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- The effect of UV-C and electrolyzed water on yeasts on fresh-cut apple at 4 degrees CPublication . Graça, Ana; Santo, David; Pires-Cabral, Paula; Quintas, CéliaThe growth of a yeast mixture, Candida sake, Hanseniaspora uvarum, Pichia fermentans, Metschnikowia pulcherrima, on fresh-cut apple (Royal gala), at 4 degrees C, was studied, as well as the reduction of yeasts using Ultraviolet-C (UV-C), acidic (AEW) and neutral (NEW) electrolyzed waters, and sodium hypochlorite (SH). Apple portions were contaminated then disinfected with UV-C (2.5-10 kJ/m(2)), AEW, NEW and SH (100 ppm). During 9 days at 4 degrees C, yeasts growth rate was 0.34 day(-1) and the stationary phase occurred after 6 days (7.42 LogCFU/g). The initial microbial reduction and the half-life time values, using the inverse hyperbola model, ranged from 1.72 to 1.81 LogCFU/g and 6.52-11.70 day (UV-C), or 0.91 to 1.96 LogCFU/g and 0.68-4.38 day (chemical treatments), where SH was the least efficient (0.92 LogCFU/g and 2.96 day). The most effective treatment was UV-C (7.5 and 10 kJ/m(2)). The yeasts psychrotrophic profile highlights the importance of avoiding contamination/cross-contaminations in all processing.
- Cracked green table olive from the south of Portugal: the influence of diferent brining conditonsPublication . Rodrigues, Neusa; Cavaco, Teresa; Quintas, Célia; Nunes, CarlaIn the south of Portugal, cracked green olives represent a traditional way of processing table olives. After harvesting and sorting, the olives are washed, broken and immediately brined (Process A) or submitted to various washing steps with water prior to brining (Process B). The objective of this work was to study the effect of different processing treatments on the evolution of microbiological and physicochemical parameters during the fermentation of cracked green olives at a homemade scale and at different temperatures (25 ºC, room temperature and 18 ºC). Yeasts were found to be the dominant group in fermented cracked green table olives. Process A originated brines without countable Enterobacteria, with higher free acidity and higher phenolic content, when compared to brines resulting from Process B, suggesting that cracking and brining them straight away, represent a preferable way of processing olives which may guarantee the safety of the final product.
- Microbial quality and yeast population dynamics in cracked green table olives' fermentationsPublication . Alves, Maria; Gonçalves, Teresa; Quintas, CéliaCracked green table olives, from the Manzanilla variety, are a fermented food produced and consumed in Portugal. The objective of the present work was to study the microbiological characteristics and yeast population evolution during the fermentation of cracked green olives. The predominant microorganisms were yeasts while lactic acid bacteria were not detected and a clear decrease of the mould population was observed. At the end of the fermentations, no viable counts of Enterobacteriaceae were found. Yeast isolates were identified by the 5.8S rRNA-ITS region restriction analysis and by sequencing the D1/D2 region of the 26S rRNA gene. During the initial phases of the fermentations a great diversity of yeasts was observed. However, as the processes evolved the biodiversity decreased with the fermentative yeasts Citeromyces matritensis, Zygotorulaspora mrakii and Saccharomyces cerevisiae becoming the dominant species. The presence of these fermentative yeasts at the end of the production process is associated to a risk of spoilage. The results obtained represent a first attempt towards the comprehension of the microbiota of this type of “Natural olives” that constitute an important component of the Mediterranean diet.
- The effect of NaCl reduction in the microbiological quality of cracked green table olives of the Macanilha Algarvia cultivarPublication . Mateus, Tânia; Santo, David; Saúde, Cíntia; Pires-Cabral, Paula; Quintas, CéliaThe present work aimed at studying the effect of the partial replacement of NaCl with KCl and CaCl2 of the fermenting brines on the microbiological quality of natural cracked green Macanilha Algarvia table olives. Olives were fermented in different salt combinations (Brine 1-8% NaCl, Brine 2-4% NaCl 4% KCl, Brine 3-4% NaCl 4% CaCl2, Brine 4-4% KCl 4% CaCl2, and Brine 5-2.7% NaCl 2.7% KCl 2.7% CaCl2) and the abundance of yeasts and enterobacteria was determined. At the end of fermentation, the main microbial safety parameters were evaluated. Samples were analyzed according to standard methodologies and using Chromocult Agar (coliforms and Escherichia colt). The yeasts collected were grouped by restriction analysis of the ITS-5.8S rRNA gene and identified by partial sequencing of the 26S rRNA. Throughout the study, a decrease of the enterobacteria population was observed in all the fermentations, which was greater and faster in brines containing potassium and calcium. The main yeasts identified were Pichia membranaefaciens, Candida boidinii, Zygosaccharomyces mrakii, Priceomyces carsonii, Saccharomyces cerevisiae, Wickerhamomyces anomalus and the yeast-like fungus Galactomyces geotrichum. The highest yeast diversity was found in olives produced in Brines 1, 2 and 3 and the lowest in Brines 4 and 5, where only the species P. membranaefaciens, C boidinii and G. geotrichum were identified. No Pseudomonas, E. coli, Salmonella, Staphylococcus aureus and Listeria monocytogenes were found in the table olives produced. (C) 2015 Elsevier B.V. All rights reserved.
- Antimicrobial activity of Drosophyllum lusitanicum, an endemic Mediterranean insectivorous plantPublication . Gonçalves, Sandra; Quintas, Célia; Gaspar, Maria Nelma; Nogueira, José Manuel F.; Romano, AnabelaThe aim of this study was to evaluate the antimicrobial activity of Drosophyllum lusitanicum leaf extract against various yeasts and bacteria species, including both standard and clinically isolated strains. The extract exhibited strong antimicrobial activity against all the tested yeast strains with inhibition zones ranging 23.67–42.23mm and with minimum inhibitory concentration (MIC) values ranging 31–63 mgL 1. All the Gram-positive bacteria studied were inhibited by the extract, showing inhibition zones ranging 17.67–43.00mm and MIC values comprising between 15.6 and 250 mgL 1. In contrast, the growth of the tested Gram-negative bacteria was not significantly affected by the extract. Among the microorganisms tested, Staphylococcus epidermidis ATCC 12228 was the most sensitive, presenting the lowest MIC value (15.6 mgL 1), while Enterococcus faecalis ATCC 29212 was the most tolerant (250 mgL 1). The extract of D. lusitanicum was analysed by gas chromatography-mass spectrometry and the major constituent found was plumbagin.