Influence of yeast and frozen storage on rheological, structural and microbial quality of frozen sweet dough

The aim of the present study was to investigate the effect of yeast content and frozen storage (9 weeks at -40°C) on the structural and rheological parameters, and fermentative activity of frozen sweet dough. Two types of dough were studied (to estimate dough shelf life): simple yeasted dough (SY) and double yeasted dough (DY). Fermentative activity (yeast viability, gassing power, and dough volume), rheological and textural parameters were assessed for frozen sweet doughs. These effects were explored by different and complementary methods: Fourier transform infrared (FTIR), dynamic rheology, texture profile analysis (TPA) and differential scanning calorimetry (DSC). The data showed that the longer the frozen storage time at -40°C, the higher the decreased of frozen sweet dough quality. The rheological attributes such as hardness, ΔS, springiness, tan δ and yeast activity declined significantly during frozen storage. This modification led to lower specific volume of frozen sweet dough during proofing. The observed changes of the frozen sweet doughs rheological properties after thawing may be attributed to the damage on the gluten cross-linking, mainly produced by the ice crystallization during frozen storage. The storage effect was particularly concentrated in the first 27 days of storage. © 2011 Elsevier Ltd. All rights reserved.Fil: Meziani, Smail. Coco LM Company (Maison Alsacienne de Biscuiterie); Francia. Nancy Université. Laboratoire d’Ingénierie des Biomolécules; FranciaFil: Jasniewski, Jordane. Nancy Université. Laboratoire d’Ingénierie des Biomolécules; FranciaFil: Ribotta, Pablo Daniel. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Córdoba. Instituto de Ciencia y Tecnología de Alimentos Córdoba. Universidad Nacional de Córdoba. Facultad de Ciencias Químicas. Instituto de Ciencia y Tecnología de Alimentos Córdoba; ArgentinaFil: Arab-Tehrany, Elmira. Nancy Université. Laboratoire d’Ingénierie des Biomolécules; FranciaFil: Muller, Jean-Marc. Coco LM Company (Maison Alsacienne de Biscuiterie); FranciaFil: Ghoul, Mohamed. Nancy Université. Laboratoire d’Ingénierie des Biomolécules; FranciaFil: Desobry, Stéphane. Nancy Université. Laboratoire d’Ingénierie des Biomolécules; Franci

Effect of freezing treatments and yeast amount on sensory and physical properties of sweet bakery products

The frozen bakery market has grown significantly in developed countries over the past decade. Of the available preservation technologies, freezing has been recognized as an excellent method of preserving the quality characteristics of bakery products. The aim of this work was to study the influence of freezing conditions (-20, -30, -40 °C and cryogenic immersion) and yeast content on the sensory and physical properties in the final baked product (Kougelhopf). Physical parameters such as specific volume, moisture, hardness, gas cells distribution and size were determined experimentally. A sensory evaluation (appearance, color, flavor, taste, texture and overall acceptability) was performed in Kougelhopf obtained from fresh and frozen sweet doughs. The experimental results showed that high freezing rates were correlated with more extended damage, yeast activity loss and lower Kougelhopf specific volume. The freezing rate also influenced the gas cells number and size. It was shown that increasing yeast in frozen sweet doughs improved the overall quality of Kougelhopf compensating for the loss of yeast activity during the freezing process. Kougelhopf produced from sweet dough with higher yeast content (DY) presented a higher specific volume, whereas freezing rate increases its hardness. Sensory tests confirmed that experimental results were detected by panelists. © 2012 Elsevier Ltd. All rights reserved.Fil: Meziani, Smail. Coco Lm Company (maison Alsacienne de Biscuiterie); Francia. Laboratoire D'ingénierie Des Biomolécules; FranciaFil: Kaci, Messaouda. Laboratoire D'ingénierie Des Biomolécules; FranciaFil: Jacquot, Muriel. Laboratoire D'ingénierie Des Biomolécules; FranciaFil: Jasniewski, Jordane. Laboratoire D'ingénierie Des Biomolécules; FranciaFil: Ribotta, Pablo Daniel. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Córdoba. Instituto de Ciencia y Tecnología de Alimentos Córdoba. Universidad Nacional de Córdoba. Facultad de Ciencias Químicas. Instituto de Ciencia y Tecnología de Alimentos Córdoba; ArgentinaFil: Muller, Jean-Marc. Coco Lm Company (maison Alsacienne de Biscuiterie); FranciaFil: Ghoul, Mohamed. Laboratoire D'ingénierie Des Biomolécules; FranciaFil: Desobry, Stéphane. Laboratoire D'ingénierie Des Biomolécules; Franci

