Salvatore E, Pes M, Falchi G, Pagnozzi D, Furesi S, Fiori M, Roggio T, Addis M F, Pirisi A
Agris Sardegna, Department of Animal Science, Loc. Bonassai, 07040 Olmedo, Italy.
Agris Sardegna, Department of Animal Science, Loc. Bonassai, 07040 Olmedo, Italy.
J Dairy Sci. 2014;97(8):4686-94. doi: 10.3168/jds.2013-7762. Epub 2014 May 23.
Ricotta cheese, particularly the ovine type, is a typical Italian dairy product obtained by heat-coagulation of the proteins in whey. The aim of this work was to investigate the influence of whey protein concentration, obtained by ultrafiltration, on yield of fresh ovine ricotta cheese. Ricotta cheeses were obtained by thermocoagulation of mixtures with protein content of 1.56, 3.10, 4.16, and 7.09g/100g from the mixing of skim whey and ultrafiltered skim whey. A fat-to-protein ratio of 1.1 (wt/wt) was obtained for all mixtures by adding fresh cream. The initial mixtures, as well as the final ricotta cheeses, were analyzed for their composition and by SDS-PAGE. Protein bands were quantified by QuantityOne software (Bio-Rad, Hercules, CA) and identified by liquid chromatography-tandem mass spectrometry. Significant differences in the composition of the ricotta cheese were observed depending on protein concentration. Particularly, ricotta cheese resulting from the mixture containing 7.09g/100g of protein presented higher moisture (72.88±1.50g/100g) and protein (10.18±0.45g/100g) contents than that prepared from the mixture with 1.56g/100g of protein (69.52±1.75 and 6.70±0.85g/100g, respectively), and fat content was lower in this sample (12.20±1.60g/100g) compared with the other treatments, with mean values between 15.72 and 20.50g/100g. Each protein fraction presented a different behavior during thermocoagulation. In particular, the recovery of β-lactoglobulin and α-lactalbumin in the cheese increased as their content increased in the mixtures. It was concluded that concentrating ovine rennet whey improved the extent of heat-induced protein aggregation during the thermal coagulation process. This resulted in a better recovery of each protein fraction in the product, and in a consequent increase of ricotta cheese yield.
乳清干酪，尤其是绵羊乳清干酪，是一种典型的意大利乳制品，通过对乳清中的蛋白质进行热凝固而制得。本研究的目的是探讨超滤获得的乳清蛋白浓度对新鲜绵羊乳清干酪产量的影响。通过对脱脂乳清和超滤脱脂乳清混合得到的蛋白质含量分别为1.56、3.10、4.16和7.09g/100g的混合物进行热凝固，制得乳清干酪。通过添加鲜奶油，所有混合物的脂肪与蛋白质比例均达到1.1（重量/重量）。对初始混合物以及最终的乳清干酪进行成分分析，并采用十二烷基硫酸钠 - 聚丙烯酰胺凝胶电泳（SDS - PAGE）分析。通过QuantityOne软件（伯乐公司，美国加利福尼亚州赫拉克勒斯）对蛋白条带进行定量，并通过液相色谱 - 串联质谱法进行鉴定。根据蛋白质浓度的不同，观察到乳清干酪的成分存在显著差异。特别是，由蛋白质含量为7.09g/100g的混合物制成的乳清干酪，其水分含量（72.88±1.50g/100g）和蛋白质含量（10.18±0.45g/100g）高于由蛋白质含量为1.56g/100g的混合物制备的乳清干酪（分别为69.52±1.75和6.70±0.85g/100g），且该样品的脂肪含量（12.20±1.60g/100g）低于其他处理组，其他处理组的脂肪含量平均值在15.72至20.50g/100g之间。在热凝固过程中，每种蛋白质组分表现出不同的行为。特别是，随着混合物中β - 乳球蛋白和α - 乳白蛋白含量的增加，它们在奶酪中的回收率也增加。研究得出结论，浓缩绵羊凝乳酶乳清可提高热凝固过程中热诱导蛋白质聚集的程度。这导致产品中每种蛋白质组分的回收率更高，从而提高了乳清干酪的产量。
