The effect of calcium content of Cheddar-style cheese on the biochemical and rheological properties of processed cheese.

摘要

The Ca content of natural cheese has a major impact on its physical properties. The effect of the Ca content of natural cheese on the functionality of processed cheese (PC) was investigated. The PC were made from Cheddar cheese with an intact casein content of 89 g/100 g total casein and with a Ca/casein ratio (mg/100 g) that was low (LCaCC, 19.6), medium (MCaCC, 24.2) or high (HCaCC, 29.8). The PC were formulated from Cheddar cheese, butter oil, emulsifying salts, preservative and water; the blend was heated to 80 degrees C with continuous shearing at 2000 rpm for 4 min. The Ca/casein ratio of the resultant PC, denoted LCaPC, MCaPC and HCaPC, were 17.86, 22.10 and 28.36 mg/00 g, respectively. The PC were analysed for composition, deformation properties on compression to 30% original sample dimensions, cooking properties (flow on heating at 280 degrees C for 4 min and 180 degrees C for 7.5 min) and changes in viscoelasticity on heating from 25 to 80 degrees C using low-amplitude strain oscillation rheometry. All PC had similar levels of moisture (approx. 47 g/100 g), protein (approx. 21 g/100 g), water-soluble N, WSN (approx. 74 g/100 g total N) and pH 4.6 soluble N (approx. 11 g/100 g total N). The fracture stress, fracture strain and firmness of HCaPC were significantly higher than those of MCaPC or LCaPC. The heat-induced flow of HCaPC and MCaPC was significantly lower than that of LCaPC. Heating of PCs from 25 to 88 degrees C resulted in a continual decrease in storage modulus (G') of HCaPC and MCaPC; however, G' for LCaPC decreased to 51 degrees C but thereafter increased sharply. The phase angle ( delta) of all PC increased to a maximum ( deltamax) at 45-54 degrees C and thereafter decreased, the decrease being most pronounced for LCaPC. Reducing the Ca content of the Cheddar cheese significantly increased deltamax and reduced the value of G' at 25 degrees C, the time to reach deltamax and the temp. at deltamax of the resultant PC. It is concluded that lower Ca levels in natural cheese give PC that are softer and shorter (more brittle), become more fluid and spreadable on heating, acquire this fluidity in a shorter time and at a lower temp., but tend to be less stable on heating at high temp. (80-100 degrees C) for longer times (>7 min).