A Quality Meter for Researchers using Near Infrared Spectroscopy

The primary focus in crop research has been prediction and management of fruit quality parameters. Moreover, the concept of fruit quality at maturity as a predictor of later post-storage quality is being increasingly exploited in breeding programs to develop varieties that can successfully meet consumer demands. Scientists are increasingly turning to portable visual NIR spectroscopies in such studies, instead of conventional techniques.

Quality Parameters

Dry matter (DM), total solids content (SSC), acidity, and firmness are quality parameters that are widely used for testing maturity, ripening, fruit grading and sorting, and warehouse logistics. It has been successfully used for cereals, proteins, fruits, and vegetables in open fields and greenhouses.

Dry matter is the total of all solids in a fruit minus its water content. It is recently gaining acceptance as a reliable and objective maturity and quality parameter.

• DM, SSC, and acidity are quickly replacing other more subjective parameters like color to measure the quality of fruit.
• Another attractive feature of using DM, SSC, and acidity is that their measurement doesn’t have to be destructive. Conventional methods use the destructive oven or microwave oven method, gas chromatography refractometers, or titration. On the other hand, portable devices based on near infrared spectroscopy that make non-destructive measurements of these parameters are also available.

NIR Spectroscopy

Visual Near Infrared (NIR) spectroscopy, as its name indicates, is based on the use of the near infrared spectra of light. This spectrum is best suited for the qualitative analysis of organic compounds that plants and animals are made of. The absorbance, transmission, or reflectance of the wavelengths can help in identifying the compound, as well as the quantities in which they are present. These attributes of NIR spectroscopy are used in quality analysis.

Spectroscopy is a complex technique that was long restricted to massive and expensive equipment. It was, therefore, used only in laboratories of large organizations, and most researchers could not benefit from the precision that this technique offers.

However, recent developments have miniaturized the technology, and NIR spectroscopy is now available in small, handheld, portable devices that can be carried to fields and orchards and are easy on the pocket too. Though farmers and growers are the target market for this device, the scientific community has been regularly using portable NIR spectroscopy in research since the inception of the technology.

Advantages of Portable Quality Meters

There are many reasons for using portable NIR spectrometers in research, although these reasons may not be easy to see. We will trace the progression of this technology by considering the case of the F-750, as an example.

The F-750 Produce Quality Meter was designed by the US-based firm Felix Instruments Applied Food Science, in partnership with the Central Queensland University of Australia. Within a decade, this device was being used globally by growers and researchers alike.

Researchers at most of the largest fruit and vegetable breeding companies have used the F-750 Produce Quality Meter for tomato, pepper, strawberry, peach, mango, apple, and kiwi breeding applications, among others.

F-750 has been most commonly used for measuring dry matter, water content, soluble solids/Brix, acid/sugar ratio, pH, and internal color. Though any trait that affects the VIS/NIR light path will work, including proprietary scales such as user preference.

Advantages of F-750 NIR Spectrometer

The following are the primary benefits that the F-750 Quality Meters offer breeders:

• F-750 data can be collected quickly, within a matter of a few seconds per sample, versus laboratory analysis, such as the oven method, which may take hours or days. This allows sampling of several plants or fruits in a single day and under similar environmental conditions.
• F-750 combines data collection and biochemical analysis in one step. The fruits or grains to be tested have to be collected, parcelled separately, and carefully labeled before being transported to the laboratory where analyses are then carried out. By analyzing the parameters on the spot, F-750 avoids these steps. This also makes the whole process more convenient. 
  Moreover, it avoids any change in value (however minute) due to a delay in analyses of fruits, between collection and analysis, making the research data more accurate.
• F-750 data can be collected from the same specimen over a period of time since it is non-destructive.
  • This feature is an advantage in research that involves time-series measurements in the growth and development of fruits or grains.
  • Also, outliers (unexpected results) can be re-measured and re-examined to confirm results.
• F-750 makes frequent measurements possible even in new breeds. In the early stages, these breeds usually have only young plants that bear few fruits. This makes analysis by destructive methods challenging since they require several fruits. Destructive sampling of fruits can restrict the number of measurements in a season or in the lifecycle of a crop.
• F-750 results are more consistent and accurate across multiple locations and give standard results; whereas, destructive analysis relies on the procedures and capabilities of each laboratory, and there could be a difference in the quality of chemicals used.
• F-750 data is completely “open.” Researchers have access to the raw spectral data and may use the included software to build calibration models or use other tools to analyze spectra and create calibration models.
• F-750 readings can be integrated into Fruit Maps. Felix Instruments, in cooperation with the Central Queensland University, created Fruit Maps, the first fruit maturity app, in 2019. For their research, scientists can now use spatial data uploaded by farmers. Also, they can add data that can be immediately used by anyone. This facilitates the free exchange of information globally, and between research and practice.

