Relationship of Water Activity to Moisture Content in Tree Nuts

Experiments were conducted to determine the effects of moisture and oil content on the water activity (a w ) of 13 tree nut meats. Kernels of almond, butternut, Brazil, cashew, Chinese chestnut, filbert, hickory, macadamia, pecan, pignolia, pistachio, and walnut (black and English) were analyzed at 21°C for moisture contents at a w values ranging from 0.12–0.81. Straight‐lined plots showing 0.20–0.80 a w at corresponding moisture levels were constructed from isotherms. Pecan nut meats contaning 63.9–76.3% oil were equilibrated at 0.68 a w and percentage moisture was determined. There was an inverse, directly proportional relationship between values obtained for percentages of moisture and oil. The moisture content of pecan nut meats at 0.68 a w was not directly proportional to the protein content, however, indicating that water‐binding capacity was dependent upon other nonoil constituents in addition to protein.