Impacto de diferentes niveles de nisina como agente bioconservador en la calidad química, sensorial y microbiológica de filetes de lubina (Dicentrarchus labrax) envasados al vacío y almacenados a 4 ± 2 °C.

Nisin is produced by Lactococcus lactis subsp. lactis and is also known as an antimicrobial agent especially effective against gram-positive bacteria. It has long been used as a preservative in foods and beverages and is generally regarded as safe (GRAS). In the present work, the effects of different concentrations of nisin (0.2, 0.4 and 0.8%) on the sensory, chemical and microbiological quality and shelf-life of vacuum-packed sea bass (Dicentrarchus labrax) fillets were investigated during chilled (4 ± 2 °C) storage. The sensory points for raw and cooked fillets increased with time during the storage period (p < 0.05). The control group, with scores of 9.08, was rejected by panelists on day 12; whereas nisin-treated groups were rejected on day 14 with scores ranging from 9.00-9.17 score. As a result of chemical analyses, lower values (p < 0.05) were obtained from the nisin groups with low oxidative rancidity. Moreover, nisin inhibited microbial growth, which shows antimicrobial activity. Consequently, it was concluded that the application of nisin (especially 0.8%) preserved the organoleptic quality and extended the shelf-life of sea bass fillets.La nisina es producida por Lactococcus lactis subsp. lactis y conocida como agente antimicrobiano, especialmente contra las bacterias grampositivas. Se ha utilizado como conservante en alimentos y bebidas durante mucho tiempo y generalmente se considera seguro (GRAS). En el presente trabajo, se investigaron los efectos de diferentes concentraciones de nisina (0,2, 0,4 y 0,8%) sobre la calidad sensorial, química y microbiológica y la vida útil de los filetes de lubina (Dicentrarchus labrax) envasados al vacío durante el enfriamiento y almacenamiento (4 ± 2 °C). La puntuación sensorial de los filetes crudos y cocidos aumentó con el tiempo durante el período de almacenamiento (p <0,05). El grupo de control con puntuación de 9,08 fue rechazado por los panelistas el día 12, mientras que los grupos de tratamiento con nisina fueron rechazados el día 14 con un rango de puntuación de 9,00-9,17. Como resultado de los análisis químicos, se obtuvieron valores más bajos (p < 0,05) de los grupos de nisina con baja rancidez oxidativa. Además, la nisina inhibió el crecimiento microbiano que muestra actividad antimicrobiana. En consecuencia, se evaluó que la aplicación de nisina (especialmente 0,8%) conservó la calidad organoléptica y prolongó la vida útil de la lubina

Latinx and Caucasian Elementary School Children’s Knowledge of and Interest in Engineering Activities

Ethnic minorities, such as Latinx people of Hispanic or Latino origin, and women earn fewer engineering degrees than Caucasians and men. With shifting population dynamics and high demands for a technically qualified workforce, it is important to achieve broad participation in the engineering workforce by all ethnicities and both genders. Previous research has examined the knowledge of and interest in engineering among students in grades five and higher. In contrast, the present study examined elementary school students in grades K–5. The study found that older students in grades 4 and 5 had both greater knowledge of engineering occupational activities and greater interest in engineering than younger students in grades K–3. Moreover, Caucasian students had greater knowledge and interest levels than Latinx students. There were no significant differences between boys and girls, nor any significant interactions among gender, grade level, and ethnicity. A significant positive correlation between knowledge of engineering occupational activities and interest in engineering was also found. The findings suggest that early engineering outreach interventions are important. Such early interventions could potentially contribute to preserving the equivalent interest levels of males and females for engineering as students grow older. Also, ethnic disparities in engineering knowledge and interest could potentially be mitigated through early interventions

Écoulements de fluides à seuil autour d'un cylindre en milieu confiné : études expérimentale et numérique

