Food Packaging Technology Past Paper 20/1 PDF

P A P E R A N D FST648 FOOD PACKAGING TECHNOLOGY P A P E R B O A R D P A C K A G I N G M A T E R I A L S TOPIC 2 20 / 1 O E Manufacturing of paper 01 FST648 FOOD PACKAGING TECHNOLOGY...

P A P E R A N D FST648 FOOD PACKAGING TECHNOLOGY P A P E R B O A R D P A C K A G I N G M A T E R I A L S TOPIC 2 20 / 1 O E Manufacturing of paper 01 FST648 FOOD PACKAGING TECHNOLOGY Types of papers and U N their properties 02 Advantages and T I disadvantages of paper and paperboard 03 L 20 / 2 CLASS FST648 FOOD PACKAGING TECHNOLOGY OBJECTIVES EXPECTATIONS AND OUTCOMES Able to discuss Able to determine the the process of various types of paper paper production and its applications 20 / 3 INTRODUCTION The word ‘Paper’ derives from plant ‘Papyrus’ FST648 FOOD PACKAGING TECHNOLOGY used by ancient Egyptians as a writing material - produced by beating & pressing together thin layers of papyrus stem. Paper was first produced in Egypt around 900 AD. Started in China – invented by Ts’aiLun (105 AD) – use mulberry bark, hemp and rags with water. Fabrication of paper was monopolised by Chinese Empire for over 500 yrs. 20 / 7  At present, 97% of world’s paper & FST648 FOOD PACKAGING TECHNOLOGY board are made of wood pulp. 85% of the wood pulp used is from spruces, firs, pine (coniferous trees) and oak trees. Other plants utilised for paper making – cotton, bamboo, kenaf etc. 20 / 4  FST648 FOOD PACKAGING TECHNOLOGY WHAT IS PAPER? a substance made in the form of thin sheets or leaves from rags, straw, bark, wood or other fibrous material for various uses PAPER PAPERBOARD VS structures < 300 um thicker than paper (>0.25 mm) 20 / 8  PAPER & PAPERBOARD FST648 FOOD PACKAGING TECHNOLOGY PAPER PAPER TYPES AND MANUFACTURING PROPERTIES Kraft paper ADVANTAGES AND Glassine paper DISADVANTAGES Greaseproof paper Parchment paper OF PAPER Waxed paper PACKAGING Paperboard 20 / 5  WOOD PULP SOFTWOOD HARDWOOD FST648 FOOD PACKAGING TECHNOLOGY Source: Pine, Spruces, Cedar, Rosewood, Source: Oak, Maple, Walnut tree, etc Kenaf, etc Compositions: Compositions: Cellulose - 42% Cellulose - 45% Hemicellulose - 27% Hemicellulose - 30% Lignin - 28% Lignin - 20% Properties: Properties: Long-fibered wood: 2 to 4 mm (the longer Short-fibered wood: < 1.5 mm the fiber, the stronger the paper). Produce finer and smoother but Provide paper strength & good runability less strong paper sheet. in paper machine. Provide good printability in the Best used for grocery bags or paperboard form of optical properties such as such as boxes which requires strength. 20 / 6 brightness and smoothness. 20 / 9 PAPER MANUFACTURING FST648 FOOD PACKAGING TECHNOLOGY STAGE 1: PULPING PROCESS Process of separation fibrous raw materials (pulp) without damaging them – can be reformed into paper sheets in papermaking process FST648 FOOD PACKAGING TECHNOLOGY PULPING METHODS MECHANICAL CHEMICAL SEMICHEMICAL PULPING PULPING PULPING Using rotating grindstone - Using chemicals such as Combination of physically taken Alkaline and Sulfates mechanical and apart/disintegrate. chemical methods 20 / 11 PULPING METHODS MECHANICAL PULPING Pulp produced by forcing log/wood against rapidly rotating grindstone – physically taken apart/disintegrate. Produced fibers with original cell-wall lignin intact (high yield because all wood fiber is utilised) FST648 FOOD PACKAGING TECHNOLOGY Groundwood pulp produced fibers that are varies in length and composition - contains 70-80% of fiber bundles, broken fibers, fines and individual fibers. Unsuitable for many uses due to lignin content - very stiffs and bulky also yellowing of pulp with time. Used mostly in manufacture of newsprint, magazine paper, tissues, paperboard for folding & moulded cartons. Advantages/disadvantages: Low cost, Quick ink-absorbing properties, High bulk, Excellent opacity, Relatively low mechanical strength 20 / 9 Thermomechanical pulping (TMP) FST648 FOOD PACKAGING TECHNOLOGY Pre-steam wood chips between 110 and 150°C. Become malleable, do not fracture under the impact of grinder. Highly flexible, gives good bonding and surface smoothing Give stronger paper. 