Mathematical modeling of infrared drying of red pitaya pulp (Stenocereus queretaroensis) for potential use of its betalains

Abstract

Red pitaya fruit has an important concentration of betalains (68.7 mg/100 g fresh sample) that potentially can be used as natural colorants for food, textiles, dye‐sensitized solar cells, etc. Nevertheless, this fruit has a short shelf life. To overcome this problem and to take advantage of their varied and attractive colors, pitayas can be infrared dried. In this work, we evaluated the kinetics of infrared drying of red pitaya pulp in the temperature range of 40–70°C. The drying rate was found to increase with temperature. The time required to diminish moisture content of red pitaya pulp from 80.5% to around 0.1%–0.3% (dry basis) decreased from 625 min at 40 to 240 min at 70°C. The experimental drying data were fitted to nine empirical drying models reported in literature and to one new model herein proposed. Based on statistical criteria, the proposed model was found the best for characterizing drying behavior of red pitaya pulp for the whole range of temperature. Effective moisture diffusivity was moisture content‐dependent, the average values for diffusivity coefficients at each drying temperature were derived from Fick's law and varied from 0.98–4.43 × 10−9 m2/s over the temperature range. Activation energy for moisture diffusion in red pitaya pulp was determined as 42.89 kJ/mol. Best drying temperature was found to be at 70°C, where a higher betalain content and a faster drying process conditions were achieved. Practical applications Betalains can be used as healthy natural colorants for food, among others. A limitation for which pitayas have not been exploited as a source of colorants is because of their short shelf life. Due to the important concentration of betalains present in this fruit, it is highly desirable to have methodologies that allow access to their use. To overcome this problem and to take advantage of their varied and attractive colors, red pitaya pulp was infrared dried for its study. Herein the proposed model exhibited an excellent fit to the red pitaya pulp drying process. The commercial exploitation of pitayas as an alternative source of natural colorant betalains may not only provide a wider color spectrum than red beetroot, but also contribute to the sustainable development of the usually underdeveloped semiarid regions.

Drying kinetic, thermodynamic and quality analyses of infrared drying of truffle slices

“…A similar process has been reported for the drying of shea fruit (Korese & Chikpah, 2023), Capsicum annuum L. var. glabriusculum (Ovando‐Medina, 2023), pear (Araujo et al., 2021), linden (Selvi et al., 2022), and red pitaya pulp (Ríos‐Moreno et al., 2022).…”

“…A similar process has been reported for the drying of shea fruit (Korese & Chikpah, 2023), Capsicum annuum L. var. glabriusculum (Ovando-Medina, 2023), pear (Araujo et al, 2021), linden (Selvi et al, 2022), and red pitaya pulp (Ríos-Moreno et al, 2022). Also, exploring the impact of thickness on drying time at various temperatures showed that using thicker samples increase the drying time.…”

Infrared drying of apple (Malus domestica) slices: Effect on drying and color kinetics, texture, rehydration, and microstructure

“…Arrhenius equation is used to show temperature dependency of effective diffusivity of food products. The activation energy for food products was determined using the plot of ln ( D eff ) versus 1/ T ; the slope of this curve is equal to (− Ea / R ) (Keneni et al, 2019; Ríos‐Moreno et al, 2022). The activation energy ( E a ) can be calculated using the following expression given in Equation (9).…”