Release and antilisterial properties of nisin from zein capsules spray-dried at different temperatures

Abstract

Nisin is an effective antimicrobial against a broad spectrum of Gram-positive bacteria. It has been proposed that reduced efficacy of nisin in foods can be improved by technologies such as encapsulation to protect it from interferences by food matrix components. The potential of spray drying, a practical technology, was studied in this work for encapsulation of nisin in zein microcapsules at four inlet temperatures between 75 and 120 °C. At 95 °C and above, no apparent loss of nisin activity was observed after spray drying. At pH 6.0, burst release of nisin was impacted by spray drying temperature more than equilibrium release, possibly due to influences on capsule structures. At pH 2.0, complete release of nisin in 30 min was observed, contrasting to limited release over 8 d at pH 8.0. Capsules produced at an inlet temperature of 105 °C showed the most sustained release of nisin at pH 6.0. For these capsules, sustained release of nisin to >80% was observed at pH 6.0 and 8.0 when NaCl was used at 0.5 mol/L. Finally, at 400 IU/mL, the encapsulated nisin demonstrated slightly improved antilisterial properties than free nisin in reduced fat (2g/100g) milk but much work is still needed to enhance the antimicrobial effectiveness.