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.

Short-chain fatty acids levels in human milk are not affected by holder pasteurization and high hydrostatic pressure processing.

Sterilized donor milk (DM) is frequently used for feeding preterm infants. To date, the effect of different modes of DM sterilization on short-chain fatty acids (SCFAs) remains unknown. We aimed to quantify SCFAs in DM samples after two types of milk sterilization: the Holder pasteurization (HoP) and a high hydrostatic pressure (HP) processing. Eight pooled DM samples were sterilized by HoP (62.5°C for 30 min) or processed by HP (350 MPa at 38°C). Raw DM was used as control. Six SCFAs were quantified by gas chromatography/mass spectrometry. Compared to raw milk, both HoP and HP treatment did not significantly modulate the concentration of acetate, butyrate, propionate and isovalerate in DM. Valerate and isobutyrate were undetectable in DM samples. In conclusion, both HoP and HP processing preserved milk SCFAs at their initial levels in raw human milk.

The Sterilization of Human Milk by Holder Pasteurization or by High Hydrostatic Pressure Processing Leads to Differential Intestinal Effects in Mice.

BACKGROUND: Human milk banks (HMBs) provide sterilized donor milk (DM) for the feeding of preterm infants. Most HMBs use the standard method of Holder pasteurization (HoP) performed by heating DM at 62.5 °C for 30 min. High hydrostatic pressure (HHP) processing has been proposed as an alternative to HoP. This study aims to evaluate intestinal barrier integrity and microbiota composition in adult mice subjected to a chronic oral administration of HoP- or HHP-DM. METHODS: Mice were treated by daily gavages with HoP- or HHP-DM over seven days. Intestinal barrier integrity was assessed through in vivo 4 kDa FITC-dextran permeability assay and mRNA expression of several tight junctions and mucins in ileum and colon. Cecal short chain fatty acids (SCFAs) and microbiota were analyzed. RESULTS: HHP-DM mice displayed decreased intestinal permeability to FITC-dextran and increased ileal mRNA expression levels of two tight junctions (Ocln and Cdh1) and Muc2. In the colon, mRNA expression levels of two tight junctions (Cdh1 and Tjp1) and of two mucins (Muc2 and Muc4) were decreased in HHP-DM mice. Cecal SCFAs and microbiota were not different between groups. CONCLUSIONS: HHP processing of DM reinforces intestinal barrier integrity in vivo without affecting gut microbiota and SCFAs production. This study reinforces previous findings showing that DM sterilization through HHP might be beneficial for the intestinal maturation of preterm infants compared with the use of HoP for the treatment of DM.

Effect of High Hydrostatic Pressure Processing and Holder Pasteurization of Human Milk on Inactivation of Human Coronavirus 229E and Hepatitis E Virus.

In preterm infants, sterilized donor milk (DM) is frequently used for feeding when breast milk is lacking. Most human milk banks use the Holder pasteurization method (HoP) to ensure the microbiological safety of DM. However, this method degrades many bioactive factors and hormones. Recently, high hydrostatic pressure (HHP) processing, which preserves bioactive factors in human milk, has been proposed as an alternative method to ensure the safety of DM. Although HHP treatment has been shown to be effective for viral inactivation, the effect of HHP on viruses that may be present in the complex nutritional matrix of human milk has not yet been defined. In the present study, we compared the efficacy of two HHP protocols (4 cycles at 350 MPa at 38 °C designated as 4xHP350 treatment, and 1 cycle at 600 MPa at 20 °C designated as 1xHP600 treatment) with the HoP method on artificially virus-infected DM. For this purpose, we used human coronavirus 229E (HCoV-229E) and hepatitis E virus (HEV) as surrogate models for enveloped and non-enveloped viruses. Our results showed that HCoV-229E is inactivated by HHP and HoP treatment. In particular, the 4xHP350 protocol is highly effective in inactivating HCoV-229E. However, our results demonstrated a matrix effect of human milk on HCoV-229E inactivation. Furthermore, we demonstrated that HEV is stable to moderate pressure HHP treatment, but the milk matrix does not protect it from inactivation by the high-pressure HHP treatment of 600 MPa. Importantly, the complex nutritional matrix of human milk protects HEV from inactivation by HoP treatment. In conclusion, we demonstrated that HHP and HoP treatments do not lead to complete inactivation of both surrogate virus models, indicating that these treatments cannot guarantee total viral safety of donor milk.

