Secagem convectiva de mamão formosa (Carica papaya L.): influência do revestimento no pré-tratamento utilizando etanol e desidratação osmótica com isomaltulose

Abstract

Papaya is a fruit appreciated worldwide for its sensory and nutritional attributes. However, it is highly perishable. Drying is an alternative that promotes the reduction of moisture content, extending the shelf life of the product, but qualitative degradations occur. Drying pre-treatments can be used to improve processing and obtain a quality product. The objective of this study was to evaluate the hot air drying kinetics and quality parameters of Formosa papaya (Carica papaya L.) coated with sodium alginate and osmotically pre-treated with isomaltulose and ethanol immersion. The papayas were selected, washed, sanitized, and 10 mm cubes of their pulp were obtained using a stainless steel mold. After cutting, the samples were immersed in a 1% (w/v) sodium alginate solution and in a 2.5% (w/v) calcium chloride solution for coating formation. Subsequently, different pre-treatments were applied to the samples: osmotic dehydration for 300 minutes with or without vacuum application in the first 20 minutes using isomaltulose at different concentrations (25% and 35%) as an osmotic agent in fresh or coated samples and immersion in 95% (v/v) ethanol, at a ratio of 1:5 (w/v), for 2 minutes, at 25 °C. Drying was carried out in a convective tunnel dryer with forced air circulation at a drying air velocity of 1.5 m/s and a temperature of 60 °C until 13% final moisture content. The results obtained after the osmotic process showed that the application of the coating reduced the solid gain by up to 26% when combined with vacuum application and the solution with 35% isomaltulose, without affecting the water loss flow and moisture reduction of the samples. When analyzing the effects of the pre-treatments on convective drying, it was found that the use of ethanol reduced the drying time by approximately 20% compared to the previously dehydrated or untreated samples, as both had the same drying time, 340 minutes. However, the shortest drying time was observed when ethanol use was associated with osmotic pre-treatment of non-coated and coated samples, 240 minutes in both treatments. Higher effective diffusivities were also observed through Fick's model for treatments with ethanol use, consequently lower energy consumption. Regarding quality, it is concluded that the coated pre- treatments showed better preservation of carotenoids, antioxidant activity, and phenolic compounds.