2018 ASHS Annual Conference
Using the Delta Absorbance™ Meter to Measure Harvest Maturity in ‘Honeycrisp’ and ‘Mcintosh’ Apples
Using the Delta Absorbance™ Meter to Measure Harvest Maturity in ‘Honeycrisp’ and ‘Mcintosh’ Apples
Thursday, August 2, 2018: 11:30 AM
Jefferson East (Washington Hilton)
Fruit maturity at harvest impacts quality and occurrence of storage disorders, but most maturity indicators are inaccurate for ‘Honeycrisp’ apples. The DA meter measures fruit peel absorbance at 670 and 720 nm and calculates the ratio as IAD units. Fruit were randomly harvested from 3-5 trees of ‘Honeycrisp’ at two harvest dates in 2015, and three in 2016, and 2017. Each harvest was replicated 3 times. ‘McIntosh’ was included in 2016. IAD was measured on two sides of each apple at harvest and ater 1.5 months cold storage at 1 °C, along with storage disorders. Starch index, SSC and flesh firmness was measured on 5-10 fruit from each IAD group (0 – 0.19, 0.20 – 0.39, 0.40 – 0.59, etc.).
IAD in ‘Honeycrisp’ decreased with advancing maturity in all 3 years. By the third harvest, IAD had decreased to zero in some apples. IAD was lower in 2016 than in 2015 and 2017. Mean IAD ranged from 0.6 to 0.8 during the 2nd harvest which corresponded with peak commercial harvest. Mean IAD of ‘McIntosh’ at peak harvest was 1.8. Within a harvest date, IAD in Honeycrisp varied substantially, as much as 1.4 IAD units, compared with ‘McIntosh’ which varied by 0.8 IAD units within a harvest date. Starch index was not related to IAD in ‘McIntosh’. Starch index in Honeycrisp was negatively related to IAD during both harvest dates in 2015, during the 1st and 2nd harvests in 2016, and during the 2nd in 2017.
Bitter pit did not occur in Honeycrisp in 2015 nor in McIntosh in 2016. Bitter pit incidence did not vary with IAD in 2016 or 2017. In 2015, soft scald was severe in fruit from the 2nd harvest, and incidence decreased with decrease in IAD. In 2016, soft scald incidence was severe in fruit from the 2nd and 3rd harvest. In fruit from the 2nd harvest, soft scald decreased with decrease in IAD, but no relationship occurred with the other 2 harvests. However, when data from all 3 harvests were pooled, soft scald incidence was negatively related to IAD consistent with the effect of maturity. In 2017, soft scald incidence was not related to IAD in fruit from the 2nd or 3rd harvest, but in fruit from the 1st harvest, it increased as IAD decreased.
IAD in ‘Honeycrisp’ decreased with advancing maturity in all 3 years. By the third harvest, IAD had decreased to zero in some apples. IAD was lower in 2016 than in 2015 and 2017. Mean IAD ranged from 0.6 to 0.8 during the 2nd harvest which corresponded with peak commercial harvest. Mean IAD of ‘McIntosh’ at peak harvest was 1.8. Within a harvest date, IAD in Honeycrisp varied substantially, as much as 1.4 IAD units, compared with ‘McIntosh’ which varied by 0.8 IAD units within a harvest date. Starch index was not related to IAD in ‘McIntosh’. Starch index in Honeycrisp was negatively related to IAD during both harvest dates in 2015, during the 1st and 2nd harvests in 2016, and during the 2nd in 2017.
Bitter pit did not occur in Honeycrisp in 2015 nor in McIntosh in 2016. Bitter pit incidence did not vary with IAD in 2016 or 2017. In 2015, soft scald was severe in fruit from the 2nd harvest, and incidence decreased with decrease in IAD. In 2016, soft scald incidence was severe in fruit from the 2nd and 3rd harvest. In fruit from the 2nd harvest, soft scald decreased with decrease in IAD, but no relationship occurred with the other 2 harvests. However, when data from all 3 harvests were pooled, soft scald incidence was negatively related to IAD consistent with the effect of maturity. In 2017, soft scald incidence was not related to IAD in fruit from the 2nd or 3rd harvest, but in fruit from the 1st harvest, it increased as IAD decreased.