Textural and cooking properties and viscoelastic changes on heating and cooling of Balkan cheeses

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 Kackavalj, Kackavalj Krstas, 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 degrees C and on cooling from 90 to 25 degrees 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 Kackavalj cheeses had relatively high levels of salt-in-moisture and pH 4.6 soluble N and low protein-to-fat ratio and levels of alpha(s1)-CN (f24-199). They fractured during compression to 75%; had relatively low values of cohesiveness, chewiness, and springiness; melted at 70 to 90 degrees C; reached maximum LT at 90 degrees C; and congealed at 58 to 63 degrees C. Conversely, the Kackavalj Krstas 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 degrees C), attained maximum fluidity at a lower temperature (72-78 degrees C), and congealed at 54 to 69 degrees 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 degrees C provides a potentially useful means of designing ingredient cheeses, with the desired attributes when heated and cooled under customized specification

Short Communication: The effect of dry period duration and dietary energy density on the rennet gelation properties of milk in early lactation

Peer-reviewedThis is the author’s version of a work that was accepted for publication in Journal of Dairy Science. Changes resulting from the publishing process, such as peer review, editing, corrections, structural formatting, and other quality control mechanisms may not be reflected in this document. Changes may have been made to this work since it was submitted for publication. A definitive version was subsequently published in Journal of Dairy Science, 93(2), February 2010, DOI:10.3168/jds.2009-2651This study was carried out to examine the effects of decreasing dry period duration (DP) and altering the energy density of the diet during early lactation on the rheological characteristics of milk. Forty mature Holstein-Friesian cows were used in a completely randomized design with a 2 × 2 factorial arrangement of treatments. Cows were randomly assigned to one of two dry period treatments and one of two nutritional treatments. The dry period treatments were continuous milking (CM) or an 8-week standard dry period (SDP), and the nutritional treatments were a standard energy diet (SE) or a high energy diet (HE). Actual dry period lengths were 6.3 ± 1.7 days and 62.1 ± 1.9 days for cows for the CM and SDP treatments, respectively. Milk samples were collected at 2, 6 and 10 weeks postpartum. The concentration of fat, protein and lactose was determined in each sample. The rennet gelation properties were measured at 31 ° C using dynamic low-amplitude strain oscillatory rheometry. The following parameters were obtained from the resultant elastic shear modulus (G′): gelation time (GT), maximum curd firming rate (CFRmax) and gel strength (GS). Reducing dry period duration from 62 to 6 days resulted in increases in milk protein concentration (31.8 vs. 34.7 g/kg; P < 0.001), CFRmax (2.58 vs. 3.60 Pa/min; P < 0.001) and GS (69.4 vs. 90.5 Pa; P = 0.003). Raising the dietary energy density decreased percentage milk fat (43.1 vs. 37.7 g/kg; P < 0.001) but otherwise had no effect. GS was correlated with CFRmax (r = 0.98; P < 0.001), and both variables were correlated with milk protein concentration (r = 0.71; P < 0.001, and r = 0.73; P < 0.001, respectively). The results indicate that decreasing the duration of DP increased milk protein concentration and improved the rennet gelation properties of milk, but that dietary energy density had little effect

Composition, microstructure and maturation of semi-hard cheeses from high protein ultrafiltered milk retentates with different levels of denatured whey protein

Standardized milks, heated at 72-100 °C to denature ~5-63% of the whey protein, were ultrafiltered to yield retentates with protein and fat levels of ~18.5 and 14%, respectively. Retentates were converted into semi-hard cheeses using specialized coagulation and gel-cutting equipment, with scalding and further syneresis being carried out in conventional cheese vats. High heat treatment of milk necessitated an increase in set temperature, a reduction in set pH and higher scalding temperatures in the cheese vat. Cheese from milk heated at 72 °C for 15 s had a mean composition of ~39.8% moisture, 28% protein, 45.1% fat-in-dry matter, 3.5% salt-in-moisture ( S M) and an ex-brine (1 day) pH of 5.27. Increasing levels of whey protein denaturation (WPD) resulted in cheeses having higher moisture, S M, and whey protein levels, lower ex-brine pH values and lower rates of pH increase during a 182-day ripening period. Cheeses with high levels of WPD also showed poorer curd fusion and lower yield (fracture) values during ripening. Higher levels of denatured whey protein in cheese were associated with a higher degree of primary proteolysis. However, the levels of small peptides ( lt 1000 Da) and amino acids were higher in the control cheese and generally decreased with increasing level of denatured whey protein in the cheese. The concentrations of most free fatty acids, especially butyric, were higher in control cheese