packaging

Packaging

Dr. Wong Kam Huei

Introduction

• Main functions:– to contain the product – to protect it against a range of hazards - adversely affect quality

• important role in marketing and selling • a wide range of packaging materials is used

– papers, paperboards, fibreboards, metals, glass, textiles, earthenware, polymer materials, and etc.

• a combination of two or more materials is employed• packaging should not give rise to any health hazard

– no leaching of harmful substances– not lead to the growth of pathogenic microb

Introduction

• Should be convenient to use• many environmental implications

– manufacture of packaging materials - energy requirements and the release of undesirable compounds into atmosphere

– recycling - positive influences– disposal of waste packaging materials - not biodegradable, is a

huge problem

Factors affecting the choice of a packaging material

• Mechanical damage – bruising of soft fruits, cracking of biscuits - sudden impacts or

shocks during handling and transport...shocks during handling and transport...– selection of a packaging material of sufficient strength and rigidity

- reduce compression loads (metal, glass & rigid plastic), the incorporation of cushioning materials into the packaging can protect against impacts, shock & vibration (cushioning materials -corrugated papers & board, pulpboard & foamed plastics) and restricting movement of the product within the package by tight-wrapping or shrink-wrapping, inserting boxes or thermoformed trays


• Permeability characteristics – rate of permeation of water vapour, gases and volatile odour

compounds into or out of the package is an important consideration– lose water - a loss of weight and deterioration in appearance and – lose water - a loss of weight and deterioration in appearance and

texture - meat, cheese– pick up moisture - dry powders lose freeflowing characteristics,

biscuits lose crispness, dehydrated product - water activity rise above critical level, microbiological spoilage

– fresh fruit and vege - respiration - humidity inside package increases - condensation may occur - packaging of semipermeable to water vapour

– vacuum packaging, by replacing the air in the package, MAP, packaging material of low permeability to gases and effectively sealed


• Permeability characteristics – respiring food - use O2 release CO2, if gas-tight container is used,

over a period of time, an anaerobic atmosphere will develop when O falls <2% - food spoil rapidlyO2 falls <2% - food spoil rapidly

– ethylene - accelerate the ripening of fruit– coffee - retain the pleasant odour, prevent the absorption of foreign

odours - taints; good barrier to volatile– suitably sealed metal and glass containers - minimised the

movement of gases and vapours


• Greaseproofness– fatty foods - egress of grease or oil on package, spoil appearance,

interfere printing and decoration– use greaseproof and parchment papers for dry fatty foods,

chocolate, milk powder; hydrophilic films or laminates for wet foods, meat or fish

• Temperature – a package - able to withstand the changes in temp - particular

important when foods are heated or cooled in the package– use metal and glass containers; recently - heat resistant laminates– glass - heated or cooled slowly– method of heating influence the choice


• Light – many food components are sensitive to light - the blue and

ultraviolet end of the spectrumultraviolet end of the spectrum– vit may be destroyed, colours may fade and fats may develop

rancidity– use opaque packaging materials; amber glass bottles and

pigmented plastic– if it is desirable that the contents be visible to check the clarity of a

liquid, coloured materials which filter out short wavelength light may be used


• Chemical compatibility of the packaging material and the contents of the package – no health hazard to the consumer– no health hazard to the consumer– to establish the safety of such packaging materials 2 Qs need to be

answered:• are there any toxic substances present in packaging material• will they leach into the product

– toxicological testing - lengthy, complicated and expensive -involving animal feeding trials - need expert interpretation -specialist organisations

– performed storage test before selection of packaging materials; use simulants instead of real foods


• Chemical compatibility of the packaging material and the contents of the package – e.g. of simulant– e.g. of simulant

• distilled water to represent low acid, aqueous foods• 3% acetic acid in aq solution = acid foods• 15% ethanol in aq solution = foods containing alcohol• rectified olive oil = fatty foods

