Comparison of deterioration of rye under two different storage regimes

Deterioration of stored rye samples was studied at different moisture contents and temperatures. Germination, presence of visible and invisible microflora, and free fatty acid values (FAV) were determined for samples at 10.0, 12.5, 15.0 and 17.5% moisture content (wet mass basis) stored at 10, 20, 30 and 40 °C for 16 weeks. Results of deterioration at constant moisture content (case 1) were compared with previously reported results for deterioration under declining moisture content (case 2). Germination rate was almost the same for all the moisture content samples stored at 10 °C for both cases, but a significant decrease was observed at other temperatures with high moisture content. Fatty acid values remained similar in both cases when rye was stored at 10 and 20 °C, whereas at 30 and 40 °C, FAVs of the rye samples in which the moisture content was maintained were high and increased with an increase in temperature and moisture content. Visible mould appeared early in the samples whose moisture content was maintained. Penicillium spp. and Aspergillus glaucus group were the predominant fungal species present in both the cases throughout the study. The rate of deterioration was significantly different between the two cases.     

The role of a low molecular weight glutenin fraction in the cooking quality of durum wheat pasta

Durum wheat glutenin fractions, composed of two low molecular weight proteins DSG-1 and DSG-2 (durum wheat (Triticum durum Desf) sulphurrich glutenin fractions) were extracted from semolina samples using a low concentration of Na tetradecanoate after extracting albumins, globulins and gliadins. DSG proteins have a high? SH plus S? S content. A highly significant correlation was found between the ? SH plus S? S content of this DSG-rich fraction and the cooking quality of pasta (0.63, P <0.01 with firmness and 0.86, P <0.001 with the state of the surface of the cooked pasta) and this seems to be a functional relationship. The use of acetic acid at various molarities showed the presence of high molecular weight glutenin fractions with differing solubility properties. In this respect, differences were found between varieties which are placed in the same group according to the classification of durum wheats based upon the composition of high molecular weight glutenin subunits.     

Detection and quantification of adulteration of durum wheat flour by flour from common wheat using reverse phase HPLC

When common wheat (Triticum aestivum L) gliadins were separated by RP-HPLC, a major doublet peak eluted at 47.20 and 47.94 min. This peak was consistently found to be absent in Durum wheat (Triticum durum Desf) gliadins separated under identical conditions. In Durum wheat gliadins a characteristic small peak eluted at 48.30 min followed at 50.47, 510.37, 52.80 min by larger peaks. The peak area ratio of the peaks eluting at 50.47 and 51.37 min was found to be 2.18 (±0.14). This ratio was found to decrease proportionally on contamination of Durum wheat flour with flour from some common wheat varieties. This ratio alone was not enough to detect and quantify adulteration by all varieties of common wheat. An alternative method was found whereby the peak emerging between 47 and 49 min in the Durum wheat gliadin elution profile was expressed as a ratio of the total protein applied. This ratio was shown to increase when Durum wheat flour was adulterated with flour from common wheat thus enabling quantitative estimation of the level of adulteration. A third method of detecting adulteration of Durum wheat flour is also proposed in which the peak emerging between 47 and 49 min is collected and the protein separated by PAGE. The presence of more than one band of γ/β-gliadins is indicative of adulteration.     

Processing and characterization of durum wheat bread enriched with antioxidant from yellow pepper flour

The effect of the addition of yellow pepper flour on bread physico-chemical and sensorial properties was addressed in this study. In particular, vegetable flour concentration was set at 25%; in order to optimize the bread sensorial properties, yellow pepper flour was separately hydrated at three different water content levels. Texture analysis were carried out on both dough and bread samples to evaluate their firmness. Furthermore, tomographic analysis was performed on the same samples in order to provide a more detailed view of their texture. Estimation of the glycemic response, determination of the carotenoids content and sensory analysis of the fortified bread were also determined. Results highlighted that the highest glycemic index was achieved in bread sample having the highest water content and that showed the worst results in terms of texture. Among the studied samples, bread with medium hydration level showed good structural characteristic, double anti-oxidant content compared to the control bread (CTRL S) and the highest sensorial quality.     

