de Freitas Lívia Dias Campêlo, Brandão Shirley Clyde Rupert, Fernandes da Silva João Henrique, Sá da Rocha Otidene Rossiter, Azoubel Patrícia Moreira
Federal University of Pernambuco, Department of Chemical Engineering, Av. Prof. Arthur de Sá, s/n, Cidade Universitária, Recife-PE, 50740-521, Brazil.
Food Technol Biotechnol. 2021 Jun;59(2):209-215. doi: 10.17113/ftb.59.02.21.7045.
Drying represents a viable unit operation for the preservation of food. Convective drying is the most used method for plant materials. However, it can result in negative changes in food nutrient composition, and other quality parameters, besides requiring high energy consumption. Pretreatments can represent an alternative to minimise these negative aspects of dried materials. This work aims to evaluate the use of ethanol and ultrasound before pineapple convective drying and its effect on the product´s colour, water activity, ascorbic acid and total carotenoid contents.
For the pretreatment step, fruit samples were immersed in ethanol solutions of different volume fractions, and experiments were carried out for 10 min with and without using ultrasound (25 kHz). Fruit samples were dried at 60 ºC. A control group (without the pretreatment step) was also dried under the same condition. Semi-theoretical models were used for drying data fitting, and the diffusional model was used to describe the moisture transfer and calculate the effective diffusivity. Water activity, ascorbic acid, total carotenoids and colour analyses were performed.
The combination of ethanol and ultrasound as a pretreatment reduced the drying time of pineapple. Higher effective moisture diffusivities were obtained when ethanol and ultrasound were applied before drying. The two-term exponential model presented the best fit for drying experimental data. The dried samples had a darker colour than the fresh sample. The pretreatment with ethanol resulted in increased retention of the studied bioactive components. The satisfactory results of this study represent an improvement in the drying process.
Ultrasound and ethanol as a pretreatment to convective drying are promising. However, each food matrix has a typical structure and composition. Therefore, the application of the pretreatment in other products or using other conditions is still necessary to deeply understand and explain their effect on the process and the quality of the dried products.
干燥是一种可行的食品保存单元操作。对流干燥是植物材料最常用的方法。然而，它除了需要高能耗外，还会导致食品营养成分和其他质量参数发生负面变化。预处理可以作为一种减少干燥材料这些负面影响的替代方法。本研究旨在评估在菠萝对流干燥前使用乙醇和超声波及其对产品颜色、水分活度、抗坏血酸和总类胡萝卜素含量的影响。
在预处理步骤中，将水果样品浸入不同体积分数的乙醇溶液中，在有和没有使用超声波（25kHz）的情况下进行10分钟的实验。水果样品在60℃下干燥。还设置了一个对照组（不进行预处理步骤）在相同条件下干燥。使用半理论模型对干燥数据进行拟合，并使用扩散模型描述水分传递并计算有效扩散率。进行了水分活度、抗坏血酸、总类胡萝卜素和颜色分析。
乙醇和超声波联合预处理缩短了菠萝的干燥时间。干燥前使用乙醇和超声波时获得了更高的有效水分扩散率。双项指数模型对干燥实验数据拟合效果最佳。干燥后的样品颜色比新鲜样品深。乙醇预处理导致所研究的生物活性成分保留率增加。本研究的良好结果代表了干燥过程的改进。
超声波和乙醇作为对流干燥的预处理方法很有前景。然而，每种食品基质都有其典型的结构和组成。因此，仍有必要在其他产品中或使用其他条件应用该预处理方法，以深入理解和解释其对干燥过程和干燥产品质量的影响。
