Abstract
Black olive has become one of the most prestigious olives processed in the olive industry, and its processing has been increased recently in different countries. The firmness of black olives may be changed by the processing methods, fermentation, and solution salts. In this study, the employment of CaCl(2), Ca-acetate, and Ca-lactate during the processing of some Iranian black olive cultivars, including Mari, Zard, Rowghani, Shengeh, Dakal, Dezful, and Fishomi, was evaluated in terms of physicochemical and phenolic compounds and textural attributes. The results showed that Ca-lactate improved the firmness of the Mari cultivar from 1455 to 1765 N/100 g in the pitted olive, and the same trend was obtained for the other cultivars. Ca-acetate improved the black shiny color of the Mari cultivar from 4.36 to 4.85 and the sensorial properties of the black olives, including gustatory and kinesthetic sensations, were improved by using a Ca-lactate solution. The application of calcium salts in the salt-free preservation solutions imparted neither bitterness to the olives nor discoloration. The highest amounts of acid (1.42-1.56%), fructose to mannitol ratio (1-1.2), and phenolic compounds (955-963 mg/kg) were found for the Zard cultivar. Furthermore, the residual content of oleuropein was higher when CaCl(2) was employed (357 mg/kg). All of the calcium salts improved the firmness of the black olives, although the maximum firmness was observed for the Ca-lactate. Consequently, the formation of a black shiny color is related to the diffusion of phenolic compounds; however, this needs further investigation to determine which kind of phenolic compound is responsible for its black color.