Quality evaluation of re-milled durum wheat semolinas used for bread-making in Southern Italy

Re-milled durum wheat semolinas from Altamura, Laterza and Matera (Southern Italy), currently used in the production of traditional breads, were tested for quality. The re-milled semolinas exhibited variable technological quality, and different bread-making techniques were observed. Alveograph P/L ranged from 0.34 to 2.50 with W values from 71×10^–4 to 176×10^–4 J. The higher values were found in samples from Laterza, which gave breads with the lowest specific volumes, due to its excessive gluten tenacity. The P/L values were correlated to SDS sedimentation height; dry gluten was correlated to both wet gluten content and protein content, and was negatively correlated to P/L. Bread protein content was correlated to the protein content of the starting material and bread specific volumes were negatively correlated to alveographic P/L values. Significant differences were found between breads from different points of origin (attributable to differences in the bread-making processes), in terms of the level of total titratable acidity and the yellow pigment content of the crumb.This revised version was published online October 2004. The errors concern the seventh column in Table 2, all the numbers need to be amended.     

Effect of blending durum wheat flour with hard white wheat flour on the quality of yellow alkaline noodles

Yellow alkaline noodles (YAN) were prepared from durum and hard white wheat flour blends and evaluated for noodle color, appearance and cooked noodle texture. Raw noodle brightness, L^∗, and yellowness, b^∗, improved significantly with durum flour addition while significant increases in a^∗ values were observed at both 2 h and 24 h. The very low noodle speck count of white wheat noodles remained constant over the 24 h period at any durum flour addition. Noodle bite, MCS, decreased with the addition of durum flour, resistance to compression (RTC) remained equivalent to the hard white flour control while an associated improvement in cooked noodle recovery (REC) was observed. The study indicates that addition of durum flour at even the 25% level, offers a viable product with improved colour characteristics, consistent RTC and improved REC textural attributes. Uniaxial stress relaxation parameters of cooked noodles significantly correlated with the empirical texture measurements.     

Agglomeration of durum wheat semolina: Thermodynamic approaches for hydration properties measurements

In the manufacturing process of pasta or couscous, durum wheat semolina agglomeration comprises successive steps, in particular a wetting and hydration stage. In this step, interactions between water molecules and semolina grains contribute to the agglomeration properties. Hydration properties of semolina have been recognised to play an important role in agglomeration.The hydration properties of semolina have been characterised using various methods which can be divided into 2 groups according to the water addition: liquid or vapour. Several parameters can be used to describe hydration properties and hydration mechanisms, such as: water sorption capacity, hydration kinetics, diffusion of water within the solid (swelling, dissolution, solid-water affinity and thermodynamic properties).In this study, sorption isotherms and diffusion coefficients have been determined by gravimetric method in specific conditions. The immersion enthalpy of the semolina and its main sub-components, starch and gluten have been measured by mixing micro-calorimetry. Hydration thermodynamic properties, Gibbs free energy, enthalpy and entropy, were calculated from these experimental data. It was found that hydration by vapour or liquid water is an exothermic reaction.The determined diffusion coefficient was used to estimate the stabilisation time of water within the solid. Being high at low relative humidity, the diffusion coefficient decreases during progressive saturation of solid sites. Sorption energy and solid-water affinity yield information about the type of interaction between water molecules and solid sites. The drop in the sorption energy during the increase in water content can be attributed to a decrease in solid-water interactions. The hydration energy of durum wheat semolina in vapour or liquid water was found to be low. This corresponds to the energy input needed to generate contact between water and grain surface and for mixture homogenisation.     

