最新亚硝酸盐含量测定课件PPT.ppt 51页

'亚硝酸盐含量测定 发酵产物中除乳酸外，还有其他，如乙醇、CO2等称异型乳酸发酵发酵中期：由于前期乳酸的积累，pH下降，嫌气状态的形成，乳酸杆菌活跃进行活跃的同型乳酸发酵，乳酸积累pH达3.5~3.8.大肠杆菌、酵母菌、霉菌等的活动受到抑制。这一期为完全成熟阶段，泡菜有酸味且清香品质最好。发酵后期：继续进行乳酸发酵，乳酸积累达1.2％以上时，乳酸杆菌的活性受到抑制，发酵速度逐渐变缓甚至停止。腌制1周左右即可开坛食用。也可随时加入新鲜蔬菜，不断取用。发酵产物中只有乳酸，称为同型乳酸发酵 （6）如果加入一些已经腌制过的泡菜汁更好，这相当于接种已经扩增的发酵菌，可减少腌制时间。1、加入白酒有什么作用？白酒可抑制泡菜表面杂菌的生长，它也是一种调味剂，可增加醇香感。思考： （4）膳食中的绝大部分亚硝酸盐随尿排出，只有在特定的条件（适宜的pH（3左右)，温度和一定微生物的作用）下才会转变成致癌物――亚硝胺，亚硝胺对动物还具有致畸和致突变作用。过度摄取亚硝酸盐或体内缺乏维生素C，会引发危害。亚硝胺可以通过胎盘引发胎儿致畸 二、亚硝酸盐含量的测定1、测定亚硝酸盐含量的原理在盐酸酸化条件下，亚硝酸盐与对氨基苯磺酸发生重氮化反应后，再与N-1－萘基乙二胺盐酸盐结合生成玫瑰红溶液。将经过反应显色后的待测样品与标准液比色，即可计算出样品中的亚硝酸盐含量。2、材料与器具泡菜、对氨基苯磺酸、N-1－萘基乙二胺盐酸盐、氯化钠、氢氧化钠、氢氧化铝、氯化镉、氯化钡、亚硝酸钠、蒸馏水、移液管、容量瓶、比色管、榨汁机等 3、步骤（1）配置溶液对氨基苯磺酸溶液：称取0.4克对氨基苯磺酸，溶解于100ml体积分数为20％的盐酸中，避光保存(4mg/ml)。N-1－萘基乙二胺盐酸盐溶液：称取0.2克N-1－萘基乙二胺盐酸盐，溶解于100ml的水中，避光保存(2mg/ml)。亚硝酸钠溶液：称取0.10克于硅胶干燥器中干燥24小时的亚硝酸钠，用水溶解至500ml，再转移5ml溶液至200ml容量瓶，定容至200ml(5ug/ml) （2）配制标准液用移液管吸取0.20ml、0.40ml、0.60ml、0.80ml、1.00ml、1.50ml亚硝酸钠溶液，分别置于50ml比色管中，再取1支比色管作为空白对照。并分别加入2.0ml对氨基苯磺酸溶液，混匀，静置3～5分钟后，再分别加入1.0mlN-1－萘基乙二胺盐酸盐溶液，加蒸馏水至50ml，混匀，观察亚硝酸钠溶液颜色的剃度变化。提取剂：分别称取50克氯化镉、氯化钡，溶解于1000ml蒸馏水中，用盐酸调节pH至1。氢氧化铝乳液和2.5mol/l的氢氧化钠溶液。 （3）制备样品处理液将3坛样品做好标记后，分别称取0.4千克泡菜，榨汁过滤得200ml汁液。取其中100ml至500ml容量瓶中，加200ml蒸馏水、100ml提取剂，混匀，再加入40ml氢氧化钠溶液，用蒸馏水定容至500ml后，立即过滤。将60ml滤液转移至100ml容量瓶中，加入氢氧化铝（吸附脱色）乳液，定容至100ml，过滤。（4）比色吸取40ml透明澄清的滤液，转移到50ml比色管中，将比色管做好标记。按步骤2的方法分别加入对氨基苯磺酸溶液和N-1－萘基乙二胺盐酸盐溶液，并定容至50ml，混匀，静置15 分钟后，观察样品颜色的变化，并与标准显色液比较，找出与标准液最相近的颜色，记录对应的亚硝酸钠含量，并计算。每隔2天测一次，将结果记录下来。2001年1月4日（封坛前）2001年1月8日2001年1月12日2001年1月15日2001年1月19日0.150.600.200.100.101号坛2号坛0.150.200.100.050.053号坛0.150.800.600.200.20泡菜腌制过程中亚硝酸盐含量的变化 4、实验结果分析和讨论选录……三只泡菜坛中的亚硝酸盐含量变化的绝对数量虽然不同，但整体的变化趋势却基本相同。在腌制后的第五天，三只泡菜坛中亚硝酸盐的含量都达到最高峰（1、2、3号坛中的亚硝酸盐分别达到0.6mg/kg、0.2mg/kg、0.8mg/kg）， 在腌制后的前6天内，泡菜中的亚硝酸盐含量就可以达到最高峰。而第9天后泡菜中的亚硝酸盐含量开始有明显下降。这可能是由于泡菜在开始腌制时，坛内环境有利于某些细菌的繁殖（包括一些硝酸盐还原菌），这些细菌可以促进硝酸盐还原为亚硝酸盐。但随着腌制时间的延长，乳酸细菌也大量繁殖，对硝酸盐还原菌产生一定的抑制作，使其生长繁殖受到影响，造成泡菜中亚硝酸盐的含量又有所下降。均样+水→捣碎→加果蔬提取剂（50gBaCl2+CdCl2→加1000ml重蒸馏水中，用浓HCl调PH为1）→振荡1小时→用NaOH调至中性→定容→过滤→滤液应无色透明 再见 TheNewsvendorModel报童模型 “Toomuch”and“toolittle”costsCo=overagecostThecostoforderingonemoreunitthanwhatyouwouldhaveorderedhadyouknowndemand.Inotherwords,supposeyouhadleftoverinventory(i.e.,youoverordered).Coistheincreaseinprofityouwouldhaveenjoyedhadyouorderedonefewerunit.Cu=underagecostThecostoforderingonefewerunitthanwhatyouwouldhaveorderedhadyouknowndemand.Inotherwords,supposeyouhadlostsales(i.e.,youunderordered).Cuistheincreaseinprofityouwouldhaveenjoyedhadyouorderedonemoreunit. BalancingtheriskandbenefitoforderingaunitOrderingonemoreunitincreasesthechanceofoverage…ExpectedlossontheQthunit=CoxF(Q)F(Q)=Distributionfunctionofdemand=Prob{Demand<=Q)…butthebenefit/gainoforderingonemoreunitisthereductioninthechanceofunderage:ExpectedgainontheQthunit=Cux(1-F(Q))Asmoreunitsareordered,theexpectedbenefitfromorderingoneunitdecreaseswhiletheexpectedlossoforderingonemoreunitincreases. NewsvendorexpectedprofitmaximizingorderquantityTomaximizeexpectedprofitorderQunitssothattheexpectedlossontheQthunitequalstheexpectedgainontheQthunit:Rearrangetermsintheaboveequation->TheratioCu/(Co+Cu)iscalledthecriticalratio.