Effects of Different Cooking Methods (Pan-Frying, Sous-Vide, Boiling, and Deep Frying) on Mineral Composition and In Vitro Bioaccessibility of Beef, Lamb, and Chicken Livers

Abstract

This study investigated the effects of pan-frying, sous-vide, boiling, and deep frying methods on the mineral content and post-in vitro digestion bioaccessibility of beef, lamb, and chicken livers. Sodium (Na), magnesium (Mg), potassium (K), phosphorus (P), iron (Fe), copper (Cu), manganese (Mn), zinc (Zn), chromium (Cr), and cobalt (Co) concentrations were quantified using inductively coupled plasma atomic emission spectrometry (ICP-OES). Significant differences in mineral contents were observed among cooking methods within the same liver type and among liver types within the same cooking method (p < 0.05). Sous-vide achieved the highest macromineral retention across all liver types, ranging from 61.52% +/- 1.83% to 101.45% +/- 6.21%. Micromineral retention varied by liver type, with boiling and sous-vide methods yielding higher rates (39.69% +/- 2.84%-141.05% +/- 9.93%). Sous-vide treatment was also associated with an apparent post-processing increase in Mg concentration (29.82%), reflecting high mineral retention efficiency and reduced moisture loss rather than de novo mineral formation. This cooking method also resulted in the highest Fe concentrations (281.6 +/- 7.86 mg/kg). In contrast, boiling caused losses of 49.24%-70.69% in Na, Mg, K, and P, while deep frying resulted in losses of 3.38%-48.90% for these elements. After in vitro digestion, boiling resulted in the lowest mineral losses across all liver types. The samples exhibiting the most pronounced post-digestion increases and the highest Fe concentrations were identified as 560.44 +/- 35.52 mg/kg for BFI (Beef Deep Frying Intestine), 636.4 +/- 12.93 mg/kg for CFI (Chicken Deep Frying Intestine), and 728.4 +/- 27.09 mg/kg for LBI (Lamb Boiling Intestine). Overall, considering both mineral retention after cooking and mineral release into the soluble fraction during in vitro digestion, sous-vide emerged as the most favorable cooking method for preserving the mineral nutritional quality of liver, while the findings should still be interpreted in the context of bioaccessibility and realistic dietary intake.