– more than one simulant may be used– amount of vinyl chloride monomer in PVC - concern– interaction between packaging material and food - affect quality

and shelf life– apply an acid resistant lacquer to the inside of the can


• Protection against microbial contamination – usually the most important in the foods that are heat-sterilised in

the package - ppc does not occurthe package - ppc does not occur– thus metal can is used, double seam– glass and plastic containers with effective heat-seals– effective seals are also necessary on cartons, cups and other

containers - aseptically filled with UHT products


• In-package microflora – permeability of packaging material and packaging procedure -

influence the type of microb– do a detailed study of the microbiological implications, type of – do a detailed study of the microbiological implications, type of

food, the treatment received before packaging, conditions of packaging, store, transportation, retail outlet and the home of the consumer

• Protection against insect and rodent infestation – control of insect infestation is largely rely on good housekeeping -

dry, cool, clean storage conditions, good ventilation,adequate turnaround of warehouse stocks, controlled use of insecticides

– packaging also contribute but an insectproof package is expensive except metal and glass containers


• Protection against insect and rodent infestation– films vary in the resistance - the thicker the film the more resistant – laminates which containing foil offer good resistance to

penetrating insectspenetrating insects– use of adhesive tape to seal any openings can help– rodents - metal containers

• Taint – the contents of a package may become tainted by absorption of

volatile compounds fr packaging materials when in direct contact or absorb odorous compounds present in the free space within the package


• Taint – paper, paperboard and fibreboard give off odours - may

contaminate food– recycled material - more likely to cause tainting– recycled material - more likely to cause tainting– clay, wax, plastic coatings applied to the above material - tainting– storage of these packaging materials in clean, dry and well

ventilated stores can reduce the problem– some varieties of wood - cedar, cypress have very strong odours– most polymers are relatively odour-free– lacquers and sealing compounds, some printing inks - possible

sources of odour contamination– careful selection of packaging materials - to lessen the risk


• Tamper-evident/resistant packages – many reports - food packages being deliberately contaminated with

toxic substances, metal or glass fragments - blackmail or revenge toxic substances, metal or glass fragments - blackmail or revenge against companies

– less serious - opening of packages to inspect, or even taste the content and returning them to the shelf

– tamper-resistant and/or tamper-evident features can be incorporated into packages

– a membrane heat-sealed to the mouth of the container, beneath the cap; polymer sleeves heat-shrunk over the necks and caps; breakable caps which are connected to a band by means of frangible bridges that break when the cap is opened


• Package must have a size ands shape which makes it easy to handle, store and display

• Equipment for packaging available at an acceptable speed, • Equipment for packaging available at an acceptable speed, low failure rate

• package must be aesthetically compatible with the contents – good quality wines - in glass– cheaper ones - in ‘bag in box’ containers or plastic bottles

Materials and Containers Used for Packaging Foods

• Types– papers, paperboards, moulded pulp & fibreboard– wooden containers– wooden containers– textiles– flexible films - regenerated cellulose, PVC, PE, PP, etc– metallised films– flexible laminates– metal materials and containers - Al foil, tinplate, etc– glass and glass containers


papers, paperboards, moulded pulp & fibreboard• papers

– almost all paper used is made fr wood– almost all paper used is made fr wood– some fr repulped waste paper - not direct contact with foods– mechanical pulp - paper relatively weak and dull compared to

chemical pulp – types of papers used for packaging foods are:

• kraft paper - strong multipurpose paper used for wrapping; fabricated into bags and multiwall sacks (fruits, vege, grains, sugar and salt in quantities up to 25kg)

• sulphite paper - general purpose paper, not as strong as kraft; used as sachets and bags (papers sachets for custard powders or cake mixes and bags for sugar and flour)


– types of papers used for packaging foods are:• greaseproof paper - is a close-textured paper with greaseproof

properties under dry conditions• glassine paper - produce by polishing the surface of greaseproof • glassine paper - produce by polishing the surface of greaseproof

paper; has some resistance to moisture penetration• vegetable parchment - has good greaseproof characteristics and

retains its strength when wet better than greaseproof paper (butter & margarine)

• tissue paper - is light and has an open structure; used to protect the surface of fruits and provide some cushioning

