Detailed Introduction to Honeysuckle Processing Techniques

There are 2 processing methods: air-drying and oven-drying.

(1) Sun-drying

Before 1970, producers in Shandong generally chose a wind-sheltered, sunny flat surface or stone slab with long sunlight exposure, spread a thin layer of flowers in the morning, and dried and collected them the same day. This method saves labor and time, but windy days and rainy or overcast weather affect quality. Since 1970, the basket-drying method has been used more often. A basket frame about 1.7 m long, about 0.7 m wide and 5-7 cm high is made from wooden rods, with a base of sorghum stalks or a mat (sorghum stalks are not peeled; the mat should be turned over to absorb water better). Each basket dries 2.5-3 kg of fresh flowers. Place the baskets in a ventilated, sunny spot oriented north-south, with the northern end raised; after drying to 80% dry, the flowers can be poured onto a mat and turned for further drying. At night or in rain, the baskets can be stacked in the yard, with two crossbars placed between baskets and a mat (or rain cover) laid on top. When the flower buds reach 80% dry, they must absolutely not be turned, otherwise they blacken and quality declines.

(2) Oven-drying

This began to be used after 1975. It is mainly carried out in a drying room. The operating procedure is mainly:

Pre-drying (room temperature 30°C) - loading flowers (35°C, swap upper and lower flower baskets every 2-3 hours) -> heating and ventilation (ventilate at 40°C; within 5-10 hours, keep the temperature at 45-50°C. Ventilate for 5 minutes each time; after 10 hours, when the temperature rises to 55°C, dry rapidly, about 18 hours in total) -> removing from the oven (reduce the fire 1 hour before removal and ventilate; when the temperature drops below 10°C and the honeysuckle is 80-90% dry, take the flower baskets out to air-dry).

For oven-drying, the drying room is generally built as a two-room type, 6 m long and 5 m wide. Two furnace openings are built at one end of the house, a return-flue type fire channel is built inside the room, and a chimney and skylight are left on the roof. At 0.3 m above the ground, a pair of opposite ventilation holes is left in the front and rear walls of each room. On each side inside the room, 20 cm from the wall, a drying rack made of steel bars or wood is installed, with a 1.4 m passage between racks. The rack is 5.6 m long, 1.6 cm wide and 2.6 m high, divided into 10 layers with 20 cm between layers. The bottom layer is 40 cm above the fire channel. Each layer holds 8 honeysuckle baskets, with 10 cm between baskets, for a total of 160 flower baskets. Before loading flowers, pre-dry first to remove indoor moisture and raise the temperature. When the room temperature rises to 35°C, the flowers can be loaded, keeping the fresh flower thickness at 3-4 cm. Arrange the baskets neatly on the drying racks, close doors and windows, block the ventilation holes, and begin baking. Every 2-3 hours of baking, swap the positions of the upper and lower baskets. After the honeysuckle is loaded, immediately increase the fire. When the room temperature rises to about 40°C, the fresh flowers begin to release water, and the skylight can be opened to discharge water vapor. Within 5-10 hours, the room temperature should be kept at 45-50°C; open the air holes so water vapor is discharged rapidly. If the temperature is not enough, block part or all of the air holes, and ventilate again when indoor moisture is high, for only about 5 minutes each time. After 10 hours, most of the water vapor from the fresh flowers has been discharged, the room temperature reaches 55°C, and the honeysuckle dries rapidly; one oven cycle lasts 18 hours. About 1 hour before removal, gradually reduce the fire and keep ventilating continuously. When the temperature drops below 40°C and the flowers feel firm in the hand and make a sound, the flower baskets can be taken out. Whether sun-dried or oven-dried, they should be dried (or sun-dried) once more after 1-2 days to make them thoroughly dry.

At present, in Shandong production areas, flower growers mainly use the basket-drying method, and drying rooms have long been closed or converted to other uses. Processing plants of medicinal materials companies mostly use the sulfur fumigation method, which should now be prohibited.

(3) Processing Research

Lu Ling'en and others used the main active components of honeysuckle, volatile oil and chlorogenic acid, as indicators to compare the effects of different processing methods on honeysuckle quality. They measured the total volatile oil and chlorogenic acid contents of different processed products (steamed, fumigated and sun-dried, stir-fried and sun-dried, and raw sun-dried) of Lonicera confuse and Lonicera similis, and the results showed the highest content in the fumigated product. Guo Hongbin and others compared 4 different processing methods for honeysuckle, namely sun-drying, shade-drying, steaming and sun-drying, and sulfur fumigation. The results showed that the shade-drying method had the highest chlorogenic acid content, with a highly significant difference compared with the other 3 methods, while the sun-drying method had the lowest chlorogenic acid content. However, the research results of Peng Guangfang and others showed that the order of chlorogenic acid content in honeysuckle under different processing methods was roughly sulfur-fumigation oven-drying > oven-drying -> sun-drying -> shade-drying, and they considered that honeysuckle processed by sulfur-fumigation oven-drying had the best quality and the shade-drying method the worst. Wu Ruying, through research on the quality of Lonicera macranthoides, found that the steamed and sun-dried product had the best quality and the raw sun-dried product the worst. Feng Weisheng and others, after measuring the chlorogenic acid content of different processed varieties, believed that nitrogen fumigation of honeysuckle could replace air-drying or oven-drying to improve the appearance quality of honeysuckle. Zhu Xiaoguang and others introduced the sulfur fumigation method for honeysuckle and believed that processing by this method could meet the requirements for appearance traits and color. After fumigation, it can be stored for 4-5 days (in the rainy season) without mildew.