Preharvest Elicitors as a Tool to Enhance Bioactive Compounds and Quality of Both Peel and Pulp of Yellow Pitahaya (Selenicereus megalanthus Haw.) at Harvest and during Postharvest Storage

Abstract

Yellow pitahaya is a tropical fruit that has gained popularity in recent years. Natural elicitors are compounds that can stimulate the resistance and quality of fruits. The objective of this study was to evaluate the effects of natural elicitors, methyl salicylate (MeSa), methyl jasmonate (JaMe), salicylic acid (SA) and oxalic acid (OA) at concentrations of 0.1 mM (MeSa and JaMe) and 5 mM (SA and OA), applied to the yellow pitahaya fruits under greenhouse conditions. After full blossom, four applications were made with a frequency of 15 days. At the time of harvest and after storage, the following variables were evaluated: firmness (whole fruit), total soluble solids (TSS), total acidity (TA), phenolics and carotenoids (in the pulp), while phenolics, carotenoids, macronutrients and micronutrients were determined in the peel. The results showed MeSa advanced the fruit maturation, according to higher TSS, lower TA and firmness than MeJa-treated fruits, for which a delayed ripening process was shown. All treatments induced a higher polyphenolic concentration during storage. Regarding the alternative use of the peel as a by-product, the application of natural elicitors significantly increased the content of polyphenols, carotenoids, macronutrients and micronutrients in the peel, especially MeSa, which can be used as a bioactive compound in the food industry. In conclusion, the results indicate that natural elicitors can be an alternative to improve the quality and shelf life of yellow pitahaya fruits.

Keywords: bioactive compounds; carotenoids; methyl jasmonate; methyl salicylate; oxalic acid; phenolics; salicylic acid.

Figure 1

Total soluble solids (TSS) and total acidity (TA) concentration in pitahaya fruits as affected by preharvest treatments with methyl salicylate (MeSa), salicylic acid (SA), methyl jasmonate (JaMe) and oxalic acid (OA) and the control (untreated). For each sampling date, bars (mean ± SE) with different letters show significant differences at p ≤ 0.05.

Figure 2

Firmness (N mm⁻¹) values in pitahaya fruits as affected by preharvest treatments with methyl salicylate (MeSa), salicylic acid (SA), methyl jasmonate (JaMe) and oxalic acid (OA) and the control (untreated). For each sampling date, bars (mean ± SE) with different letters show significant differences at p ≤ 0.05.

Figure 3

Concentration of Ca, Mg, P and K (macronutrients) and Na, Fe, Mn, Cu and Zn (micronutrients) in the peel of pitahaya fruits as affected by preharvest treatments with methyl salicylate (MeSa), salicylic acid (SA), methyl jasmonate (JaMe) and oxalic acid (OA) and the control (untreated). For each mineral, bars (mean ± SE) with different letters show significant differences among treatments at p ≤ 0.05.

Figure 4

Concentration of total phenolics and carotenoids in the peel of pitahaya fruits as affected by preharvest treatments with methyl salicylate (MeSa), salicylic acid (SA), methyl jasmonate (JaMe) and oxalic acid (OA) and the control (untreated). For each bioactive compound, bars (mean ± SE) with different letters show significant differences among treatments at p ≤ 0.05.

Figure 5

Total phenolics and hydrophilic antioxidant activity concentration in the pulp of pitahaya fruits as affected by preharvest treatments with methyl salicylate (MeSa), salicylic acid (SA), methyl jasmonate (JaMe) and oxalic acid (OA) and the control (untreated). For each sampling date, bars (mean ± SE) with different letters show significant differences at p ≤ 0.05.

Figure 6

Total carotenoids and lipophilic antioxidant activity concentration in the pulp of pitahaya fruits affected by preharvest treatments with methyl salicylate (MeSa), salicylic acid (SA), methyl jasmonate (JaMe) and oxalic acid (OA) and the control (untreated). For each sampling date, bars (mean ± SE) with different letters show significant differences at p ≤ 0.05.