Milk was collected from three spring-calving herds, on different daily herbage allowances (DHA) of perennial rye-grass (16, 20 or 24 kg dry matter (DM)/cow for a 17 week period. On five occasions, at weekly intervals in the middle of the period, the three different milks were converted into low-moisture part-skim Mozzarella cheese. Increasing the DHA resulted in significant increases in the concentrations of protein in the cheesemilk (P<0·05) and cheese whey (P<0·02). The moisture-adjusted cheese yield increased significantly (P<0·01) on raising the DHA from 16 to 24 kg grass DM/cow. DHA had no significant effects on any of the gross compositional values of the cheese (although moisture and fat-in-DM levels tended to decrease and increase respectively with increasing DHA). The hardness of the uncooked cheese and functionality of cooked cheese (i.e. melt time, flowability, stretch and viscosity) were not significantly influenced by DHA over the 115 d ripening period at 4°C.

The growth in food service and prepared consumer foods has led to increasing demand for cheese with customized textural and cooking characteristics. The current study evaluated Kačkavalj, Kačkavalj Krstaš, and Trappist cheeses procured from manufacturing plants in Serbia for texture profile characteristics, flow and extensibility of the heated cheese, and changes in viscoelasticity characteristics during heating and cooling. Measured viscoelastic parameters included elastic modulus, G', loss modulus, G″, and loss tangent, LT (G″/G'). The melting temperature and congealing temperature were defined as the temperature at which LT=1 during heating from 25 to 90°C and on cooling from 90 to 25°C. The maximum LT during heating was as an index of the maximum fluidity of the molten cheese. Significant variation was noted for the extent of flow and extensibility of the heated cheeses, with no trend of cheese type. As a group, the Kačkavalj cheeses had relatively high levels of salt-in-moisture and pH 4.6-soluble N and low protein-to-fat ratio and levels of αs1-CN (f24-199). They fractured during compression to 75%; had relatively low values of cohesiveness, chewiness, and springiness; melted at ~70 to 90°C; reached maximum LT at 90°C; and congealed at 58 to 63°C. Conversely, the Kačkavalj Krstaš and Trappist cheeses had low levels of primary proteolysis and salt-in-moisture content and a high protein-to-fat ratio. They did not fracture during compression, had high values for cohesiveness and chewiness, melted at lower temperatures (56-62°C), attained maximum fluidity at a lower temperature (72-78°C), and congealed at 54 to 69°C. There was a hysteretic dependence of G' and LT on temperature for all cheeses, with the LT during cooling being higher than that during heating, and G' during cooling being lower or higher than the equivalent values during heating depending on the cheese type. Monitoring the dynamic changes in viscoelasticity during heating and cooling of the cheese in the temperature range 25 to 90°C provides a potentially useful means of designing ingredient cheeses, with the desired attributes when heated and cooled under customized specification.

Cheddar type cheeses of diflierent fat contents were produced and denoted: full-fat (FFC), 306 gkg; hagfat (HFC), 174 gkg; and low fat (LFC, 13 gkg). Full fat Cheddar cheese (FFCH) was also prepared from milk which had been homogenized at first and second stage pressures of 25 and 5 MPa, respectively. The cheeses were held at 4C for 30 days and at 7C for the remainder of the 190day ripening period. Reducing the fat level from 174 to 13 g k g resulted in decreases in contents of moisture in nonfat substance and pH 4.6 soluble N as a percentage of total N @H4.6SN), and increases in the contents of moisture, protein and intact casein. Homogenization of cheesemilk resulted in a slight increase in moisture content and an increase in pH4.6SN. Confocal laser scanning microscopy revealed that the extent of fat globule clumping and coalescence in both the unheated and heated (to 95C) cheeses decreased with homogenization of the cheesemilk and with fat reduction. Homogenization of the cheesemilk and reducing the fat content of the cheese resulted in a decrease in the jlowability and stretchability of the melted cheese. Dynamic measurement of the viscoelastic changes on heating the cheese from 20 to 9OC showed that reduction of fat content resulted in a decrease in the magnitude of the phase angle, 6, at temperatures >50C. At temperatures < =60C, the storage modulus, G', increased on reducing the fat content from 306-1 74 g/kg to 13 gkg. Homogenization resulted in a marked decrease in 6 at temperatures > 45-SOC, with S , , typically decreasing from 5: 65-70" in the FFC to 2: 35 in the FFCH.

Summary: Dynamic confocal scanning laser microscopy (CSLM) methods were developed to enable observation of milk protein gelation and cheese melting. Protein aggregation and the formation of gel networks in renneted fullfat and low-fat milks and glucono-δ-lactone (GDL)-acidified skim milks were observed by CSLM and observations correlated with increases in shear modulus (G′) and dynamic viscosity (η*) as determined by dynamic amplitude oscillatory rheology. Confocal scanning laser microscopy observation of low-fat and full-fat cheeses showed changes in fat distribution and an increase in staining intensity during cheese melting.

No abstract