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  • Meat Processing 1 Common preservation techniques

    A webinar presented by:

    Dr Andy Bowles

    Attendee Notes

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    Meat Processing 1 Common preservation techniques

    Dr Andy Bowles

    Introduction

     In this webinar I will discuss:  General principles of preservation  Common techniques used in the meat industry  Heat treatment  Lowering of water activity (aw)  Reduction of pH  Use of chemical preservatives  Use of modified atmospheres

    Types of meat product

    Meat Preparations

    Burgers

    Sausages

    Kebab

    Cured Meat pieces

    Cured raw meat

    Cured cooked meat

    Raw-cooked meat

    Frankfurters

    Meat loaf

    Pre-cooked cooked

    products

    Black pudding

    Liver sausage

    Fermented sausages

    Salami

    Dried products

    Biltong

    Jerky

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    General principles

    Chemical Composition of meat

    PRODUCT WATER PROTEIN FAT MINERALS BEEF (LEAN) 75.0 22.3 1.8 1.2 BEEF (CARCASS) 54.7 16.5 28.0 0.8 PORK (LEAN) 75.1 22.8 1.2 1.0 PORK (CARCASS) 41.1 11.2 47.0 0.6 CHICKEN 75.0 22.5 0.9 1.2 FRANKFURTER 63.0 14.0 19.8 0.3 LIVER SAUSAGE 45.8 12.1 38.1 LIVER PATE 53.9 16.2 25.6 1.8 SALAMI 33.9 24.8 37.5

    Common processes used by meat industry

     Heat treatment  Lowering of water activity (aw)  Reduction of pH  Use of chemical preservatives  Use of modified atmospheres

     Hurdle technology

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    Heat Treatment

    Heat treatment

     Heat treatment of processed meat products serves two main purposes:  Enhancement of desirable texture,

    flavour and colour  Reduction of microbial content  Ready to eat  Appropriate shelf life

    Heat treatment

     Can be two-stage heat treatment:  As part of processing  Prior to consumption

     Frankfurters  raw-cooked sausage  Initial process used to achieve desired:  Texture  Flavour  Colour

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    Heat treatment

     Some products subject to two initial heat treatments  Raw materials pre-cooked  Further processed  For example black pudding.

     Important to be clear about the nature of heat treatment on inspection.

    (

    Thermal processing

     Different degrees of preservation:  Sterilisation  Complete destruction of micro-organisms  121°C for 15 mins

     Commercial sterility  All pathogens, toxins and spoilage bacteria destroyed.  Some thermoduric survivors

     Pasteurisation  Kills pathogens  Extends shelf life

     Blanching  Inactivates key enzymes  Reduce bacterial load

    Effect of Heat on Micro-Organisms

     Application of heat sufficient to kill micro organisms:  Results in % kill / unit time

     Characterised by “D”, “Z” and “F” values.

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    D Values

     Decimal reduction time  Varies for different

    organisms  Quoted at a particular

    temperature ie “D121”  Cells die more rapidly

    at higher temperature

    1

    10

    100

    1000

    0 5 10 15

    Su rv

    iv in

    g Sp

    or es

    Heating Time (Min)

    D Value 5 Mins

    D Values

     This is the time taken to reduce micro population by 90%  Higher “D” Value indicates higher heat resistance

     NOTE: More Micro orgs in raw material, longer it will take to get to desired level

    D Values

     Can be expressed as 5D, 8D or 12 D etc  8D process will reduce numbers by 100,000,000  5D and 8D commonly used,  12D used for low acid canning

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    Heat Resistance of Food Poisoning Bacteria

    Organism D Value (seconds) Campylobacter sp D55 = 60 Salmonella sp D60 = 34.8 Listeria sp D 71.7 = 3.3 Staph. Aureus D60 = 120 – 2000

    D71.7 = 4.1 Clostridium botulinum

    Escherichia coli

    D121 = 12.6 D62.8 = 7.8

    Z Value  Change in ºC required to

    bring about a 10 fold change in D

     aka Temperature coefficient of destruction

     D and Z values characterise the heat resistance of an organism 1

    10

    100

    1000

    90 110 120 130

    D v

    al ue

    s

    Temperature

    Z Values

    Destruction of E.coli o157 in burgers ACMSF 2007

    Temperature °C ACMSF Recommendation

    6 D reduction Z 6°C

    60 45 mins 93 mins

    65 10 mins 13.6 mins

    70 2 mins 2 mins

    75 30 secs 18 secs

    80 6 secs 3 secs

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    F Value

     Total time/temp received by a food.

