Compression characteristics, firmness, and texture perception of heat treated and unheated apples

Two cultivars of apple fruits, Malus domestica cvs. 'Golden Delicious' and 'Granny Smith', were heated for 4 days at 38°C and then held for a week at 20°C or at 0°C. At the end of this period texture, firmness and organoleptic tests were made on these apples and the results were compared with those for unheated apples. The heated apples were found by a taste panel to be crispier and sweeter than the unheated apples. Flesh firmness, tested with a Magness-Taylor penetrometer correlated well with crispiness for 'Golden Delicious' apples and less well with 'Granny Smith'. Instron compression tests of strength and stiffness correlated with crispiness in both varieties. Instron measurement of brittleness was not correlated with crispiness. We suggest that the properties of apple flesh sensed during mastication are most closely related to the properties derived from the compression test of strength and stiffness.