• wet-strength papers - retain more of their strength when wet; not used in direct contact with food but mainly for outside packaging

• wax-coated papers - are heat-sealable, moderate resistance to water and water vapour transfer; the heat seals are relatively weak and the wax coating may be damaged by creasing and abrasion (toffees)


papers, paperboards, moulded pulp & fibreboard• paperboards

– raw materials are papers– raw materials are papers– the types of paperboard used in food packaging are:

• chipboard - it is dull grey and relatively weak; seldom used in direct contact with foods, but are used as outer cartons when the food is already contained in a film pouch or bag e.g. breakfast cereals

• duplex board - used for some frozen foods, biscuits and similar products

• solid white board - used for some frozen foods, food liquids and other products requiring special protection

• paperboards - coated with wax or polymer materials - mainly used for packaging wet or fatty foods


papers, paperboards, moulded pulp & fibreboard• moulded pulp

– moulded pulp containers - have good cushioning – moulded pulp containers - have good cushioning properties and limit in-pack movement, providing good mechanical protection to the contents (trays for eggs and fruits)


papers, paperboards, moulded pulp & fibreboards• fibreboards

– available in solid or corrugated forms– available in solid or corrugated forms– solid fibreboard is rigid and resistant to puncturing– corrugated fibreboard - diff types but all have good

cushioning characteristics– wax and polymer coated fibreboards are available– fibreboard are used for unpackaged products (fruits,

vege) and also goods already packaged in pouches, cartons, cans and glass containers


• wooden containers– outer wooden containers as in the form of crates and

cases are used when a high degree of mechanical cases are used when a high degree of mechanical protection is required

– wooden drums and barrels are used for liquid products– open cases find limited use for fish, fruits and veges– casks, kegs and barrels are used for storage of wines

and spirits– oak casks are used for high quality wines and spirits– chestnut casks - lower quality wines and spirits


• Textiles– jute and cotton are woven materials used in packaging– sacks made of jute - limited extent, for fresh fruit and – sacks made of jute - limited extent, for fresh fruit and

vege, grains and dried legumes– cotton bags - used in the past for flour, sugar, salt and

similar products– cotton scrims - to pack fresh meat


• Flexible films– Nonfibrous materials in continuous sheet form, up to

0.25 mm thick– Flexible, usually transparent, unless deliberately – Flexible, usually transparent, unless deliberately

pigmented, with the exception of regenerated cellulose– A mixture of two or more polymers, and added

additives are to alter their appearance or improve their handling characteristics

• Plasticisers• Stabilisers• Colouring materials• Antioxidants


• Flexible films - regenerated cellulose– Cellophane– Differs fr the polymer films – it is made fr wood pulp– Differs fr the polymer films – it is made fr wood pulp– Plain regenerated cellullose - clear, transparent, not

heat-sealable - is little used in food packaging– provides general protect against dust and dirt, some

mechanical protection and is greaseproof– when dry - a good barrier to gases– when wet - highly permeable– code letters (A, D, M,…) are used to reflect the

properties of coated regenerated cellulose


• Flexible films - regenerated cellulose– the types of film most often used for food packaging:

• MSAT: nitrocellulose-coated on both sides, a good barrier to water vapour, gases and volatiles and heat-sealablewater vapour, gases and volatiles and heat-sealable

• QSAT: nitrocellulose-coated on both sides, more permeable to water vapour than MSAT and heat-sealeble

• DMS: nitrocellulose-coated on one side only• MXXT: copolymer coated on both sides, very good barrier to

water vapour, gases and volatiles, strong heat-seal• MXDT: copolymer coated on one side only


• Flexible films - PE– Polyethylene - commonly called polythene– the film is available in low (LDPE), medium (MDPE) and high

(HDPE) density grades– the lower density grades are most widely used in food packaging -

due to its strength, low permeability to water vapour and it forms a very strong heat seal; but it is not a good barrier to gases, oils or volatiles - in the form of pouches, bags and sacks

