Honeycrisp Fruit Maturity Report - Sept 28

Tuesday, September 28, 2021

Important Note - This information 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.

Table 1: Maturity indices for Honeycrisp fruit sampled across four regions on September 28, 2021.

The average DA value for fruit measured in all regions is above 0.35, which is ideal for long term storage. DA values will be noticeably different between the most mature and least mature fruit on a tree. Over the last week, starch conversion to sugars has progressed from last week's range of 3-6 to this week's range of 6-8 (Figure 1). Measurable soluble solids are increasing. 

Figure 1: The visual results of starch-iodine tests on a five-fruit sample across all four regions. Photos were converted to black and white to emphasize the pattern of starch (black) staining. Fruit from the two sample dates are compared to show starch conversion in sampled regions over the last week. Average ratings are reported in Table 1.

The fruit treated with ReTain on an M.111 is an anecdotal report because I am not monitoring untreated trees for comparison on the same tree age, crop load and rootstock. However, the ReTain treatment has an average DA value of 0.65 this week, which is considered immature. Starch conversion is also low.

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 five representative samples from each block.

Soluble Solids - Approximates the percentage of sugar content of the fruit. Measured using a digital refractometer. Values are an average of five 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 both the red and green sides.

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