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%.
This study evaluated the effects of ethanol pre‐treatment on convective drying and its impacts on the bioactive compounds of uvaia. The treatments consisting of control and samples pre‐treated by immersion in ethanol (99.8% v/v) for 10 and 20 min, followed by convective drying (1 m/s) at 40 and 60°C. The sample temperatures were traced over processing and the products were evaluated in relation to their content of phenolic compounds and antioxidant capacity. Pre‐treatment times in combination with temperatures influenced drying time and were associated with ethanol penetration and volatility in the sample. Furthermore, the high vapor pressure of ethanol reduced the initial temperature of the samples. Drying temperatures and pre‐treatments reduced by 16%–34% phenolics compounds and 13%–45% antioxidant capacity, which was associated with degradation and possible extraction by ethanol. The advantages of using ethanol were discussed, but also some limitations, especially on bioactive compounds.
Practical applications
Uvaia is a native fruit rich in sensory and healthy aspects. However, its high perishability and seasonality make it unfeasible for post‐harvest commercialization. This work demonstrated that drying and application of ethanol proved to be effective for preserving this fruit, resulting in a shorter processing time. Although ethanol partially extracted the bioactive compounds, significant levels are still found in the final product—which can be used as convenient products with a positive impact on consumers' health. Furthermore, the proposed approach is simple, relatively cheap, and viable techniques to obtain stable products for both industry and small producers.
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