Desidratação de resíduo de acerola em leito de jorro: efeitos de pré-tratamentos e fluidodinâmica

Abstract

Researches have shown that around 40% of the material produced in fruit processing is disposed off. Acerola residues have a high nutritional value due to the presence of ascorbic acid and bioactive, phenolic and flavonoid compounds. Chemical analyses have suggested that these residues have a considerable amount of carbohydrates, proteins, lipids and fibers, which are essential macronutrients to the human body. However, some issues, such as moisture, can diminish the shelf life of the flour produced from acerola residues. The exposition to high temperatures for a long time can affect the nutritional quality of the product. Among the drying methods, the spouted bed presents a high economic interest. Preliminary tests with acerola seeds in spouted bed revealed difficulties in the material flow material; however, this issue was solved by adding soy as inert material. The physical caracterization of soy was found to be useful to understand the flowability of acerola residues. This research aimed to evaluate the efficacy of pretreatments in the drying of acerola residues in spouted bed by comparing the nutritional properties of the residues before and after drying. The pretreatment processes evaluated were the application of ultrasound (in aqueous and ethanolic mediums) and the ethanol spraying. The results obtained showed the dehydration of (non pretreated) seeds of acerola performed at 60 ºC, air flow 5% higher than the minimum spout and percentage of acerola of 35% was satisfactory. The use of ultrasound in the aqueous medium reduced the moisture of acerola residues; however, it also degraded the ascorbic acid and phenolic contents. The immersion in ethanol and the ethanol spraying treatment presented good results and decreased the drying time in 25%. The experimental design adopted in this study allowed the analysis of the effects of variables (temperature, volume of ethanol and air flow) on the nutritional content. Computer simulations can satisfactorily contribute to predict the physical properties of the particle movement and determine the fluid dynamic behavior of particles in the spouted bed. In this context, this research also used numerical simulations to study the fluid dynamic parameters (dynamic and static angles of repose and porosity) that can affect the movement of particles in the spouted bed. The main parameters analyzed were the effects of the static and rolling friction coefficients. Parameterizations were adequate to predict models that determined the effects of parameters and their interactions with responses.