FOOD PROCESSINGCHE 432INDUSTRIAL PROCESS

HistoryFormerly, production and small scale processing done on farms & homesPresent days, centralized processing Development from cottage & community program to large scaleEarly days - grain milling, milk processing and sugar and candy processing Steps taken from product to consumer involved quality of the product and its value to end user

Types of food processinga) Refining and milling:Sugar obtained from cane or beets converted to common food product by various processes known as refiningMilling: convert grain into flour by mechanical meansModern milling industry innovations in measuring, metering, weighing, conveying, blending, applying power & sanitation

b) Canning:Fresh food eg. Fruit, vegetables, meats, fish preserved for long term storage by heat treatment and sealing into air-tight containersContainers may be metal, usually tinted or untinned steel often plastic-lined, aluminium or special strength glassRaw food packed in container, sealed and heat treated to cook the food and sterilize both container and contents

Heat treating in steam pressure vessel @ 121oC for time dependent upon size of container and nature of contentsAcid food (pH < 4.5): less time to process than food with pH 4.5 7.0Toxins prod. By microorganism toxic to humans hence processing severe enough to destroy organismHeating degrade odor and taste of food and other chemical changes take place drg canning

In general, short time high temp. cause less deterioration than long time low temp. process Agitated cookers used to ensure good heat penetration usg. short time treatment Agitation increases rate of heat transfer from container to productAgitated cooker consists of preheater, cooker and coolerCans placed in individual compartments, rotated by revolving reel on spiral trackTrack guides the compartments from inlet to outlet continuously

c) ConcentrationMethod of preservation: foodstuffs contain high % of water partially dehydrated Eg. evaporated milk and fruit juiceUsu. practice: reduce volume to of original volumeThree main processes:i. evaporation with evaporatorsii. Reverse osmosisiii. Freeze concentration

The three processes are competitiveChoice depends on nature of foodEvaporation most common and economicalRO used for separation & concentration eg. separation of lactose from wheyFreeze concentration very limited high cost, eg. wine, beer, coffee, apple and orange juices, skim milk & vinegarAdvantage: color & flavor retained compared wt. heat treatment

d) FreezingPreservation by freezing possible if food can be frozen v. quickly (supercooled) and maintained at low temp. preventing ice crystal formationQuality not greatly deteriorated and microorganisms will not increaseOrdinary slow freezing large ice crystals in cells of food rupture cells and cause structure breakdown, hence allows undesirable enzyme reactions at L temp. (-18oC) to take placePrevention: inactivation of enzymes by heat treatment (blanching) prior to freezing

Quality of final product improved if amt. of water reduced bef. FreezingFrozen food either packaged or unpackagedUnpackaged food freezes faster but dehydration become serious problemActual freezing accomplished by:i. either still or forced airii. direct contact with metal surface cooled by a refrigerantiii. immersion in liquid nitrogen Freezing only inactivate microorganism however on thawing the organisms are reactivated and food spoiled fasterFreezing retained nutrients in food

e) DryingMethod practice since ancient timesCommon technique : sun drying to preserve fruitsDried food easy to transport & store bec. occupy 1/10 volume of fresh foodMicrobial growth control bec. amt. of water not sufficient for growthMold will grow if water content 12% or higher although few mold grow at 5% moistureMost bacteria require at least 30% moistureNutritive value of dried food is unchanged but vitamin content generally reduced

Sun drying cheapest drying method but contamination of product by dust, insects, birds and rodentsDried fruits changed color from bright to dark brown unless fruit treated with SO2 before dryingMoist dried fruit, glycols are used to rehydrate and soften harder sun or mechanically dried prodt without adding moisture which allow growth of microbesFreeze dehydration utilizes vacuum conditions at triple point of water water molecules pass from solid to gaseous phase with passing through liquid phase, esp. for meat drying

f) Pasteurization and sterilizationPasteurization: HTST method exposes milk to 73oC for not less than 16 s followed by rapid cooling Purpose: kill pathogenic microorganisms, eliminating food-borne disease, inactivate enzymes to improve storage and keeping qualityProdt kept refrigerated bec. method does not kill all bacteria present

Sterilization: eg. milk sterilization ie. conditions severe enough to kill or completely inactivate all microorganisms, pathogenic and nonpathogenic, consists of more intense heat treatmentSterilized product placed in sterile container under aseptic conditions and sealedMilk treated can be stored for several months at room temperature

g) fermentation:Food processing and preservation methods aims at destroying microorganisms but not all organisms are detrimentalHumans utilized microbes and yeast in wine making, bread baking, cheese making and salting of foodsFermentation: decomposition of carbohydratesPutrefaction: action of microorganisms on proteinFermentation produces CO2 but no putrid odor, while putrefaction produces sulfur-containing protein prodts and HS

h) irradiation:Effects of radiation on various forms of life vary with complexity of living organismHowever, proven that radiation can be used to preserve food, esp. protein food eg. Meat without causing undesirable protein denaturation or altering in taste and without leaving any residual radioactivity in foodUsing low doses of radiation, less loss of vitamins in foods than that seen in canning, freezing or drying

i) packaging:purpose: shipping and storing food far from place of production and preventing deterioration drg. storage by insects, molds, yeast, microorganisms and enzymesFor many foods, container is filled before food is processedEg. Rigid metal cans, glass containers and plastic pouchesContainer sealed to avoid contamination and food spoilage

Cardboard boxes with inside liners of waxed or plastic-coated paper commonly used for dry foods packaging eg. cereals, flours, dried fruitsFood sterilized before placed in container necessitated development of aseptic packagingAdvantages of aseptic processing and packaging: longer shelf-life, ability to store perishable food without refrigerationPackaging usually rigid, rectangular cardboard construction, sterilized by hydrogen peroxide and heat

Food processing equipmentSanitary design and materials of constructionLiquids, solids and combinations must be handled without deterioration of product or damage to equipmentSanitary conditions additional consideration beyond normal unit operationChemical and biological properties usu. play predominant role than mechanical properties in designing equipment for food industry together with corrosion resistant materialsGood appearance must be maintained and pH of fluid products is the major factor in materials selection