[The evaluation of anti-nutritive components in beer on the example of oxalic acid].

BACKGROUND: Food in its composition contains anti-nutritional substances that reduces or prevents the use of valuable nutrients. The oxalic acid, as phytate and dietary fiber, occurs naturally in foods of plant origin, to which the beer is classified. The negative effect of oxalic acid is reducing the bioavailability of calcium and magnesium, and disorder of metabolism of the body's absorption of these elements from the diet. The excess of oxalic acid and its salt in the diet contributes to the formation of certain diseases, such as oxalate urolithiasis, osteoporosis, arthritis, etc. Due to the diuretic effect of beer, drinking moderate amounts of it is recommended as a preventive and support urinary tract disorders.

OBJECTIVE: The aim of this study was to determine and comparison the oxalic acid content in selected beers available on the Polish market.

MATERIAL AND METHOD: Fifty seven samples of beer were used for this study. These samples were divided into three groups depending on the alcohol concentration declared by the producers (1st group--below 5.5% vol., 2nd group--from 5.5 to 6.5% vol., 3rd group--above 6.5% vol.). The beer samples were incubated in the ultrasonic bath for 15 minutes following pH adjustments up to pH = 2 with the 1 mol/L hydrochloric acid to transform calcium oxalates into soluble form, then filtered. The oxalic acid concentration was measured by high performance liquid chromatography (HPLC) with conductivity detection.

RESULTS: The concentration of oxalic acid in tested samples of beer ranged from 1.8 to 30.3 mg/L. No considerable differences between the concentration of oxalic acid in the three tested group of beer with the various content of the alcohol were found. Basing on the average concentrations of the oxalic acid in the different groups of the tested beers the positive trend in oxalic acid concentration related to the increase of alcohol could be observed.

CONCLUSIONS: The very low concentration of oxalic acid allows to classify beer as food product safe for the human health in terms of low oxalates content.