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. 2023 Feb 8;12(2):410.
doi: 10.3390/antiox12020410.

Impact of Agronomic Treatments on the Enzymatic Browning of Eggplants (Solanum melongena L.)

Peyman Ebrahimi  1 , Carlo Nicoletto  1 , Paolo Sambo  1 , Federica Tinello  1 , Dasha Mihaylova  2 , Anna Lante  1
Affiliations

Impact of Agronomic Treatments on the Enzymatic Browning of Eggplants (Solanum melongena L.)

Peyman Ebrahimi et al. Antioxidants (Basel). .

Abstract

Enzymatic browning could negatively affect the sensory and nutritional properties of eggplants post-harvest. Polyphenols, polyphenol oxidase (PPO), and reactive oxygen species (ROS) are three material conditions involved in enzymatic browning. This paper seeks to evaluate the effect of fertilization techniques and grafting on the activity of PPO and colorimetric parameters in cultivated eggplants. Fertilization alone significantly increased the PPO activity in all eggplant fleshes (p ≤ 0.05), whereas the grafting technique combined with fertilization decreased the PPO activity in most of the samples significantly (p ≤ 0.05). Moreover, there was a significant positive correlation between the PPO activity and the a* values of the eggplants. The a* values in grafted eggplants were significantly different from each other (p ≤ 0.05), showing that grafting the fertilized eggplants could be effective in controlling the enzymatic browning. The eggplant slices exposed to air for 60 min at room temperature showed a significant increase (p ≤ 0.05) in PPO activity, browning index (BI), total color difference (ΔE), and a*, b*, and c* values. Thus, it is necessary to minimize the exposure time of the slices to air at room temperature, even if combining fertilization techniques with grafting could delay the enzymatic browning in fresh-cut eggplants.

Keywords: antioxidants; colorimetry; fertilizer; grafting; oxidation; polyphenol oxidase (PPO); polyphenols; reactive oxygen species (ROS).

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Conflict of interest statement

The authors declare no conflict of interest.

Figures

Figure 1
Figure 1
Experimental design and sample preparation methods in eggplant fleshes (a) and eggplant slices (b). PPO: polyphenol oxidase; SMS: spent mushroom compost.
Figure 2
Figure 2
The specific activity of PPO in the fleshes of eggplants. Results are indicated as mean ± SD (n = 3). A,B,C: Different capital letters show that there is a significant difference (p ≤ 0.05) between the fertilization treatments, according to one-way ANOVA and Tukey’s honestly significant difference (HSD) tests; a,b: Different small letters show that there is a significant difference (p ≤ 0.05) between grafted and not-grafted eggplants according to an independent t-test.
Figure 3
Figure 3
The specific activity of PPO in fresh-cut eggplant slices exposed to room temperature in different times. Results are indicated as mean ± SD (n = 3). a,b,c: Different small letters indicate a significant difference (p ≤ 0.05, one-way ANOVA, Tukey’s HSD test).
Figure 4
Figure 4
(a) The total color difference (ΔE) of samples comparing to time 0 min; (b) the browning index (BI) of samples; (c) the pictures of the samples in different times. Results are indicated as mean ± SD (n = 3). Different small letters indicate a significant difference (p ≤ 0.05, one-way ANOVA, Tukey’s HSD test).
Figure 5
Figure 5
Principal component analysis (PCA) of the colorimetric parameters and PPO activity of eggplant fleshes. Sample Codes are defined in Table 3.
See this image and copyright information in PMC

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