The F-750 has proven to be so reliable that it is regularly used in many private breeding companies. For example, Hazera, a global seed producer managed by a French farmers’ cooperative and a part of the international company Limagrain, was one of the first users of the F-750 Produce Quality Meter. Hazera has been using the product successfully for more than six years in their breeding programs.

 
Fig. 1. “ Spectra were collected at each of three temperatures (10 °C, 20 °C, and 30 °C) for each cherry (of 225 ‘Lapins’ sweet cherries); therefore, the figure represents 675 spectra overlaid over each other. The spectra were collected in the interactance mode using a Felix F750 spectrometer.” Toivonen et al., 2017, Image credits: Can. J. Plant Sci. 97: 1030–1035 (2017) dx.doi.org/10.1139/cjps-2017-0013

NIR Spectroscopy Use in Research Programs

NIR spectroscopy based analyses are useful in a wide range of research topics, particularly in plant breeding programs:

• To screen fruit and vegetable varieties with targeted quality parameters, especially since the quality at harvest is the most reliable predictor of post-storage quality in several cases. 
  For example, the F-750 was used to build a model for DM estimation using “Lapins” sweet cherries by the Summerland Research and Development Center in Canada. The model developed could successfully predict the internal fruit quality of three other cultivars: Staccato™, Sentennial™, and Sovereign™. Based on these results, the model was recommended as screen tests for breeding programs for sweet cherries in general; see Figure 1.
• Dry matter is sensitive to variety, agricultural practices, seasons, soil, climate, topography, and aspect. Thus, scientists can use dry matter measurements to track and analyze the efficacy of new treatments and the effect of environments on the production of the crop.
  For example, the F-750 was used to detect the difference in the quality of Barlett pears due to seasons and different temperatures from the same farms in Sacramento County, California.
  Another experiment tested the effects of environments on clonal apples in New Zealand by measuring phenotypic expressions of dry matter content, fruit maturation timing, and firmness.

Precision Tools For Research

A recent addition to the analytic toolbox for scientists, NIR spectroscopy based portable tools are already a mainstay in several research programs. The coming years will definitely see an expansion in their applications. NIR spectroscopy is useful not only for plant research, but also to study the quality and chemical composition of animal products like beef, pork, poultry, milk, and cheese. NIR spectroscopy is a powerful means of analysis that science is just beginning to exploit fully.

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Vijayalaxmi Kinhal
Science Writer, CID Bio-Science
Ph.D. Ecology and Environmental Science, B.Sc Agriculture

Sources

Toivonen, P., Batista, A., & Lannard, B. (2017). Development of a predictive model for ‘Lapins’ sweet cherry dry matter content using a visible/near infrared spectrometer and its potential application to other cultivars. Canadian Journal of Plant Science. doi: 10.1139/cjps-2017-0013

Chagné, D., Dayatilake, D., Diack, R., Oliver, M., Ireland, H., Watson, A., … Tustin, S. (2014). Genetic and environmental control of fruit maturation, dry matter and firmness in apple (Malus × domestica Borkh.). Horticulture Research, 1(1). doi: 10.1038/hortres.2014.46

Bed Khatiwada, B., Escribano, S., Biasi, B., Elkins, R., Slaughter, D., & Mitcham, B. (2016). Nondestructive Prediction of Quality for ‘Bartlett’ Pears. Retrieved from

http://www.calpear.com/_pdf/research-reports/2016/Postharvest/Nondestructive%20prediction%20of%20quality%20for%20Bartlett%20pears.pdf

NAPB Annual Meeting 2018 | Plant Agriculture. (n.d.). Retrieved from https://www.plant.uoguelph.ca/napb2018