Potato tissue samples with varying cell turgor pressures were prepared by soaking in mannitol solutions (0 to 0ร5 M). Increased concentration of mannitol in the soaking solutions decreased the cell turgor pressure in potato tissues providing samples with varying degrees of turgidity or plasmolysis. Firmness changes in potato tissues of di โ ering turgor pressure during cooking were examined using a Zwick universal testing machine and also by chewing tests. A modi-รed device attached to a Zwick machine facilitated complete immersion of a potato disc in circulating boiling water, providing rapid and reproducible heat transfer in the tissue during รrmness measurements. Tissue รrmness expressed as the force required to cause 10% strain in the sample varied in potato discs treated with di โ ering mannitol solutions. Potato discs soaked in 0 to 0ร3 M mannitol solutions were more turgid at 20ยกC than other samples and showed higher tissue รrmness. However, when discs of potato were heated in the range of 20ร 90ยกC, samples treated with 0ร4 and 0ร5 M mannitol solutions showed some increase in tissue รrmness while all other samples exhibited a rapid decline. Biteforce measurements on potato discs also indicated a rapid loss of tissue รrmness in turgid samples. Potato tissues when cooked after soaking in 0ร4 or 0ร5 M mannitol solution showed more intact and inรated cells than other samples.