6 research outputs found
Biological variation in the colour development of Golden Delicious apples in the orchard
BACKGROUND: In managing apple orchards, crop load and rate of nitrogen (N) fertilisation are two factors with a significant influence on fruit quantity and quality, because they affect all physiological processes in the tree. Both factors are strongly related to external and internal fruit quality, especially to skin colour, sugar and acid contents and mineral composition, and consequently to the keeping quality of fruits. The aim of this study was to assess the effects of both factors (three crop load levels and two N fertilisation levels) on the colour development of Golden Delicious apples during the last month on the tree in two consecutive seasons. Data on skin colour (L*, a*, b* values) were analysed using nonlinear mixed effects modelling to extract information on the variation in biological shift factor for colour and to link this variation to the different strategies used concerning N fertilisation and crop load. RESULTS: The major source of information is contained in the a* value. The behaviour of the a* value could be described by a logistic or an exponential model depending on the season and the experimental set-up. Nonlinear mixed effects analysis estimating the biological shift factor (maturity) for each individual fruit (random effect) while estimating the rate constant of the decolouration process in common (fixed effect) resulted in explained parts well over 95%. CONCLUSION: The variation in maturity stage between individual fruits is large. Season has the most profound effect on the estimated values, far more important than that of crop load or fertilisation level. The magnitude of variation in colour due to crop load and N fertilisation is not too large. Its effect on the maturity stage of fruits is more profound: the higher the crop load, the higher the variation. The effect of fertilisation seems to be opposite: the higher the fertilisation level, the lower the variation
Colour development in the apple orchard
Colour is traditionally one of the important appearance features of all fruit for consumers in deciding to buy them. Colour is therefore important in the postharvest supply chain. But where does that colour of fruit come from? Clearly the period of growing and the circumstances during growth are important for developing this important feature. During several seasons (2007-2009), the skin colour of individual apples of different cultivars (‘Braeburn’, ‘Fuji’, ‘Gala’, ‘Golden Delicious’) were measured using a Minolta CR-400 chromameter during the last 40-60 days before (commercial) harvest. By including the biological variation between individual apples in the analyses and applying non linear indexed regression analysis based on process oriented models, explained parts were obtained for the a*-value, all exceeding 90%. The estimated rate constants for the colouration process were remarkably similar for all cultivars (except ‘Fuji’) and growing conditions. That would indicate that the process of colouration is really reflecting the degradation of chlorophyll and not the production of red or yellow coloured blush (anthocyanins). The expected effect of growing conditions (fertilization and crop level, hail net or not, sunny side or shady side of the tree) did change the mechanism nor the kinetic parameter values but could all be attributed to the minimal obtainable skin colour (asymptotic values of the logistic model). This type of information from the production period may constitute an important link to postharvest supply chain management
Development and distribution of quality related compounds in apples during growth
Colour and taste are important attributes of apple fruit quality and have therefore been widely studied. Nevertheless, because of the destructive sampling methods commonly used to obtain the data, and of the subsequent traditional analyses, ignoring the effects of biological variation, the knowledge on the kinetic mechanisms of synthesis and degradation of individual quality components during fruit development and growth is still lacking. Spatio-temporal changes of taste components (sugars: fructose, sucrose, glucose, organic acids: malic, citric, shikimic and fumaric acid) and colour aspects (a) in individual apple fruits were monitored to assess the dynamics and mechanisms of change during development and ripening with respect to location within fruit as a factor and the variation between individual apples. Data were analysed with non-linear indexed regression based on either a logistic or an exponential process oriented model assessing the technical variation simultaneously. The rate constants for colour or taste component were roughly similar between cultivars, suggesting a similar mechanism of development and confirming the generic nature of the model. There was a very large biological variation in individual quality components observed in the raw data (the biological variation), which can be almost exclusively explained by the difference in the maturity stage between individual fruit. The explained parts (R2 adj) were, with one exception, higher than 0.90. The major contribution of this study is the fact that all the herein monitored taste defining components can be analysed and described with the same process-oriented model.</p
Effect of location in the canopy on the colour development of three apple cultivars during growth
BACKGROUND: Homogeneity in appearance is one of the quality aspects asked for in the supply chain. Decreasing the biological variation in batches of harvested apples (cultivars Braeburn, Fuji and Gala) becomes increasingly important. Skin colour is one of the aspects that determine both optimal harvest and stage of development. Skin colour is affected by location in the canopy. The rules of development of biological variation are now established and will be used on skin colour data. RESULTS: The Minolta colour aspects a*, b* and L* measured before commercial harvest change in a sigmoidal fashion and can be analysed including the biological variation, with a logistic model in indexed nonlinear regression, obtaining explained parts of above 90%. The mechanism of colour change is not affected by state of development or location in the canopy. The location in the canopy affects the intensity of both red and green colouring compounds. The variation in colouration is not affected by the location in the canopy. CONCLUSION: The red-coloured apple cultivar (Gala) depends more on the location in the canopy than the less-coloured cultivars (Fuji and Braeburn). The colour development in Fuji apples is considerably slower, with a much larger variation in stage of development. The location in the canopy affects all aspects of biological variation (biological shift factor and asymptotic starting level of colouration) for all three colour aspects L*, a* and b*, but only the mean value, not the standard deviation. The biological shift factors per colour aspects are linearly related. Once induced, variation remains constant during development