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COOL BANANAS!

As part of a new 30,000m² plus distribution centre, a major retailer has added the latest banana-ripening technology direct from the USA. Sean McGowan reports on the installation of the refrigeration systems that make it all possible.

In Australia, bananas are grown in both tropical and subtropical regions. This ensures the industry is diverse in terms of the geographic location of farms and availability, the varieties of bananas grown, and their flavour.

The tropical regions of Queensland produce most of the nation’s bananas, with more than 90 per cent grown in Far North Queensland. Subtropical bananas are grown in northern New South Wales and southern Queensland, as well as in Western Australia’s food bowl near Carnarvon. It usually takes eight to 10 months for a banana crop to grow, depending on the location, with banana bunch stems typically harvested green. Averaging 150–200 bananas each, a bunch stem can weigh as much as 50kg. Banana hands are removed from the bunch stem and cut into clusters of between three and nine individual bananas – like those you see at the supermarket.

These bananas are then packed into cardboard cartons, placed on pallets and put into coolrooms to bring the temperature of the fruit down to 14–16˚C before they can be transported to market. More than 28 million of these cartons are packed in Australia each year, many finding their way to supermarket distribution centres around the country.

Traditionally, bananas were stored and ripened by supermarkets in pressurised ripening rooms. These used a variety of tarps and airbags to seal off individual pallets.

But this is said to have created a number of operational and maintenance issues, as well as inefficiencies in the ripening process. Hence the advent of tarpless ripening room technology.

TARPLESS TECHNOLOGY

Championed in the US, this technology has eliminated the use of tarps by allowing each room to be more carefully controlled to the product and ripening requirements, therefore increasing ripening efficiency. In fact, such is the popularity of the tarpless ripening room technology that Thermal Technologies Inc. (TTI) – a leader in ripening rooms based in South Carolina – is responsible for ripening more than 70 per cent of all bananas in North America.

Following its own investigation into tarpless ripening room technology in the US, refrigeration specialist Cold Logic was approached by TTI about a number of new supermarket projects in Australia.

“The retailer had supplied TTI a list of preferred contractors, and Cold Logic was on the list based on our expertise and success on other projects,” says Troy Adams, Produce Executive at Cold Logic.

Cold Logic consequently worked through TTI to become the US company’s exclusive Australian partner, with an initial contract signed in 2015 before work began on the projects in 2018.

“We were contracted by the retailer to provide refrigeration upgrade design and installation to suit new ripening rooms,” says Adams, “but also engaged by TTI in our role as their Australian business partner.” Although the firm previously provided refrigeration services for other ripening room technologies, overseeing the entire installation of a tarpless system was a first for Cold Logic. And the team was eager to take on the challenge. Cold Logic’s Contracts Division Manager Grant Cannan travelled to TTI’s headquarters in Blythewood, South Carolina, to view the factory and visit some installations. He brought back a swathe of technical information and IP that allowed Cold Logic to design and size the refrigeration systems serving the rooms with certainty and without risk.

The banana ripeness chart – they left off 8, ready for banana bread.

A FRUITFUL PROJECT

Although the installation of TTI’s tarpless ripening room at one site used the refrigeration system serving existing ripening rooms, the retailer’s new distribution centre allowed for a best-practice refrigeration design.

“The existing installation makes use of a glycol system with additional heat exchangers, modified pumping system, and tempering systems for individual room control,” says Adams. Both distribution centres received a combination of banana ripening rooms and multi-fruit rooms that can be controlled to take a variety of different types of produce individually.

The rooms are designed around standard truck load sizes for pallet numbers to avoid waste in terms of both over- and under-fill of the ripening rooms. This also maximises throughput.

TTI says the advantage of its technology is that it can deliver a consistent, high-quality fruit to the exact colour stage the retailer requires, while also increasing shelf life and reducing shrinkage (product loss).

Additionally, TTI says it enables the retailer to present quality fruit at various stages of readiness to customers – effectively fruit to eat now, and to eat later. In the multi-fruit room – designed for fruits with different ripening temperatures – cooling evaporators are supplied from dual glycol loops. This is to avoid temperature shock of the fruit that requires the higher temperatures for ripening.

The new banana and multi-fruit ripening rooms shown from above. Main supply lines and controls for modified atmosphere rooms are located externally to the rooms and generally hidden out of sight.

LESSONS LEARNED

Dr Michael Riese, M.AIRAH, business development manager at Cold Logic, shares some of the lessons learned from working with tarpless ripening technology.

Attention to detail

“Small details can become significant problems and showstoppers. Putting entire rooms into a vacuum can be a significant challenge when not addressed right from the beginning. [We have to] ensure every penetration is carefully sealed right from the start rather than after the fact, or run the risk of potential leaks.”

Everyone on board

“Achieve a full understanding of the finer system details across all contractors and how they integrate – especially for personnel on the ground.”

Outside your control

“External events can have significant impacts on project requirements and are outside of your control. A good example was changes to fire regulations as a result of the Grenfell Tower fire in London. Such changes can significantly increase compliance costs that were not budgeted for in proposals.” ■ The temperature- and humidity-controlled environment replicates the climatic conditions where the bananas were grown and would have ripened naturally on the plant if not already harvested.

The new tarpless banana ripening rooms are able to operate at room temperatures between 10˚C and 20˚C, with the actual operating temperature dependent on the condition of the incoming product. This is achieved by a 918kW closed-loop, propylene glycol cooling reticulation system that runs at subzero temperatures through a tempering loop to achieve a consistent temperature.

