Main parameters for optimal nutritional content in cherries for export

Main parameters for optimal nutritional content in cherries for export

By: Emilio Martínez, Agronomist, I+D Leader at Avium; Carlos Tapia, M.Sc., Technical Director at Avium.

It is vitally important to set up the bases for mineralogical analyses of the fruit that is being produced, in order to progressively understand, in an objective manner, the results that can be obtained each season, and thus adjust agronomic management that will allow us to produce high quality fruit as a result.

The nutritional properties of fruit lead to increasingly relevant studies, since they determine post-harvest life and, undoubtedly, the organoleptic properties that the consumer values as one of fruits’ most important features. This relationship can be affected by certain features specific to each variety, rootstock combinations, climate conditions and/or production management at each site.

The logistical difficulties of the last seasons led to containers being opened over 45 days after harvest date, which promotes a clearer understanding of the fruit quality being constructed; it is worth remembering that the fruit’s conformation is mainly established through the agronomic management performed in the orchards during the season, when aiming to obtain export-quality fruit.

One of the main factors that establish quality or commercial approval in cherries is soluble solids, which is a feature that basically determines the sweetness of the fruit, as it measures the amount of sugar in it – measured in °Brix. Cherries possess, on average, over 18 °Brix, and some varieties even exceed 20 °Brix, as is generally the case with the varieties Regina, Bing and Kordia. Even though sweetness is important, there is a close relationship between sugar content and acidity – a relationship that is not always valued and properly studied within our industry. Another important aspect of sugar percentage is its relationship with dry matter contents, which are a direct indicator of fruit “firmness”. In general, when greater sugar contents are revealed, that’s because there is a greater amount of dry matter, percentage-wise.

It is important to be able to install the bases for the mineralogical analyses of the fruit that is being produced so as to progressively and objectively understand the results that are obtained each season, in order to adjust agronomic management that will successfully lead to high quality fruit. Within that search, the technical and I+D departments at Avium have set a goal for themselves to search for the main parameters for optimal nutritional content in export-grade cherries in which has undoubtedly become one of the greatest industry-wide challenges: the constant evolution to offer a final product that is the greatest possible quality and is in prime condition (Figure 1.)

The nutritional analyses performed on fruits during harvest have the main goal of gauging the quality of the nutritional plan and cultural management being performed, which allows for the association between implementations applied in orchards during the season and the balance that was reached. The aforementioned process allows producers to make adjustments before the following season.

Figure 1. Optimal nutritional contents of cherries. Carlos Tapia-Avium 2018.

After a few seasons of mineralogical analyses performed in fruits by Avium I+D, the behavior of different varieties in different seasons has become apparent. This generates quantitative information on how fruit has been constructed so far, regarding its main nutritional elements as well as other indicators, including sugar contents and dry matter. 

For the effects of this research, last year’s three most exported varieties were assessed; namely Lapins, Santina and Regina; with a share of 35%, 24% and 19% respectively, according to data published in iQonsulting’s 2022 Yearbook, which encompasses over 2/3 of fruit exported in the past year.  

The follow-up analysis focused on macronutrients: Total Nitrogen (N), Phosphorus (P), Potassium (K) and Total Calcium (Ca), with all of their concentrations expressed in mg per 100 grams of fresh fruit weight (PF) and the content of Dry Matter in each fruit (MS) measured as a percentage (%) (Fig. 2).

 Nutritional content analyses were performed with the optimal commercial harvest maturity parameters for each specific variety.

In this general analysis we can see that the levels of macronutrients between seasons have also been subject to change in each variety. We can also see a global panorama of the fruit´s nutritional state. 

Figure 2. Summary of macronutrients (mg/100 g of fresh weight) and percentage (%) of dry matter in cherry fruits in the past five seasons in the varieties Lapins, Santina and Regina (Source: Avium SpA).

Total nitrogen (N) is shown in optimal ranges of 150 to 160 mg/ 100 g PF. In Lapins and Santina we can see N levels that are consistent in the past few years, even though Lapins stands out for having greater range, over 198 mg/100 g PF in the 2019/20 season. 

The thing that stands out are the N contents of Regina, as the element’s levels are above anything previously seen, except for the 2017/18 season. It reaches an average of 193 mg/100 g. PF in the 2021/22 season.

In research performed in the year 2013 a group of consumers identified deterioration in sweetness, acidity, flavor intensity, general texture and juiciness after storage in fruits that received a nitrogen-high treatment (Swarts, N. D.,et al), conclusively the nutritional unbalances may affect the organoleptic qualities of the fruit and, truth be told, it is likely that the high Nitrogen content in Regina fruits could be one of the factors that trigger internal brown rot in cherries. Thus almost 49% of performed nutritional analyses in this variety have a greater N value than proposed (150-160 mg/ 100 g PF) as a reference point for all seasons. However, when we only analyze the 2021/22 season we can see that 82% of analyses show N levels above those previously proposed.

Potassium (K), on the other hand, is an element that actively participates in water transportation within the plants, regulation of stomatal aperture, catching of atmospheric CO2 and water flow toward tissues. This element is responsible for greater sweetness, caliber and fruit turgidity when levels are over 200 mg/100 g PF (Tapia, C., 2021). 

When Potassium contents are analyzed for different seasons, we can see indexes that are generally below what Tapia proposes for all studied varieties, Regina being the one that most closely approaches the requirement, with an average of 183 mg/100 g PF in all five seasons. Even though we could establish good numbers for Lapins in 2017/19 to 2019/20, these values have decreased in the two most recent seasons, leaving us with an average of about 167 mg/100 g PF. Consequently, in the analyzed samples the number of nutritional analyses at an optimal K level in the fruit (< 200 mg/100 g PF) does not exceed 10%, 6 and 30% in Lapins, Santina and Regina respectively, as analyzed across all seasons.

Figure 3. Evolution of mean nutritional contents per each variety in the past five seasons. 

Calcium levels can be considered adequate for Lapins and Santina, with small variations between seasons, but with acceptable levels for an export-grade fruit. In Regina we see evidence of a downward trend in the last two years with respect to the proposed amount (Fig. 1), since the level is less than 10 mg/ 100 g. PF in the last season. This nutrient is an important part of the cell wall’s structural configuration. It also plays an important role in plants’ response to abiotic stress. In general, in Santina and Regina we can see 55% of samples are over 10 mg/ 100 g PF, especially in the variety Lapins; over 63% of total performed analyses.

We can see dry matter percentages over 18% in all three varieties, however we can conclude that N is directly related with this index; for example, in the variety Regina the greater the N content is in the fruit, the smaller the % of dry matter, which can be seen clearly in the 2021/22 season (Fig. 3). Thus only 63% of analyzed samples in 2021/22 show over 18% of MS, compared to seasons 2020/21, 2019/20 and 2018/19 with 70%, 100% and 79% respectively in terms of samples with optimal dry matter percentages.

Source: 

-Swarts, N. D., Mertes, E., & Close, D. C. (2013, June). Role of nitrogen fertigation in sweet cherry fruit quality and consumer perception of quality: at-and postharvest. In VII International Cherry Symposium 1161 (pp. 503-510).

Tapia, C., Lepe, V., & Pezoa G. (2021). En busca del balance nutricional vs. Calidad de fruta en cerezos (In search of nutritional value vs. Fruit quality in cherry trees). Mundo Agro Magazine.

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