Control of Listeria monocytogenes in a dairy spread by Lactobacillus sakei subsp. sakei 2a, a bacteriocinogenic and potentially probiotic strain
International Conference and Exhibition on Probiotics - 2012
Rafael Chacon Ruiz Martinez, Matheus de Souza Barbosa, Cristina Dini Staliano, Antonio Diogo Silva Vieira, Svetoslav Dimitrov Todorov, Susana Marta Isay Saad and Bernadette Dora Gombossy de Melo Franco
BBubbles play a crucial role in many food products including bakery products, dairy foams, confectionery, breakfast cereals and
extruded snacks. They give rise to aerated structures (food foams) resulting in novel food textures with desirable appearance.
In the research and operational spheres, bubble science is still somewhat underdeveloped. Unfortunately researchers are realizing
that in many cases a detailed, quantitative understanding of aerated foods is not available. Foam texture is significantly influenced
by gas bubble size distribution and is the most difficult parameters to measure and analyse. However, its evolution with time is of
great importance, since it is closely related to the final product quality. In some systems, a uniform bubble size may be desirable
(e.g. bread dough and cake batter) which improve baking characteristics, while others, a wide spread in the distribution may be
advantageous to achieve specific mouth-feel responses. Bread has a very high gas volume fraction (of the order of 0.68? 0.8) and
therefore, has been treated as foam in the literature. An attempt has been made to understand the relationship between process
parameters, foam structure and mechanical properties to obtain the desired structured product. Bread dough and bread have
been characterized for rheology using controlled stress/ shear rheometer while the microstructure studies have been done using
confocal laser scanning microscope (CLSM) and flat bed scanner respectively. In the bread dough investigation, the change
in rheological and microstructuralproperties of bread dough as a function of water and yeast concentration is described. The
rheological properties vary with the size of the bubbles and measurements were made on controlled shear/stress rheometer.
CLSM accompanied with image analysis technique, was used to obtain microstructure of the bread dough. It was found that with
an increase in water content, the moduli values decreased and the mean bubble diameter increased. As concentration of yeast
increased, the bubbles became smaller and the moduli values increased. The effect of bubble size and bubble size distribution has
been taken into consideration and an inverse relation between bubble size and storage modulus is found. The second part of the
study on bread baking was done with similar set of parameters. Flat bed scanner, accompanied with image analysis was used to
study the surface characteristics of bread. It was found that the effect of yeast and water content on bubble size in bread dough and
bread is similar. During baking, bread was analysed at different time intervals to study the change in its rheological properties as
the structure of the final product evolves. The mean the bubble size was measured along with the bubble size distribution. It was
observed that as the baking progresses the mean bubble size decreases.
Rutuja Upadhyay did her Masters in Food Technology from Laxminarayan Institute of Technology, Nagpur and currently pursuing her PhD in
Chemical Engineering from IIT Bombay. She is working on the Rheology and Micro-structure of Food Foams. She was awarded with the GNT Poster
Award for Young Scientist for her contribution to the progress and quality of research to the development of new concepts or techniques, aiming at
improving the food sector at the ISEKI Food Conference 2011 held in Milan. Her area of research is Food Process Engineering.
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