Jet milling effect on wheat flour characteristics and starch hydrolysis

The interest for producing wheat flour with health promoting effect and improved functionality has led to investigate new milling techniques that can provide finer flours. In this study, jet milling treatment was used to understand the effect of ultrafine size reduction onto microstructure and physicochemical properties of wheat flour. Three different conditions of jet milling, regarding air pressure (4 or 8 bars) feed rate and recirculation, were applied to obtain wheat flours with different particle size (control, F1, F2 and F3 with d50 127.45, 62.30, 22.94 and 11.4 μm, respectively). Large aggregates were gradually reduced in size, depending on the intensity of the process, and starch granules were separated from the protein matrix. Damaged starch increased while moisture content decreased because of milling intensity. Notable changes were observed in starch hydrolysis kinetics, which shifted to higher values with milling. Viscosity of all micronized samples was reduced and gelatinization temperatures (To, Tp, Tc) for F2 and F3 flours increased. Controlling jet milling conditions allow obtaining flours with different functionality, with greater changes at higher treatment severity that induces large particle reduction.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

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

Βελτιστοποίηση της ποιότητας αμυλούχων προϊόντων με μελέτη των ρεολογικών τους ιδιοτήτων και της μικροδομής τους

The aim of the present study is to investigate the rheological properties and the microstructure of starch products, as they are affected by the addition of xanthan gum. Both starch and xanthan have several physical and functional properties and they are used in many foods. Their combinational use has not been adequately investigated. Thus, their study as a mixture is very interesting relatively to their behaviour in a food and the possibility of improvement of its rheological properties, texture and microstructure. At the first stage of this study, starch and xanthan were investigated as pure components and mixtures, since, later on they were added to real foods and their comportment was investigated. The main variables in all experiments were the preparation and storage conditions (temperature and time) and the composition of the final mixtures (starch/xanthan concentration, starch type). The stages of the performed study were: a) behaviour of different starch types under heating and xanthan effect on starch granules swelling, b) investigation of phase separation of xanthan-starch mixtures, with use of starch at low concentrations, c) investigation of gelation process of starch pastes of intermediate concentrations, as it is affected by xanthan addition, d) investigation of the previous produced gels during long storage (until 45 days), e) behaviour of starch/xanthan in foods. According to this research, during heating process, xanthan enhances the swelling of native wheat starch granules, and protects them against eventual disruption, when the temperature of heating is not too high. By its addition, the leakage of starch polymers into the continuous aqueous phase is increased until the temperature of approximately 80°C. Afterwards, the amount of soluble solids outside the granules is reduced relatively to the specimens without xanthan and extensive leakage is hindered by xanthan. Xanthan enhances the stability of starch gels during storage. Incompatibility phenomena between unlike polymers, i.e. amylose and xanthan were observed causing phase separation and mutual exclusion at different microphases. Consequently, xanthan local concentration increases. In mixtures of low starch concentrations and starch-xanthan of ratio 4:1, xanthan is the dominant component and determines the whole mixture rheology. This means that the rheological behaviour of such a mixture is proportional to a xanthan solution without starch of greater concentration. At greater starch concentrations, xanthan accelerates the gel formation but it does not influence its final rheological properties. During storage, xanthan increases the hardness of produced gels but it increases also their brittleness. This is more evident at low temperatures storage. Xanthan addition to commercial gel products affects positively the cohesiveness of final gels and does not alter significantly their hardness. When it is combined with starch, the behaviour of the final product is determined by starch type used. Gels similar to commercial ones are produced by soluble potato starch addition. Com starch addition preheated at high temperatures increases highly the final gel hardness The cooking sauces prepared by starch/xanthan addition are shear-thinning Whether xanthan increases or reduces shear-thinning behaviour, depends on starch type used. Structurally, it gives stiffer final products.