（临界比或关键比例）Hence,tomaximizeprofit,chooseQsuchthatwedon’thavelostsales(i.e.,demandisQorlower)withaprobabilitythatequalsthecriticalratio TheNewsvendorModel:Performancemeasures绩效指标 NewsvendormodelperformancemeasuresForanyorderquantitywewouldliketoevaluatethefollowingperformancemeasures:Expectedlostsales（期望销售损失）TheaveragenumberofunitsdemandexceedstheorderquantityExpectedsales（期望销售）(comparedtoexpecteddemand)Theaveragenumberofunitssold.Expectedleftoverinventory（期望售后剩余库存）Theaveragenumberofunitsleftoverattheendoftheseason.ExpectedprofitExpectedfillrate（期望订单完成率）ThefractionofdemandthatissatisfiedimmediatelyIn-stockprobability（存货满足概率）ProbabilityalldemandissatisfiedStockoutprobability（缺货概率）Probabilitysomedemandislost formulaExpectedsales=m-Expectedlostsalesm:ExpecteddemandL(z):lossfunction(标准正态)损失函数,随机变量超过一个固定值的期望值之和。ExpectedLeftOverInventory=Q-ExpectedSales formulaIn-stockprobability=F(Q)=Φ(z)Stockoutprobability=1–F(Q)=1–In-stockprobability TheNewsvendorModel:Thetargetin-stockprobabilityandthetargetfill-rateobjectivesforchoosingQin-stockprobability：缺货情况，对杂货店较重要fill-rate：多少顾客满足的情况，对目录零售商较重要 ChooseQsubjecttoaminimumin-stockprobabilitySupposewewishtofindtheorderquantityfortheHammer3/2thatminimizesleftoverinventorywhilegeneratingatleasta99%in-stockprobability.Step1:Findthez-statisticthatyieldsthetargetin-stockprobability.IntheStandardNormalDistributionFunctionTablewefindF(2.32)=0.9898andF(2.33)=0.9901.Choosez=2.33tosatisfyourin-stockprobabilityconstraint.Step2:Convertthez-statisticintoanorderquantityfortheactualdemanddistribution.Q=m+zxs=3192+2.33x1181=5944 ChooseQsubjecttoaminimumfillrateconstraintSupposewewishtofindtheorderquantityfortheHammer3/2thatminimizesleftoverinventorywhilegeneratingatleasta99%fillrate.Step1:Findthelostsaleswithastandardnormaldistributionthatyieldsthetargetfillrate.Step2:Findthez-statisticthatyieldsthelostsalesfoundinstep1.FromtheStandardNormalLossFunctionTable,L(1.53)=0.0274andL(1.54)=0.0267Choosethehigherz-statistic,z=1.54Step3:Convertthez-statisticintoanorderquantityfortheactualdemanddistribution.Q=m+zxs=3192+1.54x1181=5011 讨论不足成本大时（毛利高），订购量大于期望需求（关键比例大于0.5）；反之相反。剩余成本可能是可见成本，而销售损失是机会成本，在报表中看不到。剩余成本可能是积压的库存，如未及时清理，造成虚假利润除了利润最大化目标外，很多情况下会选服务水平目标，因为要考虑长期效应。 