Antioxidant and Microbiological Status of Raw Human Milk Stored Long-Term Under Hyperbaric Conditions Compared with Frozen Pasteurized Milk.

Abstract

Human milk (HM) is the optimal source of nutrition for infants and provides antioxidants such as vitamin C, glutathione, lactoferrin, and enzymatic antioxidants including catalase (CAT), glutathione peroxidase (GPx), and superoxide dismutase (SOD). However, conventional preservation methods such as pasteurization and freezing can compromise its biological quality. This study aimed to evaluate the impact of long-term hyperbaric storage (HS) on the antioxidant capacity and microbial safety of donor human milk (DHM), and to compare it with pasteurized DHM stored under standard freezing conditions. Raw DHM samples were stored for 5 mo under moderate pressures (60-130 MPa) at subzero temperatures (-5 to -12°C). Pasteurized DHM stored at -20°C under atmospheric pressure served as the control. Vitamin C content, total antioxidant capacity (TAC), oxygen radical absorbance capacity (ORAC), and the activities of CAT, GPx, and SOD were measured. Microbiological analyses included total bacterial count, coagulase-positive staphylococci, and Enterobacteriaceae. DHM stored under hyperbaric conditions retained significantly higher levels of vitamin C (63%-68% of initial), TAC (14.4%-44.1%), and ORAC (≤82.3%) compared with pasteurized milk stored at -20°C, where vitamin C and TAC decreased by ≤70% and 76.6%, respectively, and ORAC declined to 73.4%. CAT and GPx activities decreased in all variants, with the greatest losses in pasteurized milk (CAT by 71%, GPx by 86%). SOD activity remained stable. HS effectively inactivated HM microbiota: no bacteria were detected after 2 d of storage at 111 MPa/-10°C and 130 MPa/-12°C. Pasteurized HM stored at -20°C also showed no bacterial growth. HS better preserves the antioxidant properties of DHM and has the potential to ensure microbiological safety through inactivation of milk microbiota under tested conditions.