A thesis submitted in partial fulfillment of the requirements for the degree of Master of Engineering, School of Environment, Resources and Development

Thesis (M.Eng.) - Asian Institute of Technology, 1997

The starch content of two cassava varieties, i.e. R-5 and KU-50 was monitored during storage by five testing techniques namely specific gravity, dry matter, puncture testing, shear testing and compression testing (both axial and radial). Specific gravity was found by platform scale method and dry matter was found by drying. The shear testing was done by using shear set up available with Instron machine. For axial and radial compression testing, cylindrical samples 30 mm in length and 15 ·mm in diameter were used. Puncture testing was done with four punctures, different in size and shape, for unpeeled and peeled samples with Instron machine and an indigenously developed firmness tester. Estimation of cassava starch content based on the specific gravity gave correlation coefficients of 0.8377 and 0.8584 for R-5 and KU-50 varieties, respectively. While the method based on dry matter content resulted in correlation coefficients of 0.8214 and 0.8805 for R-5 and KU-50 varieties, respectively. The results with Instron testing machine showed a good relationship between firmness of cassava with starch content. In case of axial testing, the correlation coefficient was 0.9485 and 0.9457 for R-5 and 0.9072 and 0.9067 for KU-50 at 12 and 15 percent compression, respectively. For radial testing the correlation coefficient was 0.9386 and 0.9047 for R-5 and 0.8977 and 0.9479 for KU-50 at 6 and 9 percent compression, respectively. By shear testing the correlation coefficients were 0.9159 and 0.9037 for R-5 and KU-50, respectively. A simple firmness tester, inexpensive and easy to use, was fabricated during the course of study. Best results were obtained with small size flat shape puncture for peeled samples for both the varieties. The correlation coefficients were found to be 0.9312 and 0.9342 with sensitivity of 47.16% and 51.30% for R-5 and KU-50 varieties, respectively. For puncture testing by Instron machine, the small spherical puncture for peeled samples gave best results. The puncture testing technique was found to be most sensitive among all testing techniques. Considering simplicity, accuracy and sensitivity, the firmness testing has been found to be acceptable and could be commercialized.