Background. Osmotic treatment is necessary to reduce the oil on the vacuum-fried product. However, the nutrition of the treated sample is also affected, especially bioactive compounds.

Materials and methods. The Box-Behnken model was applied to evaluate the change in bioactive compounds of vacuum-fried shallots during osmotic dehydration in the pilot-scale plan. Three factors of osmotic treatment were examined, namely the concentration of maltodextrin (30–50%), concentration of citric acid (0.1–0.2%), and dehydration time (15–45 minutes). The frying conditions were constantly set at a temperature of 120±1^oC with a vacuum of 680 mmHg for 8 minutes.

Results. The results showed that all factors significantly affected the content of phenolics and flavonoids in the sample. The optimal condition of the dehydration process was found to be 38.9% maltodextrin and 0.17% citric acid in the soaking medium, and the soaking time was 31.9 minutes. The sample’s total phenolic and flavonoid content in optimal conditions were 12.44 mgGAE/g and 1841.73 µgQE/g, respectively.

Conclusion. The quality of vacuum-fried shallots was greatly affected by osmotic dehydration conditions. It was also found that under optimal conditions the biological compounds of the product are still maintained at a high level. Further studies on the techno-economic value of the product for commercialization should be considered.

Keywords: vacuum frying, shallot, osmotic, bioactive compound, Box-Behnken model