Abstract: In the present study, xanthan gum (0.4%), soybean fiber (2%), and whey protein (4%) were separately added to the batter made up of medium-gluten wheat flour, corn starch, baking powder, salt, and water. Breaded and battered fish nuggets (BBFNs) were fried at 170 ℃ for 30 to 180 s (30, 60, 90, 120, 150, and 180 s) in fresh soybean oil to measure moisture and fat content. Kinetic modeling for mass transfer during deep-fat frying was performed by Fick’s second law and first order kinetic model. Furthermore, surface oil and penetrated surface oil content were measured and oil absorption was simulated using frying experiments in Sudan red dyed oil to investigate the mass transfer mechanism of BBFNs during deep-fat frying. The results showed that moisture content of the crust of three fried BBFNs decreased with the increase of frying time, while moisture content of the core firstly decreased, then increased, and finally decreased. Fat content of the crust increased from 0 to 120 s of frying, and then decreased from 120 to 180 s. For BBFNs with soybean fiber, xanthan gum, and whey protein, the mass transfer coefficient of moisture evaporation (0.003 8, 0.003 3, and 0.003 9 s-1, respectively) was fitted to Fick’s second law, while the mass transfer coefficient of oil absorption (0.062, 0.059, and 0.061 s-1, respectively) was fitted to a first order kinetic model. The oil penetration levels for the three fried BBFNs were not significantly different from 30 to 60 s of frying, while the highest level for BBFNs with whey protein and the lowest level for BBFNs with xanthan gum were separately presented from 90 to 180 s. These findings indicated that moisture evaporation and oil absorption in BBFNs during deep-fat frying were affected by separate addition of soybean fiber, xanthan gum, and whey protein in the batter, resulting in a significant difference in mass transfer coefficient among the BBFNs.

Key words: battered and breaded fish nuggets, soybean fiber, xanthan gum, whey protein, deep-fat frying, mass transfer