Hot topic: Holder pasteurization of human milk affects some bioactive proteins

Human milk microbiota, oligosaccharide profiles, and infant gut microbiome in preterm infants diagnosed with necrotizing enterocolitis

Necrotizing enterocolitis (NEC) is a severe intestinal disease of very preterm infants with mother's own milk (MOM) providing protection, but the contribution of the MOM microbiota to NEC risk has not been explored. Here, we analyze MOM of 110 preterm infants (48 NEC, 62 control) in a cross-sectional study. Breast milk contains viable bacteria, but there is no significant difference in MOM microbiota between NEC and controls. Integrative analysis between MOM microbiota, human milk oligosaccharides (HMOs), and the infant gut microbiota shows positive correlations only between Acinetobacter in the infant gut and Acinetobacter and Staphylococcus in MOM. This study suggests that NEC protection from MOM is not modulated through the MOM microbiota. Thus, "'restoring" the MOM microbiota in donor human milk is unlikely to reduce NEC, and emphasis should instead focus on increasing fresh maternal human milk intake and researching different therapies for NEC prevention.

High-Pressure Processing of Human Milk: A Balance between Microbial Inactivation and Bioactive Protein Preservation

BACKGROUND

Donor human milk banks use Holder pasteurization (HoP; 62.5°C, 30 min) to reduce pathogens in donor human milk, but this process damages some bioactive milk proteins.

OBJECTIVES

We aimed to determine minimal parameters for high-pressure processing (HPP) to achieve >5-log reductions of relevant bacteria in human milk and how these parameters affect an array of bioactive proteins.

METHODS

Pooled raw human milk inoculated with relevant pathogens (Enterococcus faecium, Staphylococcus aureus, Listeria monocytogenes, Cronobacter sakazakii) or microbial quality indicators (Bacillus subtilis and Paenibacillus spp. spores) at 7 log CFU/mL was processed at 300-500 MPa at 16-19°C (due to adiabatic heating) for 1-9 min. Surviving microbes were enumerated using standard plate counting methods. For raw milk, and HPP-treated and HoP-treated milk, the immunoreactivity of an array of bioactive proteins was assessed via ELISA and the activity of bile salt-stimulated lipase (BSSL) was determined via a colorimetric substrate assay.

RESULTS

Treatment at 500 MPa for 9 min resulted in >5-log reductions of all vegetative bacteria, but <1-log reduction in B. subtilis and Paenibacillus spores. HoP decreased immunoglobulin A (IgA), immunoglobulin M (IgM), immunoglobulin G, lactoferrin, elastase and polymeric immunoglobulin receptor (PIGR) concentrations, and BSSL activity. The treatment at 500 MPa for 9 min preserved more IgA, IgM, elastase, lactoferrin, PIGR, and BSSL than HoP. HoP and HPP treatments up to 500 MPa for 9 min caused no losses in osteopontin, lysozyme, α-lactalbumin and vascular endothelial growth factor.

CONCLUSION

Compared with HoP, HPP at 500 MPa for 9 min provides >5-log reduction of tested vegetative neonatal pathogens with improved retention of IgA, IgM, lactoferrin, elastase, PIGR, and BSSL in human milk.

Sterilization efficacy of a new water-free breast milk pasteurizer

BACKGROUND

Breast milk, nature's optimum source of nutrition for infants, can contain undesirable microorganisms that cause severe morbidity. After an outbreak of multidrug-resistant Escherichia coli among neonates receiving breast milk donated by another mother in our neonatal intensive care unit (NICU), we were motivated to develop a high-grade breast milk pasteurizer (BMP) designed to thaw and pasteurize breast milk at 63°C for 30 min in a sealed bag without having to open the bag or immerse it in water.

METHODS

Pre-existing bacteria and spiked cytomegalovirus (CMV) were measured pre- and post-pasteurization in frozen breast milk donated by mothers of children admitted to the NICU.

RESULTS

Among 48 breast milk samples (mean ± standard deviation [SD]), pre-existing bacterial counts of 5.1±1.1 × 104 colony forming units (cfu)/mL decreased to less than 10 cfu/mL (below detection level) in 45 samples after pasteurization for 30 min. In three samples, 10-110 cfu/mL persisted. As no CMV was detected in any of the 48 samples, CMV at ≥5 × 104 pfu/mL was spiked into 11 breast milk samples. After just 10 min of pasteurization, infectious CMV was not detected (threshold <50 pfu/mL) in any sample.