     F0 = F121  Number of minutes at 121°C to heat food

    Minimum Safe Process  “Botulinum Cook”  Applied to low acid canned foods  Necessary to achieve 12D reduction of

    Clostridium botulinum spores  At 121ºC D value for Cl.botulinum is 0.21

    minutes  12 x 0.21 = 2.52 minutes (ie F0 of 3.0)  F0 values will vary according to food type etc  Sufficient margin of safety built in.

    Food safety controls: Thermal Process

     Thermal process must be adequate to control identified microbial hazards:  Salmonella spp  E.coli o157  Listeria spp  Staph.aureus etc.

     Where necessary:  C.botulinum

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    Food safety controls: Thermal Process

     Where risk from C.botulinum considered high  90°C for 10 minutes or equivalent

     Where risk from C.botulinum not considered high:  70°C for 2 minutes or equivalent

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    Lowering water activity

    aw - Water Activity

     Measure of amount of liquid water available for microbial growth

     Pure water = 1.0  Presence of solutes =

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    aw values for limiting microbial growth MICROORGANISM aw

    Pseudomonas 0.93 E.coli 0.93 Salmonella spp 0.91 – 0.95 Listeria 0.93 Clostridium botulinum (proteolytic) 0.94 Clostridium botulinum (non-proteolytic) 0.97 Clostridium perfringens 0.93 – 0.95 Bacillus species 0.90 – 0.95 Staph aureus 0.86 – 0.90 Most yeasts 0.87 – 0.90 Most moulds 0.80 – 0.85

    Reduction of pH

    Effects of pH on microbial growth  Acidophile  Lactobacillus acidophilus

     Neutrophile  Salmonella spp

     Alkaliphile  Nitrobacter spp

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    Reduction of pH

    PRODUCT pH Raw fermented sausage 4.5 – 5.2 Beef 5.4 – 6.0 Pork 5.5 – 6.2 Canned meats 5.8 – 6.2 Biltong 5.8 Ham 5.9 – 6.1 Black pudding 6.5 – 6.8

    (

    Typical pH values for some foods pH Range Food pH Low acid (pH 7.0 –5.5)

    Medium acid (pH 5.5 – 4.5)

    Acid (pH 4.5 – 3.7)

    High acid (pH

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    Effects of osmotic pressure on microbial growth

    Typical NaCl levels in some Foods

    Food NaCl (%) Bacon Ham (canned) Ham (raw) Smoked Fish Cheddar Cheese Raw Fish Raw Meat – Beef Lamb Chicken Turkey

    3.0 – 4.8 3.2 2.6 – 3.6 1.9 – 4.8 1.6 – 1.8 0.3

    0.2 0.2 0.2 0.2

    Use of modified atmospheres

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    Vacuum and modified atmosphere packaging

     MAP - a definition “packaging of a food product in something other than air” Includes:

     vacuum packaged (VP)  modified atmosphere packaged (MAP)  controlled atmosphere packaged (CAP)  gas packed/gas flushed  sous-vide  Also any other condition which will result in a similar reduction of

    oxygen e.g. deep-filled or hermetically sealed products

    Vacuum Packing (VP)

     Food Preservation technique where:  atmospheric air is removed  vacuum maintained by integrity of pack

    Vacuum Packing (VP) Advantages

     Increased shelf life  Equipment relatively

    inexpensive  Freshness and flavour

    maintained  Moisture retained  Rancidity reduced  Infestation eliminated  Wastage reduced  Portion control and

    presentation

    Disadvantages  Temperature control

    required  Inherent food safety risks  Not suitable for soft

    products  Undesirable colour

    changes in red meat

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    Modified Atmosphere Packaging (MAP)

     Food preservation technique whereby:  the composition of the atmosphere surrounding

    the food different from the normal composition of the air.

     Process involves  Removal of air  Replacement with mixture of  Carbon dioxide  Nitrogen  Oxygen

     Gas mixture varies for type of food

    Gases for MAP

     CO2  has biostatic properties against many

    psychrotrophic bacteria  O2  inhibits anaerobes, develops bright red colour in

    meat  N2  inert, used as a filler to prevent collapse of

    packaging.

    Effects of MAP on Micro-organisms

     CO2 Increases lag phase

     Gram -ve more sensitive to CO2

     CO2 can inhibit growth of spoilage moulds

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    Advantages / Disadvantages of MAP

    Advantages  Increased shelf life  Reduced distribution

    costs  High quality product  Reduced need for

    additives  Minimisation of waste

    Disadvantages  Expensive  Temperature control

    required  Different gases required

    per product  Spec