Étude des mécanismes d'action de bactériocines de la sous classe IIa

The action site of sub-class IIa bacteriocins is the cytoplasmic membrane of Gram-positive bacteria. The current view of the mechanism of action is divided into three steps: (i) adsorption of bacteriocins on the membrane; (ii) apparition of the structures of peptide and integration into the lipid double layer (iii) formation of pores. The presence of pores leads to efflux of vital cell compounds. They cause growth stop or bacterial death. The degree of penetration of mesenterocin 52A into the membrane was measured by fluorescence anisotropy of two probes, TMA-DPH and the DPH, which target the surface or the depth of the membrane, respectively. Different results were obtained with two bacterial species of the genus Listeria. In the first hand, the peptide is partially inserted into the membrane and in the second hand in depth. These results suggest that mesenterocin 52A can exhibit two different mechanisms leading to the same antibacterial effect. To better understand the interactions between bacteriocins and the target cell, the degree of penetration of mesenterocin 52A into the membrane of three Leuconostoc strains, the first sensitive, the second naturally resistant and last induced resistant, was characterized. It seems that the resistance phenotype is correlated with physical and chemical properties of the cell envelope. To generalize the results observed with mesenterocin 52A, other bacteriocins of sub-class IIa, the carnobacteriocins Cbn BM1 and Cbn B2, produced by Carnobacterium maltaromaticum CP5 strain, were studied. These bacteriocins were produced in E. coli and subsequently purified. The optimization of the production process in a reactor led to purify up to 300 mg of peptides for 1.5 liter of culture. The mode of action of carnobacteriocins, alone or in combination, was determined with prokaryotic or eukaryotic cells as targets. The carnobacteriocins Cbn BM1 and Cbn B2 have a synergistic mode of action against sensitive bacteria and are not cytotoxic against Caco-2 cell lineLe site d'action des bactériocines de la sous-classe IIa est la membrane cytoplasmique des bactéries à Gram positif. Le mécanisme d'action se décompose en trois étapes : (i) adsorption de la bactériocine sur la membrane ; (ii) structuration du peptide et insertion dans la bicouche lipidique ; (iii) formation de pores. La présence de pores provoque des fuites de composés vitaux aboutissant soit à un arrêt de la croissance soit à la mort de la bactérie. Le degré de pénétration de la mésentérocine 52A dans la membrane a été mesuré grâce à l'anisotropie de fluorescence de deux sondes, le TMA-DPH et le DPH, respectivement localisées à la surface et en profondeur de la bicouche lipidique. Des résultats différents ont été obtenus avec deux espèces bactériennes appartenant au genre Listeria. Dans un cas, le peptide s'insère partiellement dans la membrane et dans l'autre en profondeur. Ces résultats suggèrent que la mésentérocine 52A peut suivre deux mécanismes distincts aboutissant à une bactériostase. Pour mieux comprendre les interactions entre la bactériocine et la cellule cible, le degré de pénétration de la mésentérocine 52A dans la membrane de trois souches de Leuconostoc, la première sensible, la seconde naturellement insensible et la dernière rendue résistante, a été caractérisé. Il semblerait que le phénotype de résistance soit corrélé avec les propriétés physico-chimiques de l'enveloppe cellulaire. Afin de pouvoir généraliser les résultats observés avec la mésentérocine 52A, d'autres bactériocines de la sous-classe IIa, les carnobactériocines Cbn BM1 et Cbn B2, produites par la souche Carnobacterium maltaromaticum CP5, ont été étudiées. Dans un premier temps, ces bactériocines ont été produites et purifiées à partir d'une souche d'Escherichia coli recombinante. L'étape de production en fermenteur a été optimisée, des quantités de l'ordre de 300 mg de peptides ont été produites. Le mode d'action des carnobactériocines, seules ou en combinaison, a été déterminé vis-à-vis de cellules procaryotes ou eucaryotes. Les carnobactériocines Cbn BM1 et Cbn B2 ont un mode d'action synergique contre les bactéries sensibles et ne présentent pas de cytotoxicité vis-à-vis des cellules de la lignée Caco-