Στην παρούσα ερευνητική εργασία μελετήθηκαν οι ρεολογικές ιδιότητες και η μικροδομή προϊόντων αμύλου, όπως αυτές επηρεάζονται από τις συνθήκες παρασκευής και αποθήκευσης και από την προσθήκη ενός κόμμεος και συγκεκριμένα της ξανθάνης. Τόσο το άμυλο όσο και η ξανθάνη έχουν πολλαπλές φυσικές και λειτουργικές ιδιότητες και χρησιμοποιούνται σε πολλά τρόφιμα. Η χρήση τους συνδυαστικά δεν έχει διερευνηθεί επαρκώς και η μελέτη της συμπεριφοράς τους ως μίγμα παρουσιάζει ιδιαίτερο ενδιαφέρον κυρίως αναφορικά με το αν οι ιδιότητές τους σ’ ένα τρόφιμο συνδυάζονται θετικά και βελτιώνουν τα χαρακτηριστικά του τελικού προϊόντος. Ως χαρακτηριστικά εδώ εννοούνται οι ρεολογικές ιδιότητες, η υφή και η δομή των προϊόντων. Στην πρώτη φάση της μελέτης εξετάστηκε η συμπεριφορά των μιγμάτων αμύλου- ξανθάνης, ενώ στη συνέχεια εξετάστηκε η συμπεριφορά τους σε πραγματικά τρόφιμα. Σε όλες τις περιπτώσεις οι βασικές μεταβλητές ήταν οι συνθήκες παρασκευής και αποθήκευσης (θερμοκρασία, χρόνος) και η σύσταση των τελικών μιγμάτων (συγκέντρωση αμύλου/ξανθάνης, είδος αμύλου). Τα στάδια της ερευνητικής εργασίας περιελάμβαναν α) τη συμπεριφορά διαφόρων τύπου αμύλου κατά τη θέρμανσή τους και την επίδραση της ξανθάνης στη διόγκωση των αμυλόκοκκων, β) τη μελέτη διαχωρισμού φάσεων μιγμάτων αμύλου-ξανθάνης χαμηλής συγκέντρωσης αμύλου, γ) τη μελέτη της δημιουργίας πηγμάτων αμύλου μεσαίων συγκεντρώσεων με την προσθήκη ξανθάνης, δ) τη μελέτη των προηγούμενων πηγμάτων σε μακρά αποθήκευση (έως 45 ημέρες), ε) τη συμπεριφορά αμύλου/ξανθάνης σε τρόφιμα. Η ξανθάνη ενισχύει τη διόγκωση των κόκκων φυσικού αμύλου από σίτο κατά τη θέρμανση και τους προστατεύει από ενδεχόμενη διάρρηξη, τουλάχιστον όταν η θερμοκρασία θέρμανσης δεν είναι πολύ υψηλή (T<80°C). Η έκλυση διαλυτών στερεών αυξάνεται με προσθήκη της μέχρι τη θερμοκρασία των 80°C περίπου. Μετά από αυτή τη θερμοκρασία η ξανθάνη δρα παρεμποδιστικά στην έκλυση διαλυτών στερεών και η ποσότητα των διαλυτών στερεών που εκλύεται έξω από τους κόκκους είναι μικρότερη απ’ ότι στην περίπτωση που δεν υπάρχει ξανθάνη στο διάλυμα. Επίσης, η ξανθάνη αυξάνει τη σταθερότητα του ζελατινοποιημένου αμύλου κατά την αποθήκευση και διαχωρίζεται από τους αμυλόκοκκους, δημιουργώντας μικροπεριοχές αυξημένης συγκέντρωσής της. Σε μίγματα που η αναλογία συγκέντρωσης αμύλου-ξανθάνης είναι 4:1 και η συγκέντρωση του αμύλου είναι χαμηλή, το κυρίαρχο συστατικό που καθορίζει τη ρεολογία του μίγματος είναι η ξανθάνη. Η ρεολογική συμπεριφορά δηλαδή ενός τέτοιου μίγματος είναι ανάλογη με αυτή ενός διαλύματος ξανθάνης χωρίς άμυλο μεγαλύτερης συγκέντρωσης της. Σε μεγαλύτερες συγκεντρώσεις αμύλου η ξανθάνη επιταχύνει τη δημιουργία πήγματος, αλλά δεν επηρεάζει τις τελικές ρεολογικές ιδιότητές του. Κατά την αποθήκευση αυξάνει τη σκληρότητα των παραγόμενων πηγμάτων, ενώ αυξάνει επίσης την ευθραυστότητα τους. Το φαινόμενο αυτό ενισχύεται για αποθήκευση σε χαμηλές θερμοκρασίες. Η προσθήκη της σε εμπορικό προϊόν τύπου ζελέ επιδρά θετικά στη συνεκτικότητα των τελικών προϊόντων, ενώ δεν μεταβάλλει σημαντικά τη σκληρότητα. Όταν συνδυάζεται με άμυλο, η συμπεριφορά του τελικού προϊόντος καθορίζεται από το είδος του αμύλου. Με την προσθήκη τροποποιημένου αμύλου πατάτας παρασκευάζονται δείγματα πιο κοντά στα εμπορικά, ενώ με την προσθήκη αμύλου από αραβόσιτο προθερμασμένο σε υψηλή θερμοκρασία αυξάνεται πολύ η σκληρότητα του παραγόμενου προϊόντος. Τα προϊόντα τύπου μαγειρικής σάλτσας είναι γενικά ψευδοπλαστικά. Η προσθήκη της ξανθάνης, ανάλογα με το είδος του αμύλου που χρησιμοποιείται, δημιουργεί λιγότερο ή περισσότερο ψευδοπλαστικά δείγματα, ενώ ανεξάρτητα απ’ αυτό παράγονται επίσης πιο άκαμπτα δομικώς πήγματα

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

Chemical Profiling, Bioactivity Evaluation and the Discovery of a Novel Biopigment Produced by <i>Penicillium purpurogenum</i> CBS 113139

Biobased pigments are environmentally friendly alternatives to synthetic variants with an increased market demand. Production of pigments via fermentation is a promising process, yet optimization of the production yield and rate is crucial. Herein, we evaluated the potential of Penicillium purpurogenum to produce biobased pigments. Optimum sugar concentration was 30 g/L and optimum C:N ratio was 36:1 resulting in the production of 4.1–4.5 AU (namely Pigment Complex A). Supplementation with ammonium nitrate resulted in the production of 4.1–4.9 AU (namely Pigment Complex B). Pigments showed excellent pH stability. The major biopigments in Pigment Complex A were N-threonyl-rubropunctamin or the acid form of PP-R (red pigment), N-GABA-PP-V (violet pigment), PP-O (orange pigment) and monascorubrin. In Pigment Complex B, a novel biopigment annotated as N-GLA-PP-V was identified. Its basic structure contains a polyketide azaphilone with the same carboxyl-monascorubramine base structure as PP-V (violet pigment) and γ-carboxyglutamic acid (GLA). The pigments were not cytotoxic up to 250 μg/mL