20 / 9 PULPING METHODS CHEMICAL PULPING Degrade and dissolve away the lignin from the middle lamella to allow the fibers to separate with little, if any mechanical action. FST648 FOOD PACKAGING TECHNOLOGY Chemicals used influence the properties of residual lignin and carbohydrates. Methods based on either direct or indirect use of NaOH: i. Alkaline process (a) Soda process (b) Sulfate (Kraft) process ii. Sulfite process 20 / 9  Chemical pulping ALKALINE PROCESS SULFITE PROCESS Soda process Sulfate (Kraft) process Boil wood chips (indirect steam heating) at lower T and P at Boil wood chips in 4 - 6% Boil wood chips in longer time. NaOH liquor at 170°C. NaOH and sodium Use SO2 – dissolves in H2O to sulfide (Na2S) liquor at form sulfurous acid - neutralise Less than 2% pulp 170°C. with a base (type and amount currently produced using Able to pulp any wood differ – depend on the ability of this process. sulfite solutions to render lignin species particularly partially soluble). pines (more resinous Recent modification: use than firs and spruces). anthraquinone and methanol to Produce stronger pulp. make the sulfite process more competitive with Kraft process. 20 / 5 PULPING METHODS SEMICHEMICAL PULPING Combination of mechanical and chemical methods of pulping Produce as high yield as possible to obtain the best possible strength and clean pulp. FST648 FOOD PACKAGING TECHNOLOGY Chemithermomechanical pulping (CTMP) Mild pretreatment with sodium sulfite followed by pressurised refining (grinding). Increase strength properties due to longer fiber fraction and lower fines fraction Suitable for middle layer of multi-ply boards (adds bulk and rigidity/stiffness). 20 / 9 MECHANICAL PULPING CHEMICAL PULPING FST648 FOOD PACKAGING TECHNOLOGY 20 / 6 STAGE 1: DIGESTION PROCESS Process of treating wood in chip form in a pressurized vessel under controlled conditions of time, liquor concentration, pressure and FST648 FOOD PACKAGING TECHNOLOGY temperature. OBJECTIVE OF THE PROCESS To produce well-cooked To achieve maximum To ensure constant pulp, free from non- yield of raw material supply of pulp of the cellulosic portions of the (wood pulp) required quality wood (eg. lignin & corresponding to pulp hemicellulose) quality 20 / 11  KAMYR CONTINUOUS DIGESTION SYSTEM 20 / 9 STAGE 1: BLEACHING PROCESS Process of removing lignin that would cause brown discolouration of final paper. FST648 FOOD PACKAGING TECHNOLOGY Bleaching process reduces strength of pulp – necessary to reach a compromise between brightness of finished paper sheet and its tensile properties Pulps varies in colour after pulping depending on wood species, method of processing & extraneous components present. Chromophoric groups on lignin are responsible for pulp brown colour Cellulose & hemicellulose is white -not affect color 20 / 11 BLEACHING PROCESS 2 TYPE Chemically modifying chromophoric groups by oxidation or reduction but FST648 FOOD PACKAGING TECHNOLOGY minimally remove lignin or other substances from the fibers. Complete delignification process also remove some carbohydrate materials. Mechanical pulps Chemical pulps To increase the brightness of the pulp while maintaining the strength and To remove the remaining lignin yield. from the pulp to produce a bright, white paper. Bleaching agent: H2O2 and sodium peroxide (alkaline solution) Bleaching agent: use one or more of ClO2, O2, ozone and peroxide. Reaction requires 3 hrs at 40°C neutralisation and destruction of Mildest conditions performed in excess peroxide with SO2. number of stages Alkali treatment in between stages to Improved colour to limited extent dissolve degradation products (high amount of lignin from original wood). 20 / 10 STAGE 2: PAPER MAKING PROCESS Involves converting raw materials (typically wood pulp or recycled fibers) into paper. FST648 FOOD PACKAGING TECHNOLOGY Mechanically treats the fibers The pulp is diluted Further treatment in to improve their bonding with water to create a producing end used potential, flexibility, and slurry that contains paper strength about 1% fibers and 99% water 20 / 11 PAPER MAKING PROCESS BEATING AND REFINING Purpose: FST648 FOOD PACKAGING TECHNOLOGY i) To improve the strength and other physical properties of the finished sheet. ii) To influence the behaviour of the system during sheet- forming and drying steps. Beating increase the surface area of the fibres by assisting it to imbibe water. - results in additional bonding opportunities between cellulose molecules of neighboring fibres (beating time : increase inter - fiber bonding : increase tensile strength). - makes fibres more flexible, become relatively mobile and easy to deform plastically on paper machine. 