Microstructural evaluation of deep-fat fried chicken nugget batter coating using confocal laser scanning microscopy

Porosity and pore size distribution are very important microstructural properties of fried foods needed in process optimization and product development. The objective of this study was to characterize the pore properties and quantify fat distribution in deep-fat fried chicken nuggets batter coating using confocal laser scanning microscopy. Samples were fried at three temperatures namely 170, 180 and 190 °C. Detached batter coatings were stained non-covalently and 2-D images were obtained at fluorescence and reflection modes of the microscope. The images were analyzed for fat and pore distribution. Fat distribution obtained from image analysis was significantly (P < 0.05) affected by the frying temperature and time, and it decreased within the depth of the sample thickness. There was a strong correlation between fat distribution and fat content obtained by the conventional method at two temperatures, 180 and 190 °C. Porosity ranged between 4.97% and 32.7% and was significantly influenced by frying temperature. Pore size varied approximately between 1.20 and 550 μm. Frying process led to the formation of more micropores (pores < 40 μm) and bigger (pore ⩾ 216 μm) pores.