Guangdong's lychee exports are expected to surge in the years to come after scientists in the South China province achieved breakthroughs in ultralow temperature lychee preservation technologies, effectively extending the shelf life of the popular fruit.
Zhu Zhiwei, an associate professor at South China University of Technology, said that by using the special technology system of ultralow temperature freezing, dormancy and locking in the freshness of the fruits, the shelf life of lychee can be extended to one year.
"And after thawing, the 'frozen dormant lychee' can retain between 80 percent and 90 percent of the initial quality, allowing consumers to enjoy the sweet fruit all year round," Zhu said.
Thanks to the advances in lychee preservation technology, more than 200 metric tons of the fruit preserved in June 2023 have seen robust sales in supermarkets and on major e-commerce platforms, including Freshippo and JD, since May, he said.
The new technology effectively alleviates the annual pressure of seasonal concentrated sales of lychee, he said.
The round red-skinned and white pulped lychee, together with longan, mango and papaya, are regarded as four major typical fruits in South China and play a big part in Guangdong's agricultural production.
Guangdong lychee are usually seen in many major supermarkets in the United States, with prices ranging from $4.99 to $5.99 a pound (0.45 kilogram) in previous years.
The new technologies will help further strengthen the research and development of lychee deep processing products and extend the industrial chain to develop high-quality lychee-based wines, vinegar, lactic acid bacteria fermented beverages, beauty cosmetics and other high-value-added products in the future.
Guangdong's lychees are loved by many, but freshness preservation of the fruit has long troubled farmers and vendors. When refrigerated, the fruit can be stored for about 10 days.
Earlier this year, Liang Qinru, deputy director of the Guangdong provincial department of science and technology, said the special freezing technique involves immediate pre-cooling, protective coloration and freezing, thus preserving the freshness of just-picked lychee.
"The core point is to quickly freeze the flesh cells of lychee below-35 C, without damaging the original structure of the flesh, just like animals' hibernating," Liang said.
"Frozen dormant lychees" have the same bright red color as fresh varieties and the outer skin remains crystal clear, which maintains the color and aroma of the fruit after thawing, Liang added.
He said his department had given strong support to scientists tackling the problem of lychee preservation over the past year, and scientists in Guangdong have now mastered the ultralow temperature freshness preservation technology.
He added that relevant departments will strive to expand production capacity and use the new methods to preserve more than 2,000 tons of the fruit this year.
Frozen dormant lychee will hit the market in the following months when demand rises.
"Meanwhile, the new lychee preservation technology will help solve the problem of growers' incomes being affected by low prices during good harvest years," he said.
Jiang Yueming, a researcher at South China Botanical Garden, said Chinese researchers have also developed a special composite preservative that can preserve the bright color and flavor of lychee for a long time, avoiding browning and maintaining good quality.
By soaking for 4-6 minutes, the long-term color retention effect of the outer skin is achieved, significantly extending the shelf life and meeting color retention technology requirements of developed countries, including the United States and Japan, for fresh lychee imports, Jiang said.
The preservative, which is safe, reliable, cost-effective and easy to use, has become a substitute for sulfur fumigation or sulfite based preservatives, as it meets the requirements of food regulations and quarantine requirements of developed countries and regions such as Europe, the US, Japan and South Korea for lychee imports, Jiang said.
"The preservative has been promoted and applied in many lychee production areas in Guangdong," he said, adding that the new preserving agent will also be used in preserving other fruits and vegetables in the following years.
Meanwhile, Wang Hongjun, a professor at South China Agricultural University, said a 5G-powered robotic picker that mimics the movements of human hands has been introduced to help pick the fruit.
The lychee-picking robots equipped with binocular cameras, combined with machine learning and bionic knowledge with the support of image processing algorithms, can autonomously recognize fruit clusters in complex outdoor environments and accurately locate the three-dimensional spatial position of fruit clusters to realize unmanned harvesting and transportation to improve overall efficiency, he said.
The new technologies will help reduce labor inputs, and promote industry scale, mechanization and intelligent management of the lychee industry in the months to come, added Wang.
The Guangzhou bureau of science and technology said the South China metropolis is one of the major production bases for lychee in the country in terms of research strength, investment input, promotion and application of lychee technology.
The bureau has given strong support to scientists tackling the problem of lychee freshness guarantees in the past year, the authority said.
Chen Houbin, another professor at South China Agricultural University, is the chief scientist with the National Litchi Longan Industrial Technology System.
Chen urged related departments to rely on technology to promote high-quality development of the lychee industry in the following months.
"More lychee varieties with better temperature requirements should be cultivated through seed selection, hybridization and biotechnology methods," he said.
Ouyang Jianzhong, director of the Conghua Lychee Industry Research Institute, said the new lychee freezing and dormant technologies — which extend shelf life to a year — have helped solve seasonal centralized marketing and sales problems, and expand sales scope and sales cycles, thus achieving year-round global sales, greatly improving the export scale of lychee and expanding export destination countries.
Ouyang said thanks to the new freshness preservation technology, his company has also sold the fruit to South America, Russia and the Middle East this year, based on the original 15 countries and regions in North America, Europe, Southeast Asia, and China's Hong Kong and Macao.
Ouyang, who is also chairman of Hualong Fruit and Vegetable Preservation Co Ltd, said his company — which has 6.67 million square meters of lychee orchards — has taken the lead in the country to build the country's first fruit and vegetable ultralow temperature immersion freezing and freshness locking production line in July of 2023 to help extend the shelf life fruits and vegetables.
Lin Changzhen, director of the Caixianyuan Fruit and Vegetable Cooperative in Gaozhou, Guangdong, said her cooperative has been using multiple methods, including expanding e-commerce platform channels, training professional talent and enhancing industrial technology to help expand lychee sales, stabilize the market and increase income this year when lychee output has witnessed a reduction.
But extending lychee shelf life is also important, as the fruit is highly seasonal, and its sales period usually starts from May and ends in July, she said.
As a brand agricultural product, lychee has enjoyed rapid development in recent years.
However, storage and transportation losses are significant due to the preservation bottlenecks.
According to official statistics, lychee growers and traders in China suffer losses of 18-30 percent in the circulation process after harvesting, with an annual loss of about 4 billion yuan ($555.56 million), compared with less than 5 percent recorded by developed countries and regions.
China's annual export volume of fresh lychee reaches less than 10,000 metric tons, accounting for about 0.3 percent of the country's total production of the fruit.
Subtropical Guangdong, with a lychee planting area of 2,633.27 square kilometers, usually produces 1.3 million tons of the fruit annually — more than 50 percent of the country's total output. Other production locations include the Guangxi Zhuang autonomous region, the provinces of Hainan and Sichuan, and Taiwan.
However, affected by warmer winters and the continuous extreme weather, including storms, hail and tornadoes, that hit the province this year, Guangdong's lychee harvest has witnessed a year-on-year reduction of more than 50 percent so far this year, authorities said.
According to official statistics, the output of lychee in Guangdong is expected to hit 876,400 tons this year, down 51 percent year-on-year, authorities said.
The predicted output of lychee across the country this year is estimated to be 1.78 million tons, down 42.5 percent from last year.
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