Contents ◾ xxxi
Bacterial Cells ...............................................................................................520
Bacterial Endospores ....................................................................................520
Molds, Yeasts, Viruses, and Parasites ............................................................521
Application in Food Processing .............................................................................521
Conclusion ......................................................................................................................524
References .......................................................................................................................524
41 Control by a Combination of Methods (Hurdle Concept) .......................................527
Introduction ...................................................................................................................527
Mechanisms of Antimicrobial Action .............................................................................527
Current Status ................................................................................................................529
Low-Heat Processing .............................................................................................529
Low Storage Temperature ......................................................................................529
Low pH .................................................................................................................529
Low A w ..................................................................................................................529
Modified Atmosphere ............................................................................................530
Preservatives ..........................................................................................................530
Hydrostatic Pressure Processing (HPP) ..................................................................530
Conclusion ......................................................................................................................530
References .......................................................................................................................531
SeCtion Vii MiCRoBiAL DeteCtion AnD FooD SAFetY
42 Conventional, Immunological, Molecular, and Biosensor-Based Detection
Methods ....................................................................................................................535
Introduction ...................................................................................................................535
Methods Used .................................................................................................................536
Standard and Recommended Methods ...........................................................................536
Sampling for Microbial Analysis .....................................................................................537
Sample and Sampling Plan ....................................................................................537
Sampling Procedure ...............................................................................................538
Quantitative Methods for Microbial Enumeration in Foods ...........................................538
Direct Enumeration ...............................................................................................538
Microscopic Counts ......................................................................................538
Colony-Forming Units (CFU) in Nonselective Agar Media .........................538
CFU in Nonselective Differential Chromogenic Media ................................539
CFU in Selective Agar Media .......................................................................539
CFU in Selective-Differential Chromogenic Agar Media .............................539
Indirect Estimation ................................................................................................541
Dilution to Extinction in Nonselective Broths..............................................541
Most Probable Number (MPN) in Selective Broth .......................................541
Dye Reduction Test ......................................................................................541
Enumeration of Injured Microbial Groups by Selective Media ..............................541
Dilution Scheme, Plating, Incubation, Selection of Plates for Counting CFU,
and Reporting Results .......................................................................................... 542
Qualitative Methods to Isolate Microorganisms in Foods .............................................. 542
Isolation of Pathogens ........................................................................................... 542
Bacterial Cells ...............................................................................................520
Bacterial Endospores ....................................................................................520
Molds, Yeasts, Viruses, and Parasites ............................................................521
Application in Food Processing .............................................................................521
Conclusion ......................................................................................................................524
References .......................................................................................................................524
41 Control by a Combination of Methods (Hurdle Concept) .......................................527
Introduction ...................................................................................................................527
Mechanisms of Antimicrobial Action .............................................................................527
Current Status ................................................................................................................529
Low-Heat Processing .............................................................................................529
Low Storage Temperature ......................................................................................529
Low pH .................................................................................................................529
Low A w ..................................................................................................................529
Modified Atmosphere ............................................................................................530
Preservatives ..........................................................................................................530
Hydrostatic Pressure Processing (HPP) ..................................................................530
Conclusion ......................................................................................................................530
References .......................................................................................................................531
SeCtion Vii MiCRoBiAL DeteCtion AnD FooD SAFetY
42 Conventional, Immunological, Molecular, and Biosensor-Based Detection
Methods ....................................................................................................................535
Introduction ...................................................................................................................535
Methods Used .................................................................................................................536
Standard and Recommended Methods ...........................................................................536
Sampling for Microbial Analysis .....................................................................................537
Sample and Sampling Plan ....................................................................................537
Sampling Procedure ...............................................................................................538
Quantitative Methods for Microbial Enumeration in Foods ...........................................538
Direct Enumeration ...............................................................................................538
Microscopic Counts ......................................................................................538
Colony-Forming Units (CFU) in Nonselective Agar Media .........................538
CFU in Nonselective Differential Chromogenic Media ................................539
CFU in Selective Agar Media .......................................................................539
CFU in Selective-Differential Chromogenic Agar Media .............................539
Indirect Estimation ................................................................................................541
Dilution to Extinction in Nonselective Broths..............................................541
Most Probable Number (MPN) in Selective Broth .......................................541
Dye Reduction Test ......................................................................................541
Enumeration of Injured Microbial Groups by Selective Media ..............................541
Dilution Scheme, Plating, Incubation, Selection of Plates for Counting CFU,
and Reporting Results .......................................................................................... 542
Qualitative Methods to Isolate Microorganisms in Foods .............................................. 542
Isolation of Pathogens ........................................................................................... 542