Novel Processing Technologies for Fruits - Tropical and Subtropical Fruits: Postharvest Physiology, Processing and Packaging - page 74

This was observed in a number of fruits after HP treatment,
including mandarin juice (Takahashi et al., 1993), white
grape juice (Daoudi et al., 2002), guava juice (Yen and Lin,
1999), and yellow passion fruit juice (Laboissiere et al.,
2007). For some fruits, alteration of flavor and flavor pro-
file were observed due to HP-induced enzymatic action
and chemical reactions. Gas chromatographic studies
demonstrated changes in the hexanal (a volatile compound)
content of fruits after HP treatment (Navarro et al., 2002).
The changes in volatile flavor components of guava
juice during HPP (600 MPa/25 ◦ C/15 min), and storage
at 4 ◦ and 25 ◦ C, were evaluated by purge and trap-gas
chromatography-mass spectrometry (Yen and Lin, 1999).
Esters were the major volatile fraction in guava juice, and
alcohols were the second. The volatile component dur-
ing high-pressure treatment was not changed when com-
pared with the fresh fruit juice. It seems that HP treatment
maintains the volatile components and compositions of the
juice. HP-treated guava juice showed increases in methanol,
ethanol, and 2-ethylfuran with decreases in the other com-
ponents during storage period. Guava juices treated with
HP (600 MPa, 15 min) and then subjected to storage at 4 ◦ C
for 30 days maintained a volatile component profile similar
to that of the fresh juice.
Wolbang et al. (2008) evaluated the effect of cultivar
on high pressure processing performance for vitamin C
and β -carotene of three commercial melon varieties before
and after pressure treatment by HPLC and for ferric ion-
reducing capacity (FIRC) using the ferric reducing ability
of plasma (FRAP) assay. Results indicated that FIRC and
vitamin C concentrations were decreased by HPP, and these
losses were cultivar dependent for vitamin C.
High-pressure treatment (100-400 MPa) individually or
in combination with temperature (30 ◦ -60 ◦ C) produced sig-
nificant increase (10-43%) in the carotenoid content of or-
ange juice (de Ancos et al., 2000; Sanchez-Moreno et al.,
2006). The increase of total pigment content was related
with a significantly better extraction of some of the main
pigments such as violaxanthin, lutein, antheroxanthin,

5 min) indicated that the flavor was not as fresh as that of
untreated sample (Parish, 1998; Fernandez Garcıa et al.,
2001). However, the taste of HP-treated orange juice was
judged better than conventional thermally pasteurized or-
ange juice (Parish, 1998; Polydera et al., 2005). Baxter et al.
(2005) found no differences in the concentration of volatile
flavor compounds between freshly frozen, thermally treated
(85 ◦ C, 25 sec) or HP-treated (600 MPa, 18 ◦ -20 ◦ C, 60 sec)
orange juice. The results of the chemical analysis were
supported by the results of a trained sensory panel and a
consumer panel, which did not remark any differences in
odor or flavor between the differently treated orange juices.
A shelf life study of HP-treated (500 MPa, 2 ◦ C, 10 min)
grape juice revealed that the sweetness and acidity of the
samples were retained for 60 days during storage at 4 ◦ C,
but fresh fruit and grass aroma were marginally reduced
during storage (Daoudi et al., 2002). Similar results were
reported for HP-treated guava juices. The volatile flavor
compounds in HP-treated (600 MPa, 25 ◦ C, 15 min) guava
juice remained stable during 30 days storage at 4 ◦ C, how-
ever, they changed after 60 days' storage.
High-pressure treatment does not affect sugar composi-
tion in fruit products. The glass transition temperature ( T g )
of mango pulp was -87.45 ◦ C, which marginally changed
to -85.34 ◦ C after HP (400 MPa, 30 min) treatment (Ahmed
et al., 2005).

High-pressure shift freezing
HPs can be applied during the freezing of foods. Phase tran-
sition can occur either under constant pressure (pressure-
assisted freezing to obtain ice I or other types of ice (ice II,
ice III, and so on) or due to a pressure change (pressure-
shift freezing) (Knorr et al., 1998). There are two types of
high-pressure-shift freezing (HPSF): (1) expansion occurs
gradually and (2) expansion to atmospheric pressure occurs
suddenly, thus achieving considerable super cooling at at-
mospheric pressure. HPSF has been considered as the less
harmful freezing methods, for cellular structure like fruit.
A HPSF process consists of several steps (Fig. 5.3). A
brief description of the process for fruit freezing is given
here and more details are available elsewhere (Otero et al.,
2000). The test sample was placed in the pressure vessel
and the pressure increased by hydropneumatic pumps with
an ethylene glycol-water (75/25) mixture as compressing
fluid until it reached target level. The vessel was thermoreg-
ulated by means of a laterally surrounding properly isolated
coil at a temperature of -21 ◦ C. After or during the pressur-
ization, the product is cooled until the temperature reaches
the desired level, however, the product will still be in the
unfrozen state due to the freezing point depression un-
der pressure. The pressure is then quickly released within

β -

cryptoxanthin, and -carotene. The lowest influence on the

extractability of total carotenoids was found in HP treat-
ment at lower pressure (100 MPa, 60 ◦ C, 5 min), whereas
the influence was significant at a higher pressure level
(400 MPa, 40 ◦ C, 1 min). Consequently, pressure combined
with temperature in the treatments applied to orange juices
seemed not to cause any loss in carotenoids compared to
untreated orange juices.
Sensory evaluation of HP-treated juice showed mixed re-
actions among panel judges and consumers. Sensory evalu-
ation data of HP-treated orange juice (500 MPa/room tem-
perature/1.5 min or 5 min; 700 MPa/1 min or 800 MPa/

β