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Escherichia coli O157:H7 reduction in hamburgers with regard to premature browning of minced beef, colour score and method for determining doneness

Boqvist, Sofia and Fernström, Lise-Lotte and Alsanius, Beatrix and Lindqvist, Roland and Lindqvist, R. (2015). Escherichia coli O157:H7 reduction in hamburgers with regard to premature browning of minced beef, colour score and method for determining doneness. International journal of food microbiology. 215, 109-116
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Abstract

This study investigated the effect of premature browning (PMB) on the survival of Escherichia coli O157:H7 in beef hamburgers after cooking with respect to interior colour of the hamburger and recommendations to cook hamburgers to a core temperature of 71 degrees C. Assessment of doneness by visual inspection or measurement of internal temperature was compared in terms of survival and the increased relative risk of illness due to PMB was estimated. At the last consume-by-day, hamburgers made from minced meat packaged in 80/20 O-2/CO2 (MAP hamburger) and from meat minced at retail packaged in atmospheric condition (control hamburger) were inoculated with a gfp-tagged strain of E. coli O157:H7 (E. coli O157:H7gfp+). Hamburgers were cooked for different times during assessment of the core temperature every 30 s and cut in halves after cooking. Doneness was evaluated based on visual judgement of the internal colour using a score chart (C-score) from 'uncooked' (score 1) to 'tan with no evidence of pink' (score 5). An alternative five point score chart (TCC-score) including texture of the meat, clarity of meat juice and internal colour was also developed. Enumeration of viable E. coli O157:H7gfp+ in cooked hamburgers was based on fluorescent colonies recovered from plates. Results showed that MAP hamburgers developed PMB when compared with controls (P = 0.0003) and that the shortest cooking time for the highest C-score was 6 and 11 min for MAP and control hamburgers, respectively. The mean temperature in the MAP hamburger was then 60.3 degrees C. The TCC-score reduced the difference between MAP and control hamburgers. It was also shown that the survival of E. coli O157:H7gfp+ was highest in MAP hamburgers. The predicted absolute risks for illness were highest for MAP hamburgers for all C-scores and the relative risk associated with PMB increased with doneness. For a C-score of 4 (slightly pink) the predicted relative risk for illness was 300 times higher for MAP hamburger than for controls. A variable pathogen reduction was observed when cooking hamburgers to temperatures of 70-76 degrees C (the 5th and 95th percentile range was around 33 log CFU). The lower reductions, at the 5th percentile, may, depending on initial contamination levels, not be enough to ensure sufficient and safe inactivation of E. coli O157:H7. Efforts to inform consumers about PMB in minced meat packaged in high oxygen packages (>= 60% O-2) are needed with the aim to make consumers use thermometers correctly or at least not determine doneness based only on meat colour.

Authors/Creators:Boqvist, Sofia and Fernström, Lise-Lotte and Alsanius, Beatrix and Lindqvist, Roland and Lindqvist, R.
Title:Escherichia coli O157:H7 reduction in hamburgers with regard to premature browning of minced beef, colour score and method for determining doneness
Series/Journal:International journal of food microbiology (BIB9033352)
Year of publishing :2015
Volume:215
Page range:109-116
Number of Pages:8
Publisher:Elsevier
Associated Programs and Other Stakeholders:Z - SLU - Libray > Odla mera
ISSN:0168-1605
Language:English
Publication Type:Journal article
Refereed:Yes
Article category:Scientific peer reviewed
Version:Accepted version
Full Text Status:Public
Agris subject categories.:Q Food science > Q02 Food processing and preservation
Q Food science > Q03 Food contamination and toxicology
Subjects:(A) Swedish standard research categories 2011 > 1 Natural sciences > 106 Biological Sciences (Medical to be 3 and Agricultural to be 4) > Microbiology (Microbiology in the medical area to be 30109)
(A) Swedish standard research categories 2011 > 4 Agricultural Sciences > 401 Agricultural, Forestry and Fisheries > Food Science
Keywords:Bacterial inactivation, Doneness evaluation, Food safety, Modified atmosphere, Relative risk
URN:NBN:urn:nbn:se:slu:epsilon-e-3297
Permanent URL:
http://urn.kb.se/resolve?urn=urn:nbn:se:slu:epsilon-e-3297
Additional ID:
Type of IDID
Web of Science (WoS)000364244700015
DOI10.1016/j.ijfoodmicro.2015.08.023
ID Code:13104
Faculty:LTV - Fakulteten för landskapsarkitektur, trädgårds- och växtproduktionsvetenskap
NJ - Fakulteten för naturresurser och jordbruksvetenskap
VH - Faculty of Veterinary Medicine and Animal Science
Department:(LTJ, LTV) > Department of Biosystems and Technology (from 130101)
(VH) > Department of Biosystems and Technology (from 130101)

(NL, NJ) > Dept. of Microbiology (until 161231)
(VH) > Dept. of Biomedical Sciences and Veterinary Public Health
Deposited By: SLUpub Connector
Deposited On:08 Mar 2016 07:33
Metadata Last Modified:09 Mar 2016 05:00

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