Honeycrisp Fruit Maturity Report - Sept 12

Tuesday, September 12, 2023

Similar to last year, I will give short weekly updates on indicators of Honeycrisp maturity from a few example regions. This information is meant to indicate the rate of change of ripening each week and also how this year's maturity compares to past years.

Table 1: Maturity indices for regular Honeycrisp fruit sampled in the current year on Sept 12, 2023 and compared with last year's samples from Sept 13, 2022.

The average starch values for Honeycrisp fruit measured in all regions has not reached the target of 5. Relative to last year, this year's starch values are generally lower meaning that maturity is slightly delayed because starch has not converted to sugars.

The average DA value for Honeycrisp fruit measured in all regions has not reached the target of 0.60. Relative to last year, this year's DA values are generally higher meaning that more chlorophyll is present and ripening is not as far progressed. 

Last year was a year with above-average heat so it is not surprising that maturity is not as far progressed this year. Next week's measurements will report the rate of change to show how maturity is progressing.

Figure 1: Ten-fruit samples across all four locations. The blush (left) and ground colour (middle) on the sampled fruit. Ground colour is still an immature green tone. The visual results of starch-iodine tests (right) and starch ratings are reported 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 all sides but not from the interior where maturity is expected to be delayed and is most likely targeted for a second pick timing.

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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