第七章食品的热物性 Calorimetry DLTMA TMA Dilatometry TG.DTA-TG.DSC TGA DTA
第七章 食品的热物性
量热法 Thermal analysis is made up of various techniques for studying the thermal behaviour of materials.When a material is heated or cooled its structure and chemical composition undergo changes fusion,melting,crystallization, oxidation,decomposition,reaction,transition, expansion,sintering To measure these various transformations the variation in different parameters is followed up as a function of the temperature
量热法 n Thermal analysis is made up of various techniques for studying the thermal behaviour of materials. When a material is heated or cooled its structure and chemical composition undergo changes : fusion, melting, crystallization, oxidation, decomposition, reaction, transition, expansion, sintering ... To measure these various transformations the variation in different parameters is followed up as a function of the temperature
DSC DIFFERENTIAL SCANNING CALORIMETRY (DSC) Differential scanning calorimetry is a technique determining the variation in the heat flow given out or taken in by a sample when it undergoes temperature scanning in a controlled atmosphere With heating or cooling any transformation taking place in a material is accompanied by a exchange of heat DSC enables the temperature of this transformation to be determined and the heat from it to be quantified
DIFFERENTIAL SCANNING CALORIMETRY (DSC) n Differential scanning calorimetry is a technique determining the variation in the heat flow given out or taken in by a sample when it undergoes temperature scanning in a controlled atmosphere. With heating or cooling any transformation taking place in a material is accompanied by a exchange of heat ; DSC enables the temperature of this transformation to be determined and the heat from it to be quantified
DSC reference sample DSC 121 heater thermosensor 巍dib鱼tle chamber
DSC
Glass transition Tg° Tgm ge Melting Crystallization TEMPERATURE
DSC exo +ve In the absence of any EX EX discrete physical or chemical transformations, 0 the baseline signal,as at B s B above,is related to the B heat capacity of the EN sample. temperature→
DSC In the absence of any discrete physical or chemical transformations, the baseline signal, as at B above, is related to the heat capacity of the sample
DSC empty pan D(sample) Tr sample D(sapphire) sapphire T time D(sample) Cp (sample)x mass of sample = D(sapphire) Cp (sapphire)x mass of sapphire
DSC
Liquid s Wat爸vapor Solid P M D Tbw Crystal A Collapse Solution Stickiness Rubber H Ice+Solution B Softening zoeN Tu Reaction zone Entangle且cw I Ice+Solution+Solute Ice+Rubber+Solute g G Ice-GTass FSolute Glass Q Ice+Glass+Solute R 0 Solute Mass Fraction
20 ARRHENIUS 15 GLASS S10 骂 RUBBER WLF 5 0 FLUID ARRHENIUS Tm Tg -5 0.5 1.0 1.5 2.0 Tm/T
DSC DSC应用示例 a b <-MOId IBaH IeuLatoxg e g 1 Wig -100 -50 0 50100 Temperature (C) Fig.4.Thermograms of freeze-dried tomato at high moisture con- tents,Xw:(a)0.5253;(b)0.5967;(c)0.6463;(d0.7427;(e)0.7913;(fD 0.8969;(g)fresh tomato osmotically treated,Xw=0.9097
DSC应用示例