DOI: 10.5061/dryad.98sf7m0rj
title: NIR spectra of Hawaii avocados

description: Avocados are an important economic crop of Hawaii, contributing to
 approximately 3% of all avocados grown in the United States. To export
 Hawaii-grown avocados, growers must follow strict United States Department
 of Agriculture Animal and Plant Health Inspection Service (USDA-APHIS)
 regulations. Currently, only the Sharwil variety can be exported relying
 on a systems approach, which allows fruit to be exported without
 quarantine treatment; treatments that can negatively impact the quality of
 avocados. However, for the systems approach to be applied, Hawaii avocado
 growers must positively identify the avocados variety as Sharwil with
 APHIS prior to export. Currently, variety identification relies on
 physical characteristics, which can be erroneous and subjective, and has
 been disputed by growers. Once the fruit is harvested, variety
 identification is difficult. While molecular markers can be used through
 DNA extraction from the skin, the process leaves the fruit unmarketable.
 This study evaluated the feasibility of using near-infrared spectroscopy
 to non-destructively discriminate between different Hawaii-grown avocado
 varieties, such as Sharwil, Beshore, and Yamagata, Nishikawa, and
 Greengold, and to positively identify Sharwil from the other varieties
 mentioned above. The classifiers built using a bench-top system achieved
 95% total classification rates for both discriminating the varieties from
 one another and positively identifying Sharwil while the classifier built
 using a handheld spectrometer achieved 96% and 96.7% total classification
 rates for discriminating the varieties from one another and positively
 identifying Sharwil, respectively. Results from chemometric methods and
 chemical analysis suggested that water and lipid were key contributors to
 the performance of classifiers. The positive results demonstrate the
 feasibility of NIR spectroscopy for discriminating different avocado
 varieties as well as authenticating Sharwil. To develop robust and stable
 models for the growers, distributors, and regulators in Hawaii, more
 varieties and additional seasons should continue to be added.
description: <strong>Avocado samples</strong>
 931 avocados were acquired through the only packing house on the
 Island of Hawaii, Kane Plantation Avocados in Honaunau, from June 2022
 through June 2023. Avocados were kept between 4°C and 6°C until one to
 eight days before spectral measurements. The selection of avocado
 varieties was based on seasonal availability. Sharwil (n=537) avocados
 were collected in June, July, and September of 2022, as well as January
 and March of 2023. Beshore (n=52) avocados were collected between June and
 July of 2022. Yamagata (n=32) avocados were collected in June and July of
 2022. Nishikawa (n=97) avocados were collected in March 2023 and Greengold
 (n=129) avocados were collected in February and March of 2023. Two other
 non-commercial varieties were also collected in January and March 2023;
 one is colloquially known as Cannon ball (n=43) for its shape and size and
 the other is an unnamed seedling of Sharwil (n=41). The
 spectra data was collected and processed using the below
 methods: A high-power tungsten
 halogen light source (Ocean Insight, Orlando, FL, USA) and a bench-top NIR
 spectrometer (NIRQuest+2.5, Ocean Insight, Orlando, FL, USA) with an
 InGaAs detector were used to measure adsorption of incident light on
 avocado samples at wavelengths from 900 to 2500 nm. Optical fibers were
 used to couple the light source, sample holder, and spectrometer. After
 ripening in room temperature for three days, 115 Sharwil, 52 Beshore, and
 32 Yamagata from 2022 were measured at three random locations along the
 equatorial region using a desktop application (Ocean View 2.0, Ocean
 Insight, Orlando, FL, USA) with 50 ms integration time and a Boxcar width
 of 3 (i.e. 7-point averaging). Each fruit was measured at three random
 locations along the equatorial region. Average spectrum per fruit was
 calculated between 1000 and 2400 nm, truncating the shortest and the
 longest 100 nm due to sensor limitations. Standard Normal Variate (SNV)
 preprocess was applied to the raw spectra to remove additive effects and
 multiplicative scatter. 
 Subsequent experiments were carried out using a handheld NIR
 spectrometer (F-750, Felix Instruments, Camas, WA, USA) measuring 2nd
 derivative spectra between 729 nm and 975 nm. Spectra of additional 422
 Sharwil, 129 Greengold, 97 Nishikawa, 43 Cannon ball, and 41 unnamed
 Sharwil seedling from 2023 were collected at three random locations along
 the equatorial region after ripening in room temperature for one, three,
 six, seven, and/or eight days. Average spectrum per fruit was calculated
 and no additional spectral preprocessing was applied.
description: # NIR spectra of Hawaii avocados
 [https://doi.org/10.5061/dryad.98sf7m0rj](https://doi.org/10.5061/dryad.98sf7m0rj) The dataset contains two XLSX files; **OO_All199_ave_SNV** is spectra of three varieties of Hawaii avocado in 2022, collected using a bench-top near-infrared spectrometer, **Felix_2nd_ave** is spectra of five varieties of Hawaii avocado in 2023, collected using a handheld near-infrared spectrometer. ## Description of the data and file structure **OO_All199_ave_SNV** This is the common wide format for spectral data, showing absorbance at each wavelength for each sample * *Variety* Avocado varieties: Beshore, Sharwil, or Yamagata * *Sample ID* Internal reference ID for each fruit * *1000.087 - 2400.404* (Column C to Column QE) wavelengths in nm **Felix_2nd_ave** This is also in the common wide format for spectral data, showing absorbance at each wavelength for each sample * *Harvest Date* Date each avocado was harvested * *NIR Date* Date each avocado was measured using the handheld near-infrared spectrometer * *Variety* Avocado varieties * *SW* Sharwil * *GG* Greengold * *N* Nishikawa * *CB* non-commercial variety, colloquially known as Cannon ball * *SS* non-commercial variety, unnamed seedling of Sharwil * *Days in Room Temp* Days since the fruits were removed from a cold room to ripen in room temperature * *Sample ID* Internal reference ID for each fruit * *W729nm - W975nm* (Column F to Column CJ) wavelengths in nm ## Software The files can be opened and analyzed using any common statistical software.