MECHANICAL AND RHEOLOGY PROPERTIES OF DEHYDRATED FRUITS

摘要

Dried fruits that have good taste,modified texture and look appetizing are highly demanded by consumers.The texture of dried fruits can be determined using two basic groups of instrumental tests i.e.mechanical and rheological.Mechanical properties are usually determined through compressive test,sometimes through cutting test and very rarely using three point bending test.Those tests provide information on breaking force and energy that required in breaking a sample.Compression of the sample with defined size enables determination of breaking stress and modulus of elasticity,whereas double compression,known as a Texture Profile Analysis (TPA),reflects the behaviour of a material while masticating.Parameters used to quantify the masticating behaviour are hardness,cohesiveness,springiness,adhesiveness,chewiness and gumminess,which are also corresponding to the quality attributes evaluated in sensory assessment.Rheological properties of dehydrated fruits are also key criteria in determining product quality and measuring consumer’s acceptance of a product during masticating.These properties are measured through stress relaxation or creeping tests,which provide insights into viscoelastic characteristic of dehydrated fruits.This paper provides an overview on the mechanical and rheology properties of fruits dried using different drying methods.In addition,the Maxwell model,the Kelvin-Viogt model,the standard linear solid model and the Generalized Maxwell model are used to predict the stress and strain interactions in time as well as the temporal dependencies on temperature and moisture content are discussed.