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Oxidative discolouration in whole-head and cut lettuce: biochemical and environmental influences on a complex phenotype and potential breeding strategies to improve shelf-life
Lettuce discolouration is a key post-harvest trait. The major enzyme controlling oxidative discolouration
has long been considered to be polyphenol oxidase (PPO) however, levels of PPO and subsequent development of discolouration symptoms have not always correlated. The predominance of a latent state of the enzyme in plant tissues combined with substrate activation and contemporaneous suicide inactivation
mechanisms are considered as potential explanations for
this phenomenon. Leaf tissue physical properties have
been associated with subsequent discolouration and
these may be influenced by variation in nutrient
availability, especially excess nitrogen and head maturity at harvest. Mild calcium and irrigation stress has
also been associated with a reduction in subsequent
discolouration, although excess irrigation has been
linked to increased discolouration potentially through
leaf physical properties. These environmental factors,
including high temperature and UV light intensities,
often have impacts on levels of phenolic compounds
linking the environmental responses to the biochemistry
of the PPO pathway. Breeding strategies targeting the
PALand PPOpathway biochemistry and environmental
response genes are discussed as a more cost-effective
method of mitigating oxidative discolouration then
either modified atmosphere packaging or post-harvest
treatments, although current understanding of the
biochemistry means that such programs are likely to
be limited in nature and it is likely that they will need to be deployed alongside other methods for the foreseeable future
EvaluaciĂłn del efecto inhibidor de la enzima polifenol oxidasa en una salsa de aguacate (Persea americana)
Characterization of peroxidase enzyme and detoxification of phenols using peroxidase enzyme obtained from Zea mays L waste
Development and Validation of MRM Methods to Quantify Protein Isoforms of Polyphenol Oxidase in Loquat Fruits
Aumento do potencial de armazenamento refrigerado de nĂȘsperas 'Fukuhara' com o uso de tratamento tĂ©rmico Potential increasing in the cold-storage of 'Fukuhara' loquat using heat treatments
O objetivo deste trabalho foi avaliar a eficiĂȘncia de tratamentos tĂ©rmicos no aumento do potencial de frigoconservação de nĂȘsperas 'Fukuhara' e os efeitos desses tratamentos na qualidade e nas propriedades fĂsico-quĂmicas e bioquĂmicas dos frutos. Os tratamentos de condicionamento tĂ©rmico foram: armazenamento a 1ÂșC durante 60 dias (controle); armazenamento a 5ÂșC durante 60 dias (padrĂŁo); armazenamento a 5ÂșC, durante 7 dias, e 1ÂșC durante 53 dias; armazenamento a 10ÂșC, durante 7 dias, e 1ÂșC durante 53 dias; aquecimento intermitente, em ciclos de 6 dias a 1ÂșC + 1 dia a 15ÂșC, durante 60 dias; condicionamento dos frutos a 37ÂșC, durante 3 horas, e a 1ÂșC durante 60 dias; e condicionamento dos frutos a 37ÂșC, durante 6 horas, e a 1ÂșC durante 60 dias. Os frutos foram mantidos a 85-90% de umidade relativa, durante todo o armazenamento. Foram determinados: firmeza da polpa, Ăndice de escurecimento, acidez titulĂĄvel, pH, teor de sĂłlidos solĂșveis, teor de ĂĄcido ascĂłrbico, teor de compostos fenĂłlicos, atividade das enzimas fenilalanina amĂŽnia-liase (PAL), polifenoloxidase (PPO) e peroxidase (POD) apĂłs 15, 30, 45 e 60 dias de armazenamento. Houve correlação entre firmeza de polpa e atividade de POD, apĂłs 60 dias de armazenamento refrigerado. O aquecimento intermitente e o aquecimento a 37ÂșC, durante 3 horas, foram eficientes no controle do escurecimento interno. Os tratamentos tĂ©rmicos nĂŁo evitaram o enrijecimento de polpa. Tratamentos tĂ©rmicos aumentam o potencial de armazenamento de nĂȘsperas sem alterar as caracterĂsticas fĂsico-quĂmicas dos frutos.<br>The objective of this work was to evaluate the efficiency of heat treatments on the potential improvement of the cold-storage of 'Fukuhara' loquat, and the effects of these treatments on the quality and on physicochemical and biochemical properties of fruits. The treatments applied were: storage at 1ÂșC for 60 days (control); storage at 5ÂșC for 60 days (standard); storage at 5ÂșC for 7 days, and at 1ÂșC for 53 days; storage at 10ÂșC for 7 days, and at 1ÂșC for 53 days; intermittent heat, in cycles of 6 days at 1ÂșC + 1 day at 15ÂșC, for 60 days; fruit conditioning at 37ÂșC for 3 hours, and at 1ÂșC for 60 days; and fruit conditioning at 37ÂșC for 6 hours, and at 1ÂșC for 60 days. The fruits were kept at 85-90% relative humidity, over the whole storage. The following parameters were determined: pulp firmness, incidence of internal browning, titrable acidity, pH, content of soluble solids, ascorbic acid and phenolic compounds, activity of phenylalanine ammonia-lyase (PAL), polyphenol oxidase (PPO) and peroxidase (POD), in evaluations after 15, 30, 45 and 60 days of storage. There was a correlation between firmness level and POD activity, after 60 days of cold storage. Intermittent heat and at 37ÂșC for 3 hours were efficient in controling internal browning in fruit pulp. Heat treatments did not prevent the increase of pulp firmness. Heat treatments increase cold-storage potential of loquat without changing fruit physicochemical properties