Abstract: In order to improve the quality of surimi products, we investigated the effect of 2 mL/100 g soybean oil and 10 mL/100 g pre-emulsified soybean oil (i.e. soybean oil emulsion pre-emulsified by whey protein isolate or sodium caseinate, containing 2 mL/100 g soybean oil) on the gel properties, microstructure and sensory characteristics of Nemipterus virgatus surimi gel, and we compared the effect on surimi gel quality. The results showed that the whiteness of Nemipterus virgatus surimi gel was improved by adding 2 mL/100 g soybean oil, while the texture properties were deteriorated, accompanied by decreased water-holding capacity and increased cooking loss rate (P < 0.05). An uneven distribution of oil droplets with a diameter in the range of 0.10–0.175 μm was observed in the gel matrix accompanied by obvious aggregation of oil droplets. And the gel with soybean oil exhibited a three-dimensional network with large cavities, and the oxidizability of lipids in it was significantly increased compared with the control without soybean oil (P < 0.05). However, after adding 10 mL/100 g pre-emulsified soybean oil, the whiteness, water-holding capacity and bound water content were significantly increased together with a decrease in the cooking loss rate (P < 0.05), whereas the texture and the oxidizability of lipids were not significantly changed (P > 0.05). Furthermore, the sensory properties of surimi gel were significantly improved. The pre-emulsified oil droplets with a diameter of less than 0.10 μm were evenly distributed in the gel matrix, and the gel exhibited a three-dimensional network with small cavities and smooth surface. Therefore, pre-emulsified soybean oil with milk protein can effectively improve the gel properties and flavor of Nemipterus virgatus surimi, which will be useful for the development of new surimi products.

Key words: Nemipterus virgatus surimi; soybean oil; pre-emulsified soybean oil; gel texture; water-holding capacity; microstructure