When a watermelon speaks, these experts listen closely

By looking, touching, thumping and listening, Cao Jinghua, 57, can tell how sweet and ripe a watermelon is in three seconds.

A watermelon verification expert from Likou township in Shangqiu, Henan province, Cao has become much busier lately, selecting the best quality melons in Zhongwei, Ningxia Hui autonomous region.

"With the arrival of this year's sanfu days, refreshing heat-relieving fruits, such as watermelons, have received a warm welcome," he said, adding that watermelons began to ripen in the region at the end of last month.

In the Chinese lunar calendar, sanfu refers to the three 10-day periods that are predicted to be the hottest days of the year, called toufu or chufu (mid-July), zhongfu (late July to early August), and mofu (mid-August).

"Watermelons grown in Zhongwei have thin rinds and sweet red pulp," he said. "Also, the watermelons are relatively firm, which makes them suitable for long-distance transportation."

Cao and his assistants will stay in Zhongwei until mid-August and send selected watermelons to the provinces of Jiangxi, Fujian and Guangdong.

Likou, Cao's hometown, has been growing watermelons for more than 40 years. Around 800 hectares of farmland in Likou have been planted with the fruit, typically yielding 60 metric tons a hectare. The value of the town's annual watermelon harvest can reach 120 million yuan ($16.5 million).

The national push for quality has given rise to a demand for watermelon whisperers like Cao, who have learned to identify the best fruit.

"There are about 150 watermelon verification experts from our township who are distributed throughout the country's watermelon producing areas," said Cao Chongchao, Party chief of Likou's Gaozhai village. "They are engaged in melon inspections, purchasing, marketing and management work."

The village also promotes mutual help policies during the busy melon selling season.

"During the summer harvest season, we will coordinate and organize residents to help the watermelon inspectors do their work on the farms," Cao Chongchao said.

Cao Jinghua became a watermelon farmer in his 20s and has been a verification expert for more than two decades.

"My previous experience as a melon farmer laid a good foundation for me to work as a verification expert," he said. "I spend more than half the year outside selecting watermelons."

Usually, several days after Spring Festival, he travels to Yunnan province or the Guangxi Zhuang autonomous region, near Myanmar and Vietnam, to select melons, he said. And then, as the fruit ripens at different times, he gradually makes his way north.

Currently, in the main watermelon-producing areas across the country, verification experts have become much sought-after. While a few have been around for decades, they are now in short supply.

"During the watermelon trading period, when large quantities of melons are involved and cutting great numbers open is not feasible, professional verification experts are needed to standardize and control the ripeness and quality," said Li Junhui, a fruit supplier with 16 years of experience.

In every watermelon harvest season since 2018, he has hired multiple verification experts to help him select which melons are ready.

"Commercial watermelons generally need to reach 80 percent of ripeness, because there is a shelf life for later sales," he said. "Watermelons that are either too ripe or not ripe enough need to be sorted out. Melons with seeds, hollow parts or deformities are not acceptable. Identification of these require the professional expertise of verification experts."

For Cao Jinghua, listening to the watermelons is the most important skill the experts possess.

"The level of ripeness — whether the flesh is crisp or sandy — can be heard immediately," he said.

Melons of different ripeness levels have distinct vibration frequencies when thumped, he said. Hollow watermelons produce a dull sound, while solid watermelons produce a crisp sound. Immature watermelons often have a clear, lower-frequency sound.

Additionally, verification experts must rapidly assign grades to watermelons based on texture, size, shape, color and pattern. Arranging the melons for long-distance transport to ensure they are not damaged is also a technical skill.

"The top and bottom of a melon is the hardest and relatively more resistant, while the middle part is easily flattened if not placed properly," he said. "This can lead to the watermelon being crushed."

During the peak period of watermelon production, verification experts may need to work more than 10 hours a day, inspecting tens of tons of watermelons, he said.

"Each expert can verify approximately 4,000 watermelons a day, earning around 3,000 yuan, and during the busiest seasons, they can earn up to 6,000 yuan," he said.

Contact the writers at zhouhuiying@chinadaily.com.cn