– HDPE has a higher tensile strength and stiffness than LDPE -permeability to gases is lower and it can withstand higher oC - used for foods which are heated in the package, so called ‘boil in the bag’ items


• Flexible films - PVC– polyvinyl chloride – chlorination of acetylene or ethylene followed

by polymerisation under pressure in the presence of a catalyst– Clear, transparent film which on its own is brittle – addition of

plasticizers and stabilisers to the polymer - to give it flexibilityplasticizers and stabilisers to the polymer - to give it flexibility– Used in food – contains only permitted additives– Has good mechanical properties– Permeability to water vapour, gases and volatiles depends on the

type and amount of plasticizers added– Good grease barrier– Can be sealed by high-frequency welding– Is heat-shrinkable– Highly plasticised grades are available with stretch and cling

properties – ‘cling film’ used for stretch-wrapping


• Flexible films – PVdC– Polyvinylidene chloride - made by further chlorination of vinyl

chloride in the presence of a catalyst, followed by polymerisation– The polymer itself is stiff and brittle – unsuitable for use as a

flexible film– Food packaging – is a copolymer of PVdC with PVC – good

mechanical properties, very good barrier to the passage of water vapour, gases and volatiles, greaseproof and heat-sealable (shrink-wrapping foods), can withstand relatively high oC – hot filling and retorting

– Oriented form – has improved strength and barrier properties and is highly heat-shrinkable


• Flexible films – PP– Polypropylene – produced by low-pressure polymerisation of

propylene in the presence of a catalyst– Mechanical properties are good except at low oC – brittle– Permeability to water vapour and gases is relatively low– Heat-sealable, but at a very high oC, 170oC– Usually coated with PE or PVdC/PVC copolymer to facilitate heat-

sealing– Used in the form of bags or overwraps– OPP (oriented) – better mechanical properties particularly at low

oC, good barrier to water vapour but not gases, normally heat-shrinkable, stable at relatively high oC, used for in-package heat processing

– White opaque form of OPP – pearlised film


• Flexible films – PET– Polyester film used in food packaging is polyethylene terephthalate

– usually produced by a condensation reaction between terephthalic acid and ethylene glycol and extrudedterephthalic acid and ethylene glycol and extruded

– Widely used in the orientated form – good tensile strength– Coated – increase barrier properties and facilitate heat-sealing,

stable over a wide oC range, can be used for ‘boil in bag’ applications

– Metallised PET – available , has a very low permeability to gases and volatiles – packaging snack foods


• Flexible films – PS– Polystyrene – produced by reacting ethylene with benzene to form

ethylbenzene – dehydrogenated to give styrene – polymerised at low oC, catalystlow oC, catalyst

– Stiff and brittle with a clear sparkling appearance – not in food packaging

– Oriented – less brittle, increased tensile strength, high permeability to vapours and gases, is greaseproof, stable at low temp, below 0oC; shrinks on heating, may be heat-sealed

– Wrapping of fresh produce, also widely used in the form of thermoformed semirigid containers and blow-moulded bottle; foam for containers – egg cartons, fruit trays and containers for takeaway meals


• Flexible films – Pas– Nylons – produced by 2 diff reactions

• Nylon 6,6 and 6,10 (no of C atoms followed by no in the acid) –formed by condensation of diamines and dibasic acidsformed by condensation of diamines and dibasic acids

• Nylon 11 and 12 (total no of C atoms) – formed by condensation of ω-amino acids

– Clear and attractive in appearance, mechanically strong but vary with types, permeability to water vapour varies, good barriers to gases, volatiles and greases

– Stable over very wide oC range, heat-sealed at high oC 240oC– Can be coating, combined as copolymers– Packaging of meat products, cheese and condiments


• Flexible films – PC– Polycarbonate – made by the reaction of phosgene or

diphenyl carbonate with bisphenol Adiphenyl carbonate with bisphenol A– Mechanically strong and grease-resistant, high

permeability to vapours and gases, stable over 70-130oC

– Not widely used for food, but could be used for ‘boil in the bag packages, retortable pouches and frozen foods


