It is vitally important to establish the basis for mineralogical analysis of the fruit being produced and to understand, in an objective way, the results obtained in each season in order to adjust agronomic management that allows us to achieve high-quality fruit results.
By: Emilio Martínez, Agricultural Engineer, Avium R&D Leader; Carlos Tapia, M.Sc., Avium Technical Director.
The nutritional properties of fruit are a subject of study that is becoming more and more relevant every day, as they determine the post-harvest life and, without a doubt, the organoleptic properties that the consumer values as one of the most important attributes. This acceptance can be altered by the characteristics of each variety, rootstock combination, climatic conditions and/or production management in each production site.
The logistics difficulties of recent seasons have led to the opening of containers more than 45 days after harvest, which helps to better understand the quality of the fruit being produced. It is worth remembering that the shape of the fruit is mainly determined by the agronomic management carried out in the orchard during the season to obtain fruit for export.
One of the main factors that determines the quality or commercial acceptance of cherries is soluble solids, which are a characteristic that basically determines the sweetness of the fruit, since it measures the amount of sugar it contains, measured in °Brix. On average, cherries have about 18 °Brix, with some varieties even exceeding 20 °Brix, such as Cvs. Regina, Bing and Kordia generally. Although sweetness is important, there is a close relationship between sugar content and acidity, a relationship that is not always valued and studied in our industry. Another important aspect of the sugar percentage is its relationship with the dry matter content, a direct indicator of the “firmness” of the fruit. In general, when higher sugar contents are revealed, it is because there is more dry matter measured in percentage.
It is important to be able to establish the bases of mineralogical analysis of the fruit being produced and to understand, in some objective way, the results obtained in each season in order to adjust agronomic management that manages to achieve high quality fruit results. Within this search, Avium's technical and R&D departments have set out to go in search of the main parameters of optimal nutritional content for export cherries and that, without a doubt, must be one of the most important challenges of the industry, in the constant search to be able to offer a final product of better quality and condition each time (Figure 1).
The main objective of the nutritional analyses of fruits carried out during harvest is to measure the quality of the nutritional plan and cultural management being carried out, which allows the implementation of the orchard during the season to be associated with the balance achieved. This allows adjustments to be made for the following season.
Figure 1. Optimal nutritional content of cherry. Carlos Tapia-Avium 2018.
After several seasons of mineralogical analysis of fruits carried out at Avium R&D, it has been possible to know the behavior in different seasons in the different varieties, which generates quantitative information on how the fruit has been constructed up to now in terms of the main nutritional elements and other indicators, such as sugar content and dry matter.
For the purposes of the study, the three most exported varieties in the last year were monitored: Cvs. Lapins, Santina and Regina, with a share of 35%, 24% and 19% respectively, according to data published by the iQonsulting 2022 Yearbook, which covers more than 2/3 of the fruit exported in the last year.
The follow-up analysis focused on the macronutrients: Total Nitrogen (N), Phosphorus (P), Potassium (K) and Total Calcium (Ca), all expressed in concentration as mg/100 g of fresh fruit weight (PF) and the dry matter content of the fruits (DM) measured in percentage (%) (Fig. 2).
The nutritional content analyses were carried out with the optimal commercial harvest maturity parameters for each particular variety.
This general analysis shows that macronutrient levels between seasons have also changed in each variety, and that they show a global overview of the nutritional status of the fruit.
Figure 2. Summary of macronutrients (mg/100 g fresh weight) and percentage (%) of fruit dry matter in cherries from the last five seasons in the Cvs. Lapins, Santina and Regina (Source Avium SpA).
Total nitrogen (N) is shown in optimal ranges of 150 to 160 mg/100 g FP. In Lapins and Santina similar N levels have been observed in recent years, although Lapins differs in a higher range above 198 mg/100 g FP in the 2019/20 season.
What is particularly striking is the N content of Regina, since the levels of this element are higher than those seen previously, except for the 2017/18 season, reaching an average of 193 mg/100 g PF in the 2021/22 season.
In a study carried out in 2013, a group of consumers identified deterioration in sweetness, acidity, flavour intensity, overall texture and juiciness after storage in fruits that received a high nitrogen treatment (Swarts, ND,et al). Therefore, nutritional imbalances can affect the organoleptic qualities of the fruit and, why not say it, probably the high Nitrogen content of Regina fruits could be one of the factors that trigger internal browning in cherries. This is how almost 49% of the nutritional analyses carried out on this variety have a higher N value than proposed (150-160 mg/100 g PF), taken as a reference in all seasons. However, when only the 2021/22 season is analysed, it can be observed that there is 82% of the analyses on the N indices proposed above.
Potassium (K), on the other hand, is an element that actively participates in the movement of water within the plant and regulates stomatal opening, CO uptake2 atmospheric and water flow towards the tissues; it is attributed to an action on greater sweetness, size and turgor of the fruit when levels are above 200 mg/100 g PF (Tapia, C., 2021).
When analyzing the potassium contents in the different seasons, in general indices below those proposed by Tapia are observed in all the varieties studied, being cv. Regina the one that comes closest to this requirement, with an average of 183 mg/100 g FP in the five seasons. Although good numbers can be established in Lapins in 2017/19 to 2019/20, these values have decreased in the last two seasons, obtaining an average of around 167 mg/100 g FP. Consequently, in the analyzed samples the number of nutritional analyses of an optimal level of K in the fruit (< 200 mg/100 g FP), does not exceed 10%, 6 and 30% in Lapins, Santina and Regina respectively, analyzed in all seasons.
Figure 3. Evolution of average nutritional content for each variety over the last five seasons.
Calcium levels are observed to be adequate in Lapins and Santina, with small variations between seasons, but with acceptable levels for an export fruit. In Regina, a downward trend can be seen in the last two years with respect to the proposed level (Fig. 1), being less than 10 mg/100 g PF in the last season. This nutrient is an important part of the structural conformation of the cell wall, and it is also attributed to playing an important role in the responses to abiotic stress in plants. In general, in Santina and Regina, a 55% of the samples above 10 mg/100 g PF is observed, with cv. Lapins standing out above the 63% of the total analyses performed.
Dry matter percentages above 18% are observed in the three varieties, however, it can be concluded that N is indirectly related to this index; for example, in cv. Regina, the higher the N content in the fruit, the % of dry matter tends to decrease, which is clearly seen in the 2021/22 season (Fig. 3). Thus, only 63% of the samples analyzed in 2021/22 have over 18% of DM, compared to the 2020/21, 2019/20 and 2018/19 seasons with 70%, 100% and 79% respectively of samples with optimal dry matter percentages.
Fountain:
-Swarts, ND, Mertes, E., & Close, DC (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). In search of nutritional balance vs. Fruit quality in cherry trees. Mundo Agro Magazine.
