Grapefruit - Tropical and Subtropical Fruits: Postharvest Physiology, Processing and Packaging - page 355

and an optimum storage temperature of 12 ◦ C (Lurie, 2009).
These commercial conditioning and cold quarantine storage
treatments prior to and during shipment affect the quality of
'Rouge La Toma' grapefruit (Biolatto et al., 2005). The har-
vest time and storage conditions of 'Star Ruby' grapefruit
for short-distance summer consumption have been reported
(Pailly et al., 2004). Igual et al. (2010b) also reported on
the effect of thermal treatment and storage on the stabil-
ity of organic acids and the functional value of grapefruit
juice.
There have been some advances in fruits at export ter-
minals involving computerized quality control at shipping
point. A statistical sequential sampling procedure based on
computerized citrus quality control is in use at the entrance
to export terminals by inspectors. The aim of the inspection
is to identify deliveries with a high probability of substan-
dard quality (Kader, 2002; Opara, 2009).

fully-mature grapefruit. Juice from immature grapefruit
contains excessive amounts of naringin and limonin that
impart an extremely bitter flavor to the juice (Bates et al.,
2010).
Typical process for grapefruit production is similar to that
of orange juice (readers are referred to the chapter 21 on
“Orange” for more details on the process and equipment).
Briefly, the grapefruit juice extraction and processing steps
are as follows: Receiving fruit → Inspection → Washing
→ Juice extraction → Finishing or sieving → Deaera-
tion and deoiling → Sweetening (if needed) and blending
→ Pasteurization at 195 ◦ F for 30 sec → Filling at 190 ◦ F
→ →

Thermal processing (212 ◦ F, 10 Container closing

min for 12-oz cans) → Coolingto95 ◦ -105 ◦ F (Downing,

1996a).
The juice bitterness is removed by using plastic beads,
which are made from a styrene divinylbenzene cross-linked
co-polymer resin. With such polymer, it is possible to ab-
sorb the limonin and many other bitter compounds from
citrus juice. For the beads to work, the citrus juice needs
to be separated into pulp and liquid. The liquid has most
of the limonin, the bitter compound in citrus juice. When
the beads come in contact with the liquid, the limonin
molecules get trapped in the beads (along with some other
useful chemicals). After some time the columns of beads
need to be cleaned so as not to lose their capacity to trap
the limonin. This is done with ethanol, which is then re-
moved by washing the beads in stages with hydrochlo-
ric acid (HCl), sodium hydroxide (NaOH), and water. The
idea is that the hydrochloric acid and the sodium hydroxide
neutralize each other. After the removal of the limonin (a
process called debittering), citrus juice is reconstituted by
adding back some of the pulp and maybe even some citrus
oil extracted from the peel.
Other studies on debittering include the effects of deb-
ittering on red grapefruit juice concentrate (Lee and Kim,
2003) and the effects of enzymatic debittering on antioxi-
dant capacity and protective role against oxidative stress of
grapefruit juice in comparison with adsorption on exchange
resin (Cavia-Saiz et al., 2011).

FRESH-CUT AND MINIMALLY PROCESSED
PRODUCTS
Grapefruit is not marketed commercially in the fresh-cut or
minimally processed form on a scale similar to some other
tropical fruits; one exception being food service or culinary
applications in some countries. Fresh-cut grapefruit has a
potential to be developed and marketed as fresh-cut fruit
since consumption is increasing due to the rising public
demand for convenience and awareness of fresh-cut fruit's
health benefits.
Minimal processing with nonthermal methods, such as
ultrasound, air ion bombardment, pulsed electric field, and
high-pressure processing (500 MPa, 5 or 10 min cycles
with a 1 min hold), are increasingly used in the process-
ing of fruits. However, some of these processes are hardly
sufficient to inactivate micro-organisms or enzymes at in-
tensities that will not affect sensory and nutritional quality
(Ohlsson, 2000). Combination with other hurdles, such as
refrigeration, results in extension of shelf life and mini-
mal loss of fresh quality, especially in fruits like grapefruit.
In a recent hypothesis, safety and the antioxidant value of
fresh-cut fruits could be improved by using the fruits' own
by-products as a source of antimicrobial and antioxidant
additives (Ayala-Zavala et al., 2010).

Juice concentrate and juice blends
Concentrated juice is a product prepared from the unfer-
mented juice by evaporation or freezing; it is sufficiently
heat processed to ensure preservation in the hermetically
sealed containers (Downing, 1996a). The “US Grade A”
or “US Fancy” canned grapefruit juice concentrate should
have no less than 0.33 mg/g vitamin C (ascorbic acid);
total acidity between 0.1% and 0.2%; and no more than
0.0033 ml of recoverable oil per 100 g. The reconstituted

PROCESSING AND PROCESSED PRODUCTS

Juice
Grapefruit juice extraction requires larger diameter ream-
ers. As with all fruit, it is important to process high quality,