Relationship between electrical conductivity, softening and color of Fuerte avocado fruits during ripening

Abstract

To identify the most important ripening parameters of Fuerte avocado fruits, and to quantify the relationship between color changes, electrical conductivity and softening of avocado fruits, the ripening process was investigated to fulfill the consumer and market demands. Mature and high quality avocado fruits (Persea Americana Mill.) were held to ripe at 20 o C in controlled temperature rooms with 90-95% relative humidity for two weeks. Fruit quality characteristics (respiration rate, soluble solids content (SSC), total acidity (TA), ascorbic acid and oil content) during ripening period at 20 o C were evaluated. Moreover, ripening parameters as color changes, chlorophyll contents, fruit firmness and electrical conductivity and ripening enzymes (CX and PME) were also investigated throughout ripening process. During ripening period for 2 weeks at 20 o C, fruit quality criteria showed that respiration rate and oil content had a noticeable significant increase with the ripening increase. While, acidity (TA), soluble solids (SSC) and ascorbic acid content cleared a slight and significant decrease. Throughout color development, the three parameters lightness (L*), hue (h•) and chroma (C*) changed significantly, hue decreased little, lightness moderately, while chroma changed more quickly. Moreover, an significant decline in chlorophyll a and b concentration occurred and reflected to color changes during ripening process. For ripening enzyme activities, Fuerte avocado fruits showed a great increase in cellulase activity compared with gradual decrease in Pectinmethylesterase activity after ripening. Avocado fruit firmness markedly reduced gradually after harvest till ripening at 20 o C, and this decline was positively correlated with an increase of electrical conductivity of the fruit tissue suggesting a gradual loss of cell membrane integrity. This increase in conductivity was promoted by ripening process. These results have allowed us to set that ripening process had some parameters were simple and rapid to measure as ripening indices. We conclude that in Fuerte avocado fruits, electrical conductivity (EC) can serve as a good indicator of membrane permeability and that it is highly correlated with ethylene production, softening and also demonstrates a relationship between firmness and EC.

The impact of fruit softening on avocado cell microstructure changes monitored by electrical impedance and conductivity for cold‐pressed oil extraction

“…It was observed that the electrical conductivity of intact “Hass” avocado flesh increased significantly ( p < .05) as the fruit ripened (Figure ), indicating the breakdown of cell membranes in the avocado mesocarp as the fruit ripened. These results agree with the previous study of Montoya, De La Plaza, and Lopez‐Rodriguez () and Ahmed, Yousef, and Hassan () where electrical conductivity of the “Hass” and “Fuerte” avocado fruit tissue increased as the fruit softened due to ripening. The electrical conductivity of fruit pulp tissue increased significantly ( p < .05) after grinding, and the softer avocado fruit showed higher conductivity values at 0, 60, and 120 min of malaxing (Figure ), which confirms EIS results that cells in softer fruit are more likely to be disrupted releasing more ions into the apoplast.…”

“…Fv, firmometer value "Hass" avocado flesh increased significantly (p < .05) as the fruit ripened ( Figure 3), indicating the breakdown of cell membranes in the avocado mesocarp as the fruit ripened. These results agree with the previous study of Montoya, De La Plaza, and Lopez-Rodriguez (1994) and Ahmed, Yousef, and Hassan (2010) where electrical conductivity of the "Hass"…”

Cold shock treatment extends shelf life of naturally ripened or ethylene-ripened avocado fruits

“…The suppressed PG activities by CST ( Fig 5 ) were concurrent with the delayed fruit softening in both naturally ripened fruit and ethylene-treated fruit ( Fig 4 ), indicating that PG activity is one of the key modulating factors for fruit softening. Unlike PG activity, PME activity of avocado fruits tended to decrease throughout the shelf life, which was consistent with results of a previous study [ 31 ]. No significant difference in PME activity between control and cold shock-treated fruits was observed ( Fig 6 ).…”

Radio-Frequency-Identification-Based Intelligent Packaging: Electromagnetic Classification of Tropical Fruit Ripening

“…The measurements are quite stable. A dielectric contrast exists among the three states, with a nonmonotonic profile, consistent with the well-known physical/chemical variations described in the literature, which are nonmonotonic as well [27], [29], [30] (especially regarding the oil and sugar concentration). Table 1.…”