*3.5. Physicochemical and Bioactive Constituents of Strawberry* 3.5.1. Soluble Solid Content (SSC)

The effect of *A. vera* gel and lemongrass EO coating on the SSC content of strawberry fruits during the storage period of 16 days is shown in Figure 4. The SSC content in treated strawberry fruits increased gradually until day 16 of the storage period in the two experiments (Figure 4). Until the end of the trial in the treatments with control and *A. vera* gel 20%, a gradual increase in the SSC was found, which indicates that *A. vera* gel 20% and 40% + lemongrass EO 1% treatments had slowed the respiration rate of strawberry fruits during the storage period. The same result was reported previously, indicating a link between SSC and respiration rate [27]. In both experiments, the maximum increase in the SSC content was found in the control on day 16. In the case of treatment with *A. vera* gel 40% + lemongrass EO 1%, the least SSC content was observed on days 4 and 8 in the second experiment (Figure 4b). The hydrolysis of starch into sugar might cause the initial increase in the SSC and subsequently the decline in SSC could be due to the decreased respiration rate and the metabolism of sugars into organic acids [48]. A lower SSC could be related to the hydrolysis of carbohydrates into sugar [65].

**Figure 4.** SSC (mean ± S.E.) of strawberry fruits stored at 5 ◦C as affected by coating treatments when stored for different lengths of time in both experiments. The mean ± S.E. of treatments in the figures with the same letters shows a nonsignificant difference according to Duncan multiple range test for *p* ≤ 0.05. AV: *A. vera* gel. (**a**) First experiment; (**b**) second experiment.

## 3.5.2. Titratable Acidity (TA) and pH

The changes in the Titratable acidity (TA) amount and pH of fruit strawberry in the two experiments during storage are shown in Figures 5 and 6, respectively. The pH of strawberry juices increased in all treatments during the storage period until day 8 in both experiments (Figure 6). Moreover, the coated fruits in both experiments had steadied pH around 3.5. However, coating treatments slowed down the titratable acidity (TA) change in the strawberries during the shelf-life study compared with uncoated fruits (control).

The TA amount in strawberry is directly correlated to fruit organic acids content [48]. The content of fruit acid tends to decrease over time, that could due to the organic acids oxidation as the fruit ripens [75]. The edible coatings of the fruits reduce the respiration rate, decreasing the consumption of organic acids in the respiratory metabolic activities of the fruits [48,76].

**Figure 5.** Titratable acidity (%) (mean ± S.E.) of strawberry fruits stored at 5 ◦C as affected by coating treatments when stored for different lengths of time in both experiments. The mean ± S.E. of treatments in the figures with the same letters shows a nonsignificant difference according to Duncan multiple range test for *p* ≤ 0.05. AV: *A. vera* gel. (**a**) First experiment; (**b**) second experiment.

**Figure 6.** pH (mean ± S.E.) of strawberry fruits stored at 5 ◦C as affected by coating treatments when stored for different lengths of time in both experiments. The mean ± S.E. of treatments in the figures with the same letters shows a nonsignificant difference according to Duncan multiple range test for *p* ≤ 0.05. AV: *A. vera* gel. (**a**) First experiment; (**b**) second experiment.
