Optimum harvest maturity determination for African Delight plums planted in different production areas

2012

• The highest scald occurred in fruit from Harvest 1, followed by Harvest 2, with the lowest scald occurring on Harvest 3 fruit.
• Due to area differences, TSS, flesh firmness and malic acid (MA) were not accurate indicators of optimum maturity in terms of scald development. TSS : MA : firmness ratios can possibly be used to determine optimum harvest maturity.
• After cold storage, the lowest scald occurred in fruit stored for 35 days and it increased the longer the cold storage.
• After shelf life, higher scald occurred in fruit stored for 35 days than in fruit stored for longer periods, possibly due to poorer skin colour.
• Shortening the cold storage of African Delight will therefore not solely solve the problem of scald

2013

• Scald occurred at higher levels on fruit from Robertson and Franschhoek productions areas and decreased with increased maturity. Ceres fruit exhibited lower levels of scald across maturities.
• Due to area differences, individual TSS, flesh firmness and malic acid measurements were not accurate indicators of optimum harvest maturity, and hence, could not be used as tools to reduce scald incidence and improve eating quality.
• It is possible that a TSS : MA : firmness indicator calculation could be used in conjunction with these individual indicators to determine the optimum harvest maturity.
• An indicator calculation for TSS : MA : flesh firmness in the order of 2.0 was re-confirmed as optimal. This calculation should be used in combination with the existing minimum harvest indicators to determine the correct harvest maturity.

2014

• Yet again, using TSS, flesh firmness and malic acid as sole measurements were not sufficient indicators of optimum harvest maturity, and could not be used solely as tools to reduce scald incidence and improve post-storage quality of African Delight plums.
• Generally, scald could be reduced across all three the areas included in the study could be reduced by harvesting the fruit at a slightly more advanced maturity, particularly on fruit from Robertson, which exhibited higher levels of scald than Franschhoek and Simondium.
• TSS : MA : firmness ratio calculation in the order of >2.0 was re-confirmed as an optimal indicator to be used along with other maturity parameters such as TSS at ≥ 15%, a flesh firmness of ≤ 9kg and a TSS : MA ratio of > 16.