A fresh approach to extending the shelf life of broccoli
Tasmanian Institute of Agriculture PhD student Nha Huynh is investigating ways to maintain the quality of fresh fruit and vegetables after being transported long distances and while on display at the retailer, with the aim to reduce food waste.
The issue of consumer waste in Australia has been well-documented in recent years through series such as War on Waste (aired on the ABC), which highlighted the staggering volume of fresh food and other items that consumers dispose of each year.
Foodwise reports that up to 40 per cent of items that end in the bin are food, with the average Australian household disposing over a thousand dollars’ worth each year.
With these figures in mind, Tasmanian Institute of Agriculture PhD candidate Ky Nha (Nha) Huynh is currently investigating postharvest shelf life extension of fresh produce using innovative packaging technologies, and broccoli is an example of fresh produce that has commercial shelf-life issues.
Broccoli suffers accelerated senescence, or deterioration with age after harvest, as its green florets are immature and in a rapid growing state at the time of picking.
The shelf life of broccoli can be 3-4 weeks at zero degrees Celsius, but low consistent temperature is hard to maintain across the supply chain.
Quality loss occurs quickly at elevated temperature (as short as 2-3 days at 20 degrees Celsius), and is mainly characterised by wilting, yellowing and the formation of off-odours.
“Consequently, keeping broccoli cold has become a must, and the industrial practice has been topping broccoli with crushed ice in polystyrene boxes or crates for transportation,” Nha said.
The ice adds extra handling costs and can damage the floret buds, which subsequently leads to rots and the formation of off-odours. Nha’s research aims to find alternatives for top-icing and reduce the dependence on low temperatures without compromising broccoli quality.
Nha is one of 10 PhD students who are undertaking their studies at the Australian Research Council (ARC) Training Centre for Innovative Horticultural Products.
“I decided to work on this topic after consulting with experts in the field about the major concerns of producers and retailers. Broccoli is expanding in growing area and is among the vegetables that have the highest production and market value in Australia,” Nha said.
As part of her project, Nha has been trialling modified atmosphere packaging (MAP) options. Modified atmosphere is the practice of changing gas ratios within packages to improve shelf-life. These gases include oxygen, carbon dioxide and nitrogen.
“One of the main reasons for storing broccoli at low temperatures is to reduce its respiration rate; and removing ice from broccoli shipping would mean the temperature would not be as low as zero degrees Celsius,” she explained.
The use of MAP options was suggested to provide similar effects to top-icing by lowering oxygen levels and increasing carbon dioxide concentrations.
So far, Nha has found that the chlorophyll and carotenoid contents (related to colour) and marketable weights of broccoli could be retained by using suitable MAP products, even at elevated temperatures (10 days at 10 degrees Celsius as in one trial).
“Two major limitations with using MAP are the browning at stalk ends, and improper packaging choices can lead to the development of off-odours while the broccoli still looks good,” she said.
“To address these problems, I tested different MAP options to identify the most suitable ones and I am trialling anti-browning solutions that can be combined with MAP.”
Nha’s next step in her research is to up-scale to simulate bulk broccoli shipment and verify the shelf-life improvements against current practice.
Her ultimate aim is to provide solutions for improving fresh produce shelf life and reducing food waste, and she believes that MAP options could also apply to other fruits and vegetables with similar issues to broccoli.
“I think my findings would provide scientific evidence for vegetable growers and the wider industry to consider changing the current practice. Particularly for broccoli, iceless shipment would allow more room for export as well as reduce plastic (polystyrene) and food waste,” Nha says.
“In order to apply the new technologies, however, further analyses on cost-benefits and perhaps more trials on different shipping scenarios are still required.”
There has been further research conducted on broccoli storage (pre-and post-farmgate), including Identify process improvements for preserving peak freshness of broccoli and Process improvements for preserving peak freshness in broccoli (2), undertaken by Dr Jenny Ekman from Applied Horticultural Research. Other similar projects can be found by typing ‘broccoli’ into the InfoVeg database.