Calcium content in fruits
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Calcium Content in Fruits: Key Findings
Calcium Levels in Different Fruits
Studies show that calcium content varies widely among fruit types. For example, papaya has the highest calcium content among several common fruits, with 0.0376% calcium, while banana has the lowest at 0.0038% calcium. Other fruits like grapes, litchi, mango, pineapple, pomegranate, and watermelon fall between these values, but all are considered relatively low in calcium compared to other food sources . In tropical fruits from the Solomon Islands, cutnut had the highest calcium content at 41.9 mg/100g, while starfruit had the lowest .
Factors Affecting Calcium Accumulation in Fruits
The amount of calcium in fruits is influenced by several factors:
- Water Transport and Xylem Functionality: Calcium moves into fruits mainly through the xylem along with water. As fruits develop, xylem functionality decreases, reducing calcium influx. This is seen in sweet cherry, tomato, apple, and other fruits, where most calcium enters during early development, and later movement is limited 124.
- Transpiration Rate: Higher transpiration rates, often linked to lower humidity, increase calcium accumulation in fruits. For example, sweet cherry and tomato fruits held under low humidity or with higher transpiration had more calcium 257.
- Nutrient Solution and Root Pressure: In tomatoes, humid nights and dilute nutrient solutions increased calcium uptake, especially in fruit segments prone to disorders like blossom-end rot .
- Soil and Fertilization: In kiwifruit, calcium fertilization in calcareous soils was not effective in increasing fruit calcium, but manipulating transpiration rates could influence calcium accumulation .
- Pre-harvest Treatments: Spraying fig trees with calcium chloride increased fruit calcium content, improved firmness, and reduced decay, showing that external calcium applications can enhance fruit quality and storage .
Distribution and Forms of Calcium in Fruits
Calcium is not evenly distributed within fruits. In sweet cherry, the stem end has two to three times more calcium than the stylar end . In Cerasus humilis, water-soluble calcium increases during development and is more easily transported into the fruit, while other forms like calcium oxalate and phosphate tend to accumulate in the fruit stalks . Treatments such as 2,4-D can enhance calcium movement from stalks to fruits and increase overall fruit calcium content .
Nutritional Value and Health Benefits
Although fruits are not the richest sources of calcium, some, like Cerasus humilis (also called "calcium fruit"), are notable for their high calcium content and potential to improve bone health. This fruit not only provides calcium but also promotes its absorption in the body, making it a promising dietary supplement for bone health . In general, the calcium provided by most fruits covers a small percentage of the recommended dietary allowance (RDA), but they can still contribute to overall dietary calcium, especially for children .
Conclusion
Calcium content in fruits is generally low but varies significantly between species and is influenced by water transport, transpiration, and external treatments. While most fruits are not major calcium sources, certain types like Cerasus humilis and cutnut stand out for their higher calcium levels and potential health benefits. Understanding the factors that affect calcium accumulation can help improve fruit quality and nutritional value for consumers 12345678+2 MORE.
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