2019 ASHS Annual Conference

Mango fruit must be harvested at the right maturity stage to ensure good flavor and quality when ripe. Lately, a portable nondestructive device that uses near infrared spectroscopy to estimate fruit maturity is available. ‘Ataúlfo’ mango has a light-green skin at harvest, turning yellow-orange when ready to eat. The objectives of this assay were to validate a portable spectrometer on determining optimum harvesting stage of ‘Ataúlfo’ fruit using dry matter (DM) and skin color as reference values. To build the model, samples were collected on May 9, 2018, from an orchard located in Nayarit State, Mexico. Two hundred fruit were harvested at different ripening stages: 1. Unripe; 2. Green Mature 1 (GM1); 3. Green Mature 2 (GM2); 4. Green Mature 3 (GM3); and 5. Fully mature. Fruit were scanned with the F-750 (Felix Instrument Inc.) at three temperatures (15, 25, and 35 °C). Skin color (‘a’ value) was also measured at the three temperatures with a Minolta 400 Chroma meter. DM was attained in a conventional oven by drying samples for 72 h at 60 °C. We did two validations from a commercial packinghouse with six different lots of 35 fruit each on May 31 and June 18, 2018. In addition, during June 2018, we did a third validation comparing the F-750 versus the Heat Units Accumulation (HUA) technique with ‘Ataúlfo’ fruit harvested at 1,600 HU in Nayarit and Sinaloa States. The best model linearity was obtained on skin color ‘a’ (R² = 0.98) whereas for DM the R² was only 0.70. For the first validation, the best predicted value was skin color ‘a’ with an R² = 0.9144, followed by DM with an R² = 0.7056. On the second validation run, the adjusted predicted value for skin color ‘a’ had an R² = 0.8798, while DM had an R² = 0.4445. When comparing F-750 versus HUA in Nayarit, ‘Ataúlfo’ skin color ranged from -14.26 (dark green) to -6.61 (light green) while the skin color average difference between the F-750 vs the Minolta colorimeter was only -0.04. Alternatively, for ‘Ataúlfo’ harvested in Sinaloa, skin color ranged from -12.67 to -5.68. In this case, the skin color average difference between the F-750 vs the Minolta colorimeter was only -0.06, but the correlation was higher (R² = 0.90). In conclusion, using skin color with the F-750 may be a good nondestructive technique to determine the optimum harvesting stage on ‘Ataúlfo’ mango.