• Flexible films – PTFE– Made by the reaction of hydrofluoric acid with

chloroform followed by pyrolysis and polymerisationchloroform followed by pyrolysis and polymerisation– strong, low permeability to vapours and gases, grease-

resistant, stable over -190 to 190oC– not widely used in film form but could be used for

retortable packages– best known for its nonstick property - coating cooking

utensils


• Metallised films– thin metal coating on flexible packaging film– originally introduced for decorative purposes– metallising - increased resistance to the passage of water vapour

and gases up to 100%– to package snack foods


• Flexible laminates– when a single paper or film does not provide adequate protection

to the product, 2 or more flexible materials may be combined together in the form of a laminate

– laminates may be formed fr paper-paper, paper-film, film-film, paper-foil, film-foil and paper-film-foil combinations - bonded paper-foil, film-foil and paper-film-foil combinations - bonded together by adhesive

– when one or more of the layers is permeable to water vapour, an aqueous adhesive may be used, otherwise nonaqueous adhesives must be used

– examples: vegetable parchment-foil for wrapping butter and margarine; MXXT regenerated cellulose-PE for vacuum packed cheese, cooked and cured meats; PET-PE for coffee, paperboard-foil-PE for milk and fruit juice cartons; retortable pouches may be made of a threeply laminate typically of PET-foil-PP or PET-foil-HDPE


• Heat-Sealing Equipment– many films are thermoplastic and heat sealable– nonthermoplastic materials - coated with or laminated to

thermoplastic material - heat-sealing– nonthermoplastic are best sealed with a hot bar or resistance sealer– oC, pressure, contact time - influence the sealing– electronic sealing - used on thick layers of the polymer material,

mainly PVC and PVC/PVdC copolymers– ultrasonic sealing may be used to seal layers of film or foil together

- uncoated, oriented materials that are difficult to seal by other methods


• Packaging in flexible films and laminates– to overwrap items of food - film is stretched over the meat and

under the tray– made into preformed bags - filled by hand or machine then sealed– most widely used in the form of sachets, heat-sealed on all 4 edges,

Figs. 9.1 and 9.3– a pillow pack is a pouch with a longitudinal heat seal and two end

seals, Figs. 9.2 and 9.4 – form-fill-seal (FFS) system - machines may operate vertically or

horizontally - solid, liquid products– pillow packs are more economical than sachets in the use of

packaging material - thin, flexible, good slip characteristics and form a strong seal even before cooling

– sachets - stiffer material and wider range of product types


Flexible Films and Laminates

• Rigid and semirigid plastic containers– formed by LDPE, HDPE, PVC, PP, PET and PS, singly or in

combinations– acrylic plastics are also used for this purpose


– methods used to convert these materials into containers• thermoforming - produce opentopped or widemouthed containers

such as cups and tubs for yoghurt, cottage cheese or margarine, trays for eggs or fresh fruit and inserts in biscuit tins or chocolate boxes

• blow moulding - produce narrownecked containers such as bottles for oils, fruit juices and milk, squeezable bottles for sauces and syrups

• injection moulding - produce widemouthed containers such as cups and tubs for cream, yoghurt, mousses as well as phials and jars for a variety of uses

• compression moulding - produce screw caps

• Metal materials and containers– aluminium, tinplate and electrolytic chromium-coated steel

(ECCS)– aluminium - foil or rigid metal


• Metal materials and containers - Al foil– produced fr aluminium ingots by a series of rolling operations

down to a thickness in the range 0.15 - 0.008 mm– contains not less than 99.0% aluminium, with traces of silicon,

iron, copper and in some cases chromium and zinc– foil used in semirigid containers also contains up to 1.5%

manganese– foil is a bright, attractive material, tasteless, odourless and inert

with respect to most food materials

• Metal materials and containers - Al foil– for contact with acid or salty products - coated with nitrocellulose

or some polymer material– mechanically weak, easily punctured, torn or abraded - coating or

laminating - increase resistance to such damage– thin foil <0.03 mm - contain perforations and will be permeable to


