Distribution of free and bound phenolic compounds, and alkylresorcinols in wheat aleurone enriched fractions

Several companies have focused their attention on the development of technologies able to enrich/isolate the wheat aleuronic layer because it is a source of bioactive compounds. In this work two different wheat bran fractions enriched in aleurone (AF1, 55-70% aleurone and AF2, 75-90% aleurone) were obtained by a dry fractionation based on air classification. Free and bound phenolic compounds, and alkylresorcinols were determined in the two fractions by HPLC-DAD-ESI-TOF-MS and GC-MS, respectively. To our knowledge, feruloyl di-hexoside was described for the first time in wheat aleurone and flavonoids were quantified for the first time in this fraction. The results have shown that the most concentrated free phenolic compounds were flavonoids, and AF1 was the fraction that presented the highest flavonoid content; whereas trans ferulic acid was the most abundant bound phenolic acid, which highest content was obtained in AF2. Besides, total content of ferulic acid monomers in AF2 was 33.63% higher than in AF1, whereas total content of ferulic acid dimers/trimers in AF1 was 33.9% higher than in AF2. The highest content of alkylresorcinols was obtained in AF1 and it was 10.30% higher than the obtained in AF2. Therefore, it can be stated that this green technology could be used to produce enriched aleurone fractions as source of phenolic and alkylresorcinol compounds. These fractions could be of great interest for the formulation of enriched foods.

Assessment of phytochemical compounds in functional couscous: Determination of free and bound phenols and alkylresorcinols

The aim of this study was to evaluate the content of free and bound phenols and alkylresorcinols in functional couscous enriched with barley coarse fraction obtained by air classification. Two different levels of enriched barley flour (20 and 30%) were used for the formulation of couscous and they were compared with a control couscous made with 100% of semolina. HPLC-ESI-TOF-MS was used to determine the phenolic composition in couscous samples. Total free phenolic compounds content in control couscous was 182 μg/100 g d.m. This amount increases significantly when coarse barley flour is added reaching value of 2273 μg/100 g d.m. and 2978 μg/100 g d.m. when 20 and 30% of barley coarse fraction was used, respectively. Moreover, the main free phenolic compounds in enriched barley samples are represented by flavan-3-ols. Bound phenols ranged from 5242 μg/100 g d.m. for control couscous to 27,092 μg/100 g d.m. for couscous with 30% of barley coarse fraction with a strong prevalence of phenolic acids. Finally, regarding alkylresorcinol compounds, they ranged from 1.01 mg/g d.m. for control couscous to 2.46 mg/g d.m. for couscous with 30% of barley coarse fraction. In conclusion, on the basis of obtained results, barley coarse fraction can be considered a good ingredient to develop functional couscous naturally enriched of phenolic compounds and alkylresorcinols.

Industrial scale preparation of pea flour fractions with enhanced nutritive composition by dry fractionation

This study determined influence of industrial scale milling and air classification on separation of pea flours into fine and coarse fractions. Three commercial field pea flours were chosen from field peas grown in Manitoba, Canada, - whole green pea flour (WGPF), split green pea flour (SGPF), and organic split yellow pea flour (OSYPF). The ranges of 85-87% protein, 74-95% fat, and 66-76% minerals were enriched in the pea fine fractions. A range of 78-91% starch was enriched in the coarse fractions. Scanning electron microscopy and proximate analysis confirmed compositional shift between the fine and coarse fractions. The particle size analysis demonstrated that the milling in this study was sufficient and effective in reducing the flour particle size to smaller than 22 µm, which was considered to be the cut-point. The yield of the fine fraction was as high as 44% and acceptable for an industrial manufacture.

The upper size limit of the dust samples in road dust heavy metal studies: Benefits of a combined sieving and air classification sample preparation procedure

The concentrations of heavy metals and other components in road dust from a Polish coal mining district were investigated. The sample was split into eight size fractions ranging from <5 μm to 1-2 mm applying the combined classification procedure of dry sieving and air classification. For most elements, significantly higher concentrations were found in the finest size fractions. In combination with the mass fractions of the various size fractions the concentrations of the components were calculated for this road dust assuming different upper size limits. The results demonstrate the important influence of the upper size limit applied on the composition of road dust. An analysis of the composition of road dust by particle size, instead of analysing whole road dust samples, proves to have several advantages. On the one hand, a reliable comparison of the results with the concentration data available in the literature is possible and on the other hand, the results can be used in assessments, for example resuspension or wash-off by rainfall, which require different upper size limits. Upper size limit applied in road dust sampling significantly influences the results. Combined sieving and air classification sample preparation procedure allows flexible use of the results.

Variations in the composition of house dust by particle size

In this study, the distribution of heavy metals and other components in the various size fractions of house dust is investigated. A house dust sample collected from a vacuum cleaner was separated into size fractions by sieving and air classification. The analysis of the size fractions showed that the heavy metals and other components are not uniformly distributed in the various size fractions. The highest total carbon concentrations were found in the size fractions with a mass median diameter of 18-95 µm, while in the coarser size fractions and in the finest size fraction, the total carbon concentration was lower. In contrast, for many heavy metals and other metals (Al, Fe, Ca, S, Mn, Ti, Ba, Sr, As, Co, and V), the maximum concentrations were found in the finest size fraction. With increasing size of the dust fractions, the concentrations decreased. For several of these components, the dependence of the concentration on the particle size can be approximately assessed well using a power function. The distribution of Zn, Cu, Mg and Na was different. While the concentration of Na and Mg was higher in the coarser size fractions, no distinct trend was found for the concentrations of Cu and Zn.

Effect of air classification and fermentation by Lactobacillus plantarum VTT E-133328 on faba bean (Vicia faba L.) flour nutritional properties

The effects of air classification and lactic acid bacteria fermentation on the reduction of anti-nutritional factors (vicine and convicine, trypsin inhibitor activity, condensed tannins and phytic acid) and in vitro protein and starch digestibility of faba bean flour were studied. Free amino acid (FAA) profile analysis was also carried out. Air classification allowed the separation of the flour into protein and starch rich fractions, showing different chemical compositions and microstructures. Lactobacillus plantarum growth and acidification in faba bean flour and its fractions were assessed. The anti-nutritional compounds were separated mostly to the fine protein-rich fraction. Fermentation caused the decrease of vicine and convicine contents by more than 91% and significantly reduced trypsin inhibitor activity and condensed tannins (by more than 40% in the protein-rich fraction). No significant (P>0.05) variation was observed for total phenols and phytic acid content. Fermentation increased the amount of FAA, especially of the essential amino acids and γ-aminobutyric acid, enhanced the in vitro protein digestibility and significantly lowered the hydrolysis index. This work showed that the combination of air classification and fermentation improved nutritional functionality of faba bean flour which could be utilized in various food applications.