Chemical-reducing innovations for food preservation & processing

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Electrolysed water and free radicals are just some of the latest chemical-reducing alternatives currently being developed to help improve the life span of fruit and vegetables, as well as reduce the risk of contamination during food processing and packaging.

The subject of a dedicated Agri-TechE online event to be staged later this month, the latest developments in food hygiene and packaging continue to evolve rapidly, with new innovations promising substantial savings to the food industry, as well as improved sustainability, by reducing the need for chemicals and water for cleaning and decontamination.

The use of water and chemicals for cleaning and decontamination is a major cost to the food industry at every stage from seed to sandwich; it is also an environmental cost,” explains Dr Belinda Clarke, director of Agri-TechE, an independent membership organisation that brings together farmers and growers with scientists, innovators and entrepreneurs to create a global innovation hub for agtech. “Within our innovation ecosystem we can see interesting alternatives emerging that work with natural processes to reduce the power of pathogens, offering a more effective and sustainable approach.”

Fruitful enterprise

Some of those ‘interesting alternatives’ are being championed by Dr Debbie Rees, principal scientist at the Natural Resources Institute (NRI), a specialist research, development and education organisation of the University of Greenwich, UK, with a focus on food, agriculture, environment, and sustainable livelihoods.

Rees will reveal how the NRI is currently exploring ways to retain quality and reduce losses during both short-term handling and long-term storage of fresh food at the upcoming Agri-TechE conference. Working on a wide range of both temperate and tropical crops, Rees and her team nurture technologies for application after harvesting, including new approaches to packaging, storage during sea and road freight, and long-term static storage.

We are interested in anything that allows us to monitor and sustain the lifespan of fresh produce without harming it,” explains Rees. “Loss can be caused by biological changes in the produce itself, and these can be measured – for example, by measuring changes in the respiration rate of potatoes in storage or due to the stress created when apples stored at low temperature become short of oxygen. Chlorophyll fluorescence is another useful measure that can be used to monitor fruit ripening or senescence of vegetables. In both cases produce loses chlorophyll and the ability to photosynthesise as they age.”

Current projects include in-field cooling to extend storage life of soft fruit such as strawberries and raspberries, following research that revealed that there may be a delay of several hours between strawberry harvest and packing, hence the value of in-field cooling as a possible means to slow rates of deterioration.

When we followed what happens during the strawberry harvest, we saw that strawberries can often remain at ambient temperature after they’ve been picked for up to four hours before reaching the packhouse,” explains Rees. “So, we’re exploring with our partners whether, if you cool quickly in the field, that can extend storage life.”

Freshly picked strawberries awaiting packing

Freshly picked strawberries awaiting packing

Ozone ‘dry’ rather than chlorine wash

Another focus is on the use of ozone to combat pathogens and reduce rot in soft fruits and vegetables. For example, although unripe strawberries have a host of defence mechanisms to prevent fungal pathogens, as the fruit ripens, it loses defence systems, softens and sugar levels increase, increasing the risk of pathogen attack.

Currently, much fresh produce is washed with chlorinated or ozonated water to sanitise it, however Rees notes that if produce is wetted for many produce types, this only serves to increase the risk of rotting pathogens. “The extent of the problem varies by produce type,” she notes. “Strawberries are particularly sensitive to this issue.”

In response, Rees has worked with Ozone Industries Ltd to develop a method that involves flushing punnets of strawberries with gaseous ozone before sealing in film, to slow the rotting process.

Experimental system for testing and optimising the ozone treatments to extend strawberry shelf-life

Experimental system for testing and optimising the ozone treatments to extend strawberry shelf-life

Major benefits of ozone (also called ionised air, or plasma) as a disinfectant are that it is essentially ‘dry’, cheap to produce and residue-free, leaving nothing but fresh air behind. Ozone can also be easily generated in situ, avoiding the use of conventional liquid chemical storage, transportation and disposal.

Gaseous ozone has the advantage that it is not necessary to wet produce,” she explains. “Ozone (O3) is extremely reactive and will therefore damage or kill bacteria and algae and viruses. The highly reactive nature of the chemical means not only that it will kill/damage the pathogens, but it will also breakdown rapidly, leaving no residues.”

As part of an Innovate UK project led by Ozone Industries Ltd, the NRI is currently testing the use of gaseous ozone in a proof-of-concept project to develop the flushing process for industrial use. The project has been running since July 2020, with the aim to commercialise the technology by the end of March 2021.

