Bacteria and Bioactivity in Holder Pasteurized and Shelf-Stable Human Milk Products

Abstract

Background: Historically, Holder pasteurization has been used to pasteurize donor human milk available in a hospital setting. There is extensive research that provides an overview of the impact of Holder pasteurization on bioactive components of human milk. A shelf-stable (SS) human milk product, created using retort processing, recently became available; however, to our knowledge, little has been published about the effect of retort processing on human milk. Objective: We aimed to assess the ability of retort processing to eliminate bacteria and to quantify the difference in lysozyme and secretory immunoglobulin A (sIgA) activity between Holder pasteurized (HP) and SS human milk. Methods: Milk samples from 60 mothers were pooled. From this pool, 36 samples were taken: 12 samples were kept raw, 12 samples were HP, and 12 samples were retort processed to create an SS product. All samples were analyzed for total aerobic bacteria, coliform bacteria, Bacillus cereus, sIgA activity, and lysozyme activity. Raw samples served as the control. Results: One raw sample and 3 HP samples contained B. cereus at the time of culture. There were no detectable bacteria in SS samples at the time of culture. Raw samples had significantly greater lysozyme and sIgA activity than HP and SS samples (P < 0.0001). HP samples retained significantly more lysozyme and sIgA activity (54% and 87%, respectively) than SS samples (0% and 11%, respectively). Conclusions: Human milk processed using Holder pasteurization should continue to be screened for the presence of B. cereus. Clinicians should be aware of the differences in the retention of lysozyme and sIgA activity in HP and SS products when making feeding decisions for medically fragile or immunocompromised infants to ensure that patients are receiving the maximum immune protection.

Hot topic: Holder pasteurization of human milk affects some bioactive proteins

“…The pasteurization step is required to inactivate pathogenic bacteria and viruses, and it reduces spoilage to an acceptable level when delivery to health-impaired individuals or medical institutions is considered. However, heat treatment may reduce the content of some bioactive compounds in human milk (Lima et al, 2017).…”

Antimicrobial Effect of Zn2+ Ions Governs the Microbial Quality of Donor Human Milk

“…after the heat treatment [ 36 ]. This can be attributed to the germination of dormant spores into vegetative cells following exposure to heat, which is common for this species [ 37 ]. In this context, a major concern in the management of HM banks will be the post-pasteurization presence of B. cereus .…”

Impact of vaccination during pregnancy and staphylococci concentration on the presence of Bacillus cereus in raw human milk

“…B. cereus spores and vegetative cells in raw human milk are destroyed by commercial sterilization whereas the spores survive throughout pasteurization [12] and grow back (vegetative cells) in higher levels than in raw breast milk [11]. The faster growth of B. cereus in pasteurized donor milk samples could be partially due to the destruction of other microorganisms, which reduces the competition for nutrients.…”

“…B. cereus or Bacillus species was detected in 5.8% of 190 pasteurized donor milk samples [9] and 5% of 303 pasteurized donor milk samples [10]. B. cereus concentration in Holder pasteurized donor milk was 3-fold higher than raw donor milk (unpasteurized), whereas shelf-stable donor milk (retort sterilization) had no colonies of B. cereus [11]. B. cereus spores in human milk resist pasteurization and their spores can change in vegetative cells and grow during the cooling and thawing steps to become active in pasteurized donor milk [12].…”