Browsing by Author "Pedroso, L."
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- Applications of Essential Oils as Antibacterial Agents in Minimally Processed Fruits and Vegetables - A ReviewPublication . Santos, M.I.S.; Marques, C.; Mota, J.; Pedroso, L.; Lima, A.Microbial foodborne diseases are a major health concern. In this regard, one of the major risk factors is related to consumer preferences for “ready-to-eat” or minimally processed (MP) fruits and vegetables. Essential oil (EO) is a viable alternative used to reduce pathogenic bacteria and increase the shelf-life of MP foods, due to the health risks associated with food chlorine. Indeed, there has been increased interest in using EO in fresh produce. However, more information about EO applications in MP foods is necessary. For instance, although in vitro tests have defined EO as a valuable antimicrobial agent, its practical use in MP foods can be hampered by unrealistic concentrations, as most studies focus on growth reductions instead of bactericidal activity, which, in the case of MP foods, is of utmost importance. The present review focuses on the effects of EO in MP food pathogens, including the more realistic applications. Overall, due to this type of information, EO could be better regarded as an added value to the food industry
- Essential oils as antibacterial agents against food-borne pathogens: are they really as useful as they are claimed to be ?Publication . Santos, M.I.S.; Martins, S.R.; Veríssimo, C.S.C.; Nunes, M.J.C.; Lima, A.I.G.; Ferreira, Ricardo Boavida; Pedroso, L.; Sousa, IsabelMost studies evaluating the use of essential oils (EO) as antibacterial agents focus mainly on minimal inhibitory concentrations (MIC) rather than minimal bactericidal concentrations (MBC). In this work, we compared MICs and MBCs of EO from condiment plants commonly used in Mediterranean Europe, namely Origanum vulgare, Salvia lavandulaefolia, Salvia officinalis, Salvia sclarea and Rosmarinus officinalis, aiming to evaluate their application as disinfecting agents in minimally processed produce. Outbreaks-related pathogens such as Listeria monocytogenes, Pseudomonas aeruginosa and Yarrowia lipolytica were used. Results showed that all EO were able to reduce bacterial growth in all bacterial strains tested, particularly O. vulgare. However, fewer EO exhibited bactericidal activities, and were only effective against one or two bacterial strains, hence eliminating the possibility to use them as broad range disinfectants. Furthermore, the necessary concentrations were too high for food application. Hence, our work suggests the need to evaluate MBC rather than MIC and questions EO usefulness in controlling undesired microorganisms. Overall, and despite the large volume of data published on EO, results obtained were not very encouraging for a realistic application on produce and question the viability of EOs as disinfecting agents in food
- Evaluation of minimally processed salads commercialized in PortugalPublication . Santos, M.I.; Cavaco, A.; Gouveia, J.; Novais, M.R.; Nogueira, P.J.; Pedroso, L.; Ferreira, M.A.S.S.During the last decades food borne outbreaks associated with consumption of raw vegetables have been increasing and green leafy vegetables seem to be the most frequently implicated products. In order to determine the microbial quality and the incidence of the major food borne pathogens in Minimally Processed (MP) salads commercialized in Portugal, a survey was conducted in Lisbon Retail Markets, from July 2007 to August 2008, to determine microbial contamination loads and identify potential pathogenic bacteria. A total of 151 samples were purchased from 2 supermarkets: 38 romaine lettuce, 12 various spinach and 101 mixed salads with three or four different ingredients. The samples were tested for aerobic psychotropic micro-organisms (APM), Enterobacteriaceae, Escherichia coli, Listeria spp., presumptive Bacillus cereus, Aeromonas hydrophila and Clostridium perfringens counts as well as for presence of Salmonella spp., Listeria monocytogenes and E. coli O157. Samples were also evaluated for taste quality. The results showed that APM counts of romaine lettuce and mixed salads had a similar median, respectively, 6.2 and 6.5 log cfu/g and mixed spinach had the highest one (7.6 log cfu/g). The median value found for Enterobacteriaceae was 5.44 log cfu/g. Only four samples showed positive result for E. coli (2.65%) but just one (0.8%) had a slightly higher load of contamination. Although the percentage and levels of contamination loads were low, these mustn’t be ignored, for the reason that the strains in three of the samples belong to VTEC group (1.99%). E. coli O157, Salmonella spp. and C. perfringens weren’t detected in any sample. For the enumeration of Listeria spp., two samples (1.32%) had presence of Listeria innocua and L. monocytogenes had an incidence of 0.66%. A. hydrophila was identified in 11 samples (7.28%), and in 8 of them with considerable counts (>105). Contamination with B. cereus was found in 22.7% of samples analyzed, though in small numbers, which doesn’t represent a major concern to food safety. All isolated strains were assessed for its potential toxin production and it was found that 40% of these strains had this ability. Results from sensory panel showed organoleptic differences in salads during its shelf-life period
- Potential bio-activity of whey fermented extract as sanitizer of organic grown lettucePublication . Santos, M.I.S.; Martins, S.R.; Pedroso, L.; Sousa, Isabel; Ferreira, M.A.S.S.Consumption of vegetables is increasing due to demand for healthy products in peoples' diets. To reduce microbial contamination and maintain freshness, industrial processes in Portugal rely on minimally processing of vegetables with hypochlorite as sanitizer. Formation of toxic chlorine derivatives has raised concern restrictions to its use and alternatives with whey permeate as a disinfection agent has been attempted. The aim of this work was to evaluate the bio potential of fermented cheese whey, for use on disinfection of minimally processed lettuce organically grown. Assays were made with whey obtained from inoculated milk during cheese processing, fermented for 120 h at 37 C, after which, among other carbohydrates, lactic acid was measured by HPLC, giving average yields of 18 g L 1. The sanitizing effect of whey, undiluted, 75 and 50% solutions, was compared with 110 ppm sodium hypochlorite, after rinsing. Aerobic Microorganisms (AM), Psychrotrophic Microorganisms (PM) and Enterobacteriaceae (ENT), were used as indicators for hygiene quality. For a level of significance of P < 0.05, the hygiene quality standards of lettuce samples, were better using 75% whey solution (AM 6.62, PM 7.48 cfu g 1), than using sodium hypochlorite (AM 7.48, PM 8.15 cfu g 1), for the 7 days of shelf life studied. Evaluation of Enterobacteriaceae showed significant differences after 3 days, betweenwater (ENT 4.98 cfu g 1) sodium hypochlorite (ENT 4.81 cfu g 1) and 75% solution of whey (ENT 4.63 cfu g 1). Considering the actual limitations imposed to chlorine sanitation, these results point a good alternative to the food industry, especially for organic fresh vegetables, which are chemical free brands