the Determination of Lipoxygenase Activity of Durum Wheat

In this study, a practical spectrophotometric approach was used to determine the hydroperoxidation activity of durum wheat lipoxygenase (LOX). As stated in the related literature, the buffered linoleic acid solution used as the reaction medium is not optically clear enough at neutral and lower pH values due to its limited solubility. In our study, the optical clarity was obtained by the formation of sodium-salt of unreacted linoleic acid just before absorbance measurement. The durum wheat LOX was characterized in terms of pH and temperature optima as well as kinetic parameters. The maximum linoleic acid hydroperoxidation activities were determined at pH 5.0 and 6.5 and at 40°C This result can be considered as evidence for the presence of at least two LOX isoforms with respective optima at pH 5.0 and 6.5 in the crude durum wheat extract. The Michaelis constant (K_m) and maximum hydroperoxidation) activity rate (V_max) of durum wheat LOX for linoleic acid were estimated) to be 0.131 ± 0.019 mM and 42.37 ± 3.32 units/mg of protein/min, respectively. The method seems to be useful for the determination of LOX activity in durum wheat and its milling fractions.     

Pasta made from durum wheat semolina fermented with selected lactobacilli as a tool for a potential decrease of the gluten intolerance

A pool of selected lactic acid bacteria was used to ferment durum wheat semolina under liquid conditions. After fermentation, the dough was freeze-dried, mixed with buckwheat flour at a ratio of 3:7, and used to produce the "fusilli" type Italian pasta. Pasta without prefermentation was used as the control. Ingredients and pastas were characterized for compositional analysis. As shown by two-dimensional electrophoresis, 92 of the 130 durum wheat gliadin spots were hydrolyzed almost totally during fermentation by lactic acid bacteria. Mass spectrometry matrix-assisted laser desorption/ionization time-of-flight and reversed phase high-performance liquid chromatography analyses confirmed the hydrolysis of gliadins. As shown by immunological analysis by R5-Western blot, the concentration of gluten decreased from 6280 ppm in the control pasta to 1045 ppm in the pasta fermented with lactic acid bacteria. Gliadins were extracted from fermented and nonfermented durum wheat dough semolina and used to produce a peptic-tryptic (PT) digest for in vitro agglutination tests on cells of human origin. The whole PT digests did not cause agglutination. Affinity chromatography on Sepharose-6-B mannan column separated the PT digests in three fractions. Fraction C showed agglutination activity. The minimal agglutinating activity of fraction C from the PT digest of fermented durum wheat semolina was ca. 80 times higher than that of durum wheat semolina. Pasta was subjected to sensory analysis: The scores for stickiness and firmness were slightly lower than those found for the pasta control. Odor and flavor did not differ between the two types of pasta. These results showed that a pasta biotechnology that uses a prefermentation of durum wheat semolina by selected lactic acid bacteria and tolerated buckwheat flour could be considered as a novel tool to potentially decrease gluten intolerance and the risk of gluten contamination in gluten-free products.     

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.     

Effects of Drying Processing Conditions on the Quality of Uncooked and Cooked Pasta Made Up of Nonconventional Raw Material

Drying process plays a fundamental role in pasta making. The greatest number of studies have been focused on the optimization of drying conditions for semolina pasta, and the obtained results have been applied in a similar way on pasta made up of nonconventional raw materials without considering a processing optimization. The aim of this research was to evaluate the influence of different drying treatments (low, medium, and high temperature) on the quality of uncooked and cooked soft wheat pasta enriched with oat flour. Results of total organic matter and dried residue showed no significant difference between samples dried by medium and high temperature treatments. Moreover, these last samples showed a slight improvement in cooking quality over samples dried at low temperature (total organic matter results were 1.31 versus 1.66 g/100 g of dried pasta). This study revealed that the improvement of cooking quality of pasta enriched with oat flour did not require the application of high drying temperature (>80°C) that involves a considerable consumption of energy and could favor the development of a Maillard reaction, decreasing quality characteristics of this kind of product.     

钾对不同番茄线虫抗性品种生理指标的影响

采用水培试验, 研究了不同K 水平(0、4.0 mmol·L^-1、8.0 mmol·L^-1、16.0 mmol·L^-1)对易感线虫品种“早熟2 号”(HS)、抗线虫品种“06h-42”(HR)、普通品种“中杂102”(CK) 3 个番茄品种抗逆生理指标的影响。结果表明, 在0~8.0 mmol·L^-1 K 浓度范围内, 随着K 浓度的升高, 番茄体内的SOD、POD、CAT 活性及总酚和类黄酮含量显著增加, MDA 含量显著下降, 但过量的K(16.0 mmol·L^-1)则会降低HR 体内的SOD、POD、CAT 活性和类黄酮含量, 增加其MDA 含量。对于不同番茄品种而言, HR 的SOD、POD、CAT 活性及总酚和类黄酮含量显著高于CK 和HS, MDA 含量显著低于CK 和HS。通过交互作用显著性检验发现, K 有利于番茄体内保护性酶活性的提高, 在HR 中较CK 和HS 更为显著。     

