Far-Infrared Drying Technology: Flat Beans Case Study

Flat beans are commonly processed by boiling in brine and then sun-drying. In many rural areas, this method is still widely used. However, how should they be processed in the food processing industry? Is it possible to dry them in batches like mushrooms?

The far-infrared drying technology is already quite mature. However, many users in the market still lack experience in drying vegetables using carbon fiber heating tubes. During customer consultations, it was found that many customers are still using traditional hot air drying, which is inefficient and energy-consuming. In the field of vegetable drying, many companies are still in the experimental stage. The author has previously published articles on infrared drying of mushrooms, seafood, and crops. Today, using flat beans as a case study, I will share the application of carbon fiber heating tube far-infrared drying technology in the field of vegetable drying.

Flat beans belong to the legume family, and are a climbing herb that can grow up to several meters. They have pinnately compound leaves with ovate leaflets that are broad and wedge-shaped at the base. The petioles are usually shorter than the leaflets and are hairy. The racemes have long peduncles with several flowers in the upper part; the pedicels are very short, and the small bracts are ovate and early falling. The corolla is white or pink, with broad-elliptical banner petals that are notched at the apex, and the ovary is linear and hairy. The pods are band-shaped and slightly curved, with oval or long-oval seeds, red or brown seed coats, and the hilum is about three-quarters of the seed’s circumference. They flower from July to September and fruit in October. The tender pods and seeds are edible but must be boiled in brine and then cooked in fresh water before consumption. They can also be used as green manure, cover crops, and fodder.

• Carbon fiber heating tube far-infrared drying oven

• Fresh flat beans

1. Cut off both ends of the flat beans and cut them into equal lengths.
2. Arrange them evenly on the drying trays in the drying oven.
3. Weigh the samples and measure power consumption and material temperature regularly during drying until the moisture content reaches a safe level of 10%.

1. Soak the dried product in constant temperature water for 2 hours.
2. Remove and drain naturally, then blot the surface water and weigh.

• Conduct a comprehensive evaluation based on color, aroma, and transparency.

• Boil fresh flat beans in a light saline solution and drain.

The experimental results show that the drying of flat beans is influenced by three factors: drying temperature, drying time, and material thickness. The thinner the material, the better the quality. As the temperature increases, the quality decreases. After repeated verification, the optimal temperature is around 50°C. The amount of material spread should be adjusted according to the space size.

Additionally, the pretreatment stage of flat beans significantly affects product quality. Using a light saline solution with a concentration of about 1% yields the best results, promoting cell structure breakdown, accelerating water loss, and improving surface quality after drying. It is crucial not to use too high a salt concentration, as it can have adverse effects.