The metabolome of human milk is altered differentially by Holder pasteurization and high hydrostatic pressure processing.

The milk metabolome is composed of hundreds of molecules that can impact infant development. In preterm infants, sterilized donor milk (DM) is frequently used for their feeding. We aimed to identify differences in the metabolome of DM after two types of milk sterilization: the Holder pasteurization (HoP) and a high hydrostatic pressure (HP) processing. DM samples were sterilized by HoP (62.5°C for 30 min) or processed by HP (350 MPa at 38°C). 595 milk metabolites were analyzed using an untargeted metabolomic analysis. Both treatments differentially altered several classes of compounds. The major changes noted included decreased levels of free fatty acids, phospholipid metabolites, and sphingomyelins. Decreases were more strongly noted in HP samples rather than in HoP ones. Both HoP and HP treatments increased the levels of ceramides and nucleotide compounds. The sterilization of human milk altered its metabolome especially for lipids.

In Vivo Assessment of Antioxidant Potential of Human Milk Treated by Holder Pasteurization or High Hydrostatic Pressure Processing: A Preliminary Study on Intestinal and Hepatic Markers in Adult Mice.

Preterm infants are highly susceptible to oxidative stress due to an imbalance between endogenous oxidant and antioxidant systems. In addition, these newborns are frequently fed with donor milk (DM) treated by Holder pasteurization (HoP) at 62.5 °C for 30 min, which is known to alter numerous heat-sensitive factors, including some antioxidants. High hydrostatic pressure (HHP) processing was recently proposed as an innovative method for the treatment of DM. The present study aimed to measure the redox balance of HoP- and HHP-DM and to study, in vivo, the effects of HoP- and HHP-DM on the gut and liver. H2O2, vitamin A and vitamin E (α- and γ-tocopherols) concentrations, as well as the total antioxidant capacity (TAC), were measured in raw-, HoP- and HHP-DM. The gene expression level of antioxidant systems and inflammatory response were quantified in the ileum and liver of adult mice after 7 days of oral administration of HoP- or HHP-DM. HoP reduced the γ-tocopherol level, whereas HHP treatment preserved all vitamins close to the raw milk level. The milk H2O2 content was reduced by HHP but not by HoP. The total antioxidant capacity of DM was reduced after HHP processing measured by PAOT-Liquid® technology but was unaffected after measurement by ORAC assay. In mice, HHP-DM administration induced a stimulation of antioxidant defenses and reduced some inflammatory markers in both the ileum and liver compared to HoP-DM treatment. Our preliminary study suggests that the HHP processing of DM may better protect preterm infants from gut and liver pathologies compared to HoP, which is currently used in most human milk banks.

High Hydrostatic Pressure Processing of Human Milk Increases Apelin and GLP-1 Contents to Modulate Gut Contraction and Glucose Metabolism in Mice Compared to Holder Pasteurization.

BACKGROUND: High hydrostatic pressure (HHP) processing is a non-thermal method proposed as an alternative to Holder pasteurization (HoP) for the sterilization of human breast milk (BM). HHP preserves numerous milk bioactive factors that are degraded by HoP, but no data are available for milk apelin and glucagon-like peptide 1 (GLP-1), two hormones implicated in the control of glucose metabolism directly and via the gut-brain axis. This study aims to determine the effects of HoP and HHP processing on apelin and GLP-1 concentrations in BM and to test the effect of oral treatments with HoP- and HHP-BM on intestinal contractions and glucose metabolism in adult mice. METHODS: Mice were treated by daily oral gavages with HoP- or HHP-BM during one week before intestinal contractions, and glucose tolerance was assessed. mRNA expression of enteric neuronal enzymes known to control intestinal contraction was measured. RESULTS: HoP-BM displayed a reduced concentration of apelin and GLP-1, whereas HHP processing preserved these hormones close to their initial levels in raw milk. Chronic HHP-BM administration to mice increased ileal mRNA nNos expression level leading to a decrease in gut contraction associated with improved glucose tolerance. CONCLUSION: In comparison to HoP, HPP processing of BM preserves both apelin and GLP-1 and improves glucose tolerance by acting on gut contractions. This study reinforces previous findings demonstrating that HHP processing provides BM with a higher biological value than BM treated by HoP.

