Abstract: Battered and breaded fish nuggets (BBFNs) were prepared with batters with nothing (control), 0.4% xanthan gum, 2% soybean fiber or 4% whey protein added, and fried at 180 ℃ for 50 s. The loss modulus (G”) and storage modulus (G’) of the batter and the microstructure characteristics, Sudan red-dyed level and fat distribution of fried BBFNs were evaluated. The effects of the ingredients added to the batter on its rheological properties and oil penetration of BBFNs during deep-fat frying were investigated. The results showed that G” and G’ values of the four batters decreased, then increased, and finally remained stable with an increase of frying temperature. The highest G” and G’ values were observed by addition of xanthan gum among the batters. Furthermore, the crust structure of fried BBFNs with xanthan gum was compact, there were fewer small pores in it, and much higher moisture content and much lower fat content were found compared to the other groups. The control fried BBFNs had the highest Sudan red-dyed level among the batters and showed oil penetration into the core through the crust. However, the lowest Sudan red-dyed level was observed in the xanthan gum group. Oil was mainly distributed around the pores in the crust of fried BBFNs. Of all fried BBFNs, xanthan gum gave the lowest fluorescence intensity, followed by whey protein and soybean fiber, and the highest fluorescence intensity was found in the control. The results highlighted the impact of the ingredients on rheological properties of the batter, resulting in inhibition of oil penetration of BBFNs during deep-fat frying.

Key words: battered and breaded fish nuggets, deep-fat frying, rheological properties, oil penetration