The postharvest revolution

In 1910, the Union Parliament passed laws – the first such legislation in the world – to regulate fruit exports. These evolved as exports of fruit and other perishables increased. Milestones included the founding of the Perishable Products Export Control Board in 1929 and the proclamation of the Deciduous Fruit Regulatory Scheme (DFRS), which established the Deciduous Fruit Board (DFB), in 1939.

The postharvest learning curve was steep. For example, in 1934 more efficient refrigeration systems at the Cape Town harbour damaged peaches, leading to claims and court cases. But this disaster initiated the development of world-class pre-cooling facilities that increased turnover and boosted exports.

Until 1996, when it was disbanded, the DFB was the sole marketer and exporter of deciduous fruit. It appointed Unifruco in 1987 to manage marketing and research.

Unifruco became a private company after 1996, and the DFRS was terminated in 1997 – the so-called year of deregulation. The Deciduous Fruit Producer's Trust became the new coordinating body for the pome- and stone-fruit industries. It changed its name to Hortgro Services in 2007, which became Hortgro in 2013.

Controlled-atmosphere storage

The first research showing that low oxygen levels delayed ripening was published in 1821, and the first documented commercial refrigerated low-oxygen apple store dates from around 1865 in the US. But controlled-atmosphere storage only became mainstream after World War I, thanks to the work of Drs Franklin Kidd and Cyril West in England.

"The challenge they were set was to have fresh produce available for troops," explains Dr Malcolm Dodd, principal of Cold Cubed. "One of the big problems in the First World War was feeding the troops in the trenches. Particularly with fresh produce – there was a lot of scurvy."

In 1929, Kidd and West's research culminated in the first commercial controlled-atmosphere apple store, constructed in England. The second was in Elgin, built in 1935 by the Molteno brothers. "That shows you how progressive our fruit industry has always been," comments Dodd.

Unfortunately, the Elgin store failed to maintain a controlled atmosphere. "To get them leak-proof was very difficult in the early days," says Richard Hurndall, former Postharvest Programme Manager at Hortgro Science.

According to Hurndall, oxygen levels of about 8% were achieved, compared to below 2% today. "People would hold their breath to go in – you can't do that now!"

After an early conception, controlled-atmosphere storage had a slow gestation in SA. Increasing fruit volumes necessitating a longer marketing season eventually rekindled interest, and a technical working group that became the Controlled-Atmosphere Storage and Postharvest Group was founded in 1978.

In 1983, the Group persuaded the DFB to export the first controlled-atmosphere-stored apples. The success of this trial led to an explosion of controlled-atmosphere stores in SA, from a total capacity of 6 000 bins in 1978 to 50 000 bins in 1983 – a mere five years later.

The current controlled-atmosphere-storage capacity is approximately 1.5 million bins, and Hurndall believes it will continue to expand. "As long as the industry grows, controlled-atmosphere storage will grow."

Dynamic control raises the bar

Controlled-atmosphere storage delays ripening by slowing fruit metabolism through reduced temperature and oxygen. But if oxygen levels drop too low, fruit becomes stressed, and quality suffers.

"The principle of dynamic controlled-atmosphere storage is that you want as little oxygen as possible," explains Henk Griessel, Quality Assurance Manager at Tru-Cape. "The lower the oxygen levels, the longer you can store the fruit. But you need to find the line where fermentation starts."

Dynamic-control systems adjust the oxygen levels during storage according to the physiological response of the fruit. The most common system used in SA measures chlorophyll fluorescence.

Griessel relates how growers in Ceres were early adopters of chlorophyll-fluorescence-based dynamic control, while those in Grabouw were concerned about applying the technology to fruit with mixed maturities. "The chloroplast reaction turned out to be independent of fruit maturity," he says.

Nowadays, Griessel thinks Grabouw probably has more dynamic-controlled stores than Ceres. "We even store Golden Delicious in them," he reports, "because we want to supply the African market, which has strict colour requirements – the apples must be green."

