Possibilities for Detection of Adulteration of Lemon Juices and Lemon-Based Beverages

Abstract

Lemon juice and other lemon-based beverages are subject to economically motivated fraud, primarily inclu­ding a reduced fruit content closely related to excessive dilution with water, undeclared addition of sugars or synthetic citric acid, and substitution of lemons with cheaper fruit. Eight tested samples of 100% juices showed good agreement between the measured concentrations and the reference values for the following markers: formol number (range from 16.9 to 26.5 mL of 0.1M NaOH 100 mL^–1), ash (2.5 to 3.9 g L^–1), phosphorus (84 to 145 mg L^–1), potassium (931 to 1720 mg L^–1), magnesium (81 to 114 mg L^–1), malic acid (1.8 to 6.0 g L^–1), and ᴅ‑isocitric acid (277 to 560 mg L^–1). The following markers were suggested as an evidence of adulteration, processing method, and recipe alteration after the subsequent analysis of the beverage concentrates: 1) Citric acid is a substance whose content can be increased by adding synthetic citric acid. 2) Calcium content was impacted by clarification or reconstitution in some beverage concentrate samples tested. 3) Increased content of glucose and fructose confirmed exogenous sugar addition. 4) Ascorbic acid levels below 150 mg L^–1 indicated severe processing or long-term storage. The flavonoid profile, characterized mainly by the ratio of eriocitrin and hesperidin (average value 0.7), serves as an indicator of the addition of another citrus species. However, the finding for the Interdonato variety suggests that this ratio is quite variable and not entirely specific because lime juice exhibits a similar value.