(15)--13、油脂的脱胶和脱酸.ppt

Chapter4Vegetable0ilsProcessingandRefinement知识点2油脂的脱胶与脱酸

2DEGUMMINGDegumming(Figure)isawater-washingprocesstoremovephosphatides.Unlessremoved,phosphatidescanspontaneously（自然地）hydratefrommoistureintheairduringstorage.Inthecasesofoilsrichinphosphatides,suchassoybeanandcanolaoils,degummingisusuallyaseparateoperation.Hydrationmakesphosphatidesinsolubleintheoil,andtheyprecipitate.

3FIGUREProcessflowsheet（流程图）fordegumming.

4DEGUMMINGAllsoybeanoilintheexporttradeisdegummed.Phosphatidesarealsosurfactantsand,ifpresentinfryingoils,cancausedangerousfoaming.

5DEGUMMINGThemixtureisintensively（强烈）mixedandthenagitatedfor30–60minat60oC–80oCinaslowmixingvessel(hydrationtank)toallowthephosphatidestobecomefullyhydratedandtocoalesce（合并).Thegums,beingdenserthanoil,canberemovedbysettlingorfiltering;moreoften,however,theyarecentrifugedout.

6DEGUMMINGThewet-degummedoiliseitherdriedorimmediatelyneutralized.Usually,about90%ofthephosphatidesareremovedbythisprocess.Thegumstypicallycontain25%waterand75%oil-solublesubstances(ofwhichone-thirdisneutraloil).

7NEUTRALIZATION(ALKALIREFINING)Thetermneutralizationcomesfromneutralizingthenaturalacidityoftheoilemanatingfrom（源自于）thepresenceoffreefattyacids.Neutralizationisthemostimportantoperationinrefiningedibleoils.Neutralizationisachievedbythereactionofthefreefattyacidwithcausticsoda（苛性钠）(sodiumhydroxide氢氧化钠)toformsoapreferredtoassoapstock（皂脚）.

8NEUTRALIZATION(ALKALIREFINING)Saponification（皂化）referstoreactionsbetweenglyceridesandsodiumhydroxidealsotoformsoaps.Neutralizationmustbedonecorrectlyorsomeoftheglycerideswillbesaponified,resultinginincreasedrefiningloss.Theoil,lowinacidvalue,istermedneutraloil.

9NEUTRALIZATION(ALKALIREFINING)Soapstockisremovedfromtheoilbyusingcont