Organic citrus drives research into zero residue post-harvest treatments

The increasing popularity of organic citrus and demand from retailers for fewer and less chemical residues has driven research into zero residue post-harvest treatments for reducing losses and waste.

Among the leaders in the field is Citrosol, a Spanish company that has pioneered the development of coatings to protect citrus against rind damage and fruit decay, especially during cold storage and transportation.

Former CEO, now Senior Post-harvest Advisor, Dr Benito Orihuel, who addressed the 2023 Market Outlook Forum via video, said losses occurred at numerous stages in the supply chain, from the field to the packhouse, in transit, and once fruit reached the importer, retailer and consumer.

“I want to emphasise how the overall cost of correction keeps increasing,” he said in a pre-recorded video.

“And if you have to make a correction when the fruit has arrived (on) the shelves of the supermarket, when your fruit has arrived to the consumer, the cost of correction will be extremely great.”

Dr Orihuel said European retailers were increasingly placing limits on fungicide residues that were lower than accepted MRLs, and restricting the number of active ingredients allowable in samples of conventional fruit.

It was still possible to control decay under these rules, as long as the same concentration of fungicides was applied to every load of fruit that was processed, he said.

Research found loss of efficacy in drenching water was a problem in many countries, which led the company to develop the Citrosol Zero Waste System® for dosing fungicides, and Easy Kit® for testing fungicide and other chemical levels in suspension, wax and residues.

Dr Orihuel said the company also had developed a range of organic and vegan coatings for minimising rind damage and chilling injury during shipping, as well as reducing fruit weight loss and rind ageing or darkening.

They include the new Citrosol Sunseal CI-Control®, which achieved 92.3 per cent control of chilling injury compared to the original Sunseal UE plus imazalil (78.4 per cent) and was comparable to Sunseal UE plus thiabendazole at 5000ppm (96 per cent) in tests of fruit stored at 2.5 degrees Celsius for 44 days and then left at room temperature for six days.

Dr Orihuel said the biostimulants Fortisol Ca® and Fortisol Ca®PLUS were used extensively as first treatments by packers in Spain, South Africa, Peru, Turkey and elsewhere to reduce decay.

“PlantSeal® coatings are used with great success in South Africa, Peru and Chile, not only because of their chilling injury control, but also because they are excellent regarding weight loss control,” he said.

Citrosol products are available in Australia from Colin Campbell (Chemicals).