CONCLUSION

A new BMP was shown to pasteurize milk effectively with more than a 3-log reduction of microorganisms. Compared to conventional pasteurizers, this device reduces the effort involved in pasteurizing breast milk, avoids various contamination risks, and may reduce the risk of infectious disease transmission via breast milk.

Influence of Homogenization in the Physicochemical Quality of Human Milk and Fat Retention in Gastric Tubes

BACKGROUND

The retention of human milk nutrients in gastric tubes used to feed premature infants is a challenge to be overcome.

RESEARCH AIMS

To evaluate (1) the performance of six homogenizers (mixing processor, piston valve, ultrasonic bath, ultraturrax, stirring mixer, and ultrasound probe) for the fat retention reduction in gastric tubes; (2) the influence of the best homogenization conditions on the fatty acid and protein profiles of human milk; and (3) the cost/benefit ratio for the inclusion of homogenization as a new step in human milk processing.

METHODS

The influence of different levels and times of homogenization on reducing fat retention of human milk in probes was evaluated in this comparative prospective cross-sectional study. After homogenization, human milk flowed through a gavage and infusion pump apparatus used for feeding. Fat content was quantified before and after feeding. The techniques that reduced fat globule sizes and/or promoted a lower percentage of fat holding were evaluated for efficiency, variations in the fatty acid and protein profiles, and energy density and operating costs.

RESULTS

Homogenization led to a reduction in fat retention in feeding probes. The mixer processor and the ultrasound probe reduced fat retention by 99.23% (SD = 0.07) and 99.95% (SD = 0.02), respectively, and did not negatively influence fatty acid and protein profiles. The mixer processor demonstrated low energy density and low cost for human milk processing.

CONCLUSION

Homogenization promoted reduced fat retention in the feed probe and could help maintain fat nutrients of human milk during enteral feeding.

Nutrients and Bioactive Components of Human Milk After One Year of Lactation: Implication for Human Milk Banks

OBJECTIVE

Specifying the nutrient content and bioactive compounds in milk from long-term lactation for the purpose of finding additional sources of donors' milk for human milk banks.

METHOD

Human milk samples were collected from 43 mothers of term infants (term infant human milk, TIHM) (3-6 weeks of lactation) and 50 mothers who have breastfed for over a year (long-nursing human milk, LNHM). The milk collection time was 24 hours. The analyses of fat, protein, carbohydrate and energy content were performed with human milk analyzer MIRIS (Miris HMA™ ); lactoferrin and vitamin C content using high performance liquid chromatography in reversed phase (RP-HPLC); total antioxidant activity (TAC) and lysozyme by enzyme-linked immunosorbent assay (ELISA); and the activity of glutathione peroxidase (GPx) and catalase (CAT) via spectrophotometric methods. Sociodemographic characteristics of both groups of mothers have been compiled.

RESULTS

Higher fat content and energy value was found in LNHM than in TIHM. Protein content in LNHM and TIHM did not differ. Carbohydrate content was lower in LNHM than in TIHM. TAC, CAT and GPx activity were higher in LNHM compared to TIHM. No significant differences in the content of lysozyme, lactoferrin and vitamin C between the studied groups were found.

CONCLUSIONS

The findings suggest that after 12 months of lactation, human milk still has significant nutritional value, does not lose bioactive components and can be considered for use in human milk banks.

Effect of pasteurization on melatonin concentration in human breast milk

Introduction

Women who have problems with lactation can use human milk banks. Mainly this human milk is provided to premature babies and sick newborns. Human milk is the most suitable food for newborns and infants, recommended by WHO (World Health Organization). Human milk has anti-inflammatory, anti-infective, and anti-allergic properties, and also works for immunomodulation. Melatonin has a special, underestimated importance in the composition of breast milk. It is a hormone that has many body functions and, for several decades, its antioxidant potential has been increasingly talked about.

The aim of the study was to examine the effect of Holder pasteurization on melatonin concentration in human milk.

Materials and Methods

18 samples of human milk from donors from the human milk bank were used for the analysis. Melatonin concentration before and after pasteurization was determined by ELISA. In addition, the nutritional content composition of milk was analyzed using MIRIS Human Milk Analyzer and correlations examined.