Antioxidant activity and dietary fibre in durum wheat bran by-products

Milling of wheat generates by-products, which can be used to improve the technological performance and/or to integrate foods with healthy compounds. The aim of this paper was to select fractions of durum wheat bran having different functional and nutritional characteristics. Wheat bran by-products were obtained by an industrial milling process. Beside the single fractions, two commercial products Bran & Brain 50 and 70, obtained by blending some of the durum wheat fractions were also studied. All samples were investigated for water holding capacity, soluble and insoluble dietary fibre content and for their antioxidant activity. The soluble fibre content of the durum wheat by-product ranged between 0.9% and 4.1%; while that of insoluble fibre between 21% and 64%. B&B 70 has a TDF content of 61%, while B&B 50 has 42%. The water holding capacity of each fraction is strictly related to the amount of insoluble fibre and to the granulometry of the by-products. Cooking-extrusion process does not affect the amount of soluble fibre; by contrast, a significant increase of the insoluble fibre was detected. The antioxidant activity is higher for the internal bran fraction and it increases in fractions having reduced granulometry. The antioxidant activity of some durum wheat by-product fractions is comparable to that of widespread fruits and fresh vegetables, likely due to the presence of fibre-bound phenol compounds. The high fibre content and antioxidant activity of durum wheat bran by-products can be of particular interest for their use in cereal-based products.     

Protein quality of parched immature durum wheat (Frekeh)

The protein quality of parched immature Durum wheat (frekeh) produced from Deir Alla-2 variety was evaluated. Frekeh from two maturity stages was used: one at the end of the milk stage (F1) and the other at the end of the dough stage (F6). Two animal experiments were carried out in which net protein utilisation (NPU) was determined for the two samples and for mature wheat using Sprague Dawley rats, the first for 12 and the second for 11 days. Additionally, the chemical scores for these cereals were calculated. The results indicated that the protein of F1 was of higher quality than that of F6 or mature wheat; the protein efficiency ratio adjusted values for F1, F6 and wheat were respectively 2.70, 1.93 and 1.45, and the NPU_op values were 53, 46 and 44 respectively. There was agreement between these results and the chemical score values as they were 54, 41 and 42 for F1, F6 and wheat respectively. There was a significantly higher voluntary intake of cereal-based diets in comparison with the casein-based diet (P <0.05). Thus it is shown that frekeh produced from wheat harvested at an early stage of maturity was of higher protein quality than that produced at a late stage of maturity or mature wheat.     

Isolation and partial characterisation of two low molecular weight durum wheat (Triticum durum) glutenins

Two low molecular weight durum wheat (Triticum durum Desf) glutenins, DSG-1 and DSG-2 (durum-wheat sulphur-rich glutenin fractions) were isolated from two cultivars, Mondur of good technological quality and Kidur of poor technological quality. The glutenin fraction, composed mostly of DSG protein, was extracted using a low concentration of NA-tetradecanoate and then fractionted by by using molecular sieve chromatography (Bio-Gel P 30). The amino acid compositions and the N-terminal sequences of the pure DSG proteins were determined, and their hydrophobic characteristics, calculated on the basis of these data, showed that DSG-2 is more hydrophobic than DSG-1. The amino acid compositions of DSG-1 and DSG-2 were different. The N-terminal amino acids of DSG-1 and DSG-2 were also different but were identical for each of the two cultivars. In the case of DSG-1, in addition to the main chain a minor chain was found in which the first three amino acids of the main chain were missing. The minor chain represented about 30% int he DSG-1 of mondur and almost 50% in Kidur.     

Effects of processing on the distribution of pirimiphos-methyl residues in milling fractions of durum wheat

Three hundred kilograms of durum wheat of two cultivars ‘primadur’ (small kernel) and ‘ardente’ (large kernel) treated with pirimiphos-methyl (PMM) at 10 mg kg⁻¹ were processed into fractions under standard conditions of milling to evaluate the fate and distribution of the residues in the milling fractions. Half the quantity of each variety was processed 7 d after the treatment, and the second half was stored for 127 d in controlled conditions before milling. The residue content in treated grain just before milling as well as in the final 18 milling fractions was determined by GC–MS analysis carried out on crude methanol extracts. During the 127-d storage period, nearly 65% of the PMM initial content was degraded. With the first sub-sample (7 d after treatment), the amount of residue in the processed fractions compared to the total amount in grain prior to milling was reduced by 12.3% and 26.5% for primadur and ardente varieties, respectively. With the 2nd sub-sample (127 d after treatment), the residue losses induced by the milling operations were 21.8% and 24.6%, respectively. Between 79.5% and 74.5%, respectively, of the total amount of recovered residues after milling was concentrated in the bran layers 7 d after treatment and 79.5% and 80.2% after 127 d. The translocation of the residues during milling from the bran-coat to the inner endosperm was significant in all cases: a fraction from 14% to 20% of the total residue content was drawn into the semolina. An interaction between the milling operations and the residue translocation was observed. The greater translocation observed with the ardente cultivar was related to the specific characteristics of the bran-coat structure of this durum variety. With the grain batch held for the longer term, a lower rate of translocation was observed as the level of PMM fell to about a third of that at 7 d. A scenario of the behaviour of the residues during milling in relation to processing and grain conditions was proposed for the assessment of the maximum amount of PMM residues in the premium semolina fractions. The impact for consumer's health of this residual contamination of semolina used for food purposes is discussed.     

