title: Impact of Freezing Time on Dornic Acidity in Three Types of Milk: Raw Donor Milk, Mother's Own Milk, and Pasteurized Donor Milk.
abstract: OBJECTIVE
  Although under certain circumstances it is necessary to express milk, there are not many recommendations about the ideal storage conditions for human milk. The objectives of this study were to analyze the effects on Dornic acidity of frozen storage at -20 °C in three types of milk: raw donor milk, mother's own raw milk, and pasteurized donor milk.
  
  
  METHODS
  Forty-three samples of raw donor milk, 40 samples of pasteurized donor milk, and 16 samples of mother's own milk were analyzed. Dornic acidity was measured at time 0, before freezing. The remaining aliquots were frozen and analyzed after 1, 2, 3, and 4 weeks and after 2 and 3 months.
  
  
  RESULTS
  In raw donor milk, the median acidity at the start was 3 °D (interquartile range [IQR] 2-3 °D); after 3 months, it was 5 °D (IQR 3-7 °D), with a significant increase in acidity after the second week. In mother's own milk, the mean acidity at the start was 3 °D (IQR 2-4 °D) and 7 °D (IQR 4-8 °D) at 3 months. The increase was significant after the third week. In pasteurized donor milk, the mean acidity was 3 °D (IQR 2-3 °D) at the start and 2 °D (IQR 2-3 °D) at the end. When comparing the three types of milk, there were significant differences from the first week between the two types of raw milk and the pasteurized milk (p < 0.01), but not between the two raw milks (p = 0.77).
  
  
  CONCLUSIONS
  Dornic acidity in unpasteurized milk significantly increases with the duration of freezing, probably due to the action of lipases, which is lost with pasteurization. It would be advisable to reduce the length of freezing time for unpasteurized milk.
authors.affiliation: Department of Neonatology, Hospital 12 de Octubre , Madrid, Spain .
authors.forename: Sara
authors.initials: S
authors.lastname: Vázquez-Román
authors.affiliation: Department of Neonatology, Hospital 12 de Octubre , Madrid, Spain .
authors.forename: Diana
authors.initials: D
authors.lastname: Escuder-Vieco
authors.affiliation: Department of Neonatology, Hospital 12 de Octubre , Madrid, Spain .
authors.forename: Nadia Raquel
authors.initials: NR
authors.lastname: García-Lara
authors.affiliation: Department of Neonatology, Hospital 12 de Octubre , Madrid, Spain .
authors.forename: Clara
authors.initials: C
authors.lastname: Alonso-Díaz
authors.affiliation: Department of Neonatology, Hospital 12 de Octubre , Madrid, Spain .
authors.forename: David
authors.initials: D
authors.lastname: Lora
authors.affiliation: Department of Neonatology, Hospital 12 de Octubre , Madrid, Spain .
authors.forename: María Dolores
authors.initials: MD
authors.lastname: Martín-Pelegrina
authors.affiliation: Department of Neonatology, Hospital 12 de Octubre , Madrid, Spain .
authors.forename: Carmen Rosa
authors.initials: CR
authors.lastname: Pallás-Alonso
mesh_terms: D001420:Bacteria, Aerobic / Q000254:growth & development*; D015169:Colony Count, Microbial; D005260:Female; D005519:Food Preservation; D005615:Freezing; D006801:Humans; D019344:Lactic Acid / Q000378:metabolism*; D017784:Milk Banks; D008894:Milk Proteins / Q000378:metabolism; D008895:Milk, Human / Q000737:chemistry* / Q000382:microbiology; D009035:Mothers; D061352:Pasteurization; D013997:Time Factors
chemical_list: D008894:Milk Proteins; D019344:Lactic Acid