Canning of food 1 Science and technology

A webinar presented by:

Dr Andy Bowles

Attendee Notes

08/04/2018

Canning of food 1 Science and technology

A webinar by

Dr Andy Bowles

Introduction

 This webinar will consider

 The food safety concerns.

 Principles of thermal processing.

 Canning

 Flexible retort pouches

 Canadian Food Inspection Agency  http://inspection.gc.ca

Food Safety Concerns

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Food Safety Concerns

 Absence of oxygen

 Growth of Clostridium botulinum favoured

 Primary Food Safety Concern:

 Survival of Cl.botulinum spores

 Increased probability of C.botulinum toxin formation before spoilage bacteria make product unacceptable to the consumer

Characteristics of Group I and II C. botulinum. Characteristic* Group I Group II (proteolytic) (non-proteolytic) (A ,B & F) (B & E) Minimum temperature for 10 3.3 growth (oC) Maximum Temperature for 48 45 growth (oC) Inhibitory pH 4.6 5.0

Inhibitory NaCl concentration 10 5 (%)

Inhibitory aw 0.94 0.97

*Value when other conditions are optimal for growth

Typical pH values for some foods pH Range Food pH Low acid (pH 7.0 –5.5) Milk 6.3 – 6.5 Cheddar Cheese 5.9 Bacon 5.6 – 6.6 Red Meat 5.4 – 6.2 Ham 5.9 – 6.1 Poultry 5.6 – 6.4 Fish 6.6 – 6.8 Butter 6.1 – 6.4 Bread 5.3 – 5.8 Medium acid (pH 5.5 – 4.5) Cottage cheese 4.5 Green beans 4.6 – 5.5 Bananas 4.5 – 5.2 Acid (pH 4.5 – 3.7) Mayonnaise 3.0 – 4.1 Tomatoes 4.0 High acid (pH <3.7) Canned pickles, fruit 3.5 – 3.9 juice 3.1 – 3.3 Sauerkraut 3.0 – 3.5 Citrus fruit 2.9 – 3.3 Apples

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Assessment of Risk from C.botulinum

 Basic principles:

 C.botulinum must be present

 Inadequate processing or unprocessed product

 Product must support growth and toxin formation  Intrinsic  Extrinsic

 Toxin must be ingested.

Principles of thermal processing

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

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Effect of Heat on Micro-Organisms

 Application of heat sufficient to kill micro organisms:

 Results in % kill / unit time  Terms “D”, “Z” and “F” values used

D Values

D Value 5 Mins

 Decimal reduction time 1000  Varies for different organisms 100  Quoted at a particular temperature ie “D121” Surviving Surviving Spores  Cells die more rapidly 10 at higher temperature

1 0 5 10 15

Heating Time (Min)

D Values

 Can be expressed as 5D, 8D or 12 D

 8D process will reduce numbers by 100,000,000

 5D and 6D commonly used in catering,

 12D used for low acid canning

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Z Value Z Values

 Change in ºC required to 1000 bring about a 10 fold change in D 100  aka Temperature

coefficient of destruction values D 10  D and Z values characterise the heat

1 resistance of an organism 90 110 120 130 Temperature

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.

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Heat transfer

 Essential that specified Fo is applied throughout the food.  Heat penetration:

 Through container

 Throughout food  Depends on:

 Conduction (solids)

 Convection (liquids)

F Values

Product F0 Canned salmon 7.0

Canned Strawberries 1.0

Baked Beans 5.0

Dog Food 14.0

Canning of food

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Canning

 Important factors:

 Selection & preparation of raw materials

 Heat process adequate

 Seal adequate

 Can protected from damage

General Principles

 Food is prepared/cleaned  Cans sterilised  Placed in can, filled with liquid  Lid placed in position, “Exhausted”  Lid sealed  Botulinum cook  Cooling

Raw Materials

Inspection

Can wash

Filling

Brine/Syrup

Exhaust

Seal

"Cook"

Cool

Drying Labelling Storage

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Raw materials

 Raw materials

 Good quality

 Low bacterial load

 Inspection/ Metal detection

Raw Materials

 Products such as soup are prepared in vats prior to canning  Good Manufacturing Practice (GMP) very important  Prevent taints, heat stable spores

Filling  Without delay  Should be precise to ensure desired headspace achieved  Normally hot fill

 Liquids added before solids to avoid air pockets  Brine/syrup may be added

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Exhausting

 Process to remove air from the can  Can be achieved by blowing steam into headspace  Product then sealed - double seal

Sealing

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Two-piece can Source CFIA

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Key operated cans

Ring pull cans

Common Defects

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Droop

Double end

Fractured seam

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“Cooking”

 Cans heated to desired temp/time in retort  Can be saturated steam  “Venting” displaces air with steam  Air can insulate cans or lower retort temp  Usually have venting schedule - product and retort specific

Retort

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Retort

Cooling

 Post heat treatment contamination  water potable, normally chlorinated (0.5ppm)  Cooling water regularly monitored

Flexible retort pouches

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What are flexible retort packages?

 Flexible laminated food pouch  Can withstand thermal processing.  Developed by US Army  Alternative to traditional canning  Variable heat treatment:

 Sterilisation  Ambient shelf life

 Pasteurisation  Chilled shelf life

Retort pouch v Canning: Advantages

 Reduced heat treatment

 Lower temperatures

 Shorter times  Greater product range  Better taste  Package easy to open  Storage and haulage cost savings  Better presentation

Retort pouch v Canning: Disadvantages

 Reduced heat treatment

 Lower temperatures

 Shorter times  Complex thermal process

 number of critical processing parameters

 residual air, pouch thickness, steam/air mixture.  Specialist packaging required  Package less robust  Storage/haulage abuse

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Retort pouch materials

 Characteristics essential to a satisfactory retort pouch are:  Low gas permeability (oxygen)  Low moisture permeability  Temperature resistant  Heat sealable  Constructed of appropriate material  Resistant to penetration by fats, oils and other food components  Physical strength to resist physical abuse during packing, retorting, storage and distribution  Absence of solvent residues.  Bonding materials for the laminates must not migrate into the foods.  High light barrier.

Source: CFIA

Retort pouch materials

 Pouches normally pre-formed  3 or 4-ply

 Polypropylene inner

 Aluminium foil

 Nylon (optional)

 Polyester outer

Filling/Sealing

 Manual  Automatic  Semi-automatic

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Filling - automatic

Filling – semi automatic

 No spillage of product on seals

 May prevent effective seal

 No over/under fills

 Airspace preservation

Post seal handling

 Key issues:

 Protection from damage/contamination

 Time/temperature

 Cage loading

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Retorting

Retorting – process control

 Essential that critical limits:

 Achieved

 Recorded

 Parameters may be product specific

 Calibration

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Common defects

Blisters in seal

Crooked seal

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Incomplete seal

Leakers

Blown pouch

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Questions?

Dr Andy Bowles FIFST Specialist food law solicitor

[email protected] www.abcfoodlaw.co.uk 01603 274486

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