20 / 9 PROPERTIES OF PAPER PRODUCED AFTER BEATING AND REFINING PROCESS FST648 FOOD PACKAGING TECHNOLOGY Unbeaten pulp: low density, soft and low strength paper Beaten pulp: more dense, hard and strong paper Extreme beating: very dense, translucent, glassine-type sheets 20 / 9 PAPER MAKING PROCESS PAPERMAKING Paper is made by depositing very dilute consistency of aqueous fiber suspension (>99% water) - poured onto fine woven screen (>95% water removed by drainage through the wire) – fibers interlace in random manner as they are deposited on the FST648 FOOD PACKAGING TECHNOLOGY wire – paper. TECHNIQUES Sheet forming section Presses and Dryers Fourdrinier machine Cylinder machine Twin-wire formers 20 / 10  SHEET FORMING SECTION FOURDRINIER CYLINDER TWIN-WIRE MACHINE MACHINE FORMERS FST648 FOOD PACKAGING TECHNOLOGY Paper web formed by Paper web formed by Paper web formed between draining water from fiber draining water using 2 converging forming suspension using woven cylinder covered with wire screens – water drained by wire gauze (drainage table) cloth rotated and partially pressure followed by assisted by vacuum. submerged in fiber vacuum. suspension assisted by vacuum. Designed to provide new Used to produce all grades method for manufacture of of paper and paperboard. Used to produce heavy single and multi-ply sheets multi-ply boards. at high speed. 20 / 11  PRESSES AND DRYERS Sheets (75 to 90% moisture) pass through presses & dryers section for further water removal. FST648 FOOD PACKAGING TECHNOLOGY Rotary presses act as conveyor and porous receptors of water: - Solid or perforated rollers, with internal suction (60 to 70% water) - Passed through series of steam-heated rollers and dried to final moisture between 4 to 10%. 20 / 11 PAPER MAKING PROCESS CONVERTING Further surface treatment involves application of adhesives, functional products, barrier coatings, pigmentation etc. – depend on FST648 FOOD PACKAGING TECHNOLOGY the end use of paper. 20 / 9 20 / 9 CONVERTING FST648 FOOD PACKAGING TECHNOLOGY CALENDERING Reorients the surface fibresin the base sheet of paper (or coating is FST648 FOOD PACKAGING TECHNOLOGY applied to the surface) through use of pressure. Serves to smooth the surface, control surface texture & develop glossy finish. 20 / 9 SIZING AND COATING To improves appearance of paper. FST648 FOOD PACKAGING TECHNOLOGY Sizing agent penetrates into paper to increase fiber bonding and other physical properties - improve bursting, tensile, folding strength and scuffing resistance of paper surface. Sizing agent: starches, CMC, PVC, polyurethanes, fluorochemical emulsions - provide oil & grease repellency also improve strength Surface-sizing agents: prevent excess water penetration and improve paper strength. 20 / 9 ADHESIVES To bind pigment particles together to the raw stock. FST648 FOOD PACKAGING TECHNOLOGY Type and proportion determine finish paper properties: surface strength & firmness, gloss, brightness, opacity, smoothness, ink receptivity. Example: starches, casein and soy protein derivatives, various rubber latexes and other emulsions. Acrylic-based emulsions ideally suited for food packaging. 20 / 9 BARRIER COATINGS Many packaging applications require barrier against water vapour and FST648 FOOD PACKAGING TECHNOLOGY gasses. Water barrier formed by changing paper surface wettability with sizing agents. Example: paraffin wax and polyethylene (more durable and flexible coat). 20 / 9 PIGMENTS To mask or change appearance of base stock FST648 FOOD PACKAGING TECHNOLOGY Improve opacity Impart smooth and receptive surface for printing or Provide special properties for particular purposes. Example: kaolin clay, calcium carbonate, PS-based plastic pigment combined with mineral pigments. 20 / 9  FST648 FOOD PACKAGING TECHNOLOGY TYPES OF PAPER, PROPERTIES AND USES 20 / 11 KRAFT PAPER Coarse, heavy duty paper. Bleached, natural or coloured. FST648 FOOD PACKAGING TECHNOLOGY May be wet-strengthened or made water-repellant – when strength is required. Sometimes made with no calendering so that it does not slide over one another when stacked on pallets. Used for bags, multi-wall sacks & liners for corrugated board. 20 / 11  GREASEPROOF PAPER Translucent machine-finished paper - hydrated to give oil & grease resistance. FST648 FOOD PACKAGING TECHNOLOGY Used prolonged beating/refining - to fibrillate & break cellulose fibers - absorbs water becoming superficially gelatinised and sticky (hydration) – results in consolidation of the web with many of the interstitial spaces filled in. Not strictly ‘greaseproof’ – oils/fats penetrate after certain time. Used for packaging butter, baked goods & similar fatty foods. 