Food Biochemistry and Food Processing

22 Biochemistry of Fruit Processing 523

quality of the fruit is dependent on the stage of
maturity or the stage of ripening. The major physic-
ochemical parameters used in assessing fruit ripen-
ing are sugar content, acidity, starch content, and firm-
ness (Somogyi 1996a,b).
The main steps involved in the processing of most
type of juice include the extraction of the juice, clari-
fication, juice deaeration, pasteurization, concentra-

tion, essence add-back, canning or bottling, and

freezing (less frequent). Juice extractors for oranges

and grapefruits, whose peels contain bitter oils, are

designed to cause the peel oil to run down the outside

of the fruit and not enter the juice stream. Since

apples do not contain bitter oil, the whole apples are

pressed. Juice extraction should be done as quickly as

possible in order to minimize oxidation of phenolic

Figure 22.2.Amadori rearrangement. Reactions of free sugars with aqueous ammonia.