Department of Chemistry, Maynooth University, Maynooth, Co. Kildare and Teagasc Food Research Centre, Moorepark, Fermoy, Co. Cork Effect of Dairy Cow Diets on the Composition and Processing Characteristics of Milk A thesis submitted to National University of Ireland Maynooth in fulfilment of the requirements of the degree of Doctor of Philosophy By Arunima Gulati, M.Sc. May 2019 Research Supervisors: Prof. Tim Guinee, Dr. Mark Fenelon, Dr. Jennifer McManus Head of Department: Dr. Jennifer McManus Dedicated to my both set of parents and Atul Without their love and encouragement none of my success would be possible ii Declaration I hereby certify that this thesis has not been submitted before, in whole or in part, to this or any university for any degree and is, except where otherwise stated, the original work of the author. Signed: Date: Student Number: 14251884 Maynooth University iii Acknowledgments Acknowledgements I would like to thank my supervisors Tim Guinee, Jennifer McManus and Mark Fenelon for providing me with the opportunity to pursue PhD. I would sincerely like to thank them for their guidance, continuous encouragement and their valuable time throughout the programme. It was a rewarding experience to work under their supervision and this thesis would not have been appeared in its present form without their support and ideas. Tim, you have been an excellent supervisor and I can’t thank you enough. I have learnt so much from you, your enthusiasm for research and sharing knowledge. I would also like to thank researchers Eva Lewis, Emer Kennedy and Deirdre Hennessey from Teagasc Animal & Grassland Research and Innovation Centre for their valuable input in designing experiments and helpful comments on the manuscripts. I also thank Juliet Wiley, Norann Galvin, Jimmy Flynn, AnneMarie McAuliffe, Sarah Cooney, Bernard Corrigan, Martina O’Brien, Tom O’Callaghan, Judith Mittag, Sarah Cannon, Paula Reid, Trevor Cremin, JohnPaul Murphy and, MTL and farm staff for their kind assistance during milk collections, experimental work and pilot scale trials. My special and heartfelt thanks extend to Catherine Mullins; her ‘magic hands’ used to make any instrument work. I would like to thank my lab members for their support during experimental work, writing and insightful discussions; Kevany Soodam, Ashwini Shevade, Catherine McCarthy, Chak To, Yingchen Lin and Sarah Henneberry. I would like to thank my friends and colleagues, thanks for being a part of my life. I enjoyed our talks in Moorepark corridors and during tea time: Laura, Mattia, Ram, David, Natasha, Wei, Catherine Wall, Junfu, Ruinjing, Qingsong, Lizzandra, Kamrul, Bhavya, Supriya, Snehal, Shivani, Puneet and Phanindra. Special thanks to my girlfriends Ashwini, Emer and Maneesha, for our never-ending late-night talks which always made me forget the hard and long working days in Moorepark. I thank my iv Acknowledgments friends in Dublin, Mithil and Negi family, for all their love, support, care and much needed relaxing times away from work. I would also like to thank John from Moorepark security, who has such a kind heart and always brought me chocolates when I was here until crazy o’clock in the morning. Last but not the least; I would like to thank my family. I would like to thank my parents and parent-in-law, for their support and unconditional love. Special thanks to my brother Gandharv, and sister- and brother-in-law, Archana and Lava for all the long talks and pouring me with so much of their love. Finally, I thank my husband, Atul Nautiyal, for all the support, patience, and constant encouragement throughout these four years. v Abstract Abstract Milk composition is affected by many factors including stage of lactation, type and level of feed intake, and environmental conditions. Changes in milk composition affect milk processability and the yield and quality of dairy products. The overall aim of this thesis was to investigate the effect of different herbage allowance and feeding systems on seasonal changes in milk composition, biochemical, processing characteristics, or product manufacture and their quality. Effects of reducing daily herbage allowance (DHA) from 15.0 to 11.8 kg dry matter per cow to a spring-calved herd during early lactation (EL; 29-70 days in milk, DIM) on milk composition and processability (e.g., rennet gelation, heat coagulation time) were examined throughout lactation (up to 267 DIM). Reducing DHA led to reductions in milk yield and concentrations of protein during EL; otherwise, it had little effect on milk composition or on the selected processing characteristics in mid- or late lactation. The comparative effects of three different dairy cow diets or feeding systems on the milk composition and its impacts on the quality of Mozzarella cheese and low heat skim milk powder (LHSMP) were also studied: grazing perennial ryegrass (Lolium perenne L.) only (GRO), grazing perennial ryegrass and white clover (Trifolium repens L.) (GRC), and housed indoors offered total mixed ration (TMR). Feeding system affected milk composition and processability to an extent dependent on stage of lactation and year of study. Most notably, GRO-based milk had higher concentrations of protein, casein, Ca, lower concentrations of lactose, I, Cu and Se, and stronger rennet gelation characteristics than TMR milk. Milk from grass based feeding system had a higher mozzarella cheese-yielding capacity than milk from TMR based feeding system, and produced cheese which had lower levels of I, Cu and Se, was more yellow and became more fluid and flowable on heating to 95 °C. Moreover, the use of a novel technique called cavitation rheology (CR) to measure the mechanical properties of Mozzarella cheese, produced from GRO milk, during ageing at vi Abstract 4 °C. The linear modulus (E) obtained from CR was much lower when compared G′ (storage modulus) from shear rheology, but correlated significantly with G′ and firmness of the cheese. Finally, composition and functionality of low-heat skim milk powder produced from three different feeding systems was studied. Compared to TMR milk, LHSMP from GRO milk had a higher protein content and a lower lactose, I, Cu and Se content, a more green-yellow colour, and on reconstitution (10%, w/w; RSM) had better rennet coagulability. RSM from all three feeding systems had similar casein micelle size and hydration, ethanol stability and yoghurt making characteristics. The differences in milk and product characteristics obtained from different feeding systems may provide a foundation for product differentiating parameters suited to different consumers, processors and markets. vii Abbreviations Abbreviations γ̇ Shear rate % Percent -Lac -lactalbumin AMF Anhydrous milk fat ANOVA Analysis of variance BCS Body condition score -Lg -lactoglobulin CCP Colloidal calcium phosphate cm Centimetre CoTc Cross-over temperature while cooling CoTh Cross-over temperature while heating CR Cavitation rheology d Day Da Daltons df Degrees of freedom DHA Daily herbage allowance DIM Days in milk DLS Dynamic light scattering DM Dry matter DMI Dry matter intake EL Early lactation EW Work required for uniaxial extension of molten cheese FDM Fat-in-dry-matter FOF Follow on formulae FS Feeding system FTIR Fourier transform infrared spectroscopy g Gram G′40 Gel firmness at 40 min after rennet addition G′pH4.6 Storage modulus at pH 4.6 of acid-gel GFRmax Maximum gel firming rate GLM General linear model GopH Gelation onset pH GRC Grass-clover diet GRO Grass-only h Hour H2O2 Hydrogen peroxide HCl Hydrochloric acid HCT Heat coagulation time H-DHA High daily herbage allowance HNO3 Nitric acid Hz Hertz IMCU International milk coagulating units IMF Infant milk formulae K Consistency index (Pa.s) kg Kilogram L Litre L-DHA Low daily herbage allowance LHSMP Low heat skim milk powder LL Late lactation LS Lactation stage viii Abbreviations LTmax Maximum loss tangent m Metre M-DHA Medium daily herbage allowance mg Milligram min Minutes mL Millilitre ML Mid lactation mM Milimolar MNFS Moisture-in-non-fat substances Mw Molecular weight N Newton n Flow behaviour index NaCl Sodium chloride NAOH Sodium hydroxide NCN Non-casein nitrogen nm Nanometre NPN Non protein nitrogen Pa.s Pascal seconds pH 4.6-SN pH 4.6 soluble nitrogen RCT Rennet coagulation time RP-HPLC Reverse phase high pressure liquid chromatography rpm Revolutions per minute RSM Reconstituted skim milk s Seconds S/M Salt-in-moisture SH Sulfhydryl TCA Trichloroacetic acid TFA Trifluroacetic acid TMAH Tetra-methyl ammonium hydroxide TMR Total mixed ration TN Total nitrogen TS Total solids v/v Volume/volume vs. Versus w/w Weight/weight WHC Water holding capacity WPR Water-to-protein-ratio WSN Water-soluble nitrogen Ya Actual cheese yield Yn Normalised cheese yield μg Microgram σo Shear stress (Pa) ix Publications List of Publications Peer-reviewed articles 1. Gulati, A., N. Galvin, E. Lewis, D. Hennessy, M. O’Donovan, J. J. McManus, M. A. Fenelon, T. P. Guinee. 2018. Outdoor grazing of dairy cows on pasture versus indoor feeding on total mixed ration: Effects on gross composition and mineral content of milk during lactation. Journal of Dairy Science, 101, 2710 – 2723. (Based on Chapter 4) 2. Gulati, A., D. Hennessy, E. Lewis, M. O’Donovan, J. J. McManus, M. A. Fenelon, T. P. Guinee. 2018. Effect of dairy cow feeding system on milk composition and processability. European Grasslands Federation, Grass Science in Europe, 709-711. (Based on Chapter 5) 3. Gulati, A., N. Galvin, D. Hennessy, S. McAuliffe, M. O’Donovan, J. J. McManus, M. A. Fenelon, T. P. Guinee. 2018. Grazing of dairy cows on pasture versus indoor feeding on total mixed ration: Effects on low-moisture part-skim Mozzarella cheese yield and quality characteristics in mid- and late- lactation. Journal of Dairy Science, 101, 8737-8756. (Based on Chapter 6) 4. Gulati, A., N. Galvin, E. Kennedy, E. Lewis, J. J.