Assemble-to-order,make-to-orderandQuickResponsewithreactivecapacity按订单装配、按订单生产和以反应性能力快速响应 Thedemand-supplymismatchcostDefinition–thedemandsupplymismatchcostincludesthecostofleftoverinventory(the“toomuch”cost)plustheopportunitycostoflostsales(the“toolittle”cost):Themaximumprofitistheprofitwithoutanymismatchcosts,i.e.,everyunitissoldandtherearenolostsales:ThemismatchcostcanalsobeevaluatedwithMismatchcost=Maximumprofit–Expectedprofit Whenisthemismatchcosthigh?Mismatchcostasapercentofthemaximumprofitwheref(z)=densityfunctionoftheNormaldistribution(InExcelf(z)=normdist(z,0,1,0))Themismatchcostishighwhen(f(z)/F(z))and(s/m)arehigh. LowcriticalratioshighmismatchcostsThemismatchcostishighwhen(f(z)/F(z))ishigh……(f(z)/F(z))ishighwhenthecriticalratioislow: 变差系数反映预测质量，提高预测精确性，可有更高利润。关键比例小的产品，剩余成本高，容易过时的和容易腐败的产品采购少。若残值为零，关键比例即为毛利率，故食堂原材料备料库存少（毛利低，积压成本大），餐厅备料较充分，过期库存多。 不同的不匹配成本与运营管理模式MTS—报童模型不匹配成本为过量或不足，MTS适合于关键比例高、需求变动小MTO—排队系统不匹配成本为生产闲置、顾客排队MTO适合于短途运输、短提前期、机器或劳动力便宜中间状态为使用反应性能力进行快速响应两种反应性能力：第二次订购能力无限但较第一次订购昂贵的反应性能力第二次订购能力有限的反应性能力 SomeU.S.airlineindustryobservationsSincederegulation(1978)137carriershavefiledforbankruptcy.From95-99(theindustry’sbest5yearsever)airlinesearned3.5centsoneachdollarofsales:TheUSaverageforallindustriesisaround6cents.From90-99theindustryearned1centper$ofsales.Carrierstypicallyfill72.4%ofseatsandhaveabreak-evenloadof70.4%. MatchingsupplytodemandwhensupplyisfixedExamplesoffixedsupply:Travelindustries(fixednumberofseats,rooms,cars,etc).Advertisingtime(limitednumberoftimeslots).Telecommunicationsbandwidth.SizeoftheMBAprogram.Doctor’savailabilityforappointments.Revenuemanagementisasolution:Ifadjustingsupplyisimpossible–adjustthedemand!Segmentcustomersintohighwillingnesstopayandlowwillingnesstopay.Limitthenumberofticketssoldatalowprice,i.e.,controltheaveragepricebychangingthemixofcustomers. RevenuemanagementandmarginarithmeticSmallchangesinrevenuecanhaveabigimpactonprofit,especiallyforhighgrossmarginandlownetprofit%industries: EnvironmentssuitableforrevenuemanagementThesameunitofcapacity(e.g.,airlineseat)canbeusedtodeliverservicestodifferentcustomersegments(e.g.,businessandleisurecustomers)atdifferentprices.Highgrossmargins(sothatthevariablecostofadditionalsalesislow).Perishablecapacity(itcannotbestored)andlimitedcapacity(allpossiblecustomerscannotalwaysbeserved).Capacityissoldinadvanceofdemand.Thereisanopportunitytosegmentcustomers(sothatdifferentpricescanbecharged)anddifferentsegmentsarewillingtopaydifferentprices.Itisnotillegalormorallyirresponsibletodiscriminateamongcustomers. RevenueManagement:Bookinglimitsandprotectionlevels预定限额和保留水平 