The discussion on the firmness of the fruit is prolonged and as it progresses, more variables are included, as a result of the new management in pre-harvest, harvest and post-harvest, which complicates the investigation and postpones the evacuation of definitive results or universal standards.

At the time, the award-winning researcher, professor, and head of the Post-Harvest Unit of the Center for Genetic Improvement and Plant Phenomics at the University of Talca, Claudia Moggia, believed that “within the fresh blueberry industry, an objective measure of firmness, at the field and industry level, that allows defining the limits between a soft, medium or firm fruit, achieving a common language with the recipients of our fruit abroad ”.

The Blueberries Consulting International Seminars of recent years have brought together the best experts to share the results of their research and participate in round tables for discussion, but there is no common and definitive agreement on the issue of firmness. There are many variables.

Receipt criteria

In the last Seminar in Lima, Top Quality experts explained the different reasons for rejecting Peruvian fruit in the markets of Europe, the US and Asia, confirming different criteria for the arrival of the fruit at destination, concluding that this reality affects it to the whole of Latin American fruit.

Claudia Moggia maintains that at the moment there is no methodology that allows the firmness of blue fruit to be distinguished on the ground and at a productive level. If achieved, it would improve the homogeneity of the fruit in the export units, reducing the instances of rejection.

It is very important to deepen the knowledge regarding this topic since blueberries ripen sequentially within the plant, so it is very likely that the soft fruits, and therefore more susceptible to damage, have a physiological age greater than the firm fruits. This, together with the fact that the harvest index is based only on the blue color, can result in commercial harvests mixing visually similar but physiologically different fruit, increasing post-harvest variability.

Various hypotheses

Firmness is an attribute of the texture of the fruit that is related to the point of harvest, the quality for its commercialization and processing. This quality is linked to the physical-chemical and structural changes of the biological material.

The fruits can be considered engineering materials of an anisotropic nature. The mechanical behavior they can exhibit is not perfectly elastic or plastic. On the other hand, the rheological properties of this biological material are a function of its biochemical composition and its physical structure with high dependence on the time factor.

The academic Dr. Iván Balic Norambuena, maintains that his "hypothesis is that the softening of blueberries in the post-harvest is due to the loss of water and not only due to modifications in the cell wall as it happens in other fruits".

Varieties

The study by the Foundation for Agrarian Innovation, FIA: Chilean fruit growing by 2030. Main technological challenges to improve its competitiveness, in which Reinaldo Campos participated, states regarding blueberries that “the firmness of the fruit has an important varietal component and cultivars of contrasting texture have been identified as O'Neal versus Brigitta. Although practices such as early harvesting and quick access to pre-cold reduce the incidence of soft fruit ”, concluding that“ this raises the need to develop strategies that combine genetic issues (varietal characterization) with technological strategies to solve these problems ”and adds that postharvest in blueberries, in terms of fruit quality, is not resolved. It is necessary to solve challenges of firmness and dehydration upon arrival in distant markets, so from a technological perspective and facing 2030, the alternatives "should consider the development of new varieties and also the installation of process monitoring systems" .

Handles

The INIA, for its part, in its research: Adaptation of the Cropcheck Methodology for the Cultivation of Blueberries in the South of Chile, maintains that “it is possible to point out that the application of good practices of transferred checking influences the firmness of fruits at harvest. In other words, those producers who complied with the suggested pruning management, applied doses of nutrients based on the recommendation, carried out a storage period for Botrytis greater than 80% of the flowering period, and applied the quantity and distribution of irrigation water according to methodology, with a high level of precision, they will have the certainty that they will be able to harvest firm fruits and of good condition at the moment of harvest ”and evaluating the relationship between fruit firmness, foliar content of nutrients, content of nutrients in fruits and climatic variables and management in pre-harvest, concludes that "the firmness is positively correlated with the nitrogen and phosphorus content inside the fruits and in the same way with the foliar content of nitrogen and sulfur. In contrast, firmness is negatively correlated with the variables plant age, increased solar radiation, applied irrigation overdose, high content of aluminum (Al) and iron (Fe) in the leaves, and content of calcium oxide ( CaO) in the fruit ”.

Quality upon arrival

A high percentage of shipments of Latin American fruit are made by sea, so it can take between 20 and 60 days to reach the final consumer. This reality, together with its high perishability, makes quality on arrival one of the most relevant characteristics to ensure the economic returns of the industry. In the process, the fruits can suffer rots, physiological disorders, dehydration, softening and weight loss, among other alterations, being especially susceptible to mechanical damage, product of blows or poor handling, which turns into excessive softening of the fruit. , reducing its quality and consequently its final value.

Postharvest

Bruno Defilippi, who has specialized in scientific research regarding the post-harvest life of the fruit, defines 8 determining factors that aim to protect the firmness of the fruit in its different stages:

Harvest maturity stage; harvest frequency; harvest type; location of fruit and type of cane; harvest management (times); harvest temperature; temperature and relative humidity in the marketing chain; complementary treatments: AC, MAP, SO2, and others.

Concluding that the best technology to apply in the post-harvest stage is the combination of the modified atmosphere (MAP) together with sulfur dioxide (SO2).

The discussion continues. New technologies and research related to the subject emerge and at the same time the demands for firmness and quality in the target markets increase, so it is very important to continue to deepen this discussion.