Guinee T P, Feeney E P, Auty M A E, Fox P F
Dairy Products Research Centre, Fermoy, Co Cork, Ireland.
J Dairy Sci. 2002 Jul;85(7):1655-69. doi: 10.3168/jds.S0022-0302(02)74238-0.
The effects of Ca concentration and pH on the composition, microstructural, and functional properties of Mozzarella cheese were studied. Cheeses were made using a starter culture (control) or by direct acidification of the milk with lactic acid or lactic acid and glucono-delta-lactone. In each of three trials, four cheeses were produced: a control, CL, and three directly-acidified cheeses, DA1, DA2, and DA3. The cheeses were stored at 4 degrees C for 70 d. The Ca content and pH were varied by altering the pH at setting, pitching, and plasticization. The mean pH at 1 d and the Ca content (mg/g of protein) of the various cheeses were: CL, 5.42 and 27.7; DA1, 5.96 and 21.8; DA2, 5.93 and 29.6; DA3, 5.58 and 28.7. For cheeses with a high pH (i.e., approximately 5.9), reducing the Ca content from 29.6 to 21.8 mg/g of protein resulted in a significant decrease in the protein level and increases in the moisture content and mean level of nonexpressible serum (g/g of protein). Reducing the Ca concentration also resulted in a more swollen, hydrated para-casein matrix at 1 d. The decrease in Ca content in the high-pH cheeses coincided with increases in the mean stretchability and flowability of the melted cheese over the 70-d storage period. The fluidity of the melted cheese also increased when the Ca content was reduced, as reflected by a lower elastic shear modulus and a higher value for the phase angle, delta, of the melted cheese, especially after storage for <12 d. The melt time, flowability, and stretchability of the low-Ca, high-pH DA1 cheese at 1 d were similar to those for the CL cheese after storage for > or = 12 d. In contrast, the mean values for flowability and stretchability of the high-pH, high-Ca DA2 cheese over the 70-d period were significantly lower than those of the CL cheese. Reducing the pH of high-Ca cheese (27.7 to 29.6 mg/g of protein) from -5.95 to 5.58 resulted in higher flowability, stretchability, and fluidity of the melted cheese. For cheeses with similar pH and Ca concentration, the method of acidification had little effect on composition, microstructure, flowability, stretchability, and fluidity of the melted cheese.
研究了钙浓度和pH值对马苏里拉奶酪的成分、微观结构及功能特性的影响。奶酪制作采用发酵剂培养（对照）或用乳酸或乳酸与葡萄糖酸 - δ - 内酯直接酸化牛奶的方法。在三次试验中的每一次，都制作了四种奶酪：一种对照奶酪（CL），以及三种直接酸化奶酪（DA1、DA2和DA3）。奶酪在4℃下储存70天。通过改变凝乳、搅拌和塑化时的pH值来改变钙含量和pH值。不同奶酪在1天时的平均pH值和钙含量（毫克/克蛋白质）分别为：CL奶酪，5.42和27.7；DA1奶酪，5.96和21.8；DA2奶酪，5.93和29.6；DA3奶酪，5.58和28.7。对于高pH值（即约5.9）的奶酪，将钙含量从29.6毫克/克蛋白质降至21.8毫克/克蛋白质会导致蛋白质水平显著下降，水分含量和不可挤出血清的平均水平（克/克蛋白质）增加。降低钙浓度还会使1天时的副酪蛋白基质更加肿胀且水合。高pH值奶酪中钙含量的降低与70天储存期内融化奶酪的平均拉伸性和流动性增加相吻合。当钙含量降低时，融化奶酪的流动性也会增加，这表现为融化奶酪的弹性剪切模量较低，相位角δ值较高，尤其是在储存<12天后。低钙、高pH值的DA1奶酪在1天时的融化时间、流动性和拉伸性与CL奶酪储存≥12天后的情况相似。相比之下，高pH值、高钙的DA2奶酪在70天期间的流动性和拉伸性平均值显著低于CL奶酪。将高钙奶酪（27.7至29.6毫克/克蛋白质）的pH值从5.95降至5.58会导致融化奶酪具有更高的流动性、拉伸性和流体性。对于pH值和钙浓度相似的奶酪，酸化方法对融化奶酪的成分、微观结构、流动性、拉伸性和流体性影响很小。