The flow of yield stress fluids around a circular cylinder in a confined geometry has been investigated with a Poiseuille flow configuration.Experimentally, a test set-up was built which provides a continuous flow in a closed loop. We studied creeping, recirculating and vortex shedding flow regimes. New results has been realised with a Newtonian fluid and Carbopol solutions, models for yield stress behaviour in laboratory experiments and in industry. A high speed camera and a laser sheet have been used to perform images which are treated by PIV. Kinematic fields, flow morphologies and critical transition parameters have been determined.Numerically, a viscoplastic model based on the regularised Herschel-Bulkley law has been used. Results as flow morphologies, rigid areas and local flow parameters fields have been performed. That allowed us to compare the intrinsic effects of Carbopol solutions and the viscoplastic numerical model. A specific study on the wall slip has also been considered with an elasto-hydrodynamic lubrication model.Ce travail de thèse concerne les écoulements de fluides à seuil de contrainte autour d‘un obstacle cylindrique en milieu confiné avec une configuration d‘écoulement de Poiseuille.Expérimentalement, un banc d‘essai permettant d‘obtenir un écoulement en continu dans un circuit fermé a été mis en place. Les régimes d‘écoulement rampant, recirculant et instationnaire périodique ont été étudiés. De nouveaux résultats ont été obtenus avec un fluide newtonien et des solutions de Carbopol, polymère permettant de réaliser des fluides à seuil modèles utilisés en recherche et développement et dans l‘industrie. Une caméra rapide et un éclairage plan laser a servi pour l‘établissement d‘images qui ont ensuite été traitées par PIV. Les champs de vitesses cinématiques, les morphologies d‘écoulement et les paramètres critiques de transitions de régimes ont été déterminés.Numériquement, un modèle viscoplastique basé sur la loi de Herschel-Bulkley régularisée a été utilisé. Des résultats comme les morphologies d‘écoulement, la localisation des zones rigides, les champs de vitesses ont été obtenus. Ceci a permis de comparer les différences entre les effets liés à la nature des gels de Carbopol et la modélisation viscoplastiques. Une étude spécifique sur le glissement à l‘interface fluide-structure a également été réalisée avec l‘utilisation d‘un modèle de lubrification élasto-hydrodynamique

Physical, chemical, and sensory properties of water kefir produced from Aronia melanocarpa juice and pomace

Water kefir is widely consumed all over the world due to its potential health benefits. The aim of this current study was to compare non-fermented juice and fermented beverage of water kefir produced from Aronia melanocarpa juice and pomace in terms of chemical, physical and sensory quality as well as valorisation of pomace in the production of water kefir. When compared to water kefir made with aronia juice, less reduction in total phenolic content (TPC), total flavonoid content (TFC) and total anthocyanin content (TAC) was observed in samples made with aronia pomace during the fermentation process. Similarly, greater antioxidant activity was demonstrated in water kefir made with aronia pomace than juice. Based on sensory evaluation, no difference was found in overall acceptability, taste, aroma/odor, and turbidity of water kefir made with aronia pomace before and after fermentation. Results indicated that aronia pomace has potential in water kefir productio

Physical, chemical, and sensory properties of water kefir produced from Aronia melanocarpa juice and pomace

Water kefir is widely consumed all over the world due to its potential health benefits. The aim of this current study was to compare non-fermented juice and fermented beverage of water kefir produced from Aronia melanocarpa juice and pomace in terms of chemical, physical and sensory quality as well as valorisation of pomace in the production of water kefir. When compared to water kefir made with aronia juice, less reduction in total phenolic content (TPC), total flavonoid content (TFC) and total anthocyanin content (TAC) was observed in samples made with aronia pomace during the fermentation process. Similarly, greater antioxidant activity was demonstrated in water kefir made with aronia pomace than juice. Based on sensory evaluation, no difference was found in overall acceptability, taste, aroma/odor, and turbidity of water kefir made with aronia pomace before and after fermentation. Results indicated that aronia pomace has potential in water kefir production