Pectinases e alta pressão : aplicação ao controlo de qualidade dos sumos

Tese de mestrado, Controlo de Qualidade e Toxicologia dos Alimentos, Universidade de Lisboa, Faculdade de Farmácia, 2013As pectinases são enzimas que degradam substâncias pécticas e, são amplamente utilizadas pelas indústrias de sumos e bebidas para melhor a qualidade do processo e do produto. O objetivo deste trabalho foi estudar a ação conjugada de pectinases e da tecnologia de alta pressão no tratamento de sumos e, aliar a estes dois processos a pasteurização, de forma a obter um sumo clarificado e isento de microrganismos. Foram selecionadas para este estudo as pectinases de Aspergillus aculeatus e Aspergillus niger. A avaliação da atividade destas enzimas foi efetuada recorrendo ao método DNS, que consiste na determinação da concentração de glucose, derivada da degradação da pectina pois, uma unidade de glucose corresponde a uma unidade de ácido galacturónico. As enzimas foram imobilizadas pelo método de inclusão, usando como suporte o quitosano. Tanto a imobilização como o processamento a alta pressão mostraram ser eficazes na proteção destas enzimas a temperaturas elevadas. Contudo, no sumo, a temperatura elevada provocou uma diminuição da atividade das enzimas, impossibilitando a realização da pasteurização em simultâneo com os tratamentos enzimático e a alta pressão. Os melhores resultados no sumo foram obtidos a 45 oC e à pressão de 200 MPa. De ambas as pectinases, a pectinase de Aspergillus aculeatus mostrou ser mais eficaz na clarificação do sumo, apresentando uma atividade superior à pectinase de Aspergillus niger.Pectinases are enzymes that degrade pectic substances and are widely used in juice and fruit beverages to improve the quality of the process and the product. The objective of this study was study the conjugated action of pectinases and high pressure technology on juice treatment, and combine pasteurization with these two processes, in order to obtain a clarified juice and free of microorganisms. We selected for this study pectinases from Aspergillus aculeatus and Aspergilllus niger. The evaluation of the activity of these enzymes was performed using the DNS method, which consists in determining the glucose concentration derived from the degradation of pectin because one unit of glucose corresponds to a unit of galacturonic acid. Enzymes were immobilized by the inclusion method, using the chitosan as a support. Both immobilization as processing high pressure shown be effective in protecting these enzymes at high temperatures. However, on juice, the high temperature caused a decrease in the activity of enzymes, excluding the achievement of pasteurisation simultaneously with enzymatic treatments and the high pressure. The better results at juice, were obtained to 45 oC and 200 MPa of pressure. Of both pectinases, pectinase from Aspergillus aculeatus shown be most effective in clarifying juice, presenting an activity higher than pectinase from Aspergillus niger

Socially critical decisions towards low status groups: the role of meritocracy

Wemake trivial decisions everyday but, every once in a while, we face decisions that have a deep impact on others, as they may imply serious harm or the unequal distribution of relevant material or symbolic resources. These socially critical decisions (scd) constitute the core of this chapter. Its main goal is to describe the literature on these scd and present empirical research testing how the contextual salience of a meritocratic norm impacts on these decisions towards low status group members.info:eu-repo/semantics/publishedVersio

Characterisation of microbial attack on archaeological bone

As part of an EU funded project to investigate the factors influencing bone preservation in the archaeological record, more than 250 bones from 41 archaeological sites in five countries spanning four climatic regions were studied for diagenetic alteration. Sites were selected to cover a range of environmental conditions and archaeological contexts. Microscopic and physical (mercury intrusion porosimetry) analyses of these bones revealed that the majority (68%) had suffered microbial attack. Furthermore, significant differences were found between animal and human bone in both the state of preservation and the type of microbial attack present. These differences in preservation might result from differences in early taphonomy of the bones. © 2003 Elsevier Science Ltd. All rights reserved