Metabolic hormones in human breast milk are preserved by high hydrostatic pressure processing but reduced by Holder pasteurization.

In human milk banks (HMBs), donor milk (DM) is commonly sterilized by Holder pasteurization (HoP). High hydrostatic pressure (HHP) processing is an innovative, alternative method for DM sterilization. We evaluated the impact of HHP processing on the concentration of seven metabolic milk hormones. Eight samples of raw DM were aliquoted. One aliquot was sterilized by HoP (62 °C for 30 min), and another was processed by HHP (350 MPa at 38 °C). Compared with raw DM, HoP milk displayed reduced concentrations of insulin, nesfatin-1, cortisol, leptin, apelin and GLP-1, though adiponectin levels were unchanged. HHP processing maintained the levels of insulin, nesfatin-1, cortisol and leptin at their initial levels in raw DM, reduced apelin and adiponectin levels, but increased GLP-1 level. Sterilization of DM by HHP thus preserves the main metabolic hormones in human milk, underlining the interest of this method for use in HMBs.

Effects of high-pressure treatment on the muscle structure of salmon (Salmo salar).

High pressure (HP) is a non-thermal treatment that is generally used to reduce the microbiological contamination of food products, such as Atlantic salmon (Salmo salar). However, HP is known to alter the stability of proteins and can therefore affect the quality of salmon flesh. In this study, the effects of HP treatment for 5 min at 200, 400 and 600 MPa on the structure of Atlantic salmon were investigated. Transversal histological sections revealed a decrease in the fibre size from 200 MPa associated with an expansion of the extracellular spaces. Connective tissue was found to be modified from 400 MPa, resulting in an increase in its surface area. Fourier transform infrared (FT-IR) microspectroscopy revealed a reduction in the α-helix content and an increase in the aggregated ß-sheet structure content with increasing pressure, reflecting a change in the secondary structure of proteins from 200 MPa.

High hydrostatic pressure processing of human milk preserves milk oligosaccharides and avoids formation of Maillard reaction products.

BACKGROUND & AIMS: High hydrostatic pressure (HHP) processing is a non-thermal method proposed as an alternative to Holder pasteurization (HoP) for the treatment of human milk. HHP preserves numerous milk bioactive components that are degraded by HoP, but no data are available for milk oligosaccharides (HMOs) or the formation of Maillard reaction products, which may be deleterious for preterm newborns. METHODS: We evaluated the impact of HHP processing of human milk on 22 HMOs measured by liquid chromatography with fluorescence detection and on furosine, lactuloselysine, carboxymethyllysine (CML) and carboxyethyllysine (CEL) measured by liquid chromatography with tandem mass spectrometric detection (LC-MS/MS), four established indicators of the Maillard reaction. Human raw milk was sterilized by HoP (62.5 °C for 30 min) or processed by HHP (350 MPa at 38 °C). RESULTS: Neither HHP nor HoP processing affected the concentration of HMOs, but HoP significantly increased furosine, lactuloselysine, CML and CEL levels in milk. CONCLUSIONS: Our findings demonstrate that HPP treatment preserves HMOs and avoids formation of Maillard reaction products. Our study confirms and extends previous findings that HHP treatment of human milk provides safe milk, with fewer detrimental effects on the biochemically active milk components than HoP.

High-pressure processing of meat: Molecular impacts and industrial applications.

High-pressure processing (HPP) has been the most adopted nonthermal processing technology in the food industry with a current ever-growing implementation, and meat products represent about a quarter of the HPP foods. The intensive research conducted in the last decades has described the molecular impacts of HPP on microorganisms and endogenous meat components such as structural proteins, enzyme activities, myoglobin and meat color chemistry, and lipids, resulting in the characterization of the mechanisms responsible for most of the texture, color, and oxidative changes observed when meat is submitted to HPP. These molecular mechanisms with major effect on the safety and quality of muscle foods are comprehensively reviewed. The understanding of the high pressure-induced molecular impacts has permitted a directed use of the HPP technology, and nowadays, HPP is applied as a cold pasteurization method to inactive vegetative spoilage and pathogenic microorganisms in ready-to-eat cold cuts and to extend shelf life, allowing the reduction of food waste and the gain of market boundaries in a globalized economy. Yet, other applications of HPP have been explored in detail, namely, its use for meat tenderization and for structure formation in the manufacturing of processed meats, though these two practices have scarcely been taken up by industry. This review condenses the most pertinent-related knowledge that can unlock the utilization of these two mainstream transformation processes of meat and facilitate the development of healthier clean label processed meats and a rapid method for achieving sous vide tenderness. Finally, scientific and technological challenges still to be overcome are discussed in order to leverage the development of innovative applications using HPP technology for the future meat industry.

