Effect of calcium on the preservation of green olives intended for black ripe olive processing under free-sodium chloride conditions

Innovative salt replacement for green Spanish-style olives using potassium, calcium, and magnesium chlorides during packaging

This work aimed to enhance green Spanish-style Manzanilla table olives by replacing salt with K, Ca, and Mg chlorides in innovative packaging, utilising Response Surface Methodology (RSM). Both the added replacers and naturally occurring minerals were considered. RSM allowed the development of predictive models for K, Ca, Mg, and Mn (initially present) in olive flesh and their contributions to Reference Daily Intakes (RDI) based on the added salts. The sodium content in the new products decreased from 1.4 g/100 g flesh to 0.68 g/100 g flesh, while K, Ca, and Mg concentrations could increase up to 0.50, 0.45 and 0.15 g/100 g flesh, respectively. Added salt contributions to RDI could reach 25, 60, and 44 % for K, Ca, and Mg. Minimal differences between analytical data-derived minerals and predicted values were minimal, suggesting reliable model performance for nutrition labelling. Results assist the industry in creating nutritionally enhanced table olive products.

Bioaccessibility of Mineral Nutrients in Plain Green Spanish-Style Manzanilla Table Olives Packaged in Nutrient Salt Mixtures

Table olives are high in salt, which can negatively impact cardiovascular health. It is essential to reduce their salt content to mitigate such risk. The objectives of the study were to develop an appropriate protocol to determine mineral bioaccessibility in green Spanish-style Manzanilla table olives and to use it to evaluate, for the first time, the effects of replacing 50% NaCl in the packaging brine with KCl, CaCl2, and MgCl2 on this characteristic. After testing, Miller's protocol with a post-digestion re-extraction was chosen. The mineral bioaccessibility found was as follows: Na, 93-98%; K, 94-100%; Ca, 19-27% (the lowest accessibility); Mg, 78-91% (moderately accessible); and non-added P, 55-67%. Bioaccessible amounts (mg/100 g pulp) of added minerals in runs were 151-503 for K, 53-109 for Ca, and 54-143 for Mg. The bioaccessible mineral vs. salt concentrations were modelled and plotted using RSM, illustrating the possible predictions from the tested range of combinations. The bioaccessibility of Ca and Mg was approximately 70% and 15% lower than the values indicated on the label based on the chemical analysis. The results discourage Ca fortification in packaging and suggest including bioaccessibility, markedly influenced by the food matrix, on the label for accurate nutritional information.

Impact of Salts Mixtures on the Physicochemical and Sensory Characteristics of Spanish-Style Manzanilla Green Table Olives during Packaging

Using response surface methodology (RSM), this study investigates the effect of NaCl substitution (50%) with KCl, CaCl2, and MgCl2 in the packaging brines (controlled variables) on the characteristics (responses) of plain green Spanish-style Manzanilla olives, maintaining the salt-mixture level of 5%. The RSM showed that the increment of CaCl2 caused a linear significant (p-value ≤ 0.05) decrease in pH and a linear increase in firmness (instrumental), hardness (panel scores), and crunchiness. The models for bitterness and fibrousness also included quadratic (CaCl2·MgCl2) and cubic (the three salt) interactions, which led to areas of minimum and maximum scores around the central points of the CaCl2-MgCl2 and KCl-MgCl2 axes, respectively. In contrast, the increase in the KCl level linearly decreased bitterness scores. Optimisation resulted in a relatively low desirability (0.57) and the selection of a combination that may necessitate further refinement, such as increasing KCl or reducing CaCl2 levels, especially for markets sensitive to bitterness. Interestingly, the overall score and buying predisposition positively correlate with salty, smell, acid, and appearance and negatively with bitterness. Furthermore, PLS-R analysis found that the pivotal attributes influencing overall appreciation were smell and crunchiness while buying predisposition was promoted by crunchiness. Conversely, bitterness had a detrimental impact on these appreciations. Cluster analysis grouped the experimental runs into four categories, with sensory profiles predominantly diverging in bitterness, salty, and kinesthetic characteristics. Ultimately, this study elucidates four distinct sensory profiles that consumers experience.

