Optimization of low-temperature blanching combined with calcium treatment to inactivate Escherichia coli O157:H7 on fresh-cut spinach

Abstract

AimsTo develop a mild blanching method with calcium salts to ensure microbiological safety and quality of fresh-cut spinach. Methods and ResultsThe antimicrobial efficacy of eight calcium salts was evaluated on Escherichia coli O157:H7 at 45-65 degrees C and calcium hydroxide (Ca(OH)(2)) showed the greatest synergistic antimicrobial effect with heat. Combinations of low temperature treatments (45, 55, 65 degrees C), time (20, 40, 60s) and Ca(OH)(2) (025, 050, 075%) were applied for E.coli O157:H7 disinfection on fresh-cut spinach to develop a predictive model using a Box-Behnken experimental design. A suitable quadratic model was produced (R-2=098, P<0001) and the optimum condition (649 degrees C with 052% Ca(OH)(2) for 424s) was drawn by reducing 66logCFUg(-1) of E.coli O157:H7 on fresh-cut spinach. Blanching at 619 degrees C with 052% Ca(OH)(2) for 417s can inactivate E.coli O157:H7 on spinach by 54logCFUg(-1). The new method was comparable to the CDC recommendation for safe spinach cooking (711 degrees C, 15s; 50logCFUg(-1) reduction) with lower levels of weight loss of the spinach (P<005). ConclusionsThis study suggests an efficient spinach blanching method for E.coli O157:H7 disinfection. Significance and Impact of the StudyThis blanching method will enhance microbiological safety of fresh-cut produce while minimizing the use of energy and chemicals.