Exploring milk management strategies for improved food safety and health outcomes in the neonate

Milk fulfils the nutritional and energy requirements of the neonate to ensure adequate development and immunological protection during the initial critical period, with long-lasting effects across the lifespan. Mammals milk produced in the first 24 hours post-partum is known as colostrum. In bovines, colostrum consumption in calves is associated with improved health and reduced mortality. In humans, fresh mothers’ own milk is regarded as the optimum nutrition for the newborn infant. When mother’s own milk is unavailable the recommended alternative is donor human milk. Receipt of donor human milk is imperative for pre-term infants, with a very low birth weight (<1,500 g) or a serious illness, due to their increased risk of negative medical outcomes. The nutritional, bioactive and microbial properties of milk can be influenced by an array of extrinsic and intrinsic factors. This thesis investigates the influence of two common management practices of milk, in both the bovine and human context, and their subsequent influence on microbial composition. Firstly, the influence of farm management strategies, mainly antibiotic administration during dry cow therapy, on bovine colostrum. Secondly, the impact of processing techniques utilized in the milk bank setting on donor human milk. The results demonstrate factors which may affect the quality of milk and detail potential strategies to optimize milks benefit for the neonate. Additionally, the exploration of bovine colostrum as a source of microbes with health-promoting properties is undertaken. Chapter 1 outlines the value of donor human milk to vulnerable pre-term infants in the absence of mother’s own milk. Milk bank processing can influence the value and safety of donor human milk. This chapter consolidates the effects of holder pasteurization and alternative thermal and non-thermal methods, evaluating their ability to preserve milk's nutritional and bioactive properties whilst ensuring microbial inactivation. Chapter 2 provides an overview of the literature on carotenoid-fortified dairy products and infant formula. The origin and role of carotenoids in bovine and human milk, influential factors on the carotenoid content of milk and potential mechanisms to manipulate the carotenoid profile of bovine milk are discussed. In addition, challenges commonly associated with functional foods including bioacessibility and stability are presented herein. Chapter 3 details the microbial profile of Irish bovine colostrum and the impact of antibiotic treatment. The influence of parity and inter-farm level variation were also assessed. DNA extraction and 16S rRNA sequencing of colostrum samples from 90 dairy cows revealed the most abundant phyla (Firmicutes, Actinobacteriota, Bacteroidota and Proteobacteria) and genera (Acinetobacter, Corynebacterium, Facklamia, Jeotgalicoccus, Lactococcus, Leuconostoc, Psychrobacter and Staphylococcus) in colostrum. Antibiotic treatment resulted in a significant difference in the microbial composition and diversity of colostrum when compared with the colostrum of cows following natural dry cow therapy. Furthermore, a significant difference in microbial composition based on the choice of antibiotic (Cephagaurd and UbroRed) was demonstrated. Beta diversity revealed significant differences between all groups, with distinct microbial clustering in the non-antibiotic group. These results substantiate the presence of a diverse microbial population in bovine colostrum, which can be influenced by farm management practices. Our findings support the use of non-antibiotic alternatives for drying off in cows. Chapter 4 presents lactic acid bacteria strains isolated from pooled bovine colostrum. In vitro and in silico analysis revealed potential probiotic attributes of colostrum isolates, including exopolysaccharide activity, bile salt hydrolase activity and GABA production. In particular, four bacterial isolates were identified as putative bacteriocin producers following a series of well diffusion assays. Whole genome sequencing and predictive analysis confirmed the presence of five bacteriocin gene clusters. Our results demonstrate that bovine colostrum is a source of microbes with positive attributes that could be further investigated for potential use by the food or health sectors. Chapter 5 substantiates the efficacy of holder pasteurization and assesses the ability of high-pressure processing in reducing the microbial growth in human milk. In addition, we determine if the microbial safety of donor milk can be sustained for an extended storage period of 7 days. Bacterial screening on non-selective media demonstrated that milk treated with holder pasteurization or high-pressure processing at 600 MPa resulted in milk within acceptable growth limits (<10 CFU mL-1). In addition, the microbial safety of milk was maintained when stored at 4 C for 7 days. HPP at 400 MPa achieved a 3.45-log reduction in microbial counts, with undetectable growth at subsequent time-points. The results of this study suggest the microbial safety of holder pasteurised milk is maintained when stored at 4 C for 7 days. In addition, we propose high pressure processing as a potential non-thermal alternative for donor milk treatment. Chapter 6 presents findings on previously unexplored methods for the processing of donor human milk including, the application of the bacteriocin, nisin A, microfiltration and the direct inclusion of the enzyme, lactose oxidase. A > 6-log reduction in microbial growth on non-selective media and media targeting Pseudomonas and coliforms growth was achieved following microfiltration or a hybrid treatment of nisin A and holder pasteurisation. This study provides novel insights into the potential incorporation of non-conventional processing techniques in human milk banking, resulting in milk within acceptable microbial safety standards. Overall, this thesis details beneficial properties of milk from a microbial perspective with results that can help optimize the management and handling of milk for optimal value, providing improved health benefits to the neonate. Furthermore, milk as a source of health-promoting agents (carotenoids and microbes) with potential industrial applications was explored.

Grantor dc:publisher

University College Cork

Year dc:date.issued

2025

Author dc:creator

• Conboy-Stephenson, Ruth

Advisors dc:contributor.advisor

• Stanton, Catherine
• Ross, R. Paul

• Bovine colostrum
• Donor human milk
• Lactic acid bacteria
• High pressure processing
• Bacteriocin
• Antibiotic treatment
• Non thermal processing
• Carotenoids

Statement dc:rights

• © 2025, Ruth Conboy-Stephenson.

Licence dc:rights.uri

• https://creativecommons.org/licenses/by-nc-sa/4.0/

Language dc:language.iso

en

Handle dc:identifier.uri

https://hdl.handle.net/10468/18438

OAI identifier oai:identifier

oai:cora.ucc.ie:10468/18438