Results

Melatonin concentration in human milk before pasteurization was 0.65–26.24 pg/mL (Me=9.58, IQR=12.72), while after pasteurization 0.80–29.58 pg/mL (Me=9.98, IQR=11.26). There was a positive correlation between melatonin concentration before and after pasteurization (r=0.797, p<0.001).

Conclusions

The Holder pasteurization process does not affect the concentration of melatonin in milk samples, which may be a recommendation for human milk banks.

The Effect of Pasteurization on the Antioxidant Properties of Human Milk: A Literature Review

High rates of oxidative stress are common in preterm born infants and have short- and long-term consequences. The antioxidant properties of human milk limits the consequences of excessive oxidative damage. However, as the mother's own milk it is not always available, donor milk may be provided as the best alternative. Donor milk needs to be pasteurized before use to ensure safety. Although pasteurization is necessary for safety reasons, it may affect the activity and concentration of several biological factors, including antioxidants. This literature review describes the effect of different pasteurization methods on antioxidant properties of human milk and aims to provide evidence to guide donor milk banks in choosing the best pasteurization method from an antioxidant perspective. The current literature suggests that Holder pasteurization reduces the antioxidant properties of human milk. Alternative pasteurization methods seem promising as less reduction is observed in several studies.

The effect of thermal pasteurization, freeze-drying, and gamma irradiation on donor human milk

The availability of donor human milk (DHM) is currently limited by the volumes that can be thermally pasteurized and kept in long-term cold storage. This study assesses the application of freeze-drying followed by low-dose gamma irradiation of DHM for simplified, safe long-term storage. Solid-phase microextraction (SPME) GC-MS, SDS and native PAGE gel electrophoresis demonstrated that the overall changes in volatile and protein profiles in Holder pasteurized and freeze-dried DHM was negligible compared to the natural variations in DHM. Freeze-dried DHM samples (moisture < 2.2 %) processed with 2 kGy gamma irradiation did not show any significant lipid oxidation end-products and variation in protein profile. Therefore, freeze-drying followed by in-packaging gamma irradiation could be a safe method for pasteurization, convenient storage and delivery of DHM at ambient temperature. These methods may generate a means to create a reserve stock of DHM for emergencies and humanitarian aid.

Role of milk and honey in the tolerance of lactobacilli to oxidative stress

In the development of functional probiotic food, the carrier matrices should be carefully selected and optimized to ensure the highest levels of probiotic survival in the symbiotic food along storage. Because milk and honey food matrices are rich in antioxidant substances, the aim of the research was to evaluate their effect in protecting lactobacilli from reactive oxygen species (ROS) generated by the addition of hydrogen peroxide. Viability assays were performed with and without the addition of H₂O₂, in three different matrices: 0.9% peptone saline, 5% honey, or 12% reconstituted skim milk. The milk matrix provided protection for the Lacticaseibacillus paracasei DTA83 and Lacticaseibacillus rhamnosus DTA76. However, this protective effect was not observed in the survival of Lactobacillus acidophilus La 5. Honey solution did not maintain the viability of probiotic microorganisms exposed to hydrogen peroxide and, on the contrary, caused a significant reduction in the population of L. rhamnosus DTA76 (p < 0.001). Lower membrane lipid peroxidation due to H₂O₂ exposure was observed in L. acidophilus La 5 and L. rhamnosus DTA76, but this marker showed no relation with viability. It was concluded: (i) lactobacilli from the Lacticaseibacillus genus were the ones that benefited most from the lactic environment; (ii) the absence of the protective effect of honey was possibly due to the presence of Fe²⁺ which reacts with H₂O₂ to produce hydroxyl radicals; and (iii) cell viability did not correlate with membrane lipid peroxidation, and it is not a good marker to evaluate this type of damage in cells of different microorganisms.

Combination of High-Pressure Processing and Freeze-Drying as the Most Effective Techniques in Maintaining Biological Values and Microbiological Safety of Donor Milk

BACKGROUND

Human milk banks have a pivotal role in provide optimal food for those infants who are not fully breastfeed, by allowing human milk from donors to be collected, processed and appropriately distributed. Donor human milk (DHM) is usually preserved by Holder pasteurization, considered to be the gold standard to ensure the microbiology safety and nutritional value of milk. However, as stated by the European Milk Banking Association (EMBA) there is a need to implement the improvement of the operating procedure of human milk banks including preserving and storing techniques.

