Piñeiro-Lago Lorena, Franco Inmaculada, Tovar Clara A
Food Technology Area, Faculty of Sciences, Campus Universitario As Lagoas s/n, 32004 Ourense, University of Vigo, Spain.
Food Technology Area, Faculty of Sciences, Campus Universitario As Lagoas s/n, 32004 Ourense, University of Vigo, Spain.
Food Res Int. 2020 Nov;137:109693. doi: 10.1016/j.foodres.2020.109693. Epub 