Characterization of cell wall modification through thermogravimetric analysis during ripening of Chilean strawberry (Fragaria chiloensis) fruit

Effect of Exogenous Auxin Treatment on Cell Wall Polymers of Strawberry Fruit

“…However, a slight difference between 48 h after auxin treatment with respect to the other three samples was observed (Figure 2A). Additionally, the initial phase described that all samples had greater thermal stability (Figure 2A), which is similar to what has been described previously for different strawberry cultivars such as 'Camarosa' [18], 'Cristal', or 'Portola' [33], or Chilean strawberry [54]. The second region in the graphic is named the intermediate phase or region II and comprised temperatures between 200 and 350 • C. The result showed that the auxin 48 h and control 0 h treatments did not exhibit differences between them (Figure 2B), and more importantly, it resulted in greater thermal stability values than the control 48 h and TIBA 48 h treatments (Figure 2B).…”

“…The third region is named as the final phase or region III, and corresponding to temperatures between 350 and 500 • C, the analysis showed that the control 0 h treatments showed greater thermal stability values than the control 48 h, auxin 48 h, and TIBA 48 h treatments (Figure 2A). Recently, we showed that differential thermogravimetric analysis (DTG), which is obtained from the first derivative of the TGA values, can be divided into four maximum degradation peaks [16,33,53,54]. Figure 3 shows the four possible regions for these peaks.…”

“…First, peak A did not show any difference between the control 0 h sample (Figure 3A) and the control 48 h sample (Figure 3B), while the auxin-treated 48 h sample (Figure 3C) showed a slightly higher value than the 1.010 value for the control at 0 h. In turn, the sample treated with TIBA for 48 h (Figure 3D) showed a value slightly lower than that value. This is an interesting result because in the A region, it is possible to observe the decomposition of compounds (principally carbohydrates such as xylose and glucose) related to the three principal polymer compounds that form the cell wall (cellulose, hemicelluloses, and pectin) [33,[53][54][55]. The B region principally showed a decomposition of hemicellulose fractions between temperatures of 200 and 300 • C [56] and shorter chain pectin fractions at approximately 250 • C [56] (Figure 3).…”

“…Thermogravimetric analysis (TGA) was realized using a Discovery SDT-650 thermogravimetric analyzer (TA instrument) according to the methodology previously standardized in the laboratory and employed in [16,33,54,70]. With respect to the samples, the thalamus from the five fruit treatments were homogenized with a mortar and pestle, and then, the macerated thalamus samples were dried at 80 • C for 48 h, and 10 mg of the dry sample groups were employed two times to determine the chemical characteristics of the degradation process.…”

“…The total rhamnogalacturonan endolyase (RGL), total xyloglucan endotransglycosylase (XET), total polygalacturonase (PG), and total glucanase (GLU) activities were measured according to [54]. The activity of the different enzymes was measured in triplicate using a pool of five fruits per sample, with two technical replicates.…”