Effects of industrial processing on the distributions of deoxynivalenol, cadmium and lead in durum wheat milling fractions

The aim of this work was to investigate the distributions of deoxynivalenol, cadmium and lead in durum wheat milling fractions from industrial milling plants. The study focused on two milling technologies: conventional milling and debranning before milling. Initial analyses of samples of all raw materials showed contamination levels considerably lower than the limits imposed by the European Commission. Deoxynivalenol, cadmium and lead showed rather similar patterns of distribution. Semolina had lower, although not significant levels of these undesirable substances than unprocessed wheat grain; in contrast, marked concentration factors were found for the contaminants in shorts (middlings) and flour shorts. Debranning technology resulted in higher contamination levels in products intended for animal feed than conventional milling. The difference was statistically significant for deoxynivalenol and lead contamination of the shorts (middlings) fraction. As the outer parts of the kernel are generally considered richer in inorganic elements and moulds, Pearson's correlation was performed to investigate the relationship between the crude fibre contents of the different fractions, adopted as bran marker, and contaminant levels. Positive correlations were found for each of the three contaminants, although the correlation coefficients were not very high, demonstrating that crude fibre likely does not constitute a good marker for describing contaminants repartitioning in milling fractions when the levels of these substances are low.     

Oxidative stability of whole wheat bread during storage

The oxidative stability was examined in whole wheat bread packed in modified atmosphere (nitrogen) using vacuum grade plastic bags and stored for up to 5 weeks. Small, but significant, differences in oxidative stability developed with time for whole wheat bread crumb and crust. The samples were evaluated by direct electron spin resonance (ESR) spectroscopy for detection of free radicals, peroxide value (POV), overall antioxidative capacity using Trolox equivalent antioxidant capacity (TEAC) and oxygen radical absorbance capacity (ORAC) assays, and by the content of tocopherols as determined by HPLC. The overall antioxidative capacity was reduced during storage with an accumulation of lipid hydroperoxides peaking after 2-3 weeks of storage. Bread crust was generally found to be more oxidative stable when compared to crumb. Quality of bread with extended shelf life may accordingly be improved minimising oxidation.     

Effect of inulin soluble dietary fibre addition on technological, sensory, and structural properties of durum wheat spaghetti

Investigation of two inulins with differing degrees of polymerisation and crystallinity demonstrated different levels of integration with the starch-gluten matrix during pasta preparation. The impact of higher molecular weight inulin incorporation on technological and sensory properties was minimal, with deterioration in properties becoming significant only at 20% incorporation, while lower molecular weight had a greater negative impact on pasta firmness, cooking loss, and sensory acceptability. In vitro starch digestion of pasta was reduced with up to 5% addition of inulin of degree of polymerisation 12-14 (FH-D), but increased with high levels of addition. These effects were not observed in inulin with a degree of polymerisation of 7-8 (LV-100). Microscopy showed the starch granules were apparently encapsulated by a protective coat of inulin FH-D, but at 20% a disruption to the matrix was evident. For inulin FH-D, XRD analysis of digested pasta found a maximum crystallinity which coincided with the maximum reduction in starch hydrolysis, suggesting that a stronger gluten matrix enhanced by added inulin is indeed structurally different at the nanometre level.     

