An innovative design and application of natural antimicrobial gelatin based filling to control risk of listeriosis from caramel apples

Abstract

The aim of this study is to design and apply antimicrobial gelatin based filling with an innovative method in production of safe caramel apples that caused deadly listeriosis cases. For this purpose, water holding capacity and mechanical stability of gelatin (GEL) gels were improved by incorporation of soy proteins (SP) and inulin (IN), respectively. The water activity (aw) of gels were also reduced < 0.9 by addition of sucrose (SUC). The application was conducted by coring of apples, filling void core with GEL-SP–IN–SUC blend gel solution containing synergetic antimicrobials, nisin and lysozyme, and antibrowning agent ascorbic acid (each at 1% in gel). Candy sticks were then placed into gel-filled void cores of apples, and apples were kept at 4 °C for 20 h for gelation of filling before they were dip-coated with caramel. The inoculated caramel apples with antimicrobial GEL-SP–IN–SUC filling showed 2.4–2.9 D lower Listeria count than traditional inoculated caramel apples during 7-day cold storage. The active blend gel-filling also successfully prevented the discoloration of apple core and accumulation of apple juice between apple surface-caramel coating interface. Mechanical tests showed strong binding of candy sticks by GEL-SP–IN–SUC gel-filling. Active blend gel-filling applied in an innovative way showed good potential to improve safety of candied apples.