CHALLENGES WHILE PRESERVING AVOCADOS
The avocado originated in Central America and southern Mexico but now avocados are grown in many countries of the world.
The avocado is botanically classified into three races:
1. West Indian (WI) - tropical with large variably shaped fruit and lower oil content.
2. Mexican (MX) - semitropical with smaller elongated, thin-skinned fruit and higher oil content.
3. Guatemalan (G) - subtropical with mostly round, thick-skinned fruit and intermediate oil content.
Many of the commercial cultivars are hybrids of these three races. There is great variability in fruit traits and one of the most distinct differences between cultivars is the peel color when ripe. The peel of some cultivars changes from green to black or purple with increasing maturity or ripening.
On the market fresh avocados with imperfect and odd-sized fruits are usually rejected. In addition, the fruits selected require special handling because of their highly perishable nature. Their high oil content readily becomes rancid and they also have a very active oxidative browning system. Therefore, the development of new avocado products and of improved methods of preservation are of interest to avocado growers.
The majority of the cultivars are considered to be primarily G-MX hybrids and the most common and highly appreciated on the market is the Hass variety. Hass avocado produces fruit year-round and accounts for 80% of cultivated avocados in the world. Also, the Hass avocados are more easily preserved in comparison to other avocado cultivars.
Time is essential when preserving avocados, because once the avocado is plucked from the tree it starts to ripen. Avocados are one of the few fruit that contain significant quantities of oil, sometimes more than 30%, and little quantities of water.
Ripening and associated softening of avocados can be delayed by cooling soon after harvest. This is critical where long storage periods are required or where field temperatures are above 25 °C. Forced or passive air-cooling is generally carried out as rapidly after harvest as possible and it is recommended to have the target temperature vary between 5 and 15 °C. External chilling injury can occur and are generally induced by temperatures below 3 °C, but in cultivars that naturally darken during ripening, such as the Hass variety, the damage will be less apparent.
Avocados are not well adaptable to canning or to other methods of preservation because of undesirable changes in flavor, texture, or color. However, innovative freezing technologiesare coming up with new solutions that help preserve the fruits for longer and make it possible to use it in various forms.
Individual Quick Freezing (IQF) technology, especially the OctoFrost IQF system is having good result freezing avocado fruits. Avocado is a tricky product and it comes with a few challenges:
- avocado has to have the right ripeness for freezing, it cannot be too overripe as otherwise the quality will get compromised.
- too much surface water on the avocado will generate corals during freezing
- avocado is quite a sticky product
Generally, a good pre-freezing treatment is needed in order to guarantee a good freezing result. Approximately 65% of an avocado is flesh and a good practice for freezing the fruit would be the following:
1. Cut the avocado in halves
2. Scoop out the stone and remove the flesh manually
3. Put the fruit in a water bath in a hydro cooler
4. Dice or slice
5. Spray or use a bath of citric acid or lemon juice
5. Remove surface water with a dewatering shaker or air knives
6. Transport the product in the IQF tunnel for freezing
Avocado is really sensitive to mechanical impact, but the OctoFrost IQF freezer provides remarkable results due to the adjustable freezing zones and gentle bedplate movements. The OctoFrost freezing tunnel is thus managing to preserve the natural appearance, creamy texture, color and buttery flavor of IQF avocado.
Avocado is prized for its high nutrient value and has become an important part of western diet. As many customers find its perishable nature as a great disadvantage, the IQF frozen avocado will definitely become a real hit on the modern food market.