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Koocheki A.,Ferdowsi University of Mashhad | Kadkhodaee R.,Khorasan Research Institute for Food Science and Technology
Food Hydrocolloids | Year: 2011

Response surface methodology was used to investigate the influence of Alyssum homolocarpum seed gum (0.25-1%), Tween 80 (0.1-1%) and NaCl (0-1%) on characteristics of ultrasonically prepared corn oil-in-water emulsion. For each response, a second-order polynomial model was developed using multiple linear regression analysis. It was shown that increasing the gum concentration and Tween 80 content decreased the mean diameter of droplets, span and creaming index. Although the increase of gum concentration had a positive effect on viscosity, Tween 80 revealed to have no significant effect on these responses. Optimum formulation for a stable emulsion was found to be 1% A. homolocarpum seed gum, 0.96% Tween 80 and no NaCl. However, using salt at higher gum concentration did not have negative effect on the emulsion properties. © 2010 Elsevier Ltd.

Hossein Nezhad M.,Khorasan Research Institute for Food Science and Technology | Stenzel D.J.,Queensland University of Technology | Britz M.L.,University of Tasmania
Iranian Journal of Microbiology | Year: 2010

Background and Objectives: Although members of the Lactobacillus casei group are known to survive under acidic conditions, the underlying mechanisms of growth at acidic condition and the impact of low pH on the relative level of protein expression at the cell surface remain poorly studied. Material and Methods: After confirming the taxonomy of L. casei strain GCRL 12 which was originally isolated from cheese and confirmed by 16S rRNA sequence analysis, the impact of acidic pH on growth rate was determined. Results: Late log-phase cells cultured at pH 4.0 showed obvious changes in Gram staining properties while transmission electron microscopy analysis revealed evidence of structural distortions of the cell surface relative to the controls cultured at pH 6.5. When comparing cytosolic or whole cell preparations on SDS-PAGE, few changes in protein profiles were observed under the two growth conditions. However, analysis of surface protein extracted by 5M LiCl demonstrated changes in the proportions of proteins present in the molecular weight range of 10 to 80 kDa, with some proteins more dominant at pH 6.5 and other at pH 4. Conclusion: These data suggest that surface proteins of this strain are associated with growth and survival at low pH. The function of these proteins is subject to further investigation.

Soleimanpour M.,Ferdowsi University of Mashhad | Koocheki A.,Ferdowsi University of Mashhad | Kadkhodaee R.,Khorasan Research Institute for Food Science and Technology
Food Research International | Year: 2013

The effect of composition (whey protein concentrate, Lepidium perfoliatum seed gum, and oil content) of corn oil-in-water emulsions on their physical properties, droplet size and viscosity was studied using response surface methodology (RSM). For each response, a second-order polynomial model was developed using multiple linear regression analysis. The results indicated that the response surface models were significantly fitted for all response variables studied. It was shown that all emulsion components greatly influenced the physical properties of emulsion and its overall stability during storage. The main effect of L. perfoliatum seed gum was observed to be significant in most of response surface models. Therefore, the concentration of this gum should be considered as a critical variable for the formulation of emulsions. The overall optimum region resulted in a desirable emulsion was predicted to be obtained by combined level of 0.59% L. perfoliatum seed gum, 6% WPC and 21.95% oil volume fraction. © 2012 Elsevier Ltd.

Asadzadeh Shahir A.,Tarbiat Modares University | Javadian S.,Tarbiat Modares University | Razavizadeh B.B.M.,Khorasan Research Institute for Food Science and Technology | Gharibi H.,Tarbiat Modares University
Journal of Physical Chemistry B | Year: 2011

Interaction of a food dye, tartrazine, with some cationic conventional and gemini surfactants, tetradecyltrimethylammonium bromide (TTAB), N,N′-ditetradecyl-N,N,N′,N′-tetramethyl-N,N′-butanediyl- diammonium dibromide (14,4,14), and N,N′-didodecyl-N,N,N′,N′- tetramethyl-N,N′-butanediyl-diammonium dibromide (12,4,12), were first investigated comprehensively employing conductometry, tensiometry, and UV-visible spectroscopy. Tartrazine was found to behave in the same manner as aromatic counterions. The formation of ion pairs reflected as a considerable increase of the surfactant efficiency in tensiometry plots and their stoichiometry were determined by Job's method of continuous variations. For the tartrazine/TTAB system, nonionic DS3, ionic DS2-, and/or DS2 - ion pairs, their small premicelles, and tartrazine-rich micelles were constituted as well as dye-containing TTAB-rich micelles. Insoluble J-aggregates of DS- ion pairs and cylindrical surfactant-rich micelles were also formed in tartrazine/gemini surfactant systems and recognized by transmission electron microscopy. The zeta potential and the size of the aggregates were determined using dynamic light scattering and confirmed the suggested models for the processes happening in each system. Cyclic voltammetry was applied successfully to track all of these species using tartrazine's own reduction peak current for the first time. © 2011 American Chemical Society.

Nezhad M.H.,Khorasan Research Institute for Food Science and Technology | Knight M.,Australian Department of Primary Industries and Fisheries | Britz M.L.,University of Tasmania
Food Science and Biotechnology | Year: 2012

In this research, changes were observed in cell surface proteins of a typical strain of the Lactobacillus casei was investigated in response to acidic growth conditions. Two dimensional electrophoresis and Western blot analyses were carried out to detect changes in relative abundance of proteins at the cell surface. The identity of the differentially expressed proteins extracted by LiCl, a chemical routinely used to extract surface proteins of lactic acid bacteria, was determined by MALDI-TOF/TOF MS. Many enzymes involved in glycolysis were up-regulated in the cell surface fraction following growth at low pH, including enolase, lactate dehydrogenase, and glyceraldehyde-3-phosphate dehydrogenase. Several of these proteins were also related to adhesion and generalized stress responses. It is demonstrated that growth of L. casei under acidic conditions caused molecular changes at the cell surface to develop an adaptive strategy corresponding to slower growth at low pH. © 2012 The Korean Society of Food Science and Technology and Springer Netherlands.

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