Jet Milling Effect on Functionality, Quality and In Vitro Digestibility of Whole Wheat Flour and Bread

Jet milling is an ultragrinding process in order to produce superfine powders with increased functionalities. The effect of milling pressure, feed rate, vibration rate of feeder, and feedback of jet milling on whole wheat flour functionality and the potential of those flours for breadmaking with the goal of improving bread quality and digestibility were investigated. Increasing milling pressure (from 4 to 8 bar), decreasing feed rate (from 0.67 to 5.18 kg/h), and/or using recirculation augmented the severity of the process and reduced flour particle size from 84.15 to 17.02 μm. Breakage of aleurone particle layer and the reduction of particle size in jet milled flours were detected using scanning electron microscopy (SEM). Ash and protein content did not change after jet milling. However, total fiber content and digestible starch increased from 13.01 to 14.72 % and from 33.80 to 43.23 mg/100 mg, respectively, when subjected to jet milling at 8-bar air pressure. Mixolab® data indicated that water absorption increased from 64.1 to 68.0 %, while pasting temperature decreased from 63.4 to 66.1 °C owing to the milling intensity. Referring to bread, jet milled flour addition reduced the specific volume from 2.50 to 1.90 cm3/g, luminosity from 60.48 to 55.87, and moisture content from 35.78 to 33.49 %, and increased crumb hardness from 707 to 1808 g. Jet milled breads presented a slight decrease in estimated glycemic index (eGI) (from 86 to 81), suggesting that jet milling treatment could also have nutritional benefits.Part of this work was financed through the project “IKY Scholarships” from resources of operational program (OP) “Education and Lifelong Learning,” the European Social Fund (ESF) of the National Strategic Reference Framework (NSRF) 2007-2013-WP2-SHORT TERMS-19078. Financial support of Spanish Scientific Research Council (CSIC) and Generalitat Valenciana (Spain, Project Prometeo 2012/064) is acknowledged.Peer Reviewe

Fermentation Kinetics of Gluten-Free Breads: The Effect of Carob Fraction and Water Content

In this study, gluten-free doughs with rice flour, substituted by 15% fractions of different carob seed flours, were prepared by varying their water content. The coarse carob fraction A (median particle size of flour, D50: 258.55 μm) was rich in fibers, fraction B (D50: 174.73 μm) was rich in protein, C (D50: 126.37 μm) was rich in germ protein, and fraction D (D50: 80.36 μm) was a mix, reconstituted from the other fractions and pulverized using a jet mill. Τhe experimental data of the dough’s volume over time were fitted to the Gompertz model for each carob fraction and water content. The calculated parameters of the model were the maximum relative volume expansion ratio (a), the maximum specific volume growth rate (μ), and the time lag of the leavening process (tlag). Gompertz’s equation adequately described the individual experimental curves. In the next step, a composite model was applied for each carob fraction where the parameters a and tlag were expressed as quadratic functions of water content levels (W), while μ was linearly dependent on W. Each carob fraction presented an optimum water content level for which dough height was maximized and time lag was minimized. Optimized dough volume could be predicted by the composite model; it was shifted to lower values as finer carob flour was used. In respect to baked products, softer breads were produced using finer carob flour and porosity values were higher at optimum water content levels. The investigated fermentation kinetics’ models provide significant information about the role of water and carob flour on gluten-free dough development and bread volume expansion

Improving Carob Flour Performance for Making Gluten-Free Breads by Particle Size Fractionation and Jet Milling

Many different raw materials have been proposed for producing nutritious gluten-free breads, but rarely, there is a parallel analysis of the effect of physical treatment on those ingredients. The aim of this study was to incorporate carob flour fractions of varying particle size on rice gluten-free breads prepared with carob/rice (15:85) flour blends. Carob flour particle size was controlled by fractionation or jet milling application. Quality features of gluten-free breads containing carob flour and commercially available gluten-free breads were compared. Carob flour addition led to breads with improved colour parameters, crumb structure, retarded firming and lower moisture loss compared to rice bread. Further improvement in specific volume, crumb hardness, protein and ash content and estimated glycaemic index (eGI) could be obtained by a careful selection of the particle size distribution of the carob flour. Carob breads prepared either with the coarsest or the finest fraction prepared using jet milling led to end products with the highest specific volume (≈2.2 g/cm3) and the lowest crumb hardness (≈5.5 N), although they had lower specific volume and harder crumbs than breads from commercial blends (≈3–4 g/cm3, 0.6–3.8 N). Nevertheless, rice-based bread made with the finest carob flour was superior considering its slower firming, protein content and lower eGI. The incorporation of carob flour obtained by jet milling in rice-based gluten-free breads led to end products with quality characteristics and sensory acceptance resembling commercial breads and high nutritional value.Financial support of the Spanish Ministry of Economy and Competitiveness (Project AGL2014-52928-C2-1-R) and the European Regional Development Fund (FEDER)Peer reviewe

Bacterial Cellulose Production from Industrial Waste and by-Product Streams

The utilization of fermentation media derived from waste and by-product streams from biodiesel and confectionery industries could lead to highly efficient production of bacterial cellulose. Batch fermentations with the bacterial strain Komagataeibacter sucrofermentans DSM (Deutsche Sammlung von Mikroorganismen) 15973 were initially carried out in synthetic media using commercial sugars and crude glycerol. The highest bacterial cellulose concentration was achieved when crude glycerol (3.2 g/L) and commercial sucrose (4.9 g/L) were used. The combination of crude glycerol and sunflower meal hydrolysates as the sole fermentation media resulted in bacterial cellulose production of 13.3 g/L. Similar results (13 g/L) were obtained when flour-rich hydrolysates produced from confectionery industry waste streams were used. The properties of bacterial celluloses developed when different fermentation media were used showed water holding capacities of 102–138 g·water/g·dry bacterial cellulose, viscosities of 4.7–9.3 dL/g, degree of polymerization of 1889.1–2672.8, stress at break of 72.3–139.5 MPa and Young’s modulus of 0.97–1.64 GPa. This study demonstrated that by-product streams from the biodiesel industry and waste streams from confectionery industries could be used as the sole sources of nutrients for the production of bacterial cellulose with similar properties as those produced with commercial sources of nutrients