Dear Ajitesh Singh, the paper of Sapozhnikov S.B. and Ignatova A.V. entitled "Experimental and Theoretical Investigation of Deformation and Fracture of Subcutaneous Fat under Compression" published in "Mechanics of Composite Materials", 2012, No 6, probably, will be useful for you. In this paper by comparing experimental data for the fat with the mathematical shell model, three parameters are determined to describe the hyperelastic behavior of the cells in transverse compression.  

All the best

Yes, I agree with opinion which Parth Shah has been mentioned. Method of indentation (dynamic indentation is better because their more informative and convenient in case of biotissues diagnostics than static ones) is good. See, please, for example, our paper "Method for in vivo estimation of viscoelastic characteristics of skeletal muscules"  // Russian Journal of Biomechanics. – 2007. – Vol. 11, № 1. – P. 44–53.