The freeze injured tissue of most fruits will begin to brown as a result of enzymatic oxidation of phenols released by the injured tissue. When freezing occurs at the fruit surface, the glossy or browning symptoms may be visible without cutting. Often when injury is seen it is necessary to determine whether it is indeed from freezing or whether it is from some other cause. Similar symptoms can be associated with injury from other causes. Water core in apples and some senescent breakdown problems can cause flesh translucency.
Many disorders can cause internal tissue browning or even the development of gas pockets.
Surface browning may be confused with scald disorders in apples, Asian and European pears, or even chemical or mechanical injuries on many fruits. Freezing will occur on the most exposed fruit, i.e. near box openings located on the sides and corners of the pallet. Freezing injury should thus be seen first in the lowest SSC portions of the fruit and in the lowest SSC fruit within a lot. Each fruit has a typical SSC pattern. For pears and apples that we have evaluated, the lowest SSC is in the core area, the highest SSC in the outer flesh near the blossom end of the fruit.