Monitoring oxidation during the storage of pressure-treated cooked ham and impact on technological attributes.

High-pressure processing is a post-processing preservation method commonly used on meat products. However, it can affect the structural properties and the physico-chemical properties of the meat. The aim of this study was to compare the physical properties, lipid and protein oxidation of control and treated (500 MPa, 20 °C, 5 min) cooked ham during subsequent storage (21 days at 4 °C). High pressure processing induced increase of hardness and syneresis after 7 days of storage. The redness (a*) was slightly affected by the high pressure treatment but not the lightness (L*) and the yellowness (b*). However, the fluctuation of color was not clearly visible. Evaluation of primary (conjugated dienes) and secondary (malondialdehyde MDA and thiobarbituric reactive substances TBA-RS) lipid oxidation products showed that pressure increases oxidation of lipids. Whereas, high pressure processing had no immediate effect on MDA and TBA-RS content, higher amount compared to control were observed during the refrigerated storage. This lipid oxidation could be due to the release of prooxidant iron from hemoproteins after the high pressure treatment. Finally, the determination of free and accessible thiols showed that the high pressure treatment leads to a protein oxidation.

Salt Intake from Processed Meat Products: Benefits, Risks and Evolving Practices.

Currently, there is major consumer concern about dietary salt intake worldwide. However, even with the development of contemporary preservation practices, sodium chloride is still essential in processed meat products. Despite a long history of use, salt is now seriously controversial in food due to health concerns that are mostly related to high blood pressure and cardiovascular risks. Changes in meat processing methods have reduced those potential risks, but different perceptions continue to shape how consumers and society view dietary salt. The current consumer demand for additive-free food, such as the clean-label movement, has renewed consumer willingness for naturalness in food products.

Modifications of protein-related compounds of beef minced meat treated by high pressure.

In this study, we evaluated the modifications of the protein-related compounds of minced beef treated with high pressure, including refrigeration after treatment. The free amino acid content, protein carbonyls and free thiol groups were assessed. High pressure up to 200 MPa had a significant effect. Above 300 MPa, irreversible structural changes occurred, with an increase in the protein oxidation products and a modification of the amounts of amino acids after 14 days of storage. Protein carbonyls and the free thiols were correlated with the free amino acids. These results showed that protein modifications under pressure result from both conformational and chemical changes, possibly associated with lipid changes under high-pressure treatment.

Influence of xanthan gum on the structural characteristics of myofibrillar proteins treated by high pressure.

The effects of xanthan gum on the structural modifications of myofibrillar proteins (0.3 M NaCl, pH 6) induced by high pressure (200, 400, and 600 MPa, 6 min) were investigated. The changes in the secondary and tertiary structures of myofibrillar proteins were analyzed by circular dichroism. The protein denaturation was also evaluated by differential scanning calorimetry. Likewise, the protein surface hydrophobicity and the solubility of myofibrillar proteins were measured. High pressure (600 MPa) induced the loss of α-helix structures and an increase of ß-sheet structures. However, the presence of xanthan gum hindered the former mechanism of protein denaturation by high pressure. In fact, changes in the secondary (600 MPa) and the tertiary structure fingerprint of high-pressure-treated myofibrillar proteins (400 to 600 MPa) were observed in the presence of xanthan gum. These modifications were confirmed by the thermal analysis, the thermal transitions of high-pressure (400 to 600 MPa)-treated myofibrillar proteins were modified in systems containing xanthan gum. As consequence, the high-pressure-treated myofibrillar proteins with xanthan gum showed increased solubility from 400 MPa, in contrast to high-pressure treatment (600 MPa) without xanthan gum. Moreover, the surface hydrophobicity of high-pressure-treated myofibrillar proteins was enhanced in the presence of xanthan gum. These effects could be due to the unfolding of myofibrillar proteins at high-pressure levels, which exposed sites that most likely interacted with the anionic polysaccharide. This study suggests that the role of food additives could be considered for the development of meat products produced by high-pressure processing.

