Post-harvest trends: the invisible armor of the avocado

Are we aware that when we purchase fresh produce at retail, we are acquiring products that may be coated with solutions of different natures? Without necessarily realizing it, this is a very common situation with imported and exported fruit found in the local market.

Fresh foods travel thousands of kilometers, cross borders, and are stored for varying periods of time before reaching the consumer's table. Without adequate protection, much of this fruit would be lost before we had the opportunity to consume it.

Beyond the transport conditions that we can control inside refrigerated containers (temperature and oxygen levels or other gases used to slow down ripening), how we formulate our coatings becomes critically important to ensure that the fruit arrives in good condition.

From physical barriers, followed by chemical barriers and, today, biotechnological solutions, coatings have evolved into the result of multivariable designs aimed at preserving fruit condition and quality from harvest through consumption.

The Great Challenge: Distance

Avocado is a climacteric fruit; its "biological clock" accelerates after harvest, triggering the ripening process. For an exporter in Latin America, the challenge is not only to produce quantity and quality, but also to achieve the conditions that allow the fruit to travel without apparent deterioration for 30 or 40 days of maritime transit to its destination. Thus, beyond their aesthetic benefits, coatings respond to the need to keep the fruit in good condition for longer, minimizing losses caused by deterioration. This is achieved by creating selective barriers against gases, water vapor, and microorganisms.

Objectives of Coatings

The use of these thin layers on the surface of the fruit pursues three fundamental goals:

A. Control of Transpiration (Weight Loss)

Avocado loses weight primarily through water evaporation. A lipid- or wax-based coating seals the micropores in the skin, reducing the vapor pressure gradient between the fruit and the environment and thereby minimizing water loss. This aspect also has a significant economic impact.

B. Regulation of Gas Exchange (Shelf Life)

Coatings create an Individual Modified Atmosphere (IMA). By limiting the entry of O2 and the release of CO2, the fruit's respiration rate is reduced. This, in turn, delays the synthesis of ethylene, the hormone responsible for ripening, allowing the avocado to maintain its firmness for longer.

C. Phytosanitary Control Against Molds and Fungi

Many modern coatings act as carriers for active agents. They can incorporate organic compounds such as essential oils (thyme, rosemary) or biological fungicides that inhibit the growth of pathogens such as Colletotrichum gloeosporioides (anthracnose).

Trends in Postharvest Management

Current demands from consumer markets are driving (i) the reduction of chemical residues and (ii) the use of sustainable biotechnologies.

This responds both to the demands of international markets and to sustainability and efficiency policies throughout the production chain.

Coatings are no longer simply "shine waxes." Their aesthetic function has evolved into biologically active systems. We are no longer looking only for a physical barrier, but for a biochemical interaction that can influence the fruit's metabolism and selectively combat pathogens.

Among the disruptive technologies redefining avocado exports are:

1. The Use of Probiotics

This is perhaps the most significant recent innovation. Instead of using chemicals to control and eliminate fungi, beneficial microorganisms (such as strains of Lactobacillus or antagonistic yeasts) are incorporated into the coating matrix. In a project I collaborated on a little over a year ago, I had the opportunity to become familiar with this option. Commercial companies are already offering these solutions, as well as the equipment required for their proper application to the fruit.

This living shield seeks to colonize the surface of the avocado, consuming the nutrients that fungi such as anthracnose need to multiply. In essence, this is an entirely biological control mechanism.

2. New Plant-Based Waxes

Unlike traditional waxes, which were generally petroleum-derived, today modified lipids of plant origin are being used. These are highly engineered derivatives.

In this area, we find the use of carnauba wax processed through nanotechnology to create micelles so small that they penetrate the irregularities of the skin, allowing for a much thinner and less "plastic-like" coating.

On the other hand, some companies use molecules found in the seeds and peels of certain plants that are structurally identical to the molecules present in the avocado cuticle. In this way, the fruit "recognizes" the coating as its own, drastically reducing the rate of transpiration without causing anaerobic ripening (off-odors).

3. Use of Essential Oils

The use of plant-derived molecules and essential oils, integrated into biopolymer compounds such as chitosan, allows coatings to act as "slow-release natural antibiotics."

Among these phytonutrients are:

Terpenes and Phenolic Compounds: molecules extracted from oregano, thyme, cloves, or even from the avocado seed itself. They act by capturing free radicals generated during the stress associated with refrigerated transport, helping to prevent internal browning (black flesh).

Chitosan, derived from chitin, is the star polymer. It is naturally antifungal and creates a film that adapts perfectly to the rough texture of Hass avocado skin.

4. The Silk Revolution

The extraction and use of fibroin, the protein found in silk, is perhaps the most cutting-edge technology to date. It consists of extracting the silk protein and using it to create an almost invisible nanometric mesh that can be customized to allow the avocado to "breathe" exactly as needed. It is not yet widely adopted commercially, as its use remains at a stage of adjustment and adaptation.

Conclusions

Today, the avocado no longer travels alone; it travels protected by a sophisticated biotechnological armor.

The shift toward plant-based derivatives and probiotics is driven not only by environmental regulations, but also by the potential to significantly reduce rejections caused by chemical residues in Europe. This allows sustainability to become a competitive advantage.

The general trend in current and future postharvest treatments is to extend fruit shelf life by reducing losses caused by deterioration, maintaining quality, and minimizing the use of chemical products.

Coatings are not merely an aesthetic "shine"; they are a molecular engineering tool that optimizes global logistics. Their success depends on the proper combination of the active compound and the substrate matrix, according to the destination market and the avocado variety being protected, in order to preserve sensory quality intact from the packing house to the final consumer.

However, we cannot place all the responsibility on coatings; the quality of all fruit begins in the field, and every subsequent activity can only contribute to preserving this condition, not improving it. In this sense, the contribution of coatings is to maintain the quality and condition of the fruit from the time it leaves the packing house until it reaches its destination.