title: Major losses of fat, carbohydrates and energy content of preterm human milk frozen at -80°C.
abstract: OBJECTIVE
  Long-term storage of human milk (HM) requires freezing at low temperatures, the consequences of which upon macronutrients are unclear. To test the null hypothesis that HM freezing and storage for a range of 1 to 10 weeks at -80 °C does not affect HM fat, protein, lactose and energy contents.
  
  
  METHODS
  Samples of HM were obtained from 20 mothers (60 samples) of preterm infants (25 to 35 weeks gestation), who routinely expressed their milk, every 3 h, using an electric pump, from the second to the seventh week after delivery. All samples were frozen at -80 °C for 8 to 83 days (43.8 days average). After thawing and homogenization, energy and macronutrient contents were measured using an HM analyzer.
  
  
  RESULTS
  Fat, carbohydrates and energy contents were significantly lower in thawed HM than in fresh HM (fat, fresh vs thawed: 3.72±1.17 vs 3.36±1.19 g/100 ml, P<0.001; carbohydrates, fresh vs thawed: 5.86±0.71 vs 4.09±0.96 g/100 ml, P<0.001; energy, fresh vs thawed: 64.93±12.97 vs 56.63±16.82 kcal/100 ml, P<0.0001), whereas protein content remained unchanged (protein, fresh vs thawed: 1.14±0.36 vs 1.15±0.37 g/100 ml, P=0.7). The decline in carbohydrates content but not in fat and energy correlated significantly with freezing duration.
  
  
  CONCLUSIONS
  Freezing at -80 °C significantly decreases the energy content of HM, both from fat and carbohydrates. Since quantitatively the decrease in macronutrients was much higher than that published for HM storage at -20 °C, our results do not support freezing HM at -80 °C as the gold standard for long-term storage. We suggest that caloric intake calculations in preterm infants cannot be established based upon fresh HM data.
authors: Department of Neonatology, Tel Aviv Medical Center, Tel Aviv, Israel.
authors: H M
authors: HM
authors: Lev
authors: Department of Neonatology, Tel Aviv Medical Center, Tel Aviv, Israel.
authors: A
authors: A
authors: Ovental
authors: 1] Department of Neonatology, Tel Aviv Medical Center, Tel Aviv, Israel [2] Sackler Faculty of Medicine, Tel Aviv University, Tel Aviv, Israel.
authors: D
authors: D
authors: Mandel
authors: 1] Department of Pediatrics, Tel Aviv Medical Center, Tel Aviv, Israel [2] Sackler Faculty of Medicine, Tel Aviv University, Tel Aviv, Israel.
authors: F B
authors: FB
authors: Mimouni
authors: 1] Department of Neonatology, Tel Aviv Medical Center, Tel Aviv, Israel [2] Sackler Faculty of Medicine, Tel Aviv University, Tel Aviv, Israel.
authors: R
authors: R
authors: Marom
authors: 1] Department of Pediatrics, Tel Aviv Medical Center, Tel Aviv, Israel [2] Sackler Faculty of Medicine, Tel Aviv University, Tel Aviv, Israel.
authors: R
authors: R
authors: Lubetzky
mesh_terms: D002241:Carbohydrates / Q000032:analysis*; D005260:Female; D005615:Freezing; D006801:Humans; D007231:Infant, Newborn; D008055:Lipids / Q000032:analysis*; D008895:Milk, Human / Q000737:chemistry*
chemical_list: D002241:Carbohydrates; D008055:Lipids