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Articles by Paula Teixeira
Total Records ( 4 ) for Paula Teixeira
  Joana Silva , Ana Sofia Carvalho , Paula Teixeira and Paul A. Gibbs
  Cultures of Lactobacillus delbrueckii sp. bulgaricus play an important role in the production of fermented foods and are frequently used as starter cultures for dairy fermentations combined with other species. It These cultures is are particularly used in the industrial production of yoghurt and cheeses. Large scale Pproduction methods of dried L. bulgaricus powders, for inoculating the production vat directly, involve treatments that stress cells in such a way that they lose some of their original activity. containing viable and active organisms which are long-term preserved during storage in the dried state, areis presented. This review covers the environmental stress responses in cells of L. bulgaricus which have been investigated. The responses of L. bulgaricus cells to heat, cold, acid, osmotic, oxygen, starvation, drying and during storage in the dried state are described. Attempts to improve the survival of L. bulgaricus during drying and subsequent storage in the dried state are also discussed in this review.
  Cristina Santos , Joana Silva , Paul A. Gibbs and Paula Teixeira
  The aim of the present study was to investigate if the presence of sorbitol, myoinositol, xylose, mannose and Tween 80 in the growth medium increased the survival of L. sakei during heating, freezing, freeze drying and storage of freeze dried cells. Survival during freezing was enhanced by ca. 8% when glycerol was present in the growth medium. Viability during freeze-drying and storage in the dried state was improved by the presence of xylose in the growth medium. In addition to xylose, the presence of mannose and myoinositol protected cells during storage but not during drying. Cells grown in the presence myoinositol presented the highest D value at 55?C, 1.4 folder higher than control cells. In comparison with cells grown in MRS, total amino acids concentrations were the same order of magnitude for cells grown in the presence of mannose and myoinositol but were lower for cells grown in the presence of the other compounds.
  Joana Silva , Ana Sofia Carvalho , Rita Ferreira , Paula Teixeira and Paul Gibbs
  The degree of thermotolerance conferred on Lactobacillus delbrueckii ssp. bulgaricus, by an acid shock or a heat shock, when cells were grown in controlled and non-controlled pH conditions, during exponential and stationary growth phases, was evaluated. For exponential phase cells, thermotolerance was enhanced by submitting the cells to prior heat or acid shocks independently of the pH of growth conditions. Stationary phase cells were significantly more resistant to heating than cells in the exponential phase but only when growth occurred under non-controlled pH. Induced thermotolerance in stationary phase cells, was only observed for cells grown under controlled pH. Except for cells in the stationary growth phase grown under non-controlled pH, the heat or acid shock treatments resulted in an intracellular increase in the well - known heat shock proteins, GroES and GroEL. The presence of chloramphenicol negated the heat shock response and production of GroES and GroEL, confirming that de novo protein synthesis was involved in cell protection. These proteins were also identified in stationary phase cells grown under non-controlled pH, suggesting their involvement in induced thermotolerance during growth at low pH. Very few studies have investigated the response of stationary phase cells. The evaluation development of the response to sub-lethal stresses as a function of the pH conditions during growth is a new insight;. In fact, it was demonstrated that the pH of growth is a crucial factor.
  Fatima Noronha , Susana Aragao Silva , Cristina Mena , Goncalo Almeida , Tim Hogg , Paul Gibbs and Paula Teixeira
  Foodborne diseases are widely accepted as one of the major public health concerns for all countries. According to the results of various studies, the domestic sector needs to be a key element in the reduction of foodborne illness as a significant proportion of these diseasescases arises from poor food handling and hygiene practices in the domestic environment. The objective of this preliminary study was to obtain an indication of the level of hygiene of Portuguese kitchens. 10 domestic kitchens were characterized based on the presence of Escherichia coli, Staphylococcus aureus and Enterobacteriaceae in 16 different sampling points and of Listeria sp. in refrigerators and on the administration of a small questionnaire to the person responsible for the house cleaning and cooking about food safety and hygiene practices. Although based on a small number of homes, this study demonstrated that various points in the kitchen harbourharbor pathogenic organisms, thus being a possible source of food poisoning, for example through cross-contamination.
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