Perception of Quality: Color and TextureColor, a primary indicator of maturity of ripeness, is derived from the pigments found in the product. Loss of the green pigment chlorophyll to unmask yellow carotenoids is a desirable part of the ripening process in many fruits, such as peaches and yellow cultivars of apples. A similar yellowing of green vegetables such as broccoli is considered undesirable. Other pigments of important in fruits and vegetables include lycopene, the red pigment in tomatoes and watermelon: the betacyanins, the red and yellow pigments in beets; and the anthocyanins, the reds, blues, and purples of many fruits and vegetables, including apples, blueberries, and red cabbage. Browning on these products is primarily due to an enzymatic reaction that occurs in response to rupture of the cell membranes.
Texture, like appearance, is evaluated in the context of specific expectations. Crispness and crunchiness are expected in fresh apples, carrots, and celery, but softness or tenderness is desired is asparagus, peas, and plums. The texture of plant products is a consequence of cell wall structure and internal pressure within the cells. Products that maintain structure and turgor during handling and storage remain crisp and may contain an abundance of cell-wall biopolymers. Soft fruits undergo an enzymatic degradation of the cell-wall polysaccharides during ripening. In many fruits, such as peaches and tomatoes, the softening is attributed to pectinolytic enzymes, but cellulose may be important in the ripening of avocadoes. Lignin, a complex biopolymer containing phenolics, can accumulate in cell walls and lead to an objectionable woody texture in products such as asparagus. The mushy texture associated with bruises results from the release, upon rupture of cells, of enzymes that degrade cell-wall polysaccharides, primarily pectin.Perception of Quality: Color and Texture