As the strawberries go through the packing line, and are wrapped in film, the kit will flush the pack with ozone, before sealing with the film,” explains Rees.

Ozone can be used by the fresh produce industry in many ways. Various scenarios tested so far include the use of low levels of ozone in stores (typically less than 250 parts per billion), the flushing of retail packs with higher levels of ozone (typically greater than 100 parts per million); and the use of high levels in a bid to decontaminate human pathogens (E. coli, listeria, etc). “The key issue is to gauge the right ozone treatment,” urges Rees. “High enough to decontaminate, but low enough so as not to damage the produce itself.”

With regard to its impact on human contaminants, such as E.coli, Rees is upbeat: “We were comparing against no wash, and against chlorine wash, and found that ozone decontamination against the E.coli was as effective as traditional chlorine wash – it managed to take the numbers of E.coli surviving on the strawberry down to less than 1% of what they had been,” she says. “We found that it works equally effectively as chlorinated water, but of course wetting with chlorinated water has the considerable downside of encouraging fungal attack by any fungi that do remain.”

Further feasibility studies are needed to understand the practicality of introducing the necessary kit and processes to fruit packing lines, while also addressing any potential health and safety concerns, but Rees says initial results are encouraging: “We were slowed down by the pandemic, so we only made it to testing at the end of the strawberry season. But we already have some early, but very promising, results.

The team now plans to look at other commodities, with grapes next in line. “Not all fruits and vegetables are compatible with ozone – it’s to do with surface properties, such as the thickness of the protective surface tissues, so leafy vegetables are more sensitive than waxy fruits.

Cold water cleaning

David Goosey of Ozo Innovations, another speaker at the Agri-TechE event, is focused on the food-to-go market – ready meals and pre-packed sandwiches – where processing equipment needs cleaning and decontamination from allergens such as nuts, as operators switch between recipes.

“Hygiene accounts for up to 12% of the cost of food processing,” asserts Goosey. “Typically, food manufacturers use hot water at 40-60°C to sanitise equipment and then need to re-chill the environment before use. Our solution uses cold water and is effective at an ambient temperature, meaning Ozo can help to cut both energy usage and costs.”

The company’s ‘eloclear’ technology uses hypochlorite, created by electrolysing a saline solution, as an effective combined cleaner and disinfectant that reverts back to salt and water after use. The technology is widely used for wastewater and ballast water treatment in shipping, and now Ozo is introducing it to the food processing sector.

Fast Cleandown – [Image source iStock]

“We have designed scalable systems for in-situ delivery at the customer site – ‘elocube’, which delivers up to 200 litres per day; and ‘elosystem’, which delivers up to 150,000 litres per day,” he continues. “These systems electrolyse the salt and cold water solution to produce a cleaner and disinfectant solution, which we call ‘eloclear’.”

Goosey argues the food industry stands to benefit from significant energy savings, as eloclear is effective at an ambient temperature, reducing the requirement to heat water to 40-60°C and removing the need to re-chill environments after cleaning. There is also less water consumption, as the technology reduces the traditional five-step night-time cleaning process to just two steps, requiring only one rinse step, using up to 75% less water. The simplified cleaning process also allows operators to achieve up to a 35% time saving, as  well as increased operational efficiency due to availability of equipment.

A recent case study from a sausage factory showed eloclear cut the time taken for night-time cleaning from 59 to 13 minutes – a 77% time saving; while the factory also reduced its water use, from 542 litres of hot water, to just 163 litres of ambient eloclear and water – a 69.9% saving. The factory also achieved additional energy savings as it no longer had to heat the water to up to 60°C.

Considering that in the UK alone, the food industry currently accounts for 14% of energy consumption by business, as well as 10% of all industrial use of public water, Goosey believes eloclear is a major breakthrough. “Through calculations based on trial data, Ozo’s technology has been shown to help reduce carbon consumption within the food hygiene process by up to 80%,” he notes.

However, he understands it could take time for the industry to embrace such a radical new approach: “We need willingness to change chemistries at an operator level,” he says. “There’s also resistance to recognise that cooler temperatures can provide effective cleaning, while cold cleaning also requires more agitation from operators. The industry rightly takes its responsibilities to consumers seriously.”

Ozo continues to work with a range of companies, including multi-national food groups and UK-based food companies “large and small”, to further validate its technology and prove its potential benefits.

 ‘Agri-Tech Explore: Keeping it clean with agri-tech innovation’, is being held virtually on Tuesday 19th January 2021, from 14:00-16:00. Register here:

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