Puncture and stress relaxation behaviour of taro paste as affected by moisture content and puncture rate and depth

The effect of puncture rate (10, 100 and 250 mm min−1) and depth (5, 10 and 20 mm) on the stress relaxation of taro pastes of moisture content 55% and 66% was studied. The analysed parameters were hardness (HAR), fracturability (FRA), force of adhesion (FOA), force of relaxation (FOR), ratio of fracture and relaxation time (ROT), rate of relaxation (ROR), visco-elasticity index (VEI) and the unrelaxed stress (SRU). The results showed that HAR, FOR, FRA and FOA were linearly correlated to each other and increased significantly with decrease in moisture content. In addition a general reduction of SRU was observed with increase in water. VEI, ROR and SRU were significantly linearly correlated to puncture rate while ROT was linearly correlated to puncture depth. The principal component analysis revealed that the first principal component (PC1) which represented 52% of the total variance was correlated to HAR, FOA, FRA and FOR. The second principal (PC2) component correlated to VEI, ROR and SRU and represented 31% of the variance whereas the third principal component (PC3) correlated to ROT and represented 15% of the variance. It was shown that the Euclidian distance between achu of moisture content 55% and 66% increased with increase in puncture rate and depth.