Interlocking of ß-carotene in beta-lactoglobulin aggregates produced under high pressure.

Vitamin A deficiency is one of the major causes of mortality and morbidity in the developing World. This deficiency can be prevented by alimentary or pharmaceutical supplementation. However, both vitamin A oxidation and isomerization should be prevented, as these phenomenons result in loss of nutritional efficacy. The aim of this study was to investigate the effect of a food protein matrix, ß-lactoglobulin (ß-Lg) aggregates produced by high pressure (HP), on the stabilization of ß-carotene during storage and gastro-duodenal digestion and therefore on its bioavailability. In vitro gastro-duodenal digestion of ß-Lg aggregates entrapping ß-carotene showed that up to 12% and 33% of total ß-carotene was released after peptic and pancreatic digestion, respectively. Overall, our study showed that ß-Lg aggregates are efficient for caging and stabilization of ß-carotene during storage and digestion. Hence, it may be an interesting approach for the protection and the delivery of vitamin A.

Effect of high pressure and salt on pork meat quality and microstructure.

The interaction of salt (0%, 1.5%, and 3% in the final product) and a high-pressure treatment (500 MPa, 20 °C, 6 min) was investigated using pork biceps femoris muscle. The Warner-Bratzler shear force and the water holding capacity (WHC) were assessed and linked to the microstructure evaluation by environmental scanning electronic microscopy (ESEM). Pressure-treated and cooked samples showed a high Warner-Bratzler shear force with a low WHC compared to control cooked samples. These negative effects could be linked to the general shrinkage of the structure as observed by ESEM. The addition of 1.5% salt was sufficient to improve the technological properties of the high-pressure-treated samples and to counteract the negative effect of high pressure on texture and WHC. This phenomenon could be linked to the breakdown in structure observed by ESEM. This study states that it is possible to produce pressurized pork products of good eating quality by adding limited salt levels.

Dynamic proteome changes in Campylobacter jejuni 81-176 after high pressure shock and subsequent recovery.

Campylobacter jejuni is one of the most intriguing human foodborne bacterial pathogen. Its survival throughout the food processing chain and its pathogenesis mechanisms in humans remain enigmatic. Living in the animal guts and particularly in avian intestine as a commensal bacterium, this microorganism is frequently isolated from meat products. Ultra high pressure (HP) is a promising alternative to thermal technology for microbial safety of foodstuffs with less organoleptic and nutritional alterations. Its application could be extended to meat products potentially contaminated by C. jejuni. To evaluate the response of Campylobacter to this technological stress and subsequent recovery at a molecular level, a dynamic 2-DE-based proteomic approach has been implemented. After cultivation, C. jejuni cells were conditioned in a high-pressure chamber and transferred to fresh medium for recovery. The protein abundance dynamics at the proteome scale were analyzed by 2-DE during the cellular process of cell injury and recovery. Monitoring protein abundance through time unraveled the basic metabolisms involved in this cellular process. The significance of the proteome evolution modulated by HP and subsequent recovery is discussed in the context of a specific cellular response to stress and recovery of C. jejuni with 69 spots showing significant changes through time.

Proteins involved in Campylobacter jejuni 81-176 recovery after high-pressure treatment.

Campylobacteriosis has been recognized as the major bacterial food-borne infection worldwide. Campylobacter, especially C. jejuni, contaminate mainly poultry meat. Although more sensitive than other food-borne pathogens to many stresses, C. jejuni can survive food processing and go on to reach its final reservoir (the human gut). Genomic analyses of this organism indicate a lack of genes described in other gram-negative bacteria to overcome stresses. The high-pressure recovery response of C. jejuni 81-176 was analyzed from two-dimensional electrophoretic profiles of the cytoplasmic proteome. The main cellular mechanisms controlling the down- and upregulated proteins are discussed.