In contrast, the multi-fruit rooms can operate at room temperatures between 2˚C and 15˚C. This is achieved by a closed-loop subzero propylene glycol that is cooled by the main ammonia (NH3) system that is also serving other areas of the distribution centre.

Each ripening room features its own humidifier unit – controlled by a humidity sensor – to provide stable humidity settings as required.

Airflow is achieved via a series of cells, with each pallet stack provided with a dedicated cell and fans. The addition of buffers and curtains within the ripening room shape airflow to the correct flow in line with the design.

PULP NON-FICTION

On arrival to the distribution centre, the boxed green bananas require a period of 24 hours for their temperature to stabilise.

The next day, the ripening room is sealed and the vaporisation of ethylene – a naturally occurring plant hormone that contributes to the ripening and flowering of plants – is initialised. The ethylene is produced from liquid to vapour by a generator. “The amount of ethylene added to the room’s atmosphere is determined by the seasonal variation of product,” says Adams. One litre of liquid is typically used per ripening cycle.

On day three, following ethylene injection, a ripener determines whether further conditioning is required, or whether the turn of the fruit has begun. At different times of the season the fruit may be stubborn, particularly if the climate conditions are cooler when harvested.

If the turn of the fruit has begun and is minimal but visible, the fruit spores will have absorbed the ethylene, which will promote the fruit to continue its own metabolic production of ethylene. The room is vented at the end of the ethylene cycle, removing both the ethylene vapour and the CO2 that has formed in the room’s atmosphere. The space is then replenished with fresh air, allowing the fruit to respirate and continue to ripen.

At this time, personnel are able to enter the room and check the bananas for a change in colour, from green to yellow..

“The person in charge of the ripening process typically spot-checks 10 boxes of bananas,” says Adams, “and cuts the fruit open looking for latex flow under the peel. Changes are then made to the room’s setting depending on the state of the product.”

At this point, the room temperature set-point is changed.

Fresh air is increased, and the respiration rate of the room will also increase as the fruit begins to produce its own ethylene.

Daily checks of the ripening fruit are made in the days following. Depending on the progress, further changes to the room settings will be made, with fresh air turnover every three hours on days four to seven to remove any lingering CO2 that inhibits ripening.

BENDING THE TRUTH

True or false: Australians consume 5 million bananas every day. True. Put these bananas end to end, and they’d stretch from Sydney to Melbourne.

True or false: Bananas are always bent. True. Once developed, instead of growing towards the ground, bananas turn towards the sun. This is called negative geotropism.

True or False: The banana is composed of more water than a human body. False: The banana has a higher percentage of water than a human body.

True or false: Bananas are actually herbs, not fruits.

False. The banana “tree” is officially classed as a herb because its tree stem is succulent rather than woody, but the bit we eat is fruit. ■

Source: Horticulture Innovation Australia and pbs.org

RIPE ON TIME

Several noticeable changes take place simultaneously during a banana’s ripening process.

Tissue softening commences, during which starch is degraded to sugars in both the pulp and peel, and rupture strength of cell walls slowly deteriorates. The peel of the fruit turns to light green and then to yellow as chlorophyll is broken down. During colour change, the banana’s pulp becomes softer and sweeter as the ratio of sugars to starch increases, and a characteristic aroma is produced. Various enzyme systems are involved in all the changes. Eventually the peel becomes spotted brown and then completely brown and the pulp loses its firm white texture to become brown and gelatinous. ■

Source: CargoHandbook, the world’s largest database on transportation of cargoes.

“Australian retailers look for Stage 4.5 out-turn into stores,” says Adams, referring to the rating system applied to a banana’s colour where Stage 1 is green, and Stage 7 is completely ripe. Stage 4 will typically have three-quarters of the banana yellow, with the remainder still green (said to be ideal for retail display). Stage 5 sees the body of the banana yellow, with only the tips green. If after five or six days the stored bananas have prematurely reached Stage 4.5, the ripening room temperature is decreased to retard further ripening.

“The main controlling factor in this ripening process is accurate pulp temperature being consistent through the pallets and cartons,” says Adams. “Achieving excellent control of this is the intellectual property of TTI.”

A glycol mixing skid with tempering loops to ensure optimum room temperature is located outside the main building.

SECURE SUPPLY

Despite the COVID-19 pandemic interrupting both installations and limiting the movement of Cold Logic staff across state borders, the tarpless ripening rooms at both distribution centres were completed successfully. Adams says the original intent was for TTI personnel to travel from the US to supervise the first installation and commissioning, and train Cold Logic staff and operators. But with international travel restricted, they relied on extensive video conferencing instead. “We worked closely with the field team and the client ripening staff to ensure progress, while remote commissioning by TTI with Cold Logic personnel on the ground was also adopted,” he says.

With climate-change-driven weather events already shown to affect key banana growing regions, tarpless ripening rooms help ensure supply of our favourite fruit, while protecting the livelihoods of local producers.

Next time you grab a bunch of bananas from the shelves of your local supermarket, there’s a good chance they were ripened with this impressive technology. Cool bananas, huh? ■

PROJECT AT A GLANCE

THE PERSONNEL

▲ Building services and construction:

SBP Australia ▲ Electrical and controls:

Specialist Electrical Solutions (SES) ▲ Mechanical services contractor:

Cold Logic ▲ Mechanical services design:

Cold Logic ▲ Ripening room system:

Thermal Technologies Inc. (USA)

THE EQUIPMENT

▲ Controls:

Rockwell, Allen Bradley ▲ Heat exchangers: SPX ▲ Pumps:

Grundfos ▲ Sensors: IFM ▲ VSDs:

Grundfos, Danfoss ▲ Valves: Danfoss, Belimo

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