2017年雅思閱讀考試精選習(xí)題及答案(3)1851

2017年雅思閱讀考試精選習(xí)題及答案(3)TalcPowderAPeterBriggdiscovershowtalcfromLuzenac'sTrimounsinFrancefinditswayintofoodandagriculturalproducts-fromchewinggumtooliveoil.HighintheFrenchPyrenees,some1,700mabovesealevel,liesTrimouns,ahugedepositofhydratedmagnesiumsilicate-talctoyouandme.TalcfromTrimouns,andfromtenotherLuzenacminesacrosstheglobe,isusedinthemanufactureofavastarrayofeverydayproductsextendingfrompaper,paintandplastertocosmetics,plasticsandcartyres.Andofcoursethereisalwaystalc'sbestknownenduse:talcumpowderforbabies1bottoms.Butthetrueversatilityofthisremarkablemineralisnowherebetterdisplayedthaninitssometimessurprisinguseincertainnichemarketsinthefoodandagricultureindustries.BTake,forexample,thechewinggumbusiness.Everyyear,TalcdeLuzenacFrance-whichownsandoperatestheTrimounsmineandisamemberoftheinternationalLuzenacGroup(artofRioTintominerals)suppliesabout6,000tonesoftalctochewinggummanufacturersinEurope."We'vebeensellingtothissectorofthemarketsincethe1960s,"saysLaurentFournier,salesmanagerinLuzenac'sSpecialtiesbusinessunitinToulouse."Admittedly,intermsofourtotalannualsalesoftalc,theamountwesupplytochewinggummanufacturersisrelativelysmall,butweseeitasavaluablenichemarket:onewherecustomersplaceapremiumonsecuringsuppliesfromareliable,highqualitysource.Becauseofthis,longtermallegiancetoaprovensupplerisverymuchafeatureofthissectorofdietalcmarket."Switchingsources-inthewaythatyoumightchoosetobuy,say,paperclipsfromSupplierAratherthanfromSupplierB-isnotaneasyoptionforchewinggummanufacturers."Fourniersays."Thecostofreformulatingishigh,sowhencustomersareusingatalcgradethatworks,evenifit'sexpensive,theyareunderstandablyreluctanttoswitch."CButhowistalcactuallyusedinthemanufactureofchewinggum?PatrickDelord,anengineerwithadegreeinagronomics,whohasbeenwithLuzenacfor22yearsandisnowseniormarketdevelopmentmanager,AgricultureandFood,inEurope,explainsthatchewinggumshasfourmaincomponents."Themostimportantofthemisthegumbase,"hesays."It'sthegumbasethatputsthechewintochewinggum.Itbindsalltheingredientstogether,creatingasoft,smoothtexture.Tothisthemanufacturerthenaddssweeteners,softenersandflavourings.Ourtalcisusedasafillerinthegumbase.Theamountvanesbetween,say,tenand35percent,dependingonthetypeofgum.Fruitflavouredchewinggum,forexample,isslightlyacidicandwouldreactwiththecalciumcarbonatethatthemanufacturermightotherwiseuseasafiller.Talc,ontheotherhand,makesanidealfillerbecauseit'snon-reactivechemically.Inthefactory,talcisalsousedtodustthegumbasepelletsandtostopthechewinggumstickingduringthelaminationandpackingprocess,"Delordadds.DThechewinggumbusinessis,however,justoneexampleoftalc'suseinthefoodsector.Forthepast20yearsorso,oliveoilprocessorsinSpainhavebeentakingadvantageoftalc'suniquecharacteristicstohelpthemboosttheamountofoiltheyextractfromcrushedolivesAccordingtoPatrickDelord,talcisespeciallyusefulfortreatingwhathecalls"difficult"olives.Aftertheolivesareharvested-preferablyearlyinthemorningbecausetheirtasteisbetteriftheyaregatheredinthecoolofthedaytheyaretakentotheprocessingplant.Theretheyarccrushedandthenstirredfor30-45minutes.Intheolddays,theresultingpastewaspassedthroughanolivepressbutnowadaysit'smorecommontoaddwaterand(K-6IH)themixturetoseparatethewaterandoilfromthesolidmatterTheoilandwaterarethenallowedtosettlesothattheoliveoillayercanbe)andbottled.“Difficult”olivesarethosethataremorereluctantthanthenormtoyielduptheirfulloilcontent.Thismaybeattributabletotheparticularspeciesofolive,ortoitswatercontentandthetimeofyeartheolivesarccollected-atthebeginningandtheendoftheseasontheirwatercontentisofteneithertoohighortoolow.Theseolivesareeasytorecognizebecausetheyproducealotofextrafoamduringthestirringprocess,aconsequenceofanexcessofafinesolidthatactsasanaturalemulsifier.Theoilinthisemulsionislostwhenthewaterisdisposedof.Notonlythat,ifthewastewaterisdisposedofdirectlyintolocalfields-oftenthecaseinmanysmallerprocessingoperations-theemulsifiedoilmaytakesometimetobiodegradeandsobeharmfultotheenvironment.E"Ifyouaddbetweenahalfandtwopercentoftalcbyweightduringthestirringprocess,itabsorbsthenaturalemulsifierintheolivesandsobooststheamountofoilyoucanextract,"saysDelord."Inaddition,talc'sflat,'platey'structurehelpsincreasethesizeoftheoildropletsliberatedduringstirring,whichagainimprovestheyield.However,becausetalcischemicallyinert,itdoesn'taffectthecolor,taste,appearanceorcompositionoftheresultingoliveoil."FIftheuseoftalcinoliveoilprocessingandinchewinggumislongestablished,newapplicationsinthefoodandagricultureindustriesarcalsoconstantlybeingsoughtbyLuzenac.Onesuchpromisingnewmarketisfruitcropprotection,beingpioneeredintheUS.Justlikepeople,fruitcangetsunburned.Infact,inverysunnyregionsupto45percentofatypicalcropcanbeaffectedbyheatstressandsunburnHowever,inthecaseoffruit,it'snotsomuchtheultravioletrayswhichharmthecropasthehighsurfacetemperaturethatthesun'srayscreate.GTocombatthis,farmersnormallyuseeitherchemicalsorsprayacontinuousfinecanopyofmistabovethefruitfreesorbushes.Thetroubleis,thisusesalotofwater-normallyapreciouscommodityinhot,sunnyareas-anditisthereforeexpensive.What'smore,thegroundcanquicklybecomewaterlogged."Soourideawastocoatthefruitwithtalctoprotectitfromthesun,"saysGregHunter,amarketingspecialistwhohasbeenwithLuzenacfortenyears."Buttodothis,severaltechnicalchallengeshadfirsttobeovercome.Talcisveryhydrophobic:itdoesn'tlikewater.Soinordertohaveaviableproductweneededawettablepowder-somethingthatwouldgoreadilyintosuspensionsothatitcouldbesprayedontothefruit.Italsohadtobreakthesurfacetensionofthecuti