FOOD 4150 Lecture 3

Indicator Microorganisms

• reflects microbiological quality provides simple, reliable and rapid info about process failure and post-proceeding contamination

• general level of hygiene under which the food was processed and stored

• could indicate the potential for the presence of a pathogen microorganism

Indicator Organism

• refer to the selected surrogate markers

• examples:

  • coliforms

  • e.coli

  • listeria like microorganisms

Indicators of Quality

• microorganisms and/or their metabolic products i.e ethanol, lactic acid, diamines

• used to assess existing quality or to predict shelf-life

  • can be determined by initial number of microorganism in the food sample

Microbial Quality

• high total plate count in some foods indicate poor quality

• food which appear normal but show high TPC is indicative that the food is about to spoil

Limitations

• cultured food (fermented foods like yogurt) naturally contain a high microbial loads

• must know expected values for a particular food or the process stage

• the plating media does not ideally support the growth of fastidious microorganisms

• anaerobes are not detected (unless you are detecting only anaerobes)

• quality loss may occur at low counts

Coliforms

• coliform bacteria or coliforms are aerobic or facultative anaerobic, Gram-negative, non-spore-forming, rod-shape bacteria that ferment lactose, with acid and gas production within 48hr at 37C

Presence of Coliforms

• high possibility of fecal contamination

• lack of sanitation

• increases likelihood of pathogen presence

• positive for coliforms does not confirm pathogen presence

• raw food - need to determine the type of coliform

• heat processed food - not coliforms should be present - no need to determine the type of coliform

Fecal Coliforms/ E.Coli

• fecal contamination (lactose fermenters) - i.e. E.coli

• increased likelihood of pathogen presence i.e. Shiga toxin E.coli(O157:H7)

• lack of sanitation, improper handling and storage (coliforms, fecal coliforms, and E.coli)

Enterococci

• around 30 species

• gram-positive cocci, facultative anaerobe, catalase negative

• fecal material from animals

• plants

• salt tolerant

• resistance to freezing

• some are heat resistant - i.e. E.Faecalis

• very persistent in the food processing environment

• identify poor manufacturing practices

Microbiological Criteria

• the acceptability of a product or a food lot, based on the absence or presence, or a number of microorganisms including parasites, and/or quantity of their toxins/metabolites, per unit(s) of mass, volume, area, or lot

Microbiological Criteria Must Include

• a statement of the food to which the criterion applies: food description, indented use, etc

• a statement of the containments of concern i.e. escherchia coli O157:H7, staphylococcus aureus

• the analytical methods to be used for it detection, quantification or enumeration (USDA, FSIS, PHAC, etc)

• sampling plan (2 class/3class)

• the microbiological limit appropriated for the product and commensurate with the sampling plan (n, c, m, M)

Microbiological Standard

• a microbiological criteria which is part of a law or regulation- mandatory enforceable by the regulatory agency

• often focused on safety

• failure to comply constitute a violation of the law, ordinance or regulation

Microbiological Guideline

• which is used by a manufacturer or regulatory agency to monitor a food processor or system. Usually advisory by could be mandatory

• they are intended to assess processing efficiency at critical control points and conformity with good manufacturing practices (GMP)

Microbiological Specifications

• apply as a condition of acceptance (food/ingredient) by a food manufacturer or a public or private agency

• it could be advisory or mandatory, it applied at the establishment at a specified point during or after processing to monitor hygiene

• intended to guide the manufactuer and is not intended for official control purposes

Sampling

• two class attributes plans (qualitive data)

• three class plans (quantitative/qualitize data)

Two Class Attribute Plans

• qualitative data

• applied in qualitive pathogens testing: presence or absence of the specific pathogen

Three Class Plans

• quantitative or qualitative data

• use the conc. of microorganisms in the sample units to determine levels of quality and safety

Sampling Plan Two Class

• almost exclusively used for pathogens absolute: pass or fail

• n: number of samples units to be chosen from the lot

• m: a microbial limit (i.e. cfu/g) a sample is defined to be positive if its microbial content exceeds this limit

Sampling Plan Three Class

• includes a third category “marginable acceptable” represented by M

• designed to decide on acceptance or rejection of a lot

• n: number of sample units to be chosen from the lot

• m: a microbial unit (cfu/g) a sample is defined to be positive if its microbial content exceeds this limit

• c: max allowable number yielding a + result or exceeding the microbiological limit “m”

• M: applied in some cases to recognise occasional deviations. A higher level than m but one which never be exceeded

Three Class Plan

• a three class conc. based plan (i.e. where M has been defined), lot rejection results when more than c sampled fall between m and M, and/or where any sample exceeds M

• microbiological limit(s), m and M

  • acceptable (<m)

  • marginally acceptable (>m and <M)

  • unacceptable (.M)