Spaghetti making potential of Indian durum wheat varieties in relation to their protein,yellow pigment and enzyme contents

The research was carried out to evaluate spaghetti making potential of 12 Indian durum wheat varieties in relation to their protein and yellow pigment content and peroxidase, polyphenol oxidase, lipoxygenase, and protease activities. The protein content of the durum wheat varieties varied from 12.1% to 15.9% and their yellow pigments content ranged from 3.8 to 7.2 ppm. The peroxidase activity in these wheat varieties varied from 269 to 1010 U/g and polyphenol oxidase activity from 58.8 to 78.3 U/g. The lipoxygenase activity of durum wheats ranged between 1.44 and 6.88 U/g. Protease activity was in the range of 1.1–5.1 U/ g. The data for varieties MACS-1967, MACS-3125, MACS-2846, DWR-2006, HI-8498 and N-59 were indicative of their potential for the preparation of pasta products.     

Identification of durum wheat cultivars and monovarietal semolinas by analysis of DNA microsatellites

 Microsatellites isolated in bread wheat were used to identify 20 Italian durum wheat (Triticum turgidum var. durum L.) cultivars. A total of 15 microsatellite primer pairs were tested against DNA extracted from leaf tissue, single seeds and semolina. Twelve markers showed allelic polymorphism among the 20 cultivars, providing a total of 41 different alleles. Firstly, an analysis of microsatellite informativeness in the chosen set of durum wheat cultivars was made and a set of highly polymorphic microsatellites was established. Secondly, among the most polymorphic cultivars, the minimum number of microsatellites able to distinguish all cultivars was determined. A set of five microsatellites was found sufficient to differentiate the durum wheat cultivars examined. The method is directly applicable to seeds and semolina, and is suitable for detecting seed mixtures in the same seed lot. Received: 22 February 1999 / Revised version: 19 April 1999     

Trace metals in soft and durum wheat from Italy

A survey was carried out with the aim to assess the levels of some toxic (cadmium, lead) and essential (copper, zinc) trace metals in wheat grown in Italy. A total of 178 samples of soft wheat grain and 239 samples of durum wheat grain from all the Italian wheat-growing regions were pooled into 35 and 38 representative samples respectively. After dry ashing, cadmium and lead were determined by graphite furnace atomic absorption spectrometry (GFAAS), whereas copper and zinc were determined by flame atomic absorption spectrometry (FAAS). In soft wheat the mean and median contents of all samples were (on a dry weight basis) 40 and 33 mu g kg^-1 for cadmium, 16 and 14 mu g kg^-1 for lead, 3.4 and 3.2 mg kg^-1 for copper, 33 and 32 mg kg^-1 for zinc. Similar levels were found in durum wheat. In this latter case the mean and median were 42 and 39 mu g kg^-1 for cadmium, 15 and 14 mu g kg^-1 for lead, 3.5 and 3.2 mg kg^-1 for copper, 34 and 34 mg kg^-1 for zinc. Significant differences were detected for some metals in relation to geographical provenance and variety. The average intake of the four selected elements from wheat-based products was estimated for the Italian population.     

Temperature fluctuations and moisture migration in wheat stored for 15 months in a metal silo in Canada

Temperatures and moisture contents inside a metal silo filled with 20 t of wheat were monitored from August 2003 to October 2004 in Western Canada. In the summer and then repeated in the autumn of 2005, grain moisture contents inside small columns, inserted in the top of the grain bulk in the same metal silo, were measured after 4 and 8 weeks. The columns had the following configurations: 1) both the top and bottom of the column were open; 2) the top of the column was open and the bottom was sealed; and 3) the top of the column was sealed and the bottom was open.During the 15-month period, headspace temperature averaged 2.9 ± 0.2 °C higher than that of the ambient air with a maximum of 18.3 °C and a minimum of 0 °C. There was larger temperature fluctuation in the headspace than inside the grain mass. The average temperature gradient was 5.09 ± 1.24 °C/m inside the grain mass. The highest temperature gradient was 32.4 °C/m and it was located at the center of the bin at 1.6 m high. “Inside” grain had a lower moisture change than the surface grain.Grain in the top section of the column with the column configuration of Top End Open had the largest change of its moisture content, and grain in the middle section of the column with any of the configurations did not change. Grain inside the small columns at different locations in the silo had different moisture movement trends. These trends were consistent with the measured moisture migration in the entire silo. These results confirm that even in a small silo there were temperature gradients large enough to drive air movement and the induced convection currents could cause moisture migration.