The objectives of this research are to develop the semi-industrial production of
fructooligosaccharide syrup (FOS) from onion and study chemical, physical and some biological
properties of the developed product. Results showed that the sugar content of onion was 7.5% fresh
weight, or 22.8% dry weight, and was rich with oligosaccharides. Bacteria, yeasts and molds were
contaminated on onion’s surface, but the growth of microorganisms was controlled by cold
temperature (4?C). This project was successfully developing the equipment for cleaning, pressing,
and screening. The capacity of cleaning machine with whirlpool system was more than 20 kg/batch.
Most of microorganisms were killed in 4 minutes when sodium hypochlorite solution (50 ppm) was
associated in cleaning step. The operating rate of the pressing and screening machines was 8.3 kg/hr
and 6.5 l/hr. Clarity of onion juice was increased (80%) after screening. Onion juice was evaporated
using a vacuum evaporator to obtain fructooligosaccharide syrup. The sugar concentration of syrup
was 307.2?13.8 mg/ml, and the degree of polymerization (DP) was 35, while the antioxidant activity
(%inhibition on ABTS) was 78.6%.