PH: A chemical measurement of acidity or alkalinity; the higher the pH the weaker the acid. Used by some wineries as a measurement of ripeness in relation to acidity. Low pH wines taste tart and crisp; higher pH wines are more susceptible to bacterial growth. A range of 3.0 to 3.4 is desirable for white wines, while 3.3 to 3.6 is best for reds.
Phenolics: Tannins, color pigments and flavor compounds originating in the skins, seeds and stems of grapes. Phenolics, which are antioxidants, are more prevalent in red wines than in whites.
Phylloxera: Tiny aphids or root lice that attack Vitis vinifera roots. The vineyard pests were widespread in both Europe and California during the late 19th century, and returned to California in the 1980s.
Physiological Ripeness: See Polyphenolic Ripeness.