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

N. H. Kim, N. Y. Lee, S. H. Kim, H. J. Lee, Y. Kim, Jee-Hoon Ryu, Min-Suk Rhee

Research output: Contribution to journalArticle

4 Citations (Scopus)

Abstract

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)<inf>2</inf>) 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)<inf>2</inf> (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<sup>2</sup> = 0·98, P < 0·001) and the optimum condition (64·9°C with 0·52% Ca(OH)<inf>2</inf> for 42·4 s) was drawn by reducing 6·6 log CFU g<sup>-1</sup> of E. coli O157:H7 on fresh-cut spinach. Blanching at 61·9°C with 0·52% Ca(OH)<inf>2</inf> for 41·7 s can inactivate E. coli O157:H7 on spinach by 5·4 log CFU g<sup>-1</sup>. The new method was comparable to the CDC recommendation for safe spinach cooking (71·1°C, 15 s; 5·0 log CFU g<sup>-1</sup> 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.

Original languageEnglish
Pages (from-to)139-148
Number of pages10
JournalJournal of Applied Microbiology
Volume119
Issue number1
DOIs
Publication statusPublished - 2015 Jul 1

Fingerprint

Escherichia coli O157
Spinacia oleracea
Calcium
Temperature
Disinfection
Salts
Calcium Hydroxide
Safety
Cooking
Centers for Disease Control and Prevention (U.S.)
Weight Loss
Research Design
Hot Temperature

Keywords

  • Antimicrobials
  • EHEC (enterohaemorrhagic E. coli)
  • Food safety
  • Infection
  • Postharvest

ASJC Scopus subject areas

  • Applied Microbiology and Biotechnology
  • Biotechnology

Cite this

Optimization of low-temperature blanching combined with calcium treatment to inactivate Escherichia coli O157 : H7 on fresh-cut spinach. / Kim, N. H.; Lee, N. Y.; Kim, S. H.; Lee, H. J.; Kim, Y.; Ryu, Jee-Hoon; Rhee, Min-Suk.

In: Journal of Applied Microbiology, Vol. 119, No. 1, 01.07.2015, p. 139-148.

Research output: Contribution to journalArticle

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abstract = "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 (R2 = 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.",
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