Study of the mechanisms of action of sub-class IIa bacteriocins

Le site d’action des bactériocines de la sous-classe IIa est la membrane cytoplasmique des bactéries à Gram positif. Le mécanisme d’action se décompose en trois étapes : (i) adsorption de la bactériocine sur la membrane ; (ii) structuration du peptide et insertion dans la bicouche lipidique ; (iii) formation de pores. La présence de pores provoque des fuites de composés vitaux aboutissant soit à un arrêt de la croissance soit à la mort de la bactérie. Le degré de pénétration de la mésentérocine 52A dans la membrane a été mesuré grâce à l’anisotropie de fluorescence de deux sondes, le TMA-DPH et le DPH, respectivement localisées à la surface et en profondeur de la bicouche lipidique. Des résultats différents ont été obtenus avec deux espèces bactériennes appartenant au genre Listeria. Dans un cas, le peptide s’insère partiellement dans la membrane et dans l’autre en profondeur. Ces résultats suggèrent que la mésentérocine 52A peut suivre deux mécanismes distincts aboutissant à une bactériostase. Pour mieux comprendre les interactions entre la bactériocine et la cellule cible, le degré de pénétration de la mésentérocine 52A dans la membrane de trois souches de Leuconostoc, la première sensible, la seconde naturellement insensible et la dernière rendue résistante, a été caractérisé. Il semblerait que le phénotype de résistance soit corrélé avec les propriétés physico-chimiques de l’enveloppe cellulaire. Afin de pouvoir généraliser les résultats observés avec la mésentérocine 52A, d’autres bactériocines de la sous-classe IIa, les carnobactériocines Cbn BM1 et Cbn B2, produites par la souche Carnobacterium maltaromaticum CP5, ont été étudiées. Dans un premier temps, ces bactériocines ont été produites et purifiées à partir d’une souche d’Escherichia coli recombinante. L’étape de production en fermenteur a été optimisée, des quantités de l’ordre de 300 mg de peptides ont été produites. Le mode d’action des carnobactériocines, seules ou en combinaison, a été déterminé vis-à-vis de cellules procaryotes ou eucaryotes. Les carnobactériocines Cbn BM1 et Cbn B2 ont un mode d’action synergique contre les bactéries sensibles et ne présentent pas de cytotoxicité vis-à-vis des cellules de la lignée Caco-2The action site of sub-class IIa bacteriocins is the cytoplasmic membrane of Gram-positive bacteria. The current view of the mechanism of action is divided into three steps: (i) adsorption of bacteriocins on the membrane; (ii) apparition of the structures of peptide and integration into the lipid double layer (iii) formation of pores. The presence of pores leads to efflux of vital cell compounds. They cause growth stop or bacterial death. The degree of penetration of mesenterocin 52A into the membrane was measured by fluorescence anisotropy of two probes, TMA-DPH and the DPH, which target the surface or the depth of the membrane, respectively. Different results were obtained with two bacterial species of the genus Listeria. In the first hand, the peptide is partially inserted into the membrane and in the second hand in depth. These results suggest that mesenterocin 52A can exhibit two different mechanisms leading to the same antibacterial effect. To better understand the interactions between bacteriocins and the target cell, the degree of penetration of mesenterocin 52A into the membrane of three Leuconostoc strains, the first sensitive, the second naturally resistant and last induced resistant, was characterized. It seems that the resistance phenotype is correlated with physical and chemical properties of the cell envelope. To generalize the results observed with mesenterocin 52A, other bacteriocins of sub-class IIa, the carnobacteriocins Cbn BM1 and Cbn B2, produced by Carnobacterium maltaromaticum CP5 strain, were studied. These bacteriocins were produced in E. coli and subsequently purified. The optimization of the production process in a reactor led to purify up to 300 mg of peptides for 1.5 liter of culture. The mode of action of carnobacteriocins, alone or in combination, was determined with prokaryotic or eukaryotic cells as targets. The carnobacteriocins Cbn BM1 and Cbn B2 have a synergistic mode of action against sensitive bacteria and are not cytotoxic against Caco-2 cell lin

Structuration mechanism of beta-lactoglobulin: Acacia gum assemblies in presence of quercetin

Structuration mechanism of beta-lactoglobulin: Acacia gum assemblies in presence of quercetin. 248. National Meeting of the American-Chemical-Society (ACS

Gum Arabic and chitosan self-assembly: Thermodynamic and mechanism aspects

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Physicochemical characterization of pectin grafted with exogenous phenols

International audiencePectin is a natural polysaccharide, having valuable properties that enable its use in many industrial fields. The aim of this work was to study the impact of pectin modification with phenols, on the properties of this biopolymer. Results suggested that the enzymatic grafting of ferulic acid (FA) oxidation products onto the pectin altered its morphological surface and its thermal properties. Moreover, modified pectin showed a less hygroscopic behavior when water activity is less than 0.50 and a higher ability to bound water above 0.5. Additionally, modified pectin became less viscous than the native pectin and presented different calciumdependent gelation behavior. Finally, a significant improvement of the antioxidant properties of pectin after functionalization was observed. As a conclusion, the modification of pectin with phenolic compounds appeared as a promising way to produce a polysaccharide with new properties that could enlarge the field of its potential applications

Chitosan - Shea butter solid nanoparticles assemblies for the preparation of a novel nanoparticles in microparticles system containing curcumin

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Optimization of the production and purification processes of carnobacteriocins Cbn BM1 and Cbn B2 from Carnobacterium maltaromaticum CP5 by heterologous expression in Escherichia coli

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The study of curcumin interaction with micellar casein and lactic acid bacteria cell envelope

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