This work proposes the use of an electronic tongue based on flow injection coulometry for the rapid determination of the antioxidant capacity of fresh lettuce. The e‐tongue consisted of a series of 16 porous carbon electrodes, each poised at a fixed potential from +100 to +850 mV. Each injection leaded to a characteristic hydrodynamic voltammogram, whose profile reflects the composition of antioxidants. The correlation between the peak area recorded by each sensor and the 1,1‐Diphenyl‐2‐picryl‐hydrazyl (DPPH) assay was maximum ín the range of potentials between +400 and 750 mV (R2>0.97). Accordingly, the charge measured provided a direct and simple index of the antioxidant capacity. The practical utility of such index was initially demonstrated by determining the best extraction conditions. This consisted in freeze‐drying of lettuce followed by methanolic extraction. Later, the e‐tongue was used to evaluate the effect of storage (one week at 5 °C) on lettuce. The e‐tongue revealed that lettuce lost up to 25 % of their initial antioxidant activity during storage. However, when lettuce samples were pre‐treated with fast cooling or vacuum cooling, the decrease of the antioxidant index was limited to 14 and 15 %. Overall, the e‐tongue is a rapid, simple and sensitive method for the determination of the antioxidant capacity of fresh lettuce samples. Indirectly, these findings suggest also that lettuce may serve as potential dietary sources of natural phenolic antioxidants.

中文翻译：

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基于流动注射电量法的电子舌苔快速测定生菜的抗氧化能力

这项工作建议使用基于流动注射库仑法的电子舌来快速确定新鲜生菜的抗氧化能力。电子舌由一系列16个多孔碳电极组成，每个电极的电势固定在+100至+850 mV之间。每次注射都会产生特征性的流体动力学伏安图，其曲线反映了抗氧化剂的组成。每个传感器记录的峰面积与1,1-二苯基-2-吡啶基-肼基（DPPH）测定之间的相关性最大，即在+400至750 mV之间的电位范围内（R2> 0.97）。因此，所测量的电荷提供了抗氧化剂容量的直接且简单的指标。最初通过确定最佳提取条件证明了该指标的实用性。这包括生菜的冷冻干燥，然后进行甲醇提取。后来，使用电子舌来评估储存（在5°C下一周）对生菜的影响。电子舌显示，生菜在储存过程中损失了其最初抗氧化活性的25％。但是，当用快速冷却或真空冷却对生菜样品进行预处理时，抗氧化剂指数的下降仅限于14％和15％。总体而言，电子舌是测定新鲜生菜样品抗氧化能力的一种快速，简单和灵敏的方法。间接地，这些发现还表明，莴苣可以作为天然酚类抗氧化剂的潜在饮食来源。电子舌显示，生菜在储存过程中损失了其最初抗氧化活性的25％。但是，当用快速冷却或真空冷却对生菜样品进行预处理时，抗氧化剂指数的下降仅限于14％和15％。总体而言，电子舌是测定新鲜生菜样品抗氧化能力的一种快速，简单和灵敏的方法。间接地，这些发现还表明，莴苣可以作为天然酚类抗氧化剂的潜在饮食来源。电子舌显示，生菜在储存过程中损失了其最初抗氧化活性的25％。但是，当用快速冷却或真空冷却对生菜样品进行预处理时，抗氧化剂指数的下降仅限于14％和15％。总体而言，电子舌是测定新鲜生菜样品抗氧化能力的一种快速，简单和灵敏的方法。间接地，这些发现还表明，莴苣可以作为天然酚类抗氧化剂的潜在饮食来源。