030: Assessment of Microbial Safety of Bovine Milk and Structural Alterations in Bovine Lactoferrin Powder Following Ultraviolet-C Irradiation

Introduction

Conventional pasteurization techniques used in bovine milk processing ensure microbial safety but can compromise the bioactivity of native serum proteins like lactoferrin and immunoglobulins, which are crucial for nutritional and functional quality. UV-C irradiation offers a non-thermal alternative that addresses these challenges while maintaining both nutritional integrity and microbial safety.

Methods

Four vegetative bacterial strains (E. coli O157:H7, Salmonella typhimurium, Listeria monocytogenes, Staphylococcus aureus) and two spore-forming strains (Bacillus cereus, Bacillus subtilis) were inoculated into bovine milk and subjected to UV-C irradiation using a surface immersion lamp to evaluate microbial reduction. Bovine lactoferrin, reconstituted from powder, was treated with UV-C irradiation (5,000–20,000 J/L in 5,000 J/L increments) and compared to Holder and HTST pasteurization. The specific protein was studied for its structural integrity and its antimicrobial efficacy.

Results

A 5-log microbial reduction was achieved with UV-C dosages of 12,000 J/L for E. coli and S. aureus, 8,000 J/L for S. typhimurium, and 10,000 J/L for L. monocytogenes. Higher dosages (30,000 J/L) were required for B. cereus and B. subtilis. UV-C irradiation significantly increased surface hydrophobicity in bovine lactoferrin samples at 10,000, 15,000, and 20,000 J/L (p < 0.05). FT-IR analysis revealed higher amide I and II region intensities at 10,000 J/L, Holder, and 15,000 J/L, while samples treated with 5,000 and 20,000 J/L retained more secondary structure. Antimicrobial tests showed no inhibition zones for E. coli and S. aureus at 15,000 J/L and 20,000 J/L.

Significance

UV-C irradiation poses as a promising alternative to traditional pasteurization for processing sweet whey, effectively preserving the integrity of native serum proteins, including lactoferrin. As whey serves as a key raw material for manufacturing lactoferrin and other whey-based products, maintaining its functional and structural properties is crucial for producing high-quality products.

Authors: Bishal Barman, Rohit Kumar, Hussein Mohamed, Joy Waite-Cusic, David Dallas