title: Human milk bactericidal properties: effect of lyophilization and relation to maternal factors and milk components.
abstract: OBJECTIVE
  Lyophilization appears to be a viable method for storing human milk, assuring no microbiological contamination and preserving its health benefits and antibacterial properties. The aim of the study is to evaluate and compare the effects of different storage methods (lyophilization and freezing at -20°C and -80°C) and maternal factors (gestational length or time postpartum) upon the microbiological contents and bactericidal activity of human milk. The possible relation between bactericidal activity and the content of certain nutrients and functional components is also investigated.
  
  
  METHODS
  Microbiological content, bactericidal activity, sialic acid, and ganglioside contents, as well as protein, fat, and lactose concentrations were assessed in 125 human milk samples from 65 healthy donors in the Human Milk Bank of La Fe (Valencia, Spain).
  
  
  RESULTS
  Lyophilization and storage at -80°C significantly reduced the content of mesophilic aerobic microorganisms and Staphylococcus epidermidis when compared with storage at -20°C. Bactericidal activity was not significantly modified by lyophilization when compared with freezing at either -20°C or -80°C. Bactericidal activity was not correlated with fat, protein, or lactose content, but was significantly correlated to ganglioside content. The bactericidal activity was significantly greater (P < 0.05) in mature milk and in milk from women with term delivery than in milk from early lactation (days 1-7 postpartum) and milk from women with preterm delivery, respectively.
  
  
  CONCLUSIONS
  Lyophilization and storage at -80°C of human milk yields similar results and are superior to storage at -20C with regard to microbial and bactericidal capacities, being a feasible alternative for human milk banks.
authors.affiliation: *Biomedical Sciences Research Institute, University Cardenal Herrera-CEU †Division of Neonatology, University and Polytechnic Hospital La Fe ‡Department of Animal Production and Food Science & Technology, Faculty of Veterinary, University Cardenal Herrera-CEU §Pharmacy Department, Biomedical Sciences Research Institute, University Cardenal Herrera-CEU, Valencia, Spain.
authors.forename: Jaime
authors.initials: J
authors.lastname: Salcedo
authors.forename: Maria
authors.initials: M
authors.lastname: Gormaz
authors.forename: Maria C
authors.initials: MC
authors.lastname: López-Mendoza
authors.forename: Elisabetta
authors.initials: E
authors.lastname: Nogarotto
authors.forename: Dolores
authors.initials: D
authors.lastname: Silvestre
mesh_terms: D000900:Anti-Bacterial Agents / Q000032:analysis*; D003080:Cold Temperature; D005260:Female; D061353:Food Storage / Q000379:methods*; D005612:Freeze Drying; D005615:Freezing; D005732:Gangliosides / Q000032:analysis*; D005865:Gestational Age; D006801:Humans; D007231:Infant, Newborn; D007774:Lactation; D017784:Milk Banks; D008895:Milk, Human / Q000737:chemistry / Q000382:microbiology*; D049590:Postpartum Period; D047928:Premature Birth; D012034:Refrigeration; D013030:Spain; D013212:Staphylococcus epidermidis; D047929:Term Birth
chemical_list: D000900:Anti-Bacterial Agents; D005732:Gangliosides