Effect of high heat treatment and β-casein-reduction on the rennet coagulation and ripening of Cheddar and Emmental cheeses manufactured from micellar casein concentrate

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Xia, Xiaofeng
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University College Cork
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Microfiltration (MF) removed 53.60 ‒ 70.29 % of native whey protein from pasteurized skim milk to permeate, and retained micellar casein concentrate (MCC) (89.64 - 93.64 % of casein expressed as percentage of total protein) in the retentate. The objective of this thesis was to formulate cheesemilk of desired composition by using MF and to study how each component affect cheese quality. In this thesis, (1) the influence of temperature, number of diafiltration (DF) steps, composition of DF media as well as type of MF membrane on the composition of MCC was examined; (2) the effect of levels of total casein, β-casein or whey protein in cheesemilk on the qualities of semi-hard cheese (Cheddar or Emmental) made therefrom were evaluated and (3) as casein micelles is more heat stable than whey protein, the heat stability of MCC and its impact on resultant cheesemilk was also analysed. Compared to MF without a DF step, DF with water increased the removal of whey protein and small molecules, such as lactose and soluble salts, from feed milk to permeate and the depletion of solutes present in the serum phase of milk increased with an increasing number of DF steps. The rennet coagulability of cheesemilk in addition to the composition, pH, texture, yield, flowability and colour in resultant cheeses were not affected by the whey protein content of the cheesemilk. However, removing whey protein from milk increased the plasmin activity of the cheesemilk formulated therefrom and also increased the level of primary proteolysis (as measured by urea-PAGE and HPLC) in the resultant Emmental cheeses. Increasing the casein content in cheesemilk led to an increased gel firming rate in milk and an increase in hardness, pH and plasmin activity as well as a decrease in moisture content and primary proteolysis in the resultant Cheddar cheese. Reducing β-casein levels from milk by 4.25 % neither affected the rennet coagulation properties of cheesemilk nor influenced the composition, pH, plasmin activity, primary proteolysis, texture profile, flowability and colour in the resultant Emmental cheese. Depletion of milk whey protein content in milk by either 53.60 % or 70.29 % largely increased milk heat stability as measured by rennet coagulation, plasmin activity and cheese quality. Subjecting MCC with 70.29 % whey protein depletion to 90 °C for 15 s neither impaired the rennet coagulation properties of cheese milk prepared therefrom nor altered the composition, texture profile, meltability and volatile profile of resultant Cheddar cheese. However for whey protein reduced-milk (53.60 %) heated at 120 °C for 15 s, the rennet coagulability and plasmin activity in the resultant cheesemilk were significantly reduced, with the flowability in the resultant Emmental cheese decreased and redness increased. Overall, the results generated from this research will help cheesemakers to formulate cheesemilk of desired composition and milk with superior heat stability by using MF and micellar casein concentrates. This research also generated new knowledge on the interactions between cheesemilk components and processes to which the milk is subjected to and how this influences the quality of semi-hard cheeses produced therefrom.
Microfiltration , Cheddar cheese , Emmental cheese , Heat treatment
Xia, X. 2021. Effect of high heat treatment and β-casein-reduction on the rennet coagulation and ripening of Cheddar and Emmental cheeses manufactured from micellar casein concentrate. PhD Thesis, University College Cork.
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