Food Biochemistry and Food Processing

528 Part V: Fruits, Vegetables, and Cereals

to over 83°C, held for 3 minutes, filled hot into the
container (cans or bottles), and hermetically sealed.
The apple juice is held for 1 minute at 83°C and then
cooled to less than 37°C. When containers are
closed hot and then cooled, a vacuum develops, re-
ducing the available oxygen, which also aids in the
prevention of microbial growth. After heat treat-
ment, the juice may also be stored in bulk contain-
ers. Aseptic packaging is another common process
in which, after pasteurization, the juice is cooled and
packed in a closed, commercially sterile system
under aseptic conditions. This process provides shelf-
stable juice in laminated, soft-sided consumer car-
tons, bag-in-box cartons, or aseptic bags in 200–250 L
drums.

Apple juice concentration is another common

method of preservation. The single-strength apple

juice is concentrated by evaporation, preferably to

70° or 71° Brix. By an alternate method, the single-

strength juice is preconcentrated by reverse osmosis

to about 40° Brix, then further concentrated by evap-

oration methods. The reduced water content and nat-

ural acidity make the final concentrated apple juice

shelf stable at room temperature. There are several

evaporators used in apple juice production including

rising-film evaporators, falling-film evaporators, and

multieffect tubular and plate evaporators. Due to the

heat sensitivity of the apple juice, the multieffect

evaporator with aroma recovery is the most com-

monly used. The general method in a multieffect

Figure 22.5.Membrane filtration. Key: RO, reverse osmosis; UF, ultrafiltration; MF, microfiltration; F, filtration.