Effect of Calcium Salts on the Firmness and Physicochemical and Sensorial Properties of Iranian Black Olive Cultivars

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 CaCl2, 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 CaCl2 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.

Reuse of KOH Solutions during Black Ripe Olive Processing, Effect on the Quality of the Final Product and Valorization of Wastewaters as Possible Fertilizer Product

A high volume of water is needed to produce black ripe olives, which also entails a significant volume of wastewater with a high organic and inorganic contaminant charge. To reduce this problem, the reuse of KOH solutions (lyes) in a new process was studied. Once the lyes were removed from the tanks, KOH was then added for a new darkening process. Reusing the lyes up to four times gave rise to a product with similar physico–chemical and organoleptic characteristics as obtained with fresh solutions. The application of this process reduced coadjutant consumption by 32% and water by 20%, while global wastewater presented a high K content whose concentration could be valorized as a fertilizer by replacing commercial potassium nitrate.

Effect of fertilisation with black table olive wastewater solutions on production and quality of tomatoes cultivated under open field conditions

This study was aimed at making progress on the valorisation of table olive wastewater that currently represent a big environmental problem for factories. Concentrates from vacuum evaporation of the wastewater generated during processing of black ripe olives treated with KOH were tested as fertilisers of tomato plants in open field assays for three consecutive crops. Fertilisation was performed by drip irrigation every 15 days; the first treatment being 15 days after transplanting, and a total of five fertilisation treatments were carried out. A phytotoxic effect was not observed on plants or fruit in any case but higher yield (fruit/plant and g/plant) was obtained in comparison to irrigation with only tap water. Moreover, the combined use of the olive concentrate with inorganic nitrogen supply (NH₄NO₃), in order to comply with the nutrient needs of plants, was also tested. The results demonstrated that the olive concentrates could be a good substitute for inorganic potassium (as KNO₃) during the cultivation of tomato plants without any negative effect on the tomato quality (pH, °Brix, sugars, organic acids) or content of bioactive substances (phenolic compounds and carotenoids).

Calcium applications throughout fruit development enhance olive quality, oil yield, and antioxidant compounds' content

BACKGROUND

Calcium is a preservative and firming agent largely used in the table olive industry. Foliar applications of calcium (as calcium chloride, CaCl₂ ) before harvest have been proposed in other fruits to increase firmness and reduce physiological disorders or internal damage. However, there is still a shortage of information regarding the source, the concentration, the number, and the period of calcium application onto the canopy to get an effective response of olive quality. In this study, we aimed to investigate the effect of two concentrations of CaCl₂ foliar treatments (0.5% and 1.0%), applied at different stages of fruit development (at the end of fruit set, end of pit hardening, and prior to harvesting), on olive quality for two varieties ('Manzanilla de Sevilla' and 'Ascolanta tenera'), cultivated in two different geographical areas (Spain and Italy respectively).

RESULTS

The calcium concentrations applied enhanced the fruit calcium content and decreased sodium and potassium. They also improved the mechanical properties without modifying fruit morphology or cuticle thickness; nor did they cause phytotoxicity. Foliar treatments increased the oil content in the pulp (dry weight basis) and the amount of hydroxytyrosol, tyrosol, and oleuropein, among other phenols.

CONCLUSION

Calcium foliar applications during fruit development effectively increase olive quality. © 2020 Society of Chemical Industry.

Packing black ripe olives in acid conditions

The type of container (airtight and pouches with different O₂ permeability) and packing conditions (cover brine, air or N₂ atmosphere) has been studied to preserve black ripe olives in acid medium for a year. Unlike the traditional sterilized product, these acidified olives only needed pasteurization to assure its microbial safety, the absence of acrylamide being an additional advantage. Surprisingly, an increase in the oxygen diffusion through the films (i) faded the black color of the olives, (ii) softened the fruit that lost around 33% of its initial firmness in only 6 months, and (iii) produced the lipid́s oxidation forming volatile compounds that transmitted an abnormal flavor which tasters identified as rancid. Therefore, ripe olives in acid medium must be packed in airtight containers such as glass jars, cans o metallic pouches with cover brine or N₂ atmosphere. The addition of calcium is recommended to avoid olive softening.