Passion Fruit - Tropical and Subtropical Fruits: Postharvest Physiology, Processing and Packaging - page 318

In Brazil, the extraction unit most commonly utilized is
the three-stage system, consisting of a disk cutter, a per-
forated cylinder with a series of beaters that separates the
rind from the pulp and seeds, and two pulpers. The first
pulper separates the juice from the seeds and the second
does the finishing of the juice. Both types of pulpers con-
sist of cylindrical sieves with the central axle equipped with
nylon brushes.
The extracted juice is then heated to 50 ◦ C and submit-
ted to treatment with pectinolytic enzymes. This treatment
avoids the increase in viscosity that can result in deposits
and burning in the heat exchangers during pasteurization.
Centrifugation removes residual pulp. In some systems,
centrifuges that operate under pressure by an inert gas,
such as nitrogen, are used to minimize the incorporation
of oxygen. In other systems, centrifugation is followed by
deaeration. Deaeration removes air dissolved in the product
to control oxidative degradations that can bring about alter-
ations in the color, aroma, and flavor of the final product.
Pasteurization has the objective of inactivating enzymes
and eliminating pathogenic micro-organisms and other
causes of deterioration. It is generally carried out at temper-
atures

Raw fruit

Initial sorting

Washing

Final sorting

Cutting/Shredding

Juice extraction

Enzymatic treatment

Centrifugation

Deaeration

85 ◦ C. Different temperature-time combinations
are used, depending on the equipment utilized and the qual-
ity of the juice. In the plate pasteurizer, the treatment can
be done at 90 ◦ -95 ◦ C for 45 sec. Another system for the
thermal processing of passion fruit juice combines short-
time pasteurization and aseptic packaging to retain better
quality (Tocchini et al., 1995).
Since the product is of high acidity and has moderate con-
centration of sugar, passion fruit juice is a selective medium;
the micro-organisms that can survive in such conditions
are yeasts of the genera Candida and Saccharomyces. An
efficient pasteurization can result in a product of up to
100 cfu, without coliforms, fungi, and yeasts.
The heat treatment is the most delicate step in the pro-
cessing of passion fruit juice, given the extreme sensitivity
of the volatile compounds to heating and the ease with
which the starch suffers gelatinization. The heating condi-
tions should be carefully chosen. Yellow passion fruit juice
was subjected to three pasteurization conditions (85 ◦ C,
27 sec; 80 ◦ C, 41 sec; 75 ◦ C, 60 sec) and stored for 120 days
at two temperatures (25 ◦ C, 5 ◦ C) (Sandi et al., 2003). The
pasteurized samples received lower scores for sweet, char-
acteristic, and floral aroma and for sweet and acid taste.
The negative effect of heat treatment was manifested in
the higher scores for oxidized, strange, and cooked fla-
vor, although the pasteurized juices were more homoge-
nous in color. There was no significant difference in most
of the sensory characteristics of juices pasteurized under

≥

Pasteurization

Packaging Concentration

Cooling

Cooling

Cut back

Storage

Freezing

Storage ( − 20 ° C)

Figure 17.3. Flow diagram of the processing of
pasteurized juice and frozen concentrate (source:
Adapted from De Souza and S andi, 2001; Folegatti
and Matsuura, 2002).

insect attacks, diseases, mechanical damage) that can jeop-
ardize the quality of the finished product.
Cutting is a critical operation in the processing of passion
fruit juice. In some systems, cutting is carried out by the
same equipment that extracts the juice while other extrac-
tors are fed with the whole fruits.