Honeycrisp Fruit Maturity Report - Oct 4

Wednesday, October 4, 2023

In this week's Honeycrisp fruit maturity update the values represent the fruit that remain after the first pick. The DA values of the remaining fruit have changed very little from the previous week because the remaining fruit are less mature by nature. Honeycrisp maturity on the remaining fruit at the sites being monitored is at the early end of the range of optimum maturity for storage.

Table 1: Maturity indices for regular Honeycrisp fruit sampled in the current year on Oct 4, 2023 after various percentages of the first pick. The rate of change from last week is shown in brackets beside the current measurement and reflects the change from first pick to second pick samples. No data is available from last year at this time.

The average starch values for Honeycrisp fruit that remain after the first pick are approaching or greater than the target index of 5. ReTain treated fruit being monitored appear to have delayed starch degradation relative to the other blocks and regions being monitored (although not directly comparable). Maturity values are noticeably different between the most mature and least mature fruit on a tree, so actual values would vary depending on what percentage of the fruit was included in the first pick.

The average DA value for Honeycrisp fruit being monitored after the first pick is now higher than the target of 0.60. The mature fruit were harvested and now the remaining fruit are at an earlier stage of maturity and are approaching the target value of 0.60. 

Although the DA meter values do not differ much for ReTain treated fruit, the starch and sugar values are lower indicating that fruit are in fact at an earlier stage of maturity than what is suggested by the DA meter. Please note that use of the DA meter on fruit treated with ReTain has not been verified. Starch index is a more reliable indicator in this case of misalignment with the DA meter.

Figure 1: Ten-fruit samples across all four locations. The ground/shade colour (left) on the Oct 4 sampled fruit. The visual results of starch-iodine tests before the first pick on Sept 25 (middle) and after the first pick on Oct 4 (right). Average starch ratings are summarized in Table 1.

Important Note - This maturity report is for general industry purposes only. Growers are encouraged to use their own discretion to harvest trees that are exhibiting delayed colour development or exhibiting maturity indices that disagree with what is being reported here. Values were measured on an average of fruit that were representative of the block's crop load and tree vigour. Fruit representative of size and colour were taken from what is likely targeted for a second pick.

About each measurement:

Starch Index - Starch is converted to sugars as ripening progresses. The starch-iodine test is used because iodine binds to starch molecules turning them blue/black, whereas sugars are not stained and remain clear. The Cornell chart on a scale of 1 to 8 was used above and values are an average of ten representative samples from each block.

Soluble Solids - Approximates the percentage of sugar content of the fruit. Measured using a handheld refractometer. Values are an average of ten representative samples from each block.

DA Meter - The delta absorbance (DA) value is related to the chlorophyll content of the peel. AAFC researchers in Kentville developed a protocol for Honeycrisp. Values above 0.60 are immature, values 0.6 to 0.36 are ideal for long term storage, and values below 0.35 are best for short term storage because they are more prone to storage disorders. Values shown above are the average of twenty fruit taken throughout a block, with readings taken on the transition area between the sun and shade exposed sides. DA values will be noticeably different between the most mature and least mature fruit on a tree. 

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