PracticalproblemTheParkHyattPhiladelphiaattheBellevue.118King/Queenrooms.HyattoffersarL=$159(lowfare)discountfareforamid-weekstaytargetingleisuretravelers.RegularfareisrH=$225(highfare)targetingbusinesstravelers.Demandforlowfareroomsisabundant.LetDbeuncertaindemandforhighfarerooms.SupposeDhasPoissondistributionwithmean27.3.Assumemostofthehighfare(business)demandoccursonlywithinafewdaysoftheactualstay.Objective:Maximizeexpectedrevenuesbycontrollingthenumberoflowfareroomsyousell. YieldmanagementdecisionsThebookinglimitisthenumberofroomsyouarewillingtosellinafareclassorlower.Theprotectionlevelisthenumberofroomsyoureserveforafareclassorhigher.LetQbetheprotectionlevelforthehighfareclass.Qisineffectwhileyouselllowfaretickets.Sincethereareonlytwofareclasses,thebookinglimitonthelowfareclassis118–Q:Youwillsellnomorethan118-Qlowfareticketsbecauseyouareprotecting(orreserving)Qseatsforhighfarepassengers.0118QseatsprotectedforhighfarepassengersSellnomorethanthelowfarebookinglimit,118-Q TheconnectiontothenewsvendorAsingledecisionismadebeforeuncertaindemandisrealized.Thereisanoveragecost:IfDQthenyouprotectedtoofewrooms(youunderprotected)……sosomeroomscouldhavebeensoldatthehighfareinsteadofthelowfare.ChooseQtobalancetheoverageandunderagecosts. OptimalprotectionlevelOveragecost:IfDQweprotectedtoofewrooms.D–Qroomscouldhavebeensoldatthehighfarebutweresoldinsteadatthelowfare,soCu=rH-rLOptimalhighfareprotectionlevel:Optimallowfarebookinglimit=118–Q*ChoosingtheoptimalhighfareprotectionlevelisaNewsvendorproblemwithproperlychosenunderageandoveragecosts. HyattexampleCriticalratio:Poissondistributionwithmean27.3:Answer:24roomsshouldbeprotectedforhighfaretravelers.Similarly,abookinglimitof118-24=94roomsshouldbeappliedtolowfarereservations. RelatedcalculationsHowmanyhigh-faretravelerswillberefusedareservation?Expectedlostsales=4.10.Howmanyhigh-faretravelerswillbeaccommodated?Expectedsales=Expecteddemand-Lostsales=27.3-4.1=23.2Howmanyseatswillremainempty?Expectedleftoverinventory=Q-Expectedsales=24-23.2=0.8.Whatistheexpectedrevenue?$225xExp.sales+$159xBookinglimit=$20,166.Note:withoutyieldmanagementworstcasescenariois$159x118=$18,762. RevenueManagement:Overbooking Uglyreality:cancellationsandno-showsApproximately50%ofreservationsgetcancelledatsomepointintime.Inmanycases(carrentals,hotels,fullfareairlinepassengers)thereisnopenaltyforcancellations.Problem:thecompanymayfailtofilltheseat(room,car)ifthepassengercancelsattheverylastminuteordoesnotshowup.Solution:sellmoreseats(rooms,cars)thancapacity.Danger:somecustomersmayhavetobedeniedaseateventhoughtheyhaveaconfirmedreservation. Hyatt’sProblemTheforecastforthenumberofcustomersthatdonotshowup(X)isPoissonwithmean8.5.Thecostofdenyingaroomtothecustomerwithaconfirmedreservationis$350inill-willandpenalties.Howmanyrooms(Y)shouldbeoverbooked(soldinexcessofcapacity)?Newsvendorsetup:Singledecisionwhenthenumberofno-showsinuncertain.UnderagecostifX>Y(insufficientnumberofseatsoverbooked).OveragecostifXYthenwecouldhavesoldX-Ymorerooms……tobeconservative,wecouldhavesoldthoseroomsatthelowfare,Cu=rL.Overagecost:ifX