A recent research study – conducted in 2021 at Hunan Agricultural University’s Key Laboratory of Tea Science of Ministry of Education – looked at four drying technologies used to process instant pu-erh tea, and it endorsed electrostatic spray drying (ESD) as a very promising method, especially for preserving aroma during the drying step.

The study compared electrostatic spray drying to the three other technologies for processing instant tea – freeze drying, vacuum drying and conventional spray drying.

In pursuit of the most advantageous technology to shorten drying time and ensure flavor preservation, researchers found that electrostatic spray drying is a suitable alternative method for instant tea production.

Electrostatic spray drying is a continuous process technology that operates at low temperatures, saving time and reducing energy consumption. This process is only available under Fluid Air’s patented line of PolarDry spray dryers.

Naperville, Ill.-based Fluid Air, a division of Spraying Systems Co., participated in the study by providing researchers with access to the technology.

‘Significantly Better Than Vacuum Drying and Conventional Spray Drying’

To conduct the study, the university’s researchers examined sensory qualities, aroma profile and microstructural features of instant pu-erh tea.

The statistical analysis and sensory evaluation concluded that electrostatic spray drying achieved high preservation of volatile compounds, while producing powder with a similar quality of key flavor attributes as freeze drying and “significantly better than vacuum drying and conventional spray drying.”

Katherine Buzecky, lead process engineer at Fluid Air, told World Tea News: “Electrostatic spray drying is a low temperature drying technique that combines gas–liquid atomization and an electrostatic charge in a streamlined, one-step process for conversion of liquid feed to powder. In electrostatic spray drying, applying a charge improves drying efficiency by driving solvents to the surface during droplet formation and encapsulating the flavor-retaining active components in the core. This enables lower temperatures to be used in the spray drying process than with conventional spray drying.”

According to Buzecky, the new study details the challenges in making tea powders, which are retention of aroma and flavors and processes that require high energy consumption and high capital costs.

“The findings can be applied not only to the global tea industry, but to other beverage and flavor-related industries,” explained Buzecky. “Freeze drying, while also effective at preserving sensory qualities of tea, is a batch process. Therefore, drying tea by freeze drying is a highly time- and energy-consuming process. Vacuum drying and conventional spray drying, while they can be done in a continuous process like electrostatic spray drying, both yield a lower quality product due to the excessive stresses used in each process. The results of the study clearly demonstrate that ESD is the better choice for making powders from tea with higher flavor and aroma retention and low energy consumption and capital costs.”

Buzecky noted that electrostatic spray drying is often the best choice for a continuous process to make powders from materials containing thermosensitive aroma and flavor components, such as tea, as the low temperature drying helps retain the active components in the finished powder.

“With ESD, a business is going to have a complete solution to solve many common drying issues, as well as enhance product quality,” Buzecky explained. “ESD also provides an opportunity to work with new, high-value products that are not easily processed via conventional spray drying. That advantage could lead manufacturers to a market-leading position.”

Buzecky said Fluid Air recommends that companies that are interested in investing in spray drying technology should take the time to review academic studies that have used ESD technology, so their team can get a more complete view of ESD’s capabilities. “They may find that this unique, patented technology has the potential to introduce new market opportunities,” she said.

Michel Thenin, president of Fluid Air, added, “Companies manufacturing products where flavor influences success will find that PolarDry is a faster, more efficient continuous processing spray drying solution.”

Fluid Air has 40 years of experience developing equipment and custom solutions used for modifying and creating powders and particles. Its technology is used daily to help companies and businesses in the agricultural industry, like tea, as well as other markets.