Studies On Rheological Properties And Texture Evaluation Of Chocolate

Chocolate is a food liked by all people as its special taste.The main method to evaluate chocolate is sensory evalution,but the standard is misty.The study about rheological properties and texture evaluation of chocolate are less at home and aborade.The aim of this thesis was to study the rheological properties and texture evaluation of chocolate.Difference of chocolate texture was studied through puncture test.The results show that there is no difference between the same surface of one small block,there is great difference between different surface,small blocks and big blocks.In order to reduce deviation,it is better to make samples of one surface of one small block.Test conditions of puncture test,shearing test,three-point-bending and TPA,which were used to study the textural properity of Chocolate,were optimized in this paper.The results show that the choice of P2 probe,0.1mm/s test speed,1.5mm puncture depth for the puncture test;The optimum test condition of shearing test is 0.1-1.5mm/s test speed;The 0.5mm/s test speed,12mm test span was used for three-point-bending test;The best condition of TPA is 0.5mm/s test speed,60% compression ratio.The brittleness peak is found at 30.75%,brittleness value is 69.610N,the stree is 1.160N/mm~2 of 0.5mm/s test speed.At different sample size,the brittleness peak is found at about 30%,the stree is about 2.1 N/mm~2.Rheological properties of chocolate were studied uising loading-unloading,compression-stress relaxation and creep test.The results showed that the optimum test condition of loading-unloading test is 1mm/s test speed,1.5mm compression capacity;0.5mm/s test speed,0.3mm compression capacity and 30 seconds relaxtion time was used for compression-stress relaxation test;Analysis showed that four elements Maxwell model fitting relaxation curve with fitting rate 0.946.The best condition of creep test is 0.5mm/s test speed,70N compression capacity and 60 seconds creep time.Burgers model with four elements was fitting chocolate creep data with fitting rate to 0.98.Correlation coefficient of sensory evaluation and instrument test was studied in this paper.The results showed that there is difference between five brand chocolate;There is a high correlation coefficient between sensory evaluation and instrument test by TPA test.So TPA test is worth extending.Expected model of sensory parameters by instrument's has a high ANOVA explaining rate.Rheological properties in storage was studied in this paper.The results showed that there are great influence to chocolate by temperature and humidity.In storage time,character of chocolate was reduced.It must control the temperature and humidity of chocolate in storage.The optimum storing conditions of chocolate are temperature≤20℃,humidity≤50%;Expected model of storing chocolate was used by RBF artificial neural network forecast model,Correlation coefficient is high,expected veracity is chewing＞resilience＞cohesive＞brittleness＞hardness＞elasticity.The results of this study supply a powerful foundation for the chocolate's objective method creation and its quality and detection.