Stellenbosch University: Avatar against food waste in the citrus industry

Researchers at Empa’s Biomimetical Membranes and Textiles laboratory in Switzerland, with the help of horticulturalists from Stellenbosch University in South Africa, have developed a so-called “digital twin” for citrus fruit. The virtual simulation provides a virtual, real-time picture of the temperature and other conditions that export fruit experience from being harvested to eventually reaching overseas markets. Based on the information it provides, changes can be made in storage and cooling conditions where needed, to prevent unnecessary damage to the fruit and unnecessary food waste.

Their research was published in the journal Nature Food.

On the way from the place of production to the consumer’s plate, about one third of all food worldwide spoils. One reason is unfavourable storage conditions along production and supply chains, including suboptimal storage at home.

The Empa team led by Dr Chandrima Shrivastava and Dr Thijs Defraeye has been working for some time on digital solutions that could reduce this food waste.

Prof Paul Cronje and Dr Tarl Berry, two researchers who have been seconded by Citrus Research International to the Department of Horticultural Science at Stellenbosch University, were part of this international project. They believe the project, once completed, will also add value to South Africa’s citrus export industry.

Further developments are still needed before the technology can be applied, but the goal is clear: Along their production and supply chains, companies should be able to integrate the virtual fruits into their processes in order to optimize storage conditions in reality and reduce food losses.

“South Africa’s citrus industry is challenged each year to harvest 2,4 million tons of fresh citrus fruit, to pack it, send it to nearby harbours and to ship it to the northern hemisphere before there are quality losses in the approximately 161 million boxes being shipped. It is an industry of great scale and complexity, and is market driven. It needs as much sophisticated technological support as possible to remain sustainable,” says Dr Berry.

Optimal conditions in the cold chain

“A ‘digital twin’ is basically a virtual, computer driven simulation or representation that covers the life cycle of something like a fruit. Information and data are gathered from the physical world on aspects that might play a role in how the fruit physically responds to what is happening to it, and the conditions it is experiencing,” Prof Cronje explains.

“Such information is ideally gathered using sensors that are placed within the vicinity of the fruit. It is then used to develop models and simulations that can be used to make decisions on, for instance, how to prevent damage to the fruit.

“In the case of citrus fruit, for example, a person in charge of a cold chain will be able to respond to feedback from the digital twin, and make changes to storage conditions before cold damage and spoilage set in that reduce the quality and marketability of the fruit.”

The research team’s “digital twin” for the citrus industry was developed by using digital information that is in any case being gathered during the export process, but has so far been underutilised.

Every container in the world is now equipped with one or more temperature sensors,” explains Empa’s Dr Defraeye. Until now, however, the diverse information hidden in these measurement data has not yet been exploited

“Thanks to the information that such sensors gather, we were able to track the temperature history of 47 containers of citrus fruit being exported from South Africa throughout the cold chain,” Prof Cronje adds.

By mathematically evaluating the physical processes, the team was able to use the data sets to track crucial properties of the fruit over time, thereby revealing and even predicting quality losses and marketing problems.

Computer simulations were developed that defined the probability of possible damage, such as the fruit drying out or developing decay.

A wide range of cold chain simulations of corresponding quality losses were developed.

“In our study, half of all shipments were outside the optimal conditions for transport,” Dr Defraeye says. The consequences: decay, fly infestation, cold damage and spoiled goods. At the end of their 30-day journey, some of the remaining citrus fruits had a shelf life of only a few days.

Optimum conditions

Ensuring long-term quality is not simply a matter of refrigerating food. Rather, precise adjustments are needed to ensure a compromise in the transport conditions, for instance in terms of temperature and the length of time in the cold chain.

For instance: at lower temperatures, the larvae of fruit flies in the fruit are killed. On the other hand, the fruit can be damaged by the cold, which may make it unsalable.

Using digital twins, the team has now been able to determine optimal conditions in which relevant quality related risks such as fly infestation, visual defects and cold damage are weighed against each other.​