– thin foil <0.03 mm - contain perforations and will be permeable to vapours and gases - coating or laminating it with polymer material will improve its barrier properties

– stable over a wide oC range– as a component in laminates - sachets or pillow packs on FFS

equipment; in laminates used for retortable pouches and rigid plastic containers for ready meals

– a component in cartons for UHT milk and fruit juices– trays, plates, dishes made fr foil of 0.03 - 0.15 mm (up to 1.5%

manganese) for frozen pies, ready meals and desserts - can be heated in the container

• Metal materials and containers - tinplate– most common for cans– consists of low-carbon, mild steel sheet or strip, 0.50-0.15 mm

thick, coated on both sides with a layer of tin– mechanical strength and fabrication characteristics of tinplate


depend on the type of steel and its thickness - 4 types of steel are used in cans

– the corrosion resistance and appearance of tinplate depend on the tin coating - D.5.6/2.8 plate has 5.6 gm-2 of tin on one side and 2.8 gm-2 on the other - higher coating form the inside of cans

– lacquer - prevent undersirable interaction between the product and the container

• info in Table 9.1 - acid foods…; strongly coloured products….; sulphur containing foods….; products sensitive to small traces of tin...

• as a nonstick surface - solid meats packs


Metal Materials and Containers



• Table of Lacquer• Table of Lacquer


• Metal materials and containers - ECCS– electrolytic chromium-coated steel - tinfree steel - increasing use

for food cans– less resistant to corrosion - normally lacquered on both sides– less resistant to corrosion - normally lacquered on both sides– more resistant to weak acids and sulphur staining than tinplate


• Metal materials and containers - Al alloy– hard-temper al alloy - containing 1.5-5.0% magnesium - food cans– lighter but mechanically weaker, less resistant to corrosion than

tinplate - need to be lacquered– manufactured in similar manner to al foil


• Metal containers– 3-piece can - traditional, still widely used for heat-processed foods - can

body and 2 ends are made separately, one end is applied to the can body by the can maker, the other by the food processor after filling

– fig. 9.8a - the making of 3-piece can– fig. 9.9 - double-seaming– fig. 9.9 - double-seaming– DR can - drawn can is a 2-piece container - can body and base are made

in one operation fr a blank metal sheet - pressed out with a suitable die -shallow with a max height:diameter ratio of 1:2 due to the strain on the metal

– DRD can - 2-piece can - deeper than DR can - relatively small, height:diameter ratio of up to 1.2:1.0

– DWI can - drawn and wall-ironed can - fr disc of metal 0.30-0.42 mm thick - carbonated beverages - the internal pressure support the thin wall

– other metal containers - with a friction plug closure; push-on lids;...

• glass and glass containers– still widely used

• the advantages and disadvantages of using glass as the


• the advantages and disadvantages of using glass as the packaging material

– Advantages:

• Glass is inert with respect to foods.• Transparent.• Impermeable to vapours, gases and oils.• Smooth internal surface – can be washed and sterilised – can

be reused.

– Disadvantages: • Glass containers are relatively heavy.• Susceptible to mechanical damage.


• Susceptible to mechanical damage.• Cannot tolerate rapid changes in temperature (low

thermal shock resistance).• Broken glass in a food area is an obvious hazard


Glass

• These ingredients together with up to 30% recycled glass are melted in a furnace at 1350-1600oC

• two forming methods are used– the blow and blow process– the press and blow process


Glass

Materials and Containers Used for Packaging FoodsGlass


Glass

• The mechanical strength of glass containers are:are:– the resistance to internal pressure, vertical loads and impacts– increases with increasing thickness of the glass in the bodies and

bases– the design of the container also influences its strength– cylindrical containers are more durable than other shapes– the greater the radius of curvature of the shoulder, the more

resistant the container is to vertical loads– the thickness of the glass in the base is usually greater than the

body


Glass

• The resistance of glass containers to sudden changes in oC is reduced as the thickness of the glass increaseis reduced as the thickness of the glass increase– involved heating or cooling, a compromise has to be achieved

between their mechanical strength and thermal shock resistance; process rate also relatively slow to avoid thermal damage

