Convective drying of cambuci, a native fruit from the Brazilian Atlantic Forest: Effect of pretreatments with ethanol and freezing

Abstract

Cambuci is a native fruit from the Brazilian Atlantic Forest, with high sensorial and nutritional potential. However, this fruit is very perishable, which impairs its exploration and study. This work reported the convective drying of cambuci for the first time, as an approach to achieve stability. Moreover, it also evaluated for the first time the combination of ethanol and freezing pretreatments to convective drying. Pretreatments were performed by immersion of fresh and previously frozen and thawed cambuci slices in ethanol (5 min at 25 C). Pretreated samples were then convectively dried (50 C, 1 m/s). Drying time was reduced up to ~36% by combining the pretreatments, which was associated with the reduction in the external resistance to mass transfer, once the convective mass transfer coefficient increased up to 94%. In contrast, pretreatments that include freezing had a greater influence on reducing the internal resistance to mass transfer, increasing the effective diffusive coefficient. In addition, the thermal surface profile evidenced the temperature increased faster and reached high levels in pretreatments that include freezing, which could be correlated to their higher drying rates and structure modifications. The obtained results corroborate the modifications produced by freezing and the effects of ethanol on the surface of samples significantly accelerate the convective drying of cambuci. Practical ApplicationsThe present investigation shows that convective drying is a feasible alternative for cambuci processing. Further, being this fruit very perishable, with short harvest and production far from the markets, freezing is a common practice to preserve them in the farms. Consequently, the impact of this unit operation was also evaluated. In addition, the proposed pretreatments (freezing and ethanol) have great application potential to improve the conventional convective drying of fruits. It has been shown that the combination of pretreatments accelerated drying, reducing the processing time by 36%.

Structure–process interaction in mass transfer processes: Application of ethanol and ultrasound in a vascular structure

“…For instance, during convective drying in products such as potatoes (Guedes et al, 2021) and carrots (Santos et al, 2021), 30 min of pretreatment was necessary to observe significant changes in the drying parameters. In pumpkin, more than 10 min of processing were necessary (Rojas & Augusto, 2018b; Rojas, Silveira, & Augusto, 2020), since at 5 min no differences were observed (Carvalho, Rojas, et al, 2020b), similarly to the evidenced for cambuci (Rojas et al, 2021) or strawberries—2 min (Macedo et al, 2021).…”

Impact of pretreatments with ethanol and freezing on drying slice papaya: drying performance and kinetic of ultrasound‐assisted extraction of phenolics compounds

“…To date, only one study has applied the pretreatments of FG and immersion in ET in Cambuci. 13 This reinforces the importance of new studies that explore the effects of the application of these alternatives on papaya drying and its quality.…”

“…However, no studies reporting convective drying of papaya with application of simple pretreatments based on FG and application of ET were found. To date, only one study has applied the pretreatments of FG and immersion in ET in Cambuci 13 . This reinforces the importance of new studies that explore the effects of the application of these alternatives on papaya drying and its quality.…”

Steam blanching and ethanol pretreatment enhance drying rates and improve the quality attributes of apple slices via microstructure modification

“…For example, when ultrasonic and osmotic pretreatments were used in the infrared drying of ginkgo biloba seeds, microchannels appeared on the cell surface due to the cavitation effect caused by ultrasound, accelerating the transport and diffusion of solutes through the cell wall in the solid-liquid system, and leading to the highest SL (Boateng & Yang, 2021). In addition, the area near the sample surface contains a water-ethanol mixture that evaporated into the air (Rojas et al, 2021). These effects can reduce the external resistance of mass transfer, which may also be one of the reasons for WL and SL during mass transfer.…”