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- Survival and growth of Cronobacter sakazakii on fresh-cut fruit and the effect of UV-C illumination and electrolyzed water in the reduction of its populationPublication . Santo, David; Graça, Ana; Nunes, Carla; Quintas, CéliaCronobacter sakazakii, found in foods such as powdered infant formula and plant origin ready-to-eat food, is an opportunistic pathogen to infants, neonates and vulnerable adults. The objective of this study was to monitor the growth of C. sakazakii in fresh-cut 'Royal gala' apple, 'Rocha' pear, and 'Piel de sapo' melon, and the effect of UV-C illumination, acidic electrolyzed water (AEW) and neutral electfolyzed water (NEW) in the reduction of its population. Fresh-cut fruits were inoculated and incubated at different temperatures during 10 days while monitoring C. sakazakii. The inhibitory activity of different doses of UV-C (0-10 kj.m(2)), electrolyzed water and sodium hypochlorite (SH) (100 ppm chlorine) was evaluated on the fruits inoculated with C sakazakii. The bacterium showed a significant growth in the fruits at 12 and 20 C, but did not grow at 4 C, despite having survived for TO days. At 8 C, adaptation phases of 0.6-3.9 days were estimated in the fruits before exponential growth. The UV-C 7.5 and 10 kJ/m(2) produced greater C. sakazakii population decreases (2-2.4 log cfu/g) than AEW (1.3-1.8 log cfu/g), NEW (1-12 log cfu/g) and SH (0.8-1.4 log cfu/g). The UV-C decontamination system and refrigeration at 4 degrees C, may contribute to the product's safety and quality. The results help better understand the behavior of C sakazakii on fresh-cut fruit alerting producers of the necessity to respect the high hygienic practices, adequate refrigerating temperature maintenance and caution with the tendency to prolong the validity of this kind of ready-to-eat food. (C) 2016 Elsevier B.V. All rights reserved.
- 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.
- Growth of Escherichia coil, Salmonella enterica and Listeria spp., and their inactivation using ultraviolet energy and electrolyzed water, on 'Rocha' fresh-cut pearsPublication . Graça, Ana; Santo, David; Quintas, Célia; Nunes, CarlaThe present study aimed at evaluating the growth of Escherichia coil, Salmonella enterica, and Listeria spp. and studying the efficacy of Ultraviolet-C (UV-C) irradiation, acidic electrolyzed (AEW) and neutral electrolyzed (NEW) waters in the reduction of these bacteria on 'Rocha' pear. Fresh-cut pieces were inoculated and incubated at 4-20 degrees C for 8 days. Inoculated pears were treated with UV-C (2.5-10 kJ/m(2)), AEW, NEW and sodium hypochlorite (SH) and microbiological and quality parameters were evaluated. The three bacteria, inoculated at 6.1-6.2 log cfu/g, grew on the pear at high growth rates at 12 and 20 degrees C reaching populations of 8.1-8.6 log cfu/g, in 24 h. At 8 degrees C the microorganisms increased their populations by at least 1 log cfu/g in three days. At 4 degrees C adaptation phases of less than 24 h for Listeria spp. were measured before exponential growth occurred and the enterobacteria did not grow despite having survived for 8 days. AEW and NEW caused microbial reductions similar to SH, of approximately 1 log cfu/ g, while the best UV-C dose (7.5 kJ/m(2)) of at least 2.4 log cfu/g. Fresh-cut pears were a good substrate for foodborne bacteria emphasizing the importance of preventing contaminations and cross contaminations. The UV-C was more effective than the chemical decontaminations, as it provided superior microbial reductions without greatly affecting the quality of pears. (C) 2017 Elsevier Ltd. All rights reserved.
- 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.
- Yeast diversity in the Mediterranean strawberry tree (Arbutus unedo L.) fruits' fermentationsPublication . Santo, David; Galego, Ludovina; Gonçalves, Teresa; Quintas, CéliaIn the Mediterranean region the fruits of the strawberry tree (Arbutus unedo L.) may be fermented and distilled to produce a traditional beverage very much appreciated in Southern Europe. The aim of the present work was to study the diversity of the yeast population and the killer activity of the isolates identified as Saccharomyces cerevisiae, obtained during solid state industrial fermentations of the arbutus berries. The identification of the isolates was performed by the 5.8S rRNA-ITS region restriction analysis and by sequencing the D1/D2 region of the large subunit of the rRNA gene. At the start of the fermentations, various non-Saccharomyces species were detected including Aureobasidium pullulans, Dothichiza pithyophila, Dioszegia zsoltii, Hanseniaspora uvarum and yeasts belonging to the genera Metschnikowia, Cryptococcus and Rhodotorula. However, as the biological processes progressed the number of different species decreased with S. cerevisiae and Pichia membranaefaciens becoming dominant at advanced stages of the must fermentation that is characterized by high concentrations of ethanol. Forty three isolates identified as S. cerevisiae were tested for killer activity against two sensitive reference strains and Zygosaccharomyces bailii. Their killer sensitivity in relation to five killer referenced toxins (K2, K5, K8, K9 and K10) was also studied. Out of the isolates analyzed, 95.3% were sensitive and 4.7% were tolerant against the killer toxins tested. Only three isolates revealed killer activity against one sensitive strain and two of them against the spoiler yeast Z. bailii. The microbiota obtained revealed an interesting potential to be used as starter cultures to overcome unpredictable uncontrolled fermentations of the arbutus fruits as well as in other applications of biotechnological interest. (C) 2012 Elsevier Ltd. All rights reserved.
- Quality and biological properties of vinegar processed from non-valorized fruits in Southern PortugalPublication . Silva, Vanessa; Raouf Mehrpour, Gisou; Soares, Vera; Santo, David; A. Nunes, Patrícia; Quintas, CéliaThe processing of vinegar from non-valorized fruits and agricultural surpluses is an attractive strategy for biomass waste management. The present study aimed to characterize vinegar of fermented fruits, namely fresh fig, plum, dried fig, grape, raspberry, and apricot. Physicochemical and microbial quality, total phenolic content (TPC), total flavonoid content (TFC), total antioxidant capacity (TAC), mineral composition, and antimicrobial capacity against bacteria and yeasts were studied. Grape and apricot vinegar had the highest values of TAC (39.31 +/- 0.25, 34.10 +/- 1.44 DPPH mu g Trolox/100 mL, respectively), while grape contained the highest TFC (35.73 +/- 3.86 mg catechin/100 mL) and raspberry and fresh fig, the highest TPC (55.40 +/- 1.1, 64.10 +/- 0.0 mg gallic acid/ 100 mL, respectively). Potassium, calcium and sodium were the most abundant minerals in the vinegars with dried fig standing out for its richness in potassium 1223.83 +/- 89.48 mg/L, calcium 17.70 +/- 1.31 mg/L, magnesium 2.39 +/- 0.24 mg/L, and zinc 4.33 +/- 0.17 mg/L. The enterobacteria Cronobacter sakazakii and Salmonella Typhimurium were the most tolerant (10.00 +/- 0.00-26.39 +/- 1.60 mm), while Pseudomonas aeruginosa was the most sensitive bacteria (26.36 +/- 3.61-40.17 +/- 2.72 mm) as well as Gram + ( Staphylococcus aureus, Listeria innocua ) (21,20 +/- 8,37-31.11 +/- 2.41 mm). The acetification processes resulted in vinegars with a good hygienic status, and levels of acetic acid ( >= 5 %) complying with the legislation.