Contaminação, crescimento e inativação de microrganismos na cadeia de produção de alface (Lactuca sativa L.) variedade Vitória de Santo Antão

• Ano de defesa: 2009
• Autor(a) principal: Antunes, Maria Aparecida
• Orientador(a): Andrade, Nélio José de
• Banca de defesa: Peña, Wilmer Edgard Luera , Pinto, Cláudia Lúcia de Oliveira
• Tipo de documento: Tese
• Tipo de acesso: Acesso aberto
• Idioma: por
• Instituição de defesa: Universidade Federal de Viçosa
• Programa de Pós-Graduação: Doutorado em Ciência e Tecnologia de Alimentos
• Departamento: Ciência de Alimentos; Tecnologia de Alimentos; Engenharia de Alimentos
• País: BR
• Palavras-chave em Português: Alface; Microbiologia preditiva; Unidades de alimentação e nutrição
• Palavras-chave em Inglês: Lettuce; Predictive microbiology; Units of food and nutrition
• Área do conhecimento CNPq: CNPQ::CIENCIAS AGRARIAS::CIENCIA E TECNOLOGIA DE ALIMENTOS::CIENCIA DE ALIMENTOS
• Link de acesso: http://locus.ufv.br/handle/123456789/419

The production chain from farm to table of the lettuce Vitória de Santo Antão was analyzed under the guidelines of the Hazard Analysis Critical Control Point system (HACCP) and Risk Assessment of microbiological hazards system. The following stages were realized for this study: lettuce foliar surface characterization, evaluation of lettuce consumption habits and hygiene conditions of the processing in commercial restaurants, evaluation of lettuce contamination from the farm to table, identification, listing and analysis of potential hazard in a food operations; microbiological challenge tests andstorage tests using predictive microbiology; and, finally, an evaluation of microbiological risks. First, the foliar surface was characterized by electronic microscopy. Cuticle showed being hydrophobic and uneven. Stomata and ribbings had been natural adhesion sites. E. coli O157: H7 beyond the hydrophilic surfaces of injuries cuticule and cuts. The intentional microorganism adhesion in the edges and cuts in the lettuce leaf reached > 5 log. The consumption habits of lettuce in commercial restaurants had been evaluated. Small (8 g), midle (20 g) and great portions (30 g) are daily consumed by people between 10 and 40 years old, both male and female. Affirmed that do not wash the hands before meals 16.0% of the men and 11.3% of the women had. Among the restaurants consumers, 10.1% had affirmed they had diarrhea recently. The number of diarrhea cases was greater among people that frequently eat at restaurants than among the ones who sporadically eat at restaurants. The hygienical conditions of seven commercial restaurants in Viçosa, MG were evaluated. The contaminations were above of the recommendations of the APHA and Brazilian researchers in the evaluation of the air of cooled and not cooled environments. The manipulators hands in five restaurants had presented averages of counting > 2 log CFU/hand for total coliforms and aerobic mesofilic organisms. All the utensils had presented counting of aerobic mesofilic above of the recommendations of APHA (0.30 log CFU·cm-2) and few had taken care of to the recommendations most flexible (1.70 log CFU·cm-2). The contamination of the lettuce was evaluated quantitatively from the farm to table. Total coliforms, enterobacterias and filamentous molds and yeast had been present in all evaluated stages (in the farm, in the delivery and ready to eat). There was no E. coli incidence in the farm samples, but there was in the delivery samples and ready for consumption, indicating that it was spread throughout the process. It was observed that there were no satisfactory reductions of contaminants microorganisms throughout the production chain. In some cases, it increased instead of reducing. Gramnegative bacteria present in the stages “farm”, “delivery” and “ready to eat” were isolated and 18 were identified by microscopy and biochemical tests. The enterobacterias were listed and the hazards analysis of the potentially hazardous microorganisms was realized by HACCP methodology. The following were considered as potentially hazardous microrganisms: Escherichia coli, Cronobacter sakazakii and Klebsiellla pneumoniae. The prevalence of this last one was 81.5% in the samples of lettuce ready to eat in the restaurants. These microorganisms were submitted to microbiological challenge tests and storage tests. In one of the challenges, by the suspension test, the efficacy of acetic acid (vinegar) added or not to sodium chloride in the inactivation of planktonic cells of the three enterobaterias was evaluated. The solutions were efficient in reducing populations of C. sakazakii and K. pneumoniae. However, the solutions had not been approved by the test of the suspension. In another challenge, the efficacy of the water, solution of chloramine organic and solutions of acetic acid, added or not to sodium chloride, in reducing the bacteria attached to lettuce leaves were evaluated. The synergic action of the sodium chloride added to the acetic acid was observed in the C. sakazakii e K. pneumoniae inactivation. The decimal reductions were equal to the reductions with chloramine organic. There was no difference in the endobacterias resistance in relation to the treatment also. However, no sanitizer solution reached 3 decimal reduction values in the microorganism population, as recommended for sessile cells. The effectiveness of one solution of chloramine organic and one of acetic acid, in the concentrations used by the restaurants, was evaluated in inactivating K. pneumoniae attached to the lettuce leaf. The results were analyzed by two term exponential model for mixed cell population to the adjustment of inactivation curves and to obtain the constants of inactivation. In the storage tests, the increasing of K. pneumoniae in the lettuce in temperatures between 5 and 40 °C was studied. Two primary models of the predictive microbiology, modified Gompertz and Baranyi and Roberts, had been used to describe the growth curves. It was verified that the model Baranyi and Roberts was more adjusted to the answers of the microbial growth, obtaining the values of the main parameters of the microbial growth. In the temperature of distribution that occurs in the restaurants, 20 °C, the adaptation time (λ) was 1.74 h, and the specific rate of growth (μmax) 0.199·h-1. Besides, it was observed that K. pneumoniae grew at 5°C under the parameters of growth for secondary models. The Weibull model adjusted well to the data of the duration of the lag phase and simple square root model of Ratkowsky described the effect of temperature on the maximum growth rate. The analysis of microbiological risk in this experiment, considering the prevalence and the number of Klebsiella pneumoniae samples in each stage of the production chain of the lettuce Vitória de Santo Antão, since the primary production until the consumer’s table, in reason of the process, the temperature and the time, indicated the risk for consumers of ingesting high number of microorganisms.