Browsing by Author "Geeraerd, Annemie"

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    Managing Biological Variation in Skin Background Colour Along the Postharvest Chain of Jonagold Apples
    (Elsevier, 2014-06) Gwanpua, Sunny George; Vicent, Victor; Verlinden, Bert; Hertog, Maarten; Nicolaï, Bart; Geeraerd, Annemie
    Skin background colour is an important quality aspect in the grading of ‘Jonagold’ apples, with consumers usually preferring fruit with a green background colour. However, apple handlers are usually faced with large fruit-to-fruit variability of background colour within a population of fruit. In this study, a stochastic modelling approach was used to describe how the initial fruit-to-fruit variability in the background colour of ‘Jonagold’ apples present at harvest, propagates throughout the postharvest chain. Two hundred and twenty ‘Jonagold’ apple fruit were harvested and stored at 1 °C or 4 °C, under different controlled atmosphere (CA) conditions for 6 months, followed by 2 weeks exposure to shelf-life conditions, during which the background colour and ethylene production of the individual fruit were measured. A kinetic model was developed to describe the postharvest loss of skin greenness, by assuming that the loss was principally due to chlorophyll breakdown, the rate of which was dependent on the endogenous ethylene concentration. Stochastic model parameters were identified, and by treating these parameters as fruit-specific, the model could account for more than 95% of the variability of the data. By treating the stochastic model parameters as random factors, the Monte Carlo method was used to model and describe the propagation of the fruit-to-fruit variability of the background colour within a population of fruit. The model developed in this study might allow better management of variability in quality along the postharvest chain, by predicting how the initial fruit-to-fruit variability within a batch of apples will propagate throughout the postharvest chain, as a function of storage and shelf-life conditions.
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    Modelling Biological Variation in the Skin Background Colour of ‘Jonagold’ Apples during Controlled Atmosphere Storage
    (Conference: International Controlled and Modified Atmosphere Research Conference, At Trani, Italy, Volume: Acta Horticulturae: Vol. 1071., 2013-06) Gwanpua, Sunny George; Vicent, Victor; Verlinden, Bert; Hertog, Maarten; Nicolaï, Bart; Geeraerd, Annemie
    Skin background colour is a very important quality aspect in the grading of ‘Jonagold’ apples, with consumers usually preferring fruit with a green background colour. However, apple handlers are usually faced with large fruit-to-fruit variability of background colour within a population of fruit. In this study, a stochastic modelling approach is used to describe how the initial fruit-to-fruit variability in the background colour of ‘Jonagold’ apples present at harvest, propagates throughout the postharvest chain. Two hundred fruit were harvested and stored at 1 or 4°C, under different controlled atmosphere (CA) conditions for six months. The fruit were taken out of storage every two months, and the background colour and the ethylene production of individual fruit were measured. At the end of the six months storage, the fruit were placed in shelf life conditions for 15 days, during which skin background colour and ethylene production were measured every five days. A mathematical model was developed to describe the postharvest loss of the skin greenness of apples during CA storage, by assuming that the loss is principally due to chlorophyll breakdown, the rate of which is dependent on the endogenous ethylene concentration within the fruit. The stochastic model parameters in the model were identified, and by treating these parameters as fruit-specific parameters, the model could describe more than 93% of the data for the individual fruit. By considering these fruit-specific parameters as stochastic parameters, the Monte Carlo method was used to describe the propagation of the fruit-to-fruit variability of the background colour of ‘Jonagold’ apples within a population. The model developed in this study can be used to predict how the initial fruit-to-fruit variability within a batch of apple will propagate throughout the postharvest chain.
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    Pectin modifications and the Role of Pectin-degrading Enzymes during Postharvest Softening of Jonagold Apples
    (Applied Science Publishers, 2014) Gwanpua, Sunny George; Van Buggenhout, Sandy; Verlinden, Bert; Christiaens, Stefanie; Shpigelman, Avi; Vicent, Victor; Jamsazzadeh Kermani, Zahra; Nicolaï, Bart; Hendrickx, Marc; Geeraerd, Annemie
    This study aimed at understanding softening in Jonagold apple (Malus × domestica Borkh.) fruits, by investigating pectin modifications and the evolution of pectin-modifying enzymes during postharvest storage and ripening. Jonagold apples were harvested at commercial maturity and stored at different temperatures and controlled atmosphere conditions for 6 months, followed by exposure to ambient shelf life conditions (20 °C under air) for 2 weeks. The composition of the pectic material was analysed. Furthermore, the firmness and the ethylene production of the apples were assessed. Generally, the main changes in pectin composition associated with the loss of firmness during ripening in Jonagold apples were a loss of side chains neutral sugars, increased water solubility and decreased molar mass. Also, the activities of four important enzymes possibly involved in apple softening, β-galactosidase, α-arabinofuranosidase, polygalacturonase and pectin methylesterase, were measured. Pectin-related enzyme activities highly correlated with ethylene production, but not always with pectin modifications.