Alocação de matéria fresca, escurecimento enzimático e processamento mínimo de alface

• Ano de defesa: 2010
• Autor(a) principal: Flores, Milton Edgar Pereira
• Orientador(a): Finger, Fernando Luiz
• Banca de defesa: Puiatti, Mário , Costa, Franciscleudo Bezerra da
• Tipo de documento: Tese
• Tipo de acesso: Acesso aberto
• Idioma: por
• Instituição de defesa: Universidade Federal de Viçosa
• Programa de Pós-Graduação: Doutorado em Fitotecnia
• Departamento: Plantas daninhas, Alelopatia, Herbicidas e Resíduos; Fisiologia de culturas; Manejo pós-colheita de
• País: BR
• Palavras-chave em Português: Alface; Escurecimento; Polifenoloxidase; Peroxidase; Pós-colheita; Processamento mínimo
• Palavras-chave em Inglês: Lettuce; Browning; Polyphenoloxidase; Peroxidase; Postharvest; Minimally processed
• Área do conhecimento CNPq: CNPQ::CIENCIAS AGRARIAS::AGRONOMIA::FITOTECNIA
• Link de acesso: http://locus.ufv.br/handle/123456789/1138

The objectives of this research were to characterize the allocation of the accumulated fresh mass, the isoenzymes pattern, the activity of the peroxidase (POD) and polyphenoloxidase (PPO), and the effect of the ascorbic acid (AA) on the lettuce browning of minimally processed lettuce. The characteristics were studied located in leaves and mid-ribs of the outer, middle and inner foliar positions throughout of the head and in lettuce hearts of the Aurélia, Vitória and Crespa cultivars. Regardless the cultivar, there was significant difference among the leaf positions or regions of the rosette for the evaluated characteristics. Among cultivars, Aurélia and Vitória cultivars had number of leaves and pattern of distribution of the leaf fresh mass favorable for the production of whole leaves and hearts minimally processed, simultaneously. The pattern of the PPO and POD isoenzymes from mid-ribs of different leaf positions revealed the variability existence in relation to the number and intensity of bands with the development stage. The isoenzymes pattern can be composed by one or two isoenzymes of PPO (PPO-1, PPO2) and two or four isoenzymes of POD, being two cationic (POD-C1, POD-C2) and two anionic (POD-A1, POD-A2) isoenzymes, depending on the cultivar. The variability of isoenzymes number was attributed to the absence or presence of the PPO-1 and POD-A1 isoenzymes, absent in the internal leaves, and present with larger intensity in external mid-ribs in relationship with the middles leaves. The absence of the PPO-1 and POD-A1 isoenzymes, in the internal leaves mid-ribs were associated to the smallest browning of those mid-ribs in relationship of the external and intermediate leaves mid-rib. The largest browning of the midribs from external and intermediate leaves was associated with the presence of all of the isoenzymes of PPO and POD, independently of the magnitude of the specific activity of those enzymes, among the leaf positions. The treatment with immersion for one minute in solutions containing 10 to 30 mM of AA of dissected mid-ribs and leaves minimally processed from external, middle and internal region of rosette, and lettuce leaves hearts had different results depending on the leaf tissue age. The treatment with AA was favorable to reduce the degree of the browning of the cut stem surface from lettuce hearts, and it favored the maintenance of the visual quality of the heart leaves. Contrarily, the treatment with AA promoted larger browning of mid-ribs of the medium and internal leaves, and to loss of visual quality of the external and medium leaves, minimally processed. It suggests that AA treatment favored the POD activity in relation to the PPO activity, for having inhibited in a larger degree PPO or induced larger deterioration by ways not determinated in this research. The visual quality of leaves of the inner region of the rosette was not influenced significantly by AA treatment, evidencing the influence of the leaf age of the response to the acid. It was verified the existence of significant physiologic differences among the leaves of different regions from lettuce rosette, with implications in the susceptibility to browning and visual quality, which justify the existence of aspecific classification to optimize the use of the raw matter in the minimum processing.