The other main dynamic-control system measures the respiratory quotient – the ratio of carbon dioxide produced to oxygen consumed.

Service providers for dynamic-control technology are mainly European companies, but they are actively installing stores in SA. "In fact, they can even control those stores from overseas," says Hurndall.

The rise of 1-MCP

"When I started in the industry in 1993, Royal Gala was new, and we could store it for three months," remembers Dr Ian Crouch, managing director of ExperiCo Agri-Research Solutions. "Now we can store it for eight months."

Crouch explains that fruit ripens due to a hormone called ethylene. Refrigerated controlled-atmosphere storage adds roughly three months to storage life by retarding ripening indirectly through slowing fruit metabolism and reducing ethylene production. But ethylene can also be countered head-on by blocking the ethylene receptors on fruit cells.

In 1996 Drs Edward Sisler and Sylvia Blankenship made postharvest history when they patented 1-methylcyclopropane – 1-MCP – as an ethylene blocker. It was rapidly commercialised, gaining regulatory approval in the US in 2002 and SA in 2003.

"1-MCP had a bigger impact than anything else on our industry," says Griessel. "It made a massive difference – greater even than controlled-atmosphere storage."

Before 1-MCP, pome fruit were kept at -0.5 °C, and cold chains were strictly enforced. "Temperature was absolutely critical. But since 1-MCP, the trend is to store above 1.0 °C," says Crouch. "Can you imagine trying to manage a logistics chain with our current power failures if you don’t have these kinds of safety guards?"

Storing at slightly higher temperatures can mitigate internal disorders, such as browning in sensitive cultivars, while also saving energy. A 2012 survey of South African pack houses found an average energy saving of 16% for each 1 °C increase in storage temperature.

The ability of 1-MCP to buffer temperature fluctuation has also helped open markets in Africa, and the Middle and Far East.

Although peaches started South African fruit exports, stone fruit has benefitted less from new technologies than pome fruit. The response of stone fruit to 1-MCP is cultivar-specific, so it is much less widely used than in apples and pears, while controlled-atmosphere storage works best on products that naturally have a more extended storage and shelf life.

Shipping then and now

"In the first years I remember, fruit from Ceres and the Langkloof were loaded on trains," says Griessel. "There wasn't road transport." He joined the industry in 1985.

"The logistics chain has gone from a reefer to a container ship," says Crouch. "When I started, the whole deck of the ship was refrigerated. There were four decks, and cranes would load pallets of fruit into the hold."

Containerised shipping began in the late 1970s, and all stone fruit was shipped in containers by 1980. The first containers were called porthole containers because they were plugged into a central refrigeration system through a round hole. This system was soon replaced by integral containers that can be individually regulated.

"When we switched to integral containers, the effect on dual-temperature regimes for plums was a big worry," says Griessel. "Some of the cultivars we used to have, disappeared because they couldn't handle the slower temperature changes in the integral containers."

Many logistics issues plaguing the industry today are not new – strikes and wars have cost growers millions over the past century. But technologies such as real-time temperature measurement can help mitigate the risks.

"There were recording devices in the past, but the data was always provided after the event," says Dodd, "whereas if you have it in real-time, you can take action to rectify the problem; or, as soon as the product arrives, you can move it quickly."

All of these advances in storage and logistics have allowed South African fruit exports to grow from 15 000 cases of mostly grapes and peaches in 1893 to more than 200 000 tonnes of apples alone by 1993. From a season that ended in June, we've gone to exporting 12 months of the year.

The latest industry figures show a total 2021 turnover of nearly R16 billion for pome and stone fruit, with 46% of production exported.

"Changes like controlled-atmosphere storage and 1-MCP have been incredible," reflects Griessel. "In my opinion, with new technology, the faster you can implement it, the bigger the win."

Featured Image: “The shipment for the first time of the millionth box of fruit during any one season, that of 1922/23” (THE DECIDUOUS FRUIT GROWER 1960, 10(9) P243.)