Understanding changes in moisture state, wheat gluten structure and oil penetration of breaded fish nuggets during frying

Abstract

To understand the changes in moisture state, wheat gluten (WG) structure and oil penetration during deep-fat frying, batter-breaded fish nuggets (BBFNs) were prepared using the batter with a wheat starch and WG blend at a ratio of 11:1 (w/w), then fried at different temperatures (150–190 °C) and times (30–150 s). As the increase of frying temperature and the prolongation of frying time, a significant portion of bound water in the BBFNs converted to the free water, the fluorescence intensity decreased significantly and the secondary structure of WG changed from disorder to order, while the opposite trend was presented for the 190 °C and 150 s, respectively. The increase of frying temperature significantly reduced the surface hydrophobicity. In addition, the pores and cracks in the crust gradually grew larger, causing the surface oil content of fried BBFNs decreased first and then increased, accompanying with an increased content of penetrated oil and the expanded Sudan Red B dyeing area. This study indicated that frying temperature and frying time significantly changed the moisture state and WG structure in the crust, thereby affecting the oil penetration. The results could be used to provide a scientific guidance for the large-scale production of low-fat fried BBFNs.