Effect of Holder Pasteurization and Retort Processing on Bioactive Components and Nutritional Content of Human Milk
Authors: Lima Hope Katherine , Wagner‐Gillespie Montana , Hubble Courtney , Vogel Kenneth , Perrin Maryanne , Fogleman April Danielle 
Published: November 2023

Historically, donor human milk (DHM) available in the hospital setting has been processed using Holder pasteurization (62.5°C for 30 minutes). Recent changes in the landscape of DHM have introduced new human milk products processed using retort processing (121°C for 5 minutes), also referred to as commercial sterilization. There is extensive research available outlining the effect of Holder pasteurization on nutritional and bioactive components of human milk. Conversely, research reviewing the effect of retort processing on human milk is scarce. In this study, we pooled milk samples from 60 mothers; 36 samples were taken from this pool and 12 samples were kept raw (RAW), 12 samples were Holder pasteurized (HP), and 12 samples were retort processed (RP). Samples were analyzed for total protein, percent fat and solids, total and available lysine, total aerobic bacteria, coliform, Bacillus cereus, secretory immunoglobulin A (sIgA) activity, and lysozyme activity, using the RAW as the control. Percent fat and percent solids were unaffected by processing (p > 0.05). Total protein was statistically greater in RP when compared to RAW (p < 0.0001), but values between groups may not be clinically significant (1.51, 1.48, and 1.58 mg/mL, RAW, HP, and RP respectively). Total lysine analysis revealed increasing destruction of lysine with increasing treatment temperature (85.5, 76.8, and 68.3 mg/mL, for RAW, HP, and RP, respectively). Total lysine in RP was significantly less than RAW (p = 0.0006), and while HP was not statistically less than RAW, there was a trend towards significance (p = 0.09). Total lysine in HP was not statistically different from RP, though there is a trend towards significance (p = 0.08). Despite increasing destruction with increasing treatment temperature, total available lysine did not differ between groups (p = 0.31; average 24.7, 28.2, and 22.8 mg/mL for RAW, HP, and RP, respectively). HP eliminated all bacteria except Bacillus cereus, while RP eliminated all bacteria. Average sIgA activity was 1.04, 0.90, and 0.11 mg/mL for RAW, HP, and RP, respectively. Both HP and RP had significantly less sIgA activity than RAW (p < 0.0001), and RP had significantly less activity than HP (p < 0.0001). Average lysozyme activity was 7947, 5240, and 0 units/mL for RAW, HP, and RP, respectively. Lysozyme activity had similar statistical comparisons as sIgA activity, with HP and RP having significantly less lysozyme activity than RAW (p < 0.0001), and RP having significantly less activity than HP (p < 0.0001). Macronutrient levels appear to be unaffected by both HP and RP, and available lysine, usually a limiting amino acid in infants, was also similar between treatments. Bacterial screening is necessary in HP human milk to ensure absence of B. cereus. Clinicians should be aware of the differences in the activity of sIgA and lysozyme when making feeding decisions for medically fragile infants.Support or Funding InformationFunded by North Carolina State University