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Cell Wall Calcium: A Good Tool for Diagnosing Alterations in Fruit Quality
It is well known that post-harvest is a key period with a direct influence on the quality and appearance with which fruits and vegetables reach their point of sale. Even if we have done a superb job in the field, if the product does not successfully endure the period between harvest and sale, we will have failed. Several factors have a bearing in this process. One factor with a major role is tissue calcium content. Calcium’s structural function is directly related to plant tissue stability and thus to the product’s post-
ference between total calcium and soluble calcium. Such a procedure is inexact; it overestimates the bound fraction by adding the insoluble and residual fractions, which are sometimes greater than the bound fraction. The evolution of calcium fractions throughout the ripening period of the fruits (e.g. tomatoes) has been studied, comparing fruits that do and do not experience specific alterations (e.g. bitter pit in ap- ples or cracking in peaches).
harvest behavior (rotting, brown spots, loss of consistency, etc.), as well as its probability of being affected by pre-har- vest damage (creasing in citrus fruit, cracking in stone fruits, bitter pit in ap- ples, etc.). In addition to having a structural function (for cell wall bound calcium in the form of calcium pectates), calcium is involved in other functions in plant cells. It is thus also found in other plant parts, as soluble calcium in the apoplast and symplast (in the form of nitrates, chlorides and amino acids), insoluble calcium in form of precipitates in the
vacuoles (mainly in the form of phosphates, carbon- ates and oxalates) and residual calcium in highly in- soluble forms (mainly). Historically, it has been difficult to correlate struc- tural damage in fruits (pre- or post-harvest) to total calcium content of the tissue. Now, a number of sci- entific studies have demonstrated a direct relation- ship between the cell wall calcium fraction in the form of calcium pectates, on the one hand, and structural behavior of the tissue on the other. This makes wall cell calcium a powerful, innovative tool for diagnosing alterations in the quality of fruits and vegetables. Up until now, the majority of the tests conducted have estimated cell wall calcium indirectly, as the dif-
As a result of these tests, the concussion is that that cell wall calcium is a diagnostic tool for eval- uating quality parameters related to the appear- ance and market life of the product . And in certain matrices, total calcium, with quantification limits adapted to the fruit, is also a very reliable marker for assessing a number of concrete alterations.
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MARCH | APRIL 2019
Western Grower & Shipper | www.wga.com
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