Design of extraction equipment may vary depending on nature of raw material used and intended product characteristics. Equipment design and working principle also largely dependent on scale of production or processing (large scale / small scale) and economic feasibility. Some popular extraction equipment used in food industries are described below.
Bollman extractor: Bollman extractor consists of perforated bucket elevator in series into which the fresh solid are fed at one end while fresh solvent is added at another end. Solids are fed into each bucket which will be moving downward until half the way and later on, bucket will be moving upward.
Fresh solvent is fed continuously into the buckets containing almost spent solids. Later the buckets why they go to top position tilt upside down and spent solids are discharged into the hopper of peddle conveyor and are taken away. The solvent by the time it reaches bottom of up-coming side of elevator, it extracts some solute form solid and is known as half miscella. The half miscella is pumped to the top of down-coming side of elevator and is fed into the bucket into which fresh solids are fed. Thus half miscella comes in contact with fresh solids and extracts more solute and become full miscella by the time it reaches the bottom.
Hildebrandt extractor:
This extractor consists of U-shaped screw conveyor with each limb having separate screw conveyor with different rpm and bottom leg also consist of screw conveyor. The fresh solid in appropriate form are fed in one limb and fresh solvent is fed in another limb. Thus solid and solvent move in counter current direction. Here, the necessary residence time for solids can be achieved by adjusting speed of screws.
Classification of Extraction Equipment:
Above figure shows the classification of types of commonly used extraction equipment. Extraction equipment should be designed to perform the following functions.
1. Bringing solvent and solute into intimate contact
2. Efficient leaching of solute into solvent
3. Extracting much of solute and leaving as little solute in spent solid as possible
About Author
Name : Pratiksha Shrestha
pratiksha.shrestha2001@gmail.com
Ms. Shrestha holds masters degree in food engineering and bioprocess technology from Asian Institute of Technology (AIT) Thailand. She is currently working for Government of Nepal at Department of Food Technology and Quality Control (DFTQC), Kathmandu. She is also a teaching faculty in College of Applied food and Dairy Technology (CAFODAT) affiliated to Purbanchal university, Nepal.