Physical and Physicochemical Characterization of Umbu-Cajá (Spondias bahiensis) Fruit Throughout Ripening
This study demonstrates that the fully yellow ripening stage (Stage IV) of umbú-cajá fruit offers the optimal balance of technological yield, physicochemical quality, and chemical composition for both fresh consumption and agroindustrial processing, despite the green stage (Stage I) containing the highest vitamin C levels.
Original paper licensed under CC BY 4.0 (https://creativecommons.org/licenses/by/4.0/). This is an AI-generated explanation of the paper below. It is not written or endorsed by the authors. For technical accuracy, refer to the original paper. Read full disclaimer
In the semi-arid landscapes of northeastern Brazil, where the heat is intense and the soil is often dry, a native tree known as the umbu-cajazeira produces a fruit that holds significant value for local communities. This fruit, called umbu-cajá, belongs to a family of plants that also includes the mango and the cashew. Like many tropical fruits, its quality changes dramatically as it matures on the tree. When a fruit is unripe, it is hard, green, and often very sour, packed with compounds that protect the developing seed. As it ripens, the skin changes color, the flesh softens, and the internal chemistry shifts: sugars build up while acids break down, transforming the fruit from a tart, firm object into something sweet and soft. Understanding exactly how these changes happen is vital for farmers and food processors. If they harvest too early, the fruit may lack flavor; if they wait too long, it may rot before it can be sold or turned into products like jams and juices. The challenge lies in pinpointing the precise moment when the fruit is at its peak for both eating fresh and for industrial use.
Researchers set out to map these changes in the umbu-cajá fruit, specifically looking at how its physical size, internal composition, and nutritional value evolve through four distinct stages of ripeness. They collected fruit from an orchard in Currais Novos, a municipality in the state of Rio Grande do Norte, and sorted them by the color of their skin. The stages ranged from completely green to light green, then to a slightly yellow stage with the first signs of wrinkling, and finally to a fully yellow stage. By measuring each fruit carefully, the team could track how the weight, the size of the pulp, the thickness of the skin, and the size of the seed changed as the fruit matured. They also analyzed the chemical makeup of the fruit's flesh, measuring the amount of sugar, the level of acidity, the pH balance, and the content of vitamin C at each stage.
The study revealed that the fruit does not grow significantly larger or heavier as it ripens. Once the fruit reaches the green stage, it has already achieved its maximum physical size. The weight remains relatively stable, hovering around 21 to 22 grams, regardless of whether the skin is green or yellow. However, what happens inside the fruit is quite different. As the fruit turns from green to fully yellow, the proportion of edible flesh increases while the relative amount of skin and seed decreases. At the fully yellow stage, the pulp makes up 62 percent of the fruit's total weight, while the seed shrinks to just 17.62 percent. This shift is crucial for industry because a higher percentage of pulp means less waste and more product to process. The skin, which accounts for nearly 29 percent of the fruit at this final stage, becomes thinner as the fruit matures, a result of water loss and the softening of the cell walls.
Alongside these physical changes, the chemical profile of the fruit undergoes a complete transformation. The green fruit is rich in vitamin C, containing about 17 milligrams per 100 grams, but this nutrient drops significantly as the fruit ripens, falling to roughly 11 milligrams in the fully yellow stage. At the same time, the fruit becomes sweeter and less sour. The amount of sugar, measured as soluble solids, rises steadily, reaching 13 percent in the ripe fruit. Conversely, the acidity, which gives the unripe fruit its sharp bite, drops by more than half, falling from 2.3 percent in the green stage to just over 1 percent in the yellow stage. This chemical shift is reflected in the pH level, which moves from a very acidic 2.31 to a slightly less acidic 2.60. The balance between sugar and acid, a key indicator of flavor, improves dramatically, reaching a ratio of 12 to 1 in the fully ripe fruit.
The researchers concluded that while the green fruit offers the highest concentration of vitamin C, the fully yellow stage is the clear winner for both fresh consumption and industrial processing. At this final stage, the fruit has the highest amount of edible pulp, the lowest relative amount of seed, and the most balanced flavor profile, combining high sweetness with manageable acidity. The data showed that the changes in the fruit are not random; the increase in size and sugar content is tightly linked to the decrease in acidity. This means that as the fruit matures, it naturally optimizes itself for human consumption. For the local economy in the semi-arid region, identifying this specific stage of ripeness provides a clear guide for harvesters. It ensures that the fruit is picked when it offers the best yield and the best taste, supporting the production of high-quality jams, jellies, and frozen pulps that can be sold to a wider market.
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