Agriculture Reference
In-Depth Information
development of foul tasting flavors and reduce the devel-
opment of brown coloration. Avocados are first pitted in
a manner to minimize the incisions made to the pulp of
the avocado. Halving the avocado and removing the pit
from the flesh is one method to accomplish this. Once the
avocados are placed in the alkaline environment, they are
heated. This is accomplished by placing the avocados in
a boiling alkaline solution. Therefore, acidulates such as
lemon or lime juice, ascorbic acid, citric acid, or vinegar
may be added to adjust the pH to slightly acidic level. The
hot guacamole is filled into jars or cans, and sealed contain-
ers are subjected to further heat processing in a retort that
can preserve guacamole food-borne pathogens. The tem-
perature and time of thermal processing are dependent on
the factors pH, time, and temperature.
Figure 23.5. Visual appearance of
vacuum-packaged frozen avocado after 8 weeks
storage at 2 C (source: Bower and Dennison, 2003).
Freezing
The successful processing of avocado fruit for frozen prod-
ucts such as halves and chunks relies on the prevention
of enzymatic browning of fruit and maintenance of taste.
Browning could be prevented by the use of antioxidants
such as ascorbic acid, but at the concentrations required to
achieve an effect, the taste of the product can be affected. To
overcome this problem, a mild heat treatment (blanching)
can be used; peeled and sliced fruit is dipped into boiling
water for sufficient time to inactivate the browning enzyme
(PPO) as well as leach phenolics from the cut surface of
the fruit (Bower and Dennison, 2005). The latter prevents
enhanced flavor and bitterness associated with storage of
frozen avocado. Thereafter, fruit is rapidly frozen, packed,
and stored. On defrosting, the treatment was shown to be
highly effective regarding fruit browning (Bower and Den-
nison, 2005). Figure 23.5 shows frozen avocado halves
stored at 2 C for 8 weeks (Bower and Dennison, 2003).
In addition, avocado pulp can be refrigerated (short-term
storage) or frozen for long-term usage (Fig. 23.6).
process. Once the oil has been released from the avocado
pulp by the malaxing process, the released oil is separated
out by centrifugation. The avocado paste/suspension thus
obtained may be dried in a continuous manner by drum-
drying, spray-drying, or any other suitable commercial dry-
ing method. Alternatively, it may be freeze-dried using a
batch freeze-drying process.
Other patents have focused on paste concentration. Carre
(2004) described using a mixture that comprised acids from
cultured dextrose, erythorbic acid, ascorbic acid, quercetin,
and inulin. These components are mixed with avocado
“meat” to form a color-stabilized avocado concentrate. The
method described includes a sanitization step with 50 ppm
chlorine, preparation of a puree, addition of stabilizer, and
packaging. The stabilized avocado pulp concentrate can be
Drying/dehydration
Peeled and pitted fruit can be dried for use in soups and
other culinary applications. The drying of avocados should
be done at relatively low temperatures to preserve its flavor
while the use of high temperatures can result in excessive
darkening of the dried avocados.
Garcia (2010) patented a process for producing avo-
cado powder. In this process, avocado paste is warmed
to 40 -50 C for about 1 hour to release the oil from the
avocado pulp. This step is carried out in a malaxer unit that
“kneads” paste. Antibrowning agents (e.g., ascorbic acid)
may be added during heating or at any later stage of the
Figure 23.6. Packaged avocado pulp prior to
refrigeration or freezing chambers.
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