Food Oxalates: Occurrence in the Food System and Advances in Technologies for Reduction, Detection, and Quantification

Abstract

Oxalic acid (OxA) is widely recognized as an antagonist to mineral absorption, leading to chronic renal complications such as nephropathy, hyperoxaluria, and induced inflammation. The interaction of OxA with metal ions results in a divalent/monovalent anion known as oxalate. In light of the growing interest in plant-based foods, this article provides a comprehensive and unbiased overview of oxalate in foods. It discusses the changes in oxalate content caused by various thermal, non-thermal, and combined food processing methods, as well as recent advances in oxalate extraction and quantification techniques, including food oxalate sensors. The challenges and interferences encountered during oxalate extraction and measurement with different quantification techniques are highlighted to aid scientists in their future efforts related to oxalate measurement in food systems. Selecting appropriate oxalate reduction techniques and their optimal applications is expected to make low-oxalate food products more accessible, thereby enhancing mineral bioavailability by promoting increased absorption in the intestinal epithelium. Although several methods have been developed for quantifying urinary oxalates, finding a quick and highly precise technique for measuring oxalate content in plant-based foods remains challenging. Interferences from metal ions, acids, and pigments during the quantification process make accurate and reliable measurement difficult. Future efforts should focus on developing low-oxalate foods by the food processing industries that are ready-to-eat or serve or cook, minimizing concerns about their oxalate content.