Made available in DSpace on 2016-04-28T14:58:57Z (GMT). No. of bitstreams: 1 2006-Nilber Kenup Hernandes.pdf: 2004617 bytes, checksum: 031cfe61d7bb727196791c4404d4e145 (MD5) Previous issue date: 2006-12-12 / This study was aimed at investigating the effects of low-dose gamma irradiation on shelf-life extension and phytosanitary safety of minimally processed red beet with basis on physicochemical; microbiological; chemical and sensory analyses. The samples (Beta vulgaris ssp. vulgaris L.), Early Wonder cultivar, were cultivated in the experimental area of the Horticulture Sector of the Departamento de Fitotecnia of the Instituto de Agronomia, Universidade Federal Rural do Rio de Janeiro, Serop?dica, RJ, as part of two experiments performed during the second semester of 2005. In each experiment, 1200 plants (40 per linear meter of terrain) were sowed. Physicochemical analyses (fresh mass; length; average diameter and total soluble solids) of the edible part of the red beets (their tuberous roots) were periodically carried out in order to assess the most appropriate time for harvest by monitoring the development of the plants. Those times were found to be 104 and 73 days after transplanting, respectively. The harvested edible part of the roots were minimally processed and separated in two groups: (1) gamma irradiated (with doses of 0.5; 1.0 and 1.5 kGy) and (2) non-irradiated (control). All samples were stored at 8 ?C. Microbiological analyses were performed during the storage period (22 and 21 days, for experiments 1 and 2, respectively) in order to evaluate the phytosanitary quality of the samples (Salmonella sp.; coliforms and total count of mesophilic aerobic and lactic acid bacteria). The samples irradiated with 1.0 and 1.5 kGy were found to remain appropriate for consumption for 21 days, as compared to only 7 days for the control. Monitoring of chemical composition was also performed and included the determination of saccharose; glucose; fructose and vitamins B1 and B2. No difference was found between the concentrations of those vitamins in irradiated and control samples at the end of the storage period, whereas significant changes in sugar contents were detected independently of the dose. In addition, physicochemical analyses investigated the evolution of pH; total acidity; total soluble solids and ascorbic acid throughout storage. Samples from experiment 2 were also subjected to sensory analyses for overall appearance and aroma at 4 different post-irradiation times. The results indicated that the samples irradiated with 1.0 and 1.5 kGy remained good for consumption for 20 days. Therefore it can be concluded that the application of those doses extended the shelf life of the samples without harming their nutritional and sensory quality. Finally, the results indicate that the dose of 1.0 kGy is the most appropriate for the conservation of red beet among those tested. / O objetivo deste estudo foi avaliar, por meio de an?lises microbiol?gicas; qu?micas; f?sicoqu?micas e sensoriais, os efeitos de baixas doses de radia??o gama na extens?o da vida ?til e na garantia da seguran?a microbiol?gica da beterraba vermelha (Beta vulgaris ssp. vulgaris L.), cultivar Early Wonder minimamente processada. Dois experimentos foram realizados, em condi??es de campo, em ?rea experimental do Setor de Horticultura do Departamento de Fitotecnia do Instituto de Agronomia da UFRRJ, Serop?dica, RJ, no segundo semestre de 2005. Em cada experimento, foram transplantadas 1200 mudas (40 por metro linear de canteiro). Foram realizados ensaios f?sico-qu?micos (massa fresca; comprimento; di?metro m?dio e teor de s?lidos sol?veis totais) da parte comest?vel (por??o tuberosa) da beterraba, para avalia??o do est?gio de desenvolvimento das plantas, visando ? determina??o do ponto ideal de colheita. As beterrabas dos experimentos 1 e 2 foram colhidas 104 e 73 dias ap?s o seu transplante, respectivamente. As partes tuberosas foram minimamente processadas e separadas em 2 grupos de amostras: controle (n?o irradiadas) e irradiadas (0,5; 1,0 e 1,5 kGy), sendo que todas foram armazenadas a 8 ?C. Avalia??es realizadas ao longo do per?odo de armazenamento (22 e 21 dias, nos experimentos 1 e 2, respectivamente) permitiram monitorar a: qualidade microbiol?gica (Salmonella sp.; coliformes; contagem total de bact?rias aer?bias mes?filas e contagem de bact?rias l?ticas); a composi??o qu?mica (determina??o dos teores de: sacarose; glicose e frutose e vitaminas B1 e B2) e as propriedades f?sico-qu?micas (pH; acidez total titul?vel; teor de s?lidos sol?veis totais e teor de ?cido asc?rbico). As amostras do experimento 2 foram tamb?m submetidas a an?lises sensoriais (apar?ncia e aroma) em quatro ocasi?es ap?s a irradia??o. Os resultados das an?lises microbiol?gicas indicaram que somente as amostras irradiadas com 1,0 e 1,5 kGy mantiveram-se pr?prias para o consumo por 21 dias, enquanto que as n?o irradiadas apresentaram vida ?til inferior a 7 dias. Ao fim do per?odo de avalia??o, n?o foi observada diferen?a entre os teores das vitaminas B1 e B2 das amostras irradiadas em rela??o ?s de controle. Os teores dos a??cares, por outro lado, sofreram altera??es significativas ao longo do tempo, independentemente das doses aplicadas. Em contraste, n?o foram constatadas altera??es indesej?veis nas propriedades f?sico-qu?micas ocasionadas pela irradia??o. Os resultados das an?lises sensoriais indicaram que as amostras irradiadas com doses de 1,0 e 1,5 kGy mantiveram-se dentro dos padr?es de aceitabilidade por 20 dias. Consistentemente, verificou-se que a aplica??o dessas doses foi eficaz para estender a vida ?til, sem prejudicar a qualidade nutricional ou sensorial das amostras. Finalmente, conclui-se que a dose de 1,0 kGy mostrou-se como a mais apropriada, dentre aquelas estudadas, para a irradia??o de beterraba vermelha minimamente processada.