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Optimization of low‐temperature blanching combined with calcium treatment to inactivate Escherichia coli O157:H7 on fresh‐cut spinach
Author(s) -
Kim N.H.,
Lee N.Y.,
Kim S.H.,
Lee H.J.,
Kim Y.,
Ryu J.H.,
Rhee M.S.
Publication year - 2015
Publication title -
journal of applied microbiology
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.889
H-Index - 156
eISSN - 1365-2672
pISSN - 1364-5072
DOI - 10.1111/jam.12815
Subject(s) - spinach , blanching , escherichia coli , food science , chemistry , calcium hydroxide , antimicrobial , calcium , browning , biochemistry , organic chemistry , gene
Aims To develop a mild blanching method with calcium salts to ensure microbiological safety and quality of fresh‐cut spinach. Methods and Results The antimicrobial efficacy of eight calcium salts was evaluated on Escherichia coli O157:H7 at 45–65°C and calcium hydroxide (Ca(OH) 2 ) showed the greatest synergistic antimicrobial effect with heat. Combinations of low temperature treatments (45, 55, 65°C), time (20, 40, 60 s) and Ca(OH) 2 (0·25, 0·50, 0·75%) 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 = 0·98, P < 0·001) and the optimum condition (64·9°C with 0·52% Ca(OH) 2 for 42·4 s) was drawn by reducing 6·6 log CFU g −1 of E. coli O157:H7 on fresh‐cut spinach. Blanching at 61·9°C with 0·52% Ca(OH) 2 for 41·7 s can inactivate E. coli O157:H7 on spinach by 5·4 log CFU g −1 . The new method was comparable to the CDC recommendation for safe spinach cooking (71·1°C, 15 s; 5·0 log CFU g −1 reduction) with lower levels of weight loss of the spinach ( P < 0·05). Conclusions This study suggests an efficient spinach blanching method for E. coli O157:H7 disinfection. Significance and Impact of the Study This blanching method will enhance microbiological safety of fresh‐cut produce while minimizing the use of energy and chemicals.