Modelling the biological variance of the yellow aspect of Granny Smith apple colour

A mechanistic modelling approach to understand 1-MCP inhibition of ethylene action and quality changes during ripening of apples

BACKGROUND

1-Methylcyclopropene (1-MCP) inhibits ripening in climacteric fruit by blocking ethylene receptors, preventing ethylene from binding and eliciting its action. The objective of the current study was to use mathematical models to describe 1-MCP inhibition of apple fruit ripening, and to provide a tool for predicting ethylene production, and two important quality indicators of apple fruit, firmness and background colour.

RESULTS

A model consisting of coupled differential equations describing 1-MCP inhibition of apple ripening was developed. Data on ethylene production, expression of ethylene receptors, firmness, and background colour during ripening of untreated and 1-MCP treated apples were used to calibrate the model. An overall adjusted R² of 95% was obtained. The impact of time from harvest to treatment, and harvest maturity on 1-MCP efficacy was modelled. Different hypotheses on the partial response of 'Jonagold' apple to 1-MCP treatment were tested using the model. The model was validated using an independent dataset.

CONCLUSIONS

Low 1-MCP blocking efficacy was shown to be the most likely cause of partial response for delayed 1-MCP treatment, and 1-MCP treatment of late-picked apples. Time from harvest to treatment was a more important factor than maturity for 1-MCP efficacy in 'Jonagold' apples. © 2017 Society of Chemical Industry.

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.

Preventing the wound-induced deterioration of Yali pears by chitosan coating treatments

Yali pears (Pyrus bretschneideri Rehd.) are susceptible to mechanical damage. In this study, the protective effects of chitosan treatments on the quality of bruised pears were evaluated. The fruit were treated with 1.5% chitosan before or after bruise damage, respectively. Then, the fruit were stored at 16 °C and 85-90% relative humidity. Postharvest quality parameters were analyzed during the storage. Bruise damage accelerated the decrease of firmness and the ratio of sugar to acid, while a delay of firmness and sugar-to-acid ratio in those pears treated with chitosan before or after was found. Meanwhile, chitosan treatments both before and after damage delayed the color changes caused by damage, inhibited disease incidence increase, and enhanced the bruise recovery during the storage. Our results suggested that chitosan treatment could be used to control the physiological responses induced by bruise damage.