Effect of treatment with natural phytoregulators on purple carrots (Daucus carota L.) during storage

Introduction: Dark-colored carrots are known for their attractive color and high content in antioxidant pigments such as carotenoids and anthocyanins, which protect against pathologies. However, both organoleptic and health-promoting properties are altered during storage. In this respect, deterioration in sensorial quality, together with a decrease in antioxidant content, is usually observed after 5-7 days without refrigeration. The objective of this research was to propose an approach based on natural phytoregulators enabling purple carrot shelf-life to be extended with no need for artificial preservatives.

Methods: Visual appearance, juiciness, moisture content, total soluble solids, acidity and maturity index were measured as quality physicochemical parameters. Total and individual carotenoid contents were determined by absorbance at 485 nm and HPLC-DAD, respectively. Total anthocyanin content was measured by the pH differential method. Antioxidant activity was determined by DPPH and FRAP assays.

Results: Untreated purple carrots, used as a control, exhibited a natural increase in carotenoids over cold storage (three times higher) and an increase in the stability of anthocyanins, but a significant decrease (from 62% to 49%) in the maturity index. Treatment with natural phytoregulators (i.e., methyl jasmonate and abscisic acid) resulted in higher carotenoid content and a considerable improvement in quality parameters (maturity index of 75%). In contrast, anthocyanins and antioxidant activity mostly decreased with the treatments. In particular, a drop from 2.23 mg ECGg⁻¹DW in fresh untreated samples to 0.30 mg ECGg⁻¹DW in ABA-treated samples was measured.

Conclusions: Treatment with methyl jasmonate and abscisic acid enables purple carrot spoilage to be delayed over cold storage. This is reflected in the preservation of visual appearance and maturity index. Considering the commercial importance of these variables, these results are promising. The aim now is to optimize the procedure in such a way that the improvements in quality parameters and carotenoid content attained here are maintained while the partial loss of antioxidant properties is avoided.