• The cap is made of metal or plastic– screwed on, crimped on or pushed in or onto the finish of the

container– roll on caps are used as tamper-evident closures– 3 diff closures:

• normal seal, vacuum seal, pressure seal


Glass

– Pressure seals are necessary when packaging carbonated drinks

• singletrip glass containers are used for liquids such as some beers, soft drinks, wines, sauces, salad dressings and vinegars; for dry foods such as coffee and milk powders

• multitrip containers are used for pasteurised milk, some beers and soft drinks

• products heated in glass containers include sterilised milk, beer, fruit juices and pickled veges.

Modified Atmosphere Packaging

• MAP - involves replacing air inside a package with a predetermined mixture of gases prior to sealing it

• once sealed, no further control• the composition may change during storage - due to

respiration of the contents and/or solution of some of the respiration of the contents and/or solution of some of the gas in the product

• vacuum packaging - air is drawn out but no other gases are introduced - cured meats and cheese

• MAP is created by one of two methods– air removed by a vacuum pump and the appropriate mixture of

gases introduced– air is displaced by flushing it through with the gas mixture


• Horticultural products - equilibrium composition depend on the rate of respiration of the food and the permeability of the packaging material to gases

• the gases involved in MAP - CO2, N2, O2• the gases involved in MAP - CO2, N2, O2

• CO2 -– reacts with water to form carbonic acid - lower pH of food; – inhibits the growth of certain microb (moulds and some aerobic

bacteria) - gas at conc. 5-50%– lactic acid bacteria and most yeasts are resistant to CO2

– anaerobic bacteria - food poisoning organisms are little affected -potential health hazard

– higher conc. The greater is its inhibitory power– the inhibition increases as the oC decrease


• strict oC control is essential to ensure the safety of MAP foods

• N2 -– no direct effect on microb or foods– no direct effect on microb or foods– to replace O2 - inhibit oxidation of fats– solubility in water is low– used as a bulking material to prevent the collapse of

MAP packages when the CO2 dissolves in the food– also useful in packages which may consolidate under

vacuum


• O2 -– red meat - maintain the red colour - oxygenation of the

myoglobin pigments– fish - to reduce the risk of botulism

• other gases have antimicrobial effects -• other gases have antimicrobial effects -– CO : inhibit the growth of many bacteria, yeasts and moulds;

conc. ~ 1%; toxic and explosive nature, not used commercially

– SO2 : used to inhibit the growth of moulds and bacteria in some soft fruits and fruit juices; concern - some people may be hypersensitive to SO2

– noble gases : argon, helium, xenon and neon - used in MAP

Aseptic Packaging

• UHT-treatment products have to be packaged under conditions which prevent microb contamination

• High-acid food (pH<4.5) – cool the product after UHT treatment to just below 100oC, fill into a clean container, seal the container and hold it at that temp for some minutes before cooling – will inactivate microb that may have been before cooling – will inactivate microb that may have been in the container or entered during the filling operation

• Low-acid food (pH>4.5) – aseptic filling must involve sterilising the empty container or the material fr which the container is made, filling it with the UHT-treated product and sealing it without it being contaminated with microb

• Rigid metal containers – superheated steam at 260oC may be used to sterilise the empty containers and maintain a sterile atmosphere during the filling and sealing operations

Aseptic Packaging

• Glass containers and some plastic and composite containers may be aseptically filled by the same method

• Cartons made fr a laminate of paper/al foil/PE are widely used for UHT products such as liquid milk and fruit juices –this type of packaging material cannot be sterilised by heat alone, a combination of heat and chemical sterilant is usedalone, a combination of heat and chemical sterilant is used

• H2O2 at 35% in H2O and 90oC is very effective against heat-resistant, sporeforming microb – widely used as sterilant in aseptic packaging in laminates

• Form-fill-seal systems are available, an example being the Tetra Brik system by Tetra Pak Ltd. Fig. 9.13.

• Similar systems are available to aseptically fill into the preformed plastic cups.

