Changes in soil chemistry associated with the establishment of forest gardens on eroded, acidified grassland soils in Sri Lanka

Topsoil properties were determined in forest gardens established about 20 years ago on eroded grassland soils (abandoned tea lands) in the wet zone of the Sri Lankan highlands. They were compared with adjacent, eroded grasslands (abandoned tea lands) on strongly weathered soils vs soils at earlier stages of pedogenic development in a two-way analysis of variance. Soil pH in forest gardens was, on average, 6.1, nearly one unit higher than in the adjacent grasslands. In the garden soils, the cation exchange capacity (CEC measured at pH 4.8) was nearly double, exchangeable calcium concentrations five times and exchangeable magnesium three times as high as in the grasslands soils. Total soil N content was found to be nearly 40% higher in the gardens. Topsoil gravel contents in the gardens were less than half as high as in the grasslands. The increases in exchangeable bases and N in gardens, relative to grasslands, were attributed to increased nutrient retention and acquisition. Higher retention was partly due to the higher CECpH4.8, and probably to reduced erosion and increased, continuous fine root density in the garden topsoils. Higher field CEC in gardens was likely to result from generally higher C contents and from the reversal of acidification, presumably caused by base accumulation and decomposition processes. Our results suggest that forest garden establishment on degraded grasslands can lead to accumulation of mobile nutrients in the topsoil, probably due to increased nutrient retention, subsoil uptake and litter input exceeding nutrient uptake by the standing biomass

Activity of cell wall-associated enzymes in ripening olive fruit

Enzymatically active cell wall isolaled from olive (Olea europaea) fruit was employed Hi investigate some hydrolytic enzymes bound to the cell wall and the changes in these during ripening. Seven glycosidases. β-glucosidase (EC 3.2.1.21) α-galactosidase (EC 3.2.1.22). β-galactosidase (EC 3.2.1.23). α-arabinosidase (EC 3.2.1.55), α-mannosidase (EC 3.2.1,24). β-xylosidase (EC 3.2.1.37) and β-N-acetylglucosamidase (EC 3.2.1.30). as well as Cx-cellulase (EC 3.2.1.4) and endo-polygalacturonase (EC 3.2.1.15). were identified in the cell wall preparation, at four stages of ripeness (mature green. changing colour, black and black-ripe). Activities of all these cell wall-associated enzymes fionicallv and covalently linked) were determined either by cell wall incubation with artificial substrate or after extraction from the cell wall with buffers of high salt concentration (Cx-cellulase). and were compared to those of forms solubilized from acetone powders with 500 nM citrate buffer (cytoplasmic and/or apoplastic plus ionically hound to cell wall) In general, the activities of low ionic strength buffer-soluble enzymes were found to be much higher than those of the bound enzymes. The bound enzymes are present in the fruit at the green colour stage, whereas the activities of the soluble enzymes only increased from the changing colour stage onwards. The tenacity of binding of enzymes to the wall was investigated by treating the walls with high salt and measuring residual activity. The nature of the ionic and covalent binding and the changes during ripening were also established for wall-hound glycosidase During ripening there was a marked change in the percentages of covalently- and tonically linked activities of β-glucosidase and β-galaclosidase: al the changing colour stages about 75–80% of the bound active in was present in high ionic strength buffer while al the black-ripe stage it was only 15–20. A possible role for these cell wall degradative enzymes in olive softening is discussed.Peer reviewe

Armazenamento de melão 'Orange Flesh' minimamente processado sob atmosfera modificada Storage of 'Orange Flesh' mellons minimally processed and packaged under modified atmosphere

O aumento da demanda por produtos minimamente processados traz um grande desafio para a ciência e tecnologia de alimentos, considerando-se a escassez de informações sobre a manutenção da qualidade desses produtos. O armazenamento desses em condições adequadas é um ponto fundamental para o sucesso dessa tecnologia. Objetivou-se com este trabalho avaliar o efeito da atmosfera modificada ativa na conservação do melão tipo Orange Flesh minimamente processado. Os frutos, após o processamento, foram embalados sob atmosfera modificada (AM Passiva- Controle, AM Ativa com 5% de CO2 e 5% de O2 e AM Ativa com 10% de CO2 e 2% de O2), armazenados em câmara fria (6 ± 1 ºC e UR 85 ± 5%) durante 8 dias e as amostras retiradas para análises de pH, sólidos solúveis totais (SST), acidez total titulável (ATT), açúcares solúveis totais (AST), firmeza, pectina total (PT), pectina solúvel (PS), e as enzimas pectinametilesterase (PME) e poligalacturonase (PG) a cada 2 dias de armazenamento. A atmosfera modificada ativa pouco influenciou no comportamento das variáveis pH, acidez total titulável (ATT), firmeza e pectina total com relação á atmosfera modificada passiva. No entanto, menor solubilização de pectinas foi detectada nas amostras armazenadas sob atmosfera com 10% de CO2 e 2% de O2. Não foram detectadas atividades das enzimas pectinametilesterase e poligalacturonase nos tratamentos analisados.<br>The increase of the demand for products minimally processed brings a great challenge for the food science and technology, considering the shortage of information about the maintenance of the quality of those products. The storage of those products in appropriate conditions is a fundamental point for the success of such technology. The objective of this work was to evaluate the effect of the active modified atmosphere on the quality and conservation of the 'Orange Flesh' melons processed minimally. The fruits, after the processing, were wrapped under modified atmosphere (Passive MA - Control, Active MA- with 5% of CO2 and 5% of O2 and Active MA with 10% of CO2 and 2% of O2), stored in a cold chamber (6 ± 1 ºC and 85 ± 5% RH) during 8 days and sampled for analyses of pH, total soluble solids, tritable acidity, total soluble sugars, firmness, total pectin, soluble pectin and pectinametylesterase and polygalacturonase activities every 2 days of storage. The variables firmness, total acidity and total pectin were not affected by the active modified atmosphere. However, smaller solubilization of pectins were detected in melons under atmosphere with 10% of CO2 and 2% of O2. Enzymatic activity was not detected in fruits from all treatments