NIR - Fruit Ripeness

Equipment for testing the ripeness of fruit today is expensive or creates waste. New technology developed by ams OSRAM promises a high-performance, portable alternative at an affordable price.

One of the toughest problems in agriculture is timing the harvesting of fruit to ensure that it reaches the supermarket ripe after shipment across oceans and continents.

Today, growers test ripeness with specialist test instruments which are bulky, heavy, and often cost thousands of dollars. The market is crying out for a smaller, cheaper solution which is affordable by small as well as large growers, and which can be used easily in the field or orchard.

Now ams OSRAM has developed a demonstration system which uses Near Infrared (NIR) spectroscopy to measure the sugar and dry matter content of fruit and other crops. Based on the company’s world-class sensor and LED technology, the ams OSRAM solution could be the basis for test instruments which could cost less than $100 and are portable enough to be deployed anywhere. 


Fruit ripeness testing today: expensive and destructive

The problem for growers of fruit crops - let´s use kiwis and avocados as examples - is the distance over which fruits are shipped before reaching the consumer. The grower has to harvest the crop when it is just immature enough that the journey will give it sufficient time to ripen before it reaches the supermarket shelf.

To measure ripeness, farmers monitor the growing fruits’ sugar content, in degrees BRIX, and its dry matter content, or DMC. The technology most commonly used today for measuring BRIX and DMC at orchards and in fruit distribution centers is either expensive or wasteful. Many growers use a low-cost refractometer. To use this device, fruits are cut open and the juice measured. The item is then discarded, and cannot be sold.

NIR spectroscopy is an alternative method which eliminates this waste. In an NIR spectrometer, a broadband NIR emitter illuminates the surface of the fruit. Every object— in our case today a kiwi, avocado or tomato-reflects or absorbs the wavelength spectrum in different ways, creating a unique optical signature captured by a spectrometer and analysed in application-specific software.
Unlike the use of a refractometer, NIR spectroscopy leaves the fruit undamaged. But today, the products used for spectroscopy are portable or lab-grade spectrometers which typically cost from $1,000. This means that today, BRIX and DMC measurement instruments are deployed in low numbers even at large orchards and facilities, and not at all at many small or medium-sized family farms. So most fruit is not tested and the fruit that is tested never reaches the consumer.

Because fruits are tested in such limited numbers, the supply chain operates on imperfect information about fruit maturity. This reduces the aggregate value of the fruit, and also raises sustainability concerns, as some fruit ripens before reaching the retailer and is usually destroyed.


Chip-scale spectral sensing breakthrough

Now ams OSRAM has developed a demonstration design for a superior NIR spectrometer for fruit testing. This development drew on many years of collaboration in the field of spectroscopy between the former OSRAM Opto Semiconductors and the ams optical sensors business unit. The new design replaces the legacy technology inside conventional spectrometers with advanced optical semiconductors: the Oslon P1616 SFH4737, a broadband NIR emitter, and a 64-channel NIR spectrometer IC which measures just 6.6mm x 6.0mm x 2.2mm. This means that the ams OSRAM system is small, light and portable, and the cost of a commercial fruit tester product can reach prices every day users can afford.

The ams OSRAM prototype of a fruit ripeness testing machine


This innovative design offers a dramatic cost reduction, while maintaining performance at a level comparable to that of trusted NIR spectrometers on the market today. Accurate NIR spectroscopy requires a broadband NIR emitter and a sensor which precisely distinguishes different wavelengths of NIR light. The Oslon P1616 SFH 4737 emitter has a wide wavelength range of 650-1050 nm, with a flat power distribution free of distorting peaks or troughs. At just 1.6mm x 1.6mm x 0.9mm, it is the world’s smallest NIRED for spectroscopy applications, and also the ideal partner to the spectral sensor, which provides high sensitivity and selectivity across the 750-1050 nm wavelength range.

The sensor’s spectral measurements are post-processed by dedicated chemical analysis models to produce values for BRIX and DMC. The graphs below show that the ams OSRAM demonstration system produces measurement results comparable to those of a reference instrument costing thousands of dollars.  

Measurements from a test instrument in use by growers today (top) and from the ams OSRAM demonstration design (bottom), showing that the ams OSRAM system achieves comparable accuracy


Real-time ripeness tracking

The low-cost, high-performance ams OSRAM system paves the way to a new future in which growers, distributors and retailers can perform ripeness testing at every stage of the supply chain. One day, an NIR spectrometer built into smartphones could even enable consumers to gauge the ripeness and nutrient content of produce on the shelf before selecting it.

The ams OSRAM vision is that spectral testing of fruit maturity could become so cheap that multiple testers could be mounted in orchards as densely as one per 1000m2, providing real-time ripeness data for crops which are in a single orchard, but exposed to varying levels of sunshine, moisture and air temperature.

The wider deployment of accurate maturity testing will also enable growers and shippers to fine-tune the harvesting and shipment of fruit, so that more produce arrives on the supermarket shelf in optimal condition, dramatically reducing food waste while increasing the value of fruit to growers and marketers.

> More information on Near Infrared Emitter Technology

> More information on Spectral Sensing Technology