Polyphenol Content and Antioxidant Activity in Homemade and Commercial Soups: A Theoretical and Experimental Approach.

Abstract

Background: Most studies on polyphenols and antioxidant activity focus on raw ingredients, often overlooking the impact of technological processes-a gap that is particularly notable given that many population studies rely on theoretical calculations from nutritional databases. Therefore, it is essential to verify whether these theoretical values align with experimental findings on model dishes and to determine the extent to which processing affects polyphenol content and antioxidant activity in processed foods. Methods: As model dishes, this study analyzed soups prepared through thermal processing, along with commercially available ready-to-eat and instant soups. Total polyphenol content was measured using the Singleton-Rossi method, while antioxidant activity was assessed using the FRAP (ferric-reducing antioxidant potential) method and an electrochemical method. Theoretical calculations were performed based on original recipes from Polish nutritional value tables, as well as data from available polyphenol and antioxidant activity databases for raw ingredients. Results: The total polyphenol content varied significantly between experimental measurements and theoretical calculations, with deviations ranging from -42% to +1370%. FRAP antioxidant activity also differed, ranging from -62% to +524%, depending on the type of soup. The polyphenol content in homemade soups ranged from 3.692 to 16.534 mg GAE/100 mL, in ready-to-eat soups from 4.387 to 18.431 mg GAE/100 mL, and in instant soups from 1.624 to 7.254 mg GAE/100 mL, with tomato soups consistently having the highest polyphenol content across all categories. FRAP values ranged from 0.021 to 0.189 mmol/100 g in homemade soups, 0.029 to 0.269 mmol/100 g in ready-to-eat soups, and 0.033 to 0.134 mmol/100 g in instant soups, with tomato soups again showing the highest FRAP values. Antioxidant activity measured electrochemically ranged from 44.410 to 52.467 mC/g in homemade soups, 22.750 to 58.900 mC/g in ready-to-eat soups, and 22.515 to 47.680 mC/g in instant soups, with broccoli soups showing the highest values. Conclusions: This study demonstrates that theoretical models alone are insufficient for accurately determining polyphenol content and antioxidant activity in food, reinforcing the importance of experimental validation in processed food.