Tetraploid Wheat—A Resource for Genetic Improvement of Durum Wheat Quality

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. Tetraploid wheat subspecies show a wide diversity in grain protein composition and content, which are major factors determining the pasta-making quality of durum cultivars. In this study, the specific focus was the identification of accessions expressing one or more superior pasta-making traits. In all, 33 accessions were surveyed representing five different subspecies; var. durum (13 accessions), polonicum (7 accessions), persicum (3 accessions), turanicum (6 accessions), and turgidum (4 accessions). These accessions and the durum cultivars Wollaroi and Kamilaroi (in both years) and Yallaroi (in 1998 only) were grown at Tamworth, Australia in 1997 and 1998. Grain, semolina, and spaghetti cooking quality were evaluated using a range of tests. Several accessions were identified with larger grain size and protein content and higher semolina extraction. Although many of the accessions were weaker in dough strength, a few were equal to the commercial cultivars and produced pasta of comparable quality. The main disadvantage with these accessions was the low yellow color. These quality defects can be corrected by conventional breeding.     

Biotechnological production of vitamin B2-enriched bread and pasta

Lactic acid bacteria (LAB) were obtained from durum wheat flour samples and screened for roseoflavin-resistant variants to isolate natural riboflavin-overproducing strains. Two riboflavin-overproducing strains of Lactobacillus plantarum isolated as described above were used for the preparation of bread (by means of sourdough fermentation) and pasta (using a prefermentation step) to enhance their vitamin B2 content. Pasta was produced from a monovarietal semolina obtained from the durum wheat cultivar PR22D89 and, for experimental purposes, from a commercial remilled semolina. Several samples were collected during the pasta-making process (dough, extruded, dried, and cooked pasta) and tested for their riboflavin content by a high-performance liquid chromatography method. The applied approaches resulted in a considerable increase of vitamin B2 content (about 2- and 3-fold increases in pasta and bread, respectively), thus representing a convenient and efficient food-grade biotechnological application for the production of vitamin B2-enriched bread and pasta. This methodology may be extended to a wide range of cereal-based foods, feed, and beverages. Additionally, this work exemplifies the production of a functional food by a novel biotechnological exploitation of LAB in pasta-making.     

Effects of Suni Bug (Eurygaster spp.) Damage on Milling Properties and Semolina Quality of Durum Wheats (Triticum durum L.)

Economic losses due to suni‐bug (Eurygaster spp. and Aelia spp.) damage are important for the cereal industry in East European and Middle East countries. Samples of five durum wheat cultivars (Diyarbakir, Firat, Ege, Svevo, and Zenith) with zero, medium, and high levels of suni‐bug damage were used to determine the effects of suni‐bug damage on milling properties and semolina quality. As the damage level increased, semolina yields of all cultivars decreased significantly. The loss of semolina yield was greater than decreases in total yield of semolina plus flour, indicating that semolina yields were affected to a higher extent than were flour yields. The ash contents of the semolina samples increased significantly in all cultivars with increasing suni‐bug damage. The falling number values were not correlated with suni‐bug damage level and amylase activities of all samples were quite low. The pasting properties did not differ to a great extent depending on the suni‐bug damage level. Gluten quality of semolina samples substantially deteriorated as suni‐bug damage level increased, as determined by SDS‐sedimentation and mixograph analyses. It was concluded that suni‐bug damage would decrease profits of durum wheat millers substantially by affecting semolina yield and quality.     

Does Fumigation of Durum Wheat and Semolina with Sulfuryl Fluoride Affect Quality of the Grain,Semolina, and Derived Spaghetti and Bread?

There is no information on the effect of sulfuryl fluoride (SF) on durum wheat technological properties and products made from fumigated durum wheat. Durum wheat and semolina were exposed to a range of SF applications under conditions that might be typically encountered in bulk storage facilities used in many countries. SF greatly reduced the germination percentage of fumigated durum wheat, with increasing impact under higher SF concentration, grain moisture content, and fumigation temperature. SF greatly reduced seed germination percentage, impacting more the higher the SF concentration. SF had little to no effect on grain test weight, 1,000‐grain weight, hardness, protein content, semolina ash content, and mixograph properties. At the highest SF concentration (31.25 mg/L for 48 h) there was a tendency for pasta cooking loss to be increased but still acceptable, and other pasta properties were largely unaffected. Fumigation with SF did not have any impact on the baking properties of a wholemeal durum flour–commercial flour mix. Therefore, SF is not recommended if the grains are to be used as seeds for agricultural production, but for the production of semolina, pasta, and bread, SF used under typical fumigation conditions has little to no impact on technological properties of durum wheat.