Agriculture Reference
In-Depth Information
the micro-organism to be removed, the type of vegetable,
the pH, and the temperature of the water used in wash-
ing (FDA, 2001). Sanitizers used or with potential use in
reducing the microbial load of avocados are presented as
follows.
Even though the peel is discarded in some avocado prod-
ucts before processing, in other methods the halves with
peel are mechanically crushed to separate the pulp. In this
type of operation, it is very important to keep the peel free
of pathogens, otherwise they may reach the final product,
and pathogens, like Listeria monocytogenes, will survive
and grow at refrigeration temperatures.
The most widely used sanitizer in avocado processing
is sodium hypochlorite. Food service operations mainly
employ iodine solution, which is a mix of 2% elemental
iodine and 2% potassium iodide in 70% alcohol. Iodine is
nontoxic when used at the right concentrations, and it shows
a high spectrum of antimicrobial activity, including molds
and yeasts (Gonzalez-Aguilar et al., 2005). Other sanitizers
potentially useful for avocado have been described by the
same authors, as follows: peroxyacetic acid, which is a mix
of oxygen peroxide and acetic acid, approved for its use in
washing water as disinfectant of fresh-cut vegetables; and
acid electrolyzed water (AEW), generated by the electrol-
ysis of brine as an accelerating agent that goes through the
anode of a membrane electrolyzer. The efficiency of AEW
has been proved against several pathogens of high interest
in the food industry.
Regarding pretreatments for minimally processed av-
ocado, one of the most important is the addition of
enzymatic-browning inhibitors. The ban on the use of sul-
fites, which were widely used to keep the green color, in-
duced researchers into finding other alternatives. In 1998,
Dorantes-Alvarez et al. tested 10 different antibrowning
agents to inhibit browning in avocado slices. After 5 days of
storage, results showed that the best agents were (1) sodium
metabisulfite; (2) a mixture of cystein, sodium erythor-
bate, and sodium ethylene diamine tretracetate (EDTA);
and (3) tetrasodium pyrophosphate. Considering that the
use of sodium metabisulfite is forbidden in some countries
and that erythorbate and EDTA are already used to control
browning in commercial avocado products, further experi-
ments were done using cysteine and variable pyrophosphate
concentration, a w , and pH values. From the results obtained
in this work, it was concluded that a combination of cystein
and tetrasodium pyrophosphate as well as convenient val-
ues of pH and a w of selected formulations gave acceptable
results for color, flavor, and texture (strength), comparable
to those given by metabisulfite.
Figure 23.4. Visual appearance of fresh-cut avocado
after storage at 2 C for 21 days (source: Bower and
Dennison, 2003).
at 5 C presented a shelf life of 5 days, based mainly on
appearance, with a score of 7.3 (between “like moderately”
and “like very much”) on a 1-9 point hedonic scale.
Consumption trends: growth, types of products
A significant share of avocado production is intended for
the fresh market. The most popular avocado products with
minimal processing are pulps, which in turn are used as ba-
sis for spreads and dips, such as the ones mixed with onion,
garlic, salt, and lemon juice for guacamole-type products.
These products are sold at room temperature, frozen, or
refrigerated. In Mexico, and recently in the United States
and Europe, guacamole and occasionally avocado slices
are offered in several Tex-Mex-type restaurants and other
food service operations such as salad bars. Given the high
potential for enzymatic browning and tissue softening of
avocado after ripening, the use of enzymatic inhibitors and
texture stabilizers is needed.
Pretreatments and sanitizer use
Processing of minimally processed avocados begins with a
selection step, where the unsuitable fruit is discarded, the
peduncle is removed, and the fruit is washed with common
detergents. The next step is the sanitizer treatment. The use
of sanitizers is one of the issues to be considered in the
food safety aspects. The efficiency of sanitizers in remov-
ing and/or inactivating micro-organisms adhering to and
living on the surface of fruits depends on the type and con-
centration of the product, the exposure time, the nature of
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