EFFECT OF PULSED LIGHT TREATMENT ON PHYSICOCHEMICAL AND PHYTOCHEMICAL PARAMETERS OF BEETROOT, BLACKBERRY AND RED PRICKLY PEAR

The use of emerging nonthermal technologies, like pulsed light (PL), have gained interest due to their potential to induce the synthesis of bioactive compounds in different plant matrices without compromising their overall quality. The objective of this study was to evaluate the influence of different pulsed light treatments on physicochemical and phytochemical parameters in beetroot (Beta vulgaris), blackberry (Rubus spp.), and red prickly pear (Opuntia ficus-indica). Fresh samples were obtained from a local market in Monterrey, Nuevo León, Mexico. A completely randomized 2x2 factorial design was used, evaluating two fluence levels (9 and 20 J/cm²), and two distances from the lamp (4.45 and 7.01 cm), resulting in four PL treatment and an untreated control. Samples were treated using a Xenon X-1100 system and stored at 7°C for 5 days. Physicochemical (pH, °Brix, titratable acidity and color) and phytochemical parameters (total phenolic compounds, betalain content and antioxidant activity) were evaluated. The pulsed light treatments did not significantly affect the physicochemical characteristics of the samples (pH 2.4-6.9; °Brix 9-13), preserving the quality of the products. However, phytochemical responses were strongly dependent on the fruit type and treatment conditions. Total phenolic content (TPC) increased significantly in all samples during storage, especially in prickly pear, which exhibited a gradual increase reaching maximum values at day 5 (up to 81 mg GAE/100 g FW). For betalains it showed a matrix dependent behavior, beetroot showed an increase by day 3 (370-430 µg eq betacyanins/100 g FW; 182-217 µg eq indicaxanthin/100 g FW) followed by degradation at day 5 (56-102 µg eq betacyanins/100 g FW; 77-95 µg eq indicaxanthin/100 g FW), while prickly pear had a gradual increase in both betacyanins (up to 131 µg betacyanins/100 g FW) and betaxanthins (up to 55 µg eq indicaxanthin/100 g FW), specially under moderate fluence conditions, suggesting activation of secondary metabolism. Overall, these findings demonstrate that pulsed light can act as an abiotic elicitor to enhance phenolic compounds and betalains while maintaining physicochemical quality. Intermediate fluence conditions were identified as the most effective for promoting bioactive compound accumulation