Effects of High-Pressure Processing, UV-C Irradiation and Thermoultrasonication on Donor Human Milk Safety and Quality

Breast milk preservation: thermal and non-thermal processes and their effect on microorganism inactivation and the content of bioactive and nutritional compounds

Human Breast Milk (HBM) is widely acknowledged as the best nutritional source for neonates. Data indicates that, in 2019, 83.2% of infants in the United States received breast milk at birth, slightly reducing to 78.6% at 1 month. Despite these encouraging early figures, exclusive breastfeeding rates sharply declined, dropping to 24.9% by 6 months. This decline is particularly pronounced when direct breastfeeding is challenging, such as in Neonatal Intensive Care Units (NICU) and for working mothers. Given this, it is vital to explore alternative breast milk preservation methods. Technologies like Holder Pasteurization (HoP), High-Temperature Short-Time Pasteurization (HTST), High-Pressure Processing (HPP), UV radiation (UV), and Electric Pulses (PEF) have been introduced to conserve HBM. This review aims to enhance the understanding of preservation techniques for HBM, supporting the practice of extended exclusive breastfeeding. It explicitly addresses microbial concerns, focusing on critical pathogens like Staphylococcus aureus, Enterococcus, Escherichia coli, Listeria monocytogenes, and Cytomegalovirus, and explores how various preservation methods can mitigate these risks. Additionally, the review highlights the importance of retaining the functional elements of HBM, particularly its immunological components such as antibodies and enzymes like lysozyme and Bile Salt Stimulated Lipase (BSSL). The goal is to provide a comprehensive overview of the current state of HBM treatment, critically assess existing practices, identify areas needing improvement, and advocate for extended exclusive breastfeeding due to its vital role in ensuring optimal nutrition and overall health in infants.

High hydrostatic pressure is similar to Holder pasteurization in preserving donor milk antimicrobial activity

BACKGROUND

The microbiological safety of donor milk (DM) is commonly ensured by Holder pasteurization (HoP, 62.5 °C for 30 min) in human milk banks despite its detrimental effects on bioactive factors. We compared the antimicrobial properties of DM after Holder pasteurization treatment or High Hydrostatic Pressure processing (HHP, 350 MPa at 38 °C), a non-thermal substitute for DM sterilization.

METHODS

We assessed lactoferrin and lysozyme concentrations in raw, HHP- and HoP-treated pools of DM (n = 8). The impact of both treatments was evaluated on the growth of Escherichia coli and Group B Streptococcus in comparison with control media (n = 4). We also addressed the effect of storage of HHP treated DM over a 6-month period (n = 15).

RESULTS

HHP milk demonstrated similar concentrations of lactoferrin compared with raw milk, while it was significantly decreased by HoP. Lysozyme concentrations remained stable regardless of the condition. Although a bacteriostatic effect was observed against Escherichia coli at early timepoints, a sharp bactericidal effect was observed against Group B Streptococcus. Unlike HoP, these results were significant for HHP compared to controls. Stored DM was well and safely preserved by HHP.

CONCLUSION

Our study demonstrates that this alternative sterilization method shows promise for use with DM in human milk banks.

IMPACT

Antimicrobial activity of donor milk after High Hydrostatic Pressure treatment has not been clearly evaluated. Donor milk lactoferrin is better preserved by High Hydrostatic Pressure than conventional Holder pasteurization, while lysozyme concentration is not affected by either treatment. As with Holder pasteurization, High Hydrostatic Pressure preserves donor milk bacteriostatic activity against E. coli in addition to bactericidal activity against Group B Streptococcus. Donor milk treated by High Hydrostatic Pressure can be stored safely for 6 months.

High-Pressure Inactivation of Bacillus cereus in Human Breast Milk

Although Holder pasteurization is the recommended method for processing breast milk, it does affect some of its nutritional and biological properties and is ineffective at inactivating spores. The aim of this study was to find and validate an alternative methodology for processing breast milk to increase its availability for newborn babies and reduce the financial loss associated with discarding milk that has become microbiologically positive. We prepared two series of breast milk samples inoculated with the Bacillus cereus (B. cereus) strain to verify the effectiveness of two high-pressure treatments: (1) 350 MPa/5 min/38 °C in four cycles and (2) cumulative pressure of 350 MPa/20 min/38 °C. We found that the use of pressure in cycles was statistically more effective than cumulative pressure. It reduced the number of spores by three to four orders of magnitude. We verified that the method was reproducible. The routine use of this method could lead to an increased availability of milk for newborn babies, and at the same time, reduce the amount of wasted milk. In addition, high-pressure treatment preserves the nutritional quality of milk.

Impact of time-temperature combinations on the anti-Cytomegalovirus activity and biological components of human milk

BACKGROUND

There is extensive evidence that Holder pasteurization (HoP) (30 min at 62.5 °C) has harmful effects on the bioactivities of human milk (HM). We previously demonstrated that lowering HoP temperature is sufficient to inactivate Cytomegalovirus (HCMV). Here, we analyzed the effect of lowering time/temperature on the antiviral activity against HCMV and IgA levels of HM.

METHODS

Eighty HM samples from five mothers were pasteurized in a range of temperature (62.5-56 °C) and time (40-10 min) in a conventional setting of Human Milk Bank. Unpasteurized HM from each mother was used as control. The samples were assayed against HCMV-AD169 strain in cell cultures and IgA levels were determined by ELISA.

RESULTS

All HM samples exhibited anti-HCMV activity, to a different extent. An improvement of antiviral activity was observed in samples treated at 60, 58 and 56 °C compared to those at 62.5 °C, with ID50 values near those of unpasteurized milk. Similarly, better retention in IgA levels was observed by reducing the temperature of treatment.

CONCLUSIONS

We demonstrated that a 2.5 °C reduction of heat treatment significantly preserved the IgA content and fully restored the anti-HCMV activity of HM, supporting this variant of HoP as a valid alternative to preserve HM bioactivities.

IMPACT

This work questions the standard HoP and opens the debate on whether the pasteurization temperature commonly used in Human Milk Banks should be lowered to better preserve the biological components of the milk. A reduction of HoP temperature at 60 °C determined a significant preservation of anti-HCMV activity and IgA content of donor HM, compared to standard HoP. This alternative HoP is highly feasible compared to other substitute pasteurization techniques, since it would employ the same pasteurizer equipment found in most Human Milk Banks.