Active Packaging

• Active packaging has been used with many food products• Active packaging refers to the incorporation of certain

additives into packaging film or within packaging containers with the aim of maintaining and extending containers with the aim of maintaining and extending product shelf life

• Active packaging includes additives or ‘freshness enhancers’ that are capable of scavenging O2, adsorbing CO2, moisture, ethylene and /or flavour/ odour taints, releasing ethanol, sorbates, antioxidants and/or other preservatives and/or maintaining oC control

Active Packaging

• Table 9.3 lists some of the food applications that have benefited fr active packaging technology. Example:technology. Example:– For fruit juices, fish,…and dairy products

• Flavour/ odour absorbers

– For fruit, vegetable and other horticultural products

• Ethylene scavengers

Active Packaging

• Selected examples of active packaging systems

• Selected commercial oxygen scavenger • Selected commercial oxygen scavenger systems

Active Packaging

• O2 scavengers– The main advantage – capable of reducing O2 levels to

less than 0.01%, much lower than the typical 0.3-3.0% residual O levels achievable by MAPresidual O2 levels achievable by MAP

– Can be used alone or in combination with MAP– Nonmetallic O2 scavengers – enzyme-based, glucose

oxidase or ethanol oxidase – be incorporated into sachets, adhesive labels or immobilised onto packaging film surfaces

Active Packaging

• CO2 scavengers/emitters – produce significant volumes of CO2 needed

• Ethylene scavenger – to remove or to suppress its effects• Ethanol emitters – ethanol as an antimicrobial agent• Preservative releasers – antimicrobial and antioxidant • Preservative releasers – antimicrobial and antioxidant

packaging – extend shelf life• Moisture absorbers – excess moisture – cause food

spoilage• Flavour/odour adsorbers• Temp control packaging – the use of innovative insulating

materials – self-heating and self-cooling cans

Active Packaging

• Food safety and regulations related to the active packaging of foods– Any need for food contact approval must be established – Any need for food contact approval must be established

before any form of active packaging is used.– It is important to consider environmental regulations

covering active packaging materials.– Need for labelling in cases where active packaging may

give rise to consumer confusion.– It is pertinent to consider the effects of active packaging

on the microbial ecology and safety of foods

Calculation• A method to calculate the shelf life of packaged dry foods,

based on the permeability of the pack, the water activity and equilibrium moisture content of the food, the eqn.:ln[(Me – Mi)/(Me – Mc)] = (P/X) x (A/Ws) x (Po/b) x (ts)

where M = equilibrium moisture content of the food,where Me= equilibrium moisture content of the food,Mi = initial moisture content of the food, Mc = critical moisture content of the food, P/X = permeability of the packaging material (g water day-1m-2), A = area of package (m2), Ws = weight of dry solids in the food, Po= vapour pressure of pure water at the storage temperature (Torr), b = slope of the moisture sorption isotherm (g H2O/g solids per unit aw) and ts = time to the end of the shelf life (days)

Example - Question

Cream crackers that are packaged in a 0.4 m2 sealed bag are found to be having 200g of dry solids. Packaging materials are made from barrier film, which has a water vapour transmission rate of 0.015 ml day-1 m-2. The crackers are expected to be stored at 28oC and the vapour pressure of pure water at the expected to be stored at 28 C and the vapour pressure of pure water at the storage temperature = 18 Torr. From the studies of the sorption isotherm of the crackers, the equilibrium moisture content = 0.05 g per g of solids, initial moisture content = 0.015 g per g of solids, the critical moisture content = 0.02 g per g of solids, and the slope of the moisture sorption isotherm = 0.06 g H2O/ g solids per units aw. Calculate the expected shelf life using this film.

SolutionsLn[(Me – Mi)/ (Me – Mc)] = (P/X) x (A/Ws) x (Po/b) x (ts)

ts = ln[(0.05 – 0.015)/ (0.05 – 0.02)]/ [0.015 x (0.4/200) x (18/0.06)]

= 0.1542/ 9.0 x 10-3 = 0.1542/ 9.0 x 10 = 17.1 days

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