Alface minimamente processada: efeito da aplicação de ácidos orgânicos
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2013
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A avaliação dos produtos minimamente processados depende da análise de parâmetros qualitativos. O interesse de se encontrar alternativas ao cloro mais amigas do ambiente e com menores riscos para a saúde humana, fez com que se estudasse o efeito dos ácidos orgânicos na conservação da qualidade da alface durante o seu período de vida útil.
A presente dissertação teve como objectivos o acompanhamento da evolução da alface minimamente processada ao longo de 8 dias de armazenamento, à temperatura de 4ºC. Deste modo, as metodologias utilizadas passaram pela análise do efeito do vinagre comercial (6% de ácido acético na sua constituição) na lavagem, assim como a utilização do ácido ascórbico e ácido láctico na melhoria de características organolépticas da alface. O trabalho laboratorial incluiu análises à perda de massa, textura, cor, compostos fenólicos totais, capacidade antioxidante e pigmentos da alface (clorofila a, clorofila b e carotenóides).
A lavagem com solução de vinagre a 1% conferiu à alface um aspecto inaceitável e odor a vinagre extremamente activo. A introdução de um enxaguamento pós-lavagem trouxe melhorias muito significativas no aspecto da alface, assim como na eliminação do odor a vinagre. A embalagem 2 (BN200) reduziu o escurecimento da alface. Com soluções de vinagre a 0,25 ou 0,5% na lavagem a perda de massa foi menor. A cor e textura da alface foi melhor preservada com solução de vinagre a 0,25% e 1% de ácido ascórbico. O ácido láctico mostrou-se ineficaz como agente tanto de lavagem como de tratamento. As amostras apenas lavadas com água (C) apresentaram maior teor de clorofila a. O teor de clorofila b foi superior nas amostras lavadas somente com água (C) e com 1% de ascórbico (ASC). O tratamento com solução 0,25% de vinagre e 1% de ascórbico (V+ASC) apresentou maior teor de compostos fenólicos. A actividade antioxidante da alface não foi afectada pelos tratamentos. O tratamento com solução de vinagre a 0,25% evidenciou um decréscimo de microrganismos aeróbios mesófilos totais em relação às alfaces sem tratamento.
A lavagem da alface em solução de vinagre (0,25%) e tratamento com ácido ascórbico (1%) mostraram poder ser uma alternativa ao uso de cloro na produção de alface minimamente processada.
The evaluation of minimally processed products depends on the analysis of several qualitative parameters. With an interest in finding alternatives to chlorine, more environmentally friendly and safer in terms of public health, a study was conducted on the effects of organic acids on lettuce and their conservation of its quality during its shelf life. This dissertation follows the evolution of minimally processed lettuce stored for a period of 8 days at 4ºC. The effects of washing with vinegar (constituted by 6% acetic acid) were evaluated, as were the improvements of the organoleptic characteristics of lettuce after being treated with ascorbic acid and lactic acid. The work included measurement and analysis of water loss, texture, color, phenolic compounds content, antioxidant capacity and pigmentation (chlorophyll a and b and carotenoids). Washing with a 1% vinegar solution gave the lettuce an unacceptable appearance and an extremely active odor. Rinsing after washing greatly improved the appearance of the lettuce, and also eliminated the resulting vinegar smell. Packaging 2 (BN200) reduced lettuce darkening. Washing with 0,25 and 0,5% vinegar solutions reduced mass loss. Lettuce color and texture were better preserved with a 0,25% vinegar and 1% ascorbic acid solution. Lactic acid proved ineffective as both a washing and a treatment agent. Samples washed only with water (C) showed greater chlorophyll a content. Chlorophyll b content was higher in samples washed only with water (C) and with a 1% ascorbic acid solution (ASC). Treatment with a 0,25% vinegar and 1% ascorbic acid solution resulted in a higher phenolic compounds content. The antioxidant activity was not affected by the treatments. Treatment with a 0,25% vinegar solution showed a decrease in mesophilic aerobic microorganisms relative to untreated lettuce. Washing with a vinegar solution (0,25%) and treating with ascorbic acid (1%) could be a viable alternative to the use of chlorine in the production of minimally processed lettuce.
The evaluation of minimally processed products depends on the analysis of several qualitative parameters. With an interest in finding alternatives to chlorine, more environmentally friendly and safer in terms of public health, a study was conducted on the effects of organic acids on lettuce and their conservation of its quality during its shelf life. This dissertation follows the evolution of minimally processed lettuce stored for a period of 8 days at 4ºC. The effects of washing with vinegar (constituted by 6% acetic acid) were evaluated, as were the improvements of the organoleptic characteristics of lettuce after being treated with ascorbic acid and lactic acid. The work included measurement and analysis of water loss, texture, color, phenolic compounds content, antioxidant capacity and pigmentation (chlorophyll a and b and carotenoids). Washing with a 1% vinegar solution gave the lettuce an unacceptable appearance and an extremely active odor. Rinsing after washing greatly improved the appearance of the lettuce, and also eliminated the resulting vinegar smell. Packaging 2 (BN200) reduced lettuce darkening. Washing with 0,25 and 0,5% vinegar solutions reduced mass loss. Lettuce color and texture were better preserved with a 0,25% vinegar and 1% ascorbic acid solution. Lactic acid proved ineffective as both a washing and a treatment agent. Samples washed only with water (C) showed greater chlorophyll a content. Chlorophyll b content was higher in samples washed only with water (C) and with a 1% ascorbic acid solution (ASC). Treatment with a 0,25% vinegar and 1% ascorbic acid solution resulted in a higher phenolic compounds content. The antioxidant activity was not affected by the treatments. Treatment with a 0,25% vinegar solution showed a decrease in mesophilic aerobic microorganisms relative to untreated lettuce. Washing with a vinegar solution (0,25%) and treating with ascorbic acid (1%) could be a viable alternative to the use of chlorine in the production of minimally processed lettuce.
Descrição
Dissertação de Mestrado em Engenharia Agronómica
Palavras-chave
Alface , Vinagre , Qualidade , Textura , Cor , Ácido ascórbico , Massa