AIM

The purpose of this study was to assess the effectiveness and safety of the selected new combination of methods for preserving donor human milk in comparison with thermal treatment (Holder pasteurization).

METHODS

We assessed (1) the concentration of bioactive components (insulin, adiponectin, leptin, activity of pancreatic lipase, and hepatocyte growth factor) and (2) microbiological safety in raw and pasteurized, high-pressure processed and lyophilization human breast milk.

RESULTS

The combination of two techniques, high-pressure processing and freeze-drying, showed the best potential for preserving the nutritional value of human milk and were evaluated for microbiological safety. Microbiological safety assessment excluded the possibility of using freeze-drying alone for human milk sample preservation. However, it can be used as a method for long-term storage of milk samples, which have previously been preserved via other processes.

CONCLUSION

The results show that high-pressure treatment is the best method for preservation that ensures microbiological safety and biological activity but subsequent freeze-drying allowed long-term storage without loss of properties.

Stability of the Antimicrobial Capacity of Human Milk Against Cronobacter Sakazakii During Handling

BACKGROUND

Neonatal infections with Cronobacter sakazakii have recently been associated with the consumption of expressed human milk.

STUDY AIMS

(1) To evaluate whether human milk has antimicrobial capacity against C. sakazakii and (2) to determine the stability of its capacity when it is subjected to various treatments.

METHODS

The antimicrobial capacity of human milk against C. sakazakii was evaluated using an observational, cross-sectional, comparative design. Mature human milk samples (N = 29) were subjected to different treatments. After incubation at 37°C for 72 hr, samples were compared with fresh milk on the stability of their antimicrobial capacity. Two-way analysis of variance (ANOVA) was performed.

RESULTS

In fresh milk, counts of C. sakazakii were reduced by 47.26% (SD = 6.74) compared to controls. In treated milk, reductions were: refrigeration at 4°C for 72 hr (M = 33.84, SD = 13.84), freezing at -20°C for 1, 2, and 3 months (M = 40.31, SD = 9.10; M = 35.96, SD = 9.39; M = 26.20, SD = 13.55, respectively), Holder pasteurization (M = 23.56, SD = 15.61), and human milk bank treatment with (M = 14.37, SD = 18.02) and without bovine fortifier (M = 3.70, SD = 23.83). There were significant differences (p < .05) between fresh and treated milk.

CONCLUSIONS

Human milk has antimicrobial capacity against C. sakazakii. However, its capacity is negatively influenced by common preservation and hygienization methods. Milk should be stored refrigerated for a maximum of 72 hr or frozen for a short period of time.

The Revolution of Breast Milk: The Multiple Role of Human Milk Banking between Evidence and Experience-A Narrative Review

The review recalls the importance of breast milk and deepens the theme of human milk banking, a virtuous reality that is expanding all over the world but is still little known. In the last 15 years, modern biological technologies have crystallized the concept of uniqueness and irreproducibility of human milk, by establishing three new principles: first: human milk: a "life-saving" drug; second: human milk: the best food for preterm infants; and third: human milk: the main component of premature infant care. Our experience teaches us that human milk banking plays many roles that need to be known and shared.

Human milk bank and personalized nutrition in the NICU: a narrative review

The number of infants born preterm including extremely premature babies is rising worldwide, particularly in low- and middle-income countries, which challenge neonatologists and milk banks for the provision of the most adequate nutrition for successful infant's growth and development. The benefits of mother's own milk (MOM) have been extensively recognized, but the use of donor milk (DM) is a commonly routine practice in preterm neonates admitted to the NICU. Pasteurized mature milk from milk banks is not the same composition than the mother's colostrum and premature milk, the characteristics of which protect the infant from the risk for necrotizing enterocolitis, late-onset sepsis, and other comorbidities associated with prematurity. The development of a personalized nutrition unit (PNU) allows to obtain DM from mothers who have their infants admitted to the NICU and produce an excess of milk, a practice that matches MOM by gestational age and the stage of lactation, ensuring an adequate composition of DM to target the nutritional requirements of premature infants.Conclusion: This narrative review presents salient data of our current knowledge and concerns regarding milk feeding of preterm infants in the NICU, with special emphasis on personalized DM as a result of establishing a PNU. What is Known: • Donor milk bank is mature or pooled milk from lactating mothers at different stages of lactation. • Milk composition varies by gestational age and stage of lactation. What is New: • Donor milk from mothers delivered prematurely have the most adequate composition for preterm infant feeding. • Personalized nutrition for premature infants with preterm donor milk is feasible.

