Relationships between Na, K, and Ca mineral nutrients in brine and table olive flesh. Nutritional labelling implications

The mineral equilibrium between olive flesh/moisture (in-flesh) and the surrounding brines has been studied for the first time. A pseudo-distribution coefficient, K-d, has been defined and applied to fermented Gordal, Manzanilla (green Spanish-style) and packaged Alorena de Malaga (natural green) olives. K-d had values < 1 for Na and K in the flesh but >1 for Ca, suggesting lower and higher contents in olive flesh than in brine. When the equilibrium for Na and K was referred to the flesh moisture, most K-d approached 1, implying a trend for equilibrium. However, Ca exhibited values above 1, indicating a higher concentration also in the flesh moisture, suggesting that part of this element may also form complexes with soluble olive flesh components. Kd was not significantly related to the concentrations of Na, K, or Ca in brines, although the Na model explained 80% variance. Simple and multiple regressions deduced the mineral nutrients in the flesh as a function of their concentrations in brine, but the second only increased the explained variance (about 10%) in the case of Na. For nutritional labelling purposes in the EU (where sodium must be expressed as salt), both functions can estimate the Na, K, and Ca contents in olive flesh from their concentrations in brine since their variabilities were within tolerance limits, particularly when the initial fermentation/packaging brines were fortified with K or Ca.