20 / 11 VEGETABLE PARCHMENT Not a good barrier for gases. FST648 FOOD PACKAGING TECHNOLOGY Non-toxic, high wet strength, free of lint, odour & taste, grease/oil resistant – suitable for wet & greasy foods. Strips away easily from food material without defibriling - use as interleaver between slices of food such as meat or pastry. Made as labels & insert in products with high oil/grease content Can be treated with mould inhibitors & used to wrap food such as cheese. 20 / 11  WAXED PAPER Primary purpose is to provide moisture, liquid & vapours barrier & heat-sealable laminant. Made by waxing base paper (greaseproof, glassine paper). FST648 FOOD PACKAGING TECHNOLOGY Add special resins or plastic polymers to wax - to improve adhesion & low temperature performance & to prevent cracking due to folding or bending of paper. Wet waxed paper - have continuous surface film & imparts high degree of gloss on the coated surface. Dry waxed paper - produced using heated rollers, do not have continuous film on the surfaces. Wax-laminated paper - bonded with continuous film of wax – acts as adhesive. 20 / 11  GLASSINE PAPER Glassy, smooth surface, high density and transparent. FST648 FOOD PACKAGING TECHNOLOGY Produced by further treatment on the grease-proof paper. Transparency vary widely depending on degree of hydration of pulp & basis weight of paper. Add withTiO2 – makes the paper opaque and frequently plasticized to increase its toughness. 20 / 11 PAPERBOARD PRODUCTS Type of paper with basis weight generally > 224 g/m2, FST648 FOOD PACKAGING TECHNOLOGY thickness between 0.2-1.0 mm and weight/surface area that varies between 120-700 g/m2. Boards containing postconsumer waste papers are not used for food contact purposes (presence of inks, coatings, etc.). Corrugated layer is used for protect the food product from impact of surroundings 20 / 11 Made from sheets of paperboard (thickness 300 -1100 um) – cut and scored for bending into desired shapes. FST648 FOOD PACKAGING TECHNOLOGY Surface layer on top of board is of an elastic nature and relatively high strength compared to the inside layers (will be compressed). Coating and laminating are carried out when special barrier properties are required: - wax lamination: moisture barrier - lining with glassine: grease resistance - plastic materials coating/lamination: heat sealing 20 / 11  Consists of layers of bleached and unbleached paperboard coated internally and externally with LDPE – impermeable to liquids and heat sealing. Design: Gabletop, flat-and plastic-topped with FST648 FOOD PACKAGING TECHNOLOGY plastic screw caps, reclosable spouts etc. Brick-shaped cartons: liquid tight, hermetically sealed widely used for aseptic packaging – milk, juices, soups and wines – commercially sterile for 6 to 9 months. Retortable square-shaped paperboard cartons: for soups, ready meals, vegetables and pet food – similar structure with aseptic carton but LDPE coat replaced with PP – shelf life at ambient conditions of 18 months. 20 / 11 Used to describe 3D packaging and food-service articles manufactured from aqueous slurry of cellulosic fibers, formed into discrete products on screened FST648 FOOD PACKAGING TECHNOLOGY mould. Moulding process: (a) Pressure injection process – moulded to profile of bottle. (b) Suction moulding process – egg cartons, food trays, etc. Thin thermoplastic films (PET) can be laminated to one surface – enable it to function as dual-ovenability container (microwave & convection oven for frozen dinner products). 20 / 11  FST648 FOOD PACKAGING TECHNOLOGY ADVANTAGES AND DISADVANTAGES OF PAPER PACKAGING 20 / 11  ADVANTAGES DISADVANTAGES Superior printability – offers wide variety of Naturally poor properties - such as porous, designs such as offset printing, flexographic opaque, low barrier to moisture & gasses, not printing & typographic printing. oil/grease resistant. FST648 FOOD PACKAGING TECHNOLOGY Easy processing – simple fabrication process, Does not prevent loss of flavour components or enable mass production. volatiles from foods. Appropriate stiffness – suitable stiffness to Cannot be heat-sealed. keep packaging intact & to protect contents. Cannot be co-extruded to produce laminate, Lightweight – easy to transport (compact, must use adhesives. foldable and collapsible). Easily torn. Cheap – cheaper than other type of containers. Laminate materials – to improve its physical properties eg. laminated with aluminium, plastics, waxes. Mechanical strength – enough strength to support product weight. Biodegradable – good environmental image. 20 / 6