High-Temperature Short-Time Preserves Human Milk's Bioactive Proteins and Their Function Better Than Pasteurization Techniques With Long Processing Times

Donor human milk is generally processed by holder pasteurization (HoP) at 62. 5°C for 30 min. This temperature-time combination is sufficient for eliminating pathogens in donor milk, but also negatively affects several bioactive milk components. Long heating up times may further affect the bioactive properties of pasteurized milk. High-Temperature-Short-Time (HTST), a treatment with shorter processing times (72°C for 15 sec), was investigated as a suitable alternative to HoP. In addition, pasteurization methods that follow the same temperature regime but with varying heating up times were compared. Human milk samples from four different donors were combined into one pool, which was then used to perform all analyses. The effects of these methods on the levels and functionality of immunoglobulin A, lactoferrin, lysozyme and bile salt-stimulated lipase, were evaluated with LC-MS/MS-based proteomics and activity assays, while the pasteurization efficacy was evaluated with an alkaline phosphatase test. HoP, a treatment with long processing times, times, caused the highest reduction in all proteins studied (reduced by 50-98%). Compounds such as lactoferrin and bile salt-stimulated lipase that are more sensitive to heat treatments were better retained with HTST, but their levels and functionality were still significantly lower than those of untreated donor milk (52 and 81% reduction of lactoferrin and bile salt-stimulated lipase activity, respectively). Our findings showed that a treatment with considerably shorter processing times, such as HTST, may reduce the thermal damage caused to the bioactive proteins compared to HoP, without affecting pasteurization efficacy. Since the vast majority of the donor human milk banks that are currently operating on a global level apply HoP to donor milk, our findings may provide relevant information for the optimization of donor milk processing.

Biological activities of commercial bovine lactoferrin sources

Lactoferrin (Lf) samples from several manufacturers were evaluated in vitro. The purity and protein form of each Lf were examined by SDS-PAGE, Western blot, and proteomics analysis. Assays were conducted to evaluate uptake of Lfs and iron from Lfs by enterocytes as well as Lf bioactivities, including effects on intestinal cell proliferation and differentiation, IL-18 secretion, TGF-β1 transcription, and growth of enteropathogenic Escherichia coli (EPEC). Composition of the Lfs varies; some only contain a major Lf band (∼80 kDa), and some also contain minor forms. All Lfs and iron from the Lfs were absorbed by Caco-2 cells, with various efficiencies. The bioactivities of the Lfs varied considerably, but there was no consistent trend. All Lfs promoted intestinal cell proliferation, secretion of IL-18, and transcription of TGF-β1. Some Lfs exhibited pro-differentiation effects on Caco-2 cells. Effects of pasteurization (62.5 °C for 30 min, 72 °C for 15 s, or 121 °C for 5 min) on integrity, uptake, and bioactivities were examined using Dicofarm, Tatua, and native bovine Lfs. Results show that pasteurization did not affect protein integrity, but variously affected uptake of Lf and its effects on intestinal proliferation, differentiation, and EPEC growth. To choose a Lf source for a clinical trial, assessment of bioactivities is recommended.

Innovative Techniques of Processing Human Milk to Preserve Key Components

Human milk not only contains all nutritional elements that an infant requires, but is also the source of components whose regulatory role was confirmed by demonstrating health-related deficiencies in formula-fed children. A human milk diet is especially important for premature babies in the neonatal intensive care unit (NICU). In cases where breastfeeding is not possible and the mother's own milk is insufficient in volume, the most preferred food is pasteurized donor milk. The number of human milk banks has increased recently but their technical infrastructure is continuously developing. Heat treatment at a low temperature and long time, also known as holder pasteurization (62.5 °C, 30 min), is the most widespread method of human milk processing, whose effects on the quality of donor milk is well documented. Holder pasteurization destroys vegetative forms of bacteria and most viruses including human immunodeficiency virus (HIV) herpes and cytomegalovirus (CMV). The macronutrients remain relatively intact but various beneficial components are destroyed completely or compromised. Enzymes and immune cells are the most heat sensitive elements. The bactericidal capacity of heat-pasteurized milk is lower than that of untreated milk. The aim of the study was for a comprehensive comparison of currently tested methods of improving the preservation stage. Innovative techniques of milk processing should minimize the risk of milk-borne infections and preserve the bioactivity of this complex biological fluid better than the holder method. In the present paper, the most promising thermal pasteurization condition (72 °C-75 °C,) and a few non-thermal processes were discussed (high pressure processing, microwave irradiation). This narrative review presents an overview of methods of human milk preservation that have been explored to improve the safety and quality of donor milk.

High Hydrostatic Pressure Processing Better Preserves the Nutrient and Bioactive Compound Composition of Human Donor Milk

BACKGROUND

When mother's milk is insufficient, pasteurized human donor milk (DM) is the recommended supplement for hospitalized very-low-birth-weight infants. The current method of pasteurization (Holder, 62.5°C, 30 min) negatively affects heat-sensitive nutrients and bioactive proteins.

OBJECTIVES

Objectives of this study were to compare changes in DM composition after thermal pasteurization (Holder and flash-heating) and nonthermal methods [UV-C irradiation and high hydrostatic pressure (HHP)]. We hypothesized that nonthermal techniques would result in fewer changes to composition.

METHODS

Holder, flash-heating (brought to boil), UV-C irradiation (250 nm, 25 min), and HHP (500 MPa, 8 min) were studied. Pools of milk from 17 women known to contain bacteria at >5 × 107 colony forming units (CFU)/L were collected from the Rogers Hixon Ontario Human Milk Bank and underwent each pasteurization technique. Macronutrients, heat-sensitive micronutrients (vitamin C, folate), and bioactive components [bile-salt-stimulated lipase (BSSL), lysozyme, lactoferrin] were measured in raw and pools of pasteurized milk. Milk was cultured to determine how well each technique produced a culture negative result (detection limit <1 × 103 CFU/L).

RESULTS

Folate was reduced by 24-27% after Holder, flash-heating, and UV-C (P < 0.05); no reduction was observed after HHP. All pasteurization methods reduced vitamin C (60-75%, P < 0.001). BSSL was abolished after Holder and flash-heating (P < 0.001), reduced after UV-C (48%, P < 0.001), but unaffected by HHP. Lysozyme activity was reduced after flash-heating (44%) and UV-C (74%, P < 0.004) but unaffected by Holder or HHP. Lactoferrin was reduced by all methods (P < 0.02) but most severely by flash-heating (74%) and least severely by HHP (25%). Holder and UV-C reduced lactoferrin by ∼48%. All pasteurization methods reduced the number of culture positive DM samples (P < 0.001).

CONCLUSIONS

HHP better preserves human milk composition than Holder pasteurization. Future research on the feasibility of HHP for pasteurizing human milk is warranted because its implementation may improve the nutritional status and health of DM-fed infants.

Oxidative Stress and Necrotizing Enterocolitis: Pathogenetic Mechanisms, Opportunities for Intervention, and Role of Human Milk

This review will examine the role of oxidative stress (OS) in the pathogenesis of necrotizing enterocolitis (NEC) and explore potential preventive and therapeutic antioxidant strategies. Preterm infants are particularly exposed to OS as a result of several perinatal stimuli and constitutive defective antioxidant defenses. For this reason, OS damage represents a contributing factor to several complications of prematurity, including necrotizing enterocolitis (NEC). Being NEC a multifactorial disease, OS may act as downstream component of the pathogenetic cascade. To counteract OS in preterm infants with NEC, several antioxidant strategies have been proposed and different antioxidant compounds have been experimented. It is well known that human milk (HM) is an important source of antioxidants. At the same time, the role of an exclusive HM diet is well recognized in the prevention of NEC. However, donor HM (DHM) processing may impair antioxidant properties. As DHM is becoming a common nutritional intervention for high risk PI, the antioxidant status of preterm and DHM and potential ways to preserve its antioxidant capacity may merit further investigation.