THE TEXTURAL ANALYSIS OF COOKED POTATO .1. PHYSICAL PRINCIPLES OF THE SEPARATE MEASUREMENT OF SOFTNESS AND DRYNESS

The texture of cooked potatoes was described by two physical parameters: softness, resulting from both cell cleavage and cell separation, and dryness, depending on the ratio of cell separation to cell cleavage. The softness of potato tissue was measured by determining its resistance to cutting with a thin stainless steel wire. Softness increased rapidly with cooking time, particularly when the cultivar was predicted to be soft in texture by published taste panel trials. Raw potato tissue released intercellular fluid from fractured surfaces due to cell cleavage. After cooking less fluid was released, i.e. the texture became drier, as cell separation increased. The erosion of cells from cooked potato tissue by a high-pressure jet of water was used to measure dryness quantitatively. Erosion increased during cooking. Carrot tissue, whose cells do not separate on cooking, did not erode, but anomalous results with apple tissue suggested that measurement of dryness in this way might not be fully independent of softness.