Biphenyl Absorption of Citrus Fruits: The Effect of Variety, Color Class, and Injury by Freezing, Peeling, and Lack of Oxygen

Excerpts from the report: Biphenyl has been used as a fungistatic agent in the control of citrus fruit decay since Tomkins first reported its effectiveness in 1935. In commercial practice, pads of kraft paper treated with biphenyl are placed inside cartons of citrus fruit during packaging. The biphenyl volatilizes from the pads into the atmosphere of the carton. The biphenyl vapor controls decay in citrus fruit through inhibition of fungal vegetative growth and normal spore formation. At the same time, however, biphenyl is absorbed by the citrus fruit in the carton. The accumulation of biphenyl in the fruit must be kept below the legal tolerance of 110 p. p.m. for the United States and 70 p. p.m. for the European Economic Community (EEC). Some biological and environmental factors affecting biphenyl absorption were investigated to determine to what extent biphenyl residues could be controlled during storage and shipping. Tests were undertaken to determine the effect of (1) color class, (2) 2-chloroethane phosphonic acid (Ethrel), (3) oxygen-free atmospheres, and (4) mechanical and freezing injury on biphenyl absorption by citrus fruits. In addition, the daily and weekly accumulation of biphenyl by oranges and lemons was followed in a near-saturated atmosphere of biphenyl to determine how much biphenyl would be absorbed by citrus fruits.