Reflectance Spectroscopy to Determine Dry Matter Content in ‘Hass' Avocado Fruit, Poster Board #037

Avocado fruit maturity is usually assessed by measuring its pulp dry matter (DM) content, a destructive and time-consuming process that could only be performed on harvested fruit. An alternate non-destructive method that could be used in situ to determine avocado DM content would therefore be beneficial to producers and other stakeholders. The objective of this investigation was to assess the potential of reflectance spectroscopy to determine DM content in ‘Hass’ avocado fruit. In a first experiment, fruit from three avocado lots from the same orchard were analyzed weekly in Nayarit, Mexico. Individual intact fruit were used for spectra data acquisition by two methods: a) without changing the fruit between sampling; and b) changing the fruit. Ten spectra were obtained for each fruit in the dorsal or ventral position in the top, middle, and bottom part using an Ocean Optics USB 4000 spectrometer in the 345–1047 nm spectral region. The DM content of each fruit was also determined using the microwave method. Spectra and DM were correlated. In the second experiment, 10 trees were selected from an orchard located in Tepic county, Nayarit. Thirty fruit per tree were tagged when they were 2–3 cm in length. Harvests were performed from 5 July to 15 September 2011. At harvest, 20 fruit were analyzed with the same spectrometer as in the first experiment. Five readings were taken in the dorsal-middle part of each fruit. Also, DM content was considered and data were correlated. For the first experiment, significant differences were detected for getting the spectra without changing the fruit or changing the fruit, being the first one better. In addition, significant differences were detected for dry matter content among harvest dates, sides and positions of fruit. Furthermore, a significant (P < 0.0001) but negative correlation (R²= –0.469) was detected between reflectance and dry matter content. For the second experiment, reflectance at 820 nm was weakly correlated with DM. Results suggest that it is not possible to predict avocado maturity using reflectance spectroscopy in the spectral window used in these experiments. Reflectance spectroscopy measurements further in the near-infrared (1000–2500 nm) will be investigated to assess avocado maturity.