Examining the interrelationship between milk storage and production conditions on milk and dairy products quality

The Irish dairy industry has expanded significantly over the last five years since the abolition of the milk quotas in 2015. The Food Harvest Programme predicted that the milk production would increase by 50% by 2020. The expansion opportunity for Irish dairying has the potential to contribute greatly to the national economy; however, the consistent production of high quality dairy products in accordance with specific international quality parameters is essential to hold market share. The aim of this thesis is to investigate how cold storage conditions at farms can influence the microbiological quality and processability of raw milk, as well as how the quality of raw milk can impact the quality of dairy products. The experimental chapters are divided into two parts; in the first part the studies focused on evaluating the relationship between raw milk cooling conditions on-farm and quality, while in the second part the relationship between raw milk quality, processability and effects on the quality of dairy products were investigated. The thesis was divided into six studies, the specific objectives of each were: (i) to determine the effect of storage temperature and time on the microbiological quality and composition of milk; (ii) to determine the effect of different pre-cooling rates on the microbiological load and composition of milk, as well as on energy requirements; (iii) to monitor the microbiological load of milk throughout the manufacturing process of low-heat skim milk powder, from farm bulk tanks to final product; (iv) to investigate the dynamics of levels of chlorate, perchlorate, trichloromethane, quaternary ammonium compounds and iodine throughout the manufacturing process of skim milk powder; (v and vi) and to determine the effect of different levels of a thermo-resistant protease, produced by a Pseudomonas fluorescens strain, on the cheese-making properties of milk and quality of Cheddar cheese