Detección de la metabolización de sorbato en alimentos empleando tecnología MWIR.

Las levaduras son agentes cada vez más relevantes en el deterioro de alimentos siendo algunas de sus principales manifestaciones el crecimiento en superficie, y la producción de gas, sabores y olores desagradables. El ácido sórbico y sus sales derivadas son empleadas habitualmente como conservantes. Estos conservantes son agentes fungistáticos que originan alteraciones morfológicas y metabólicas en dichos microorganismos con el fin de evitar su crecimiento. Sin embargo, existen microorganismos que pueden metabolizarlos produciendo un deterioro del producto. En este trabajo se han empleado muestras procedentes de agua saborizada embotellada, cuya composición incluye agua, zumo de pera, ácido cítrico, zumo de maracuyá y melocotón, aromas naturales, edulcorantes, antioxidantes y conservadores (sorbato potásico). Dicha botella presentaba una contaminación fúngica y un fuerte olor a petróleo, presuntamente debido a la descarboxilación en 1-3 pentadieno del conservante alimenticio, sorbato potásico, que figuraba en su composición. La conclusión principal de este estudio es que es viable emplear la espectroscopía MIR para la cuantificación de la presencia de pentadieno en muestras líquidas de alimentos, siendo éste un compuesto derivado de la descarboxilación del ácido sórbico y sus sales asociadas

A simple mathematical model that describes the growth of the area and the number of total and viable cells in yeast colonies

We propose a model, based on the Gompertz equation, to describe the growth of yeasts colonies on agar medium. This model presents several advantages: (i) one equation describes the colony growth, which previously needed two separate ones (linear increase of radius and of the squared radius); (ii) a similar equation can be applied to total and viable cells, colony area or colony radius, because the number of total cells in mature colonies is proportional to their area; and (iii) its parameters estimate the cell yield, the cell concentration that triggers growth limitation and the effect of this limitation on the specific growth rate. To elaborate the model, area, total and viable cells of 600 colonies of Saccharomyces cerevisiae, Debaryomyces fabryi, Zygosaccharomyces rouxii and Rhodotorula glutinis have been measured. With low inocula, viable cells showed an initial short exponential phase when colonies were not visible. This phase was shortened with higher inocula. In visible or mature colonies, cell growth displayed Gompertz-type kinetics. It was concluded that the cells growth in colonies is similar to liquid cultures only during the first hours, the rest of the time they grow, with near-zero specific growth rates, at least for 3 weeks

Detection of Biological CO2 and 1,3-Pentadiene Using Non-refrigerated Low-Cost MWIR Detectors

The early detection of spoiling metabolic products in contaminated food is a very important tool to control quality. Some volatile compounds produce unpleasant odours at very low concentrations, making their early detection very challenging. This is the case of 1,3-pentadiene produced by microorganisms through decarboxylation of the preservative sorbate. In this work, we have developed a methodology to use the data produced by a low-cost, compact MWIR (Mid-Wave IR) spectrometry device without moving parts, which is based on a linear array of 128 elements of VPD PbSe coupled to a linear variable filter (LVF) working in the spectral range between 3 and 4.6 ?m. This device is able to analyze food headspace gases through dedicated sample presentation setup. This methodology enables the detection of CO2 and the volatile compound 1,3-pentadiene, as compared to synthetic patrons. Data analysis is based on an automated multidimensional dynamic processing of the MWIR spectra. Principal component and discriminant analysis allow segregating between four yeast strains including producers and no producers. The segregation power is accounted as a measure of the discrimination quality

Las levaduras en los alimentos : ¿buenas amigas, peores enemigas?

Oportunidades que las nuevas tecnologías en la producción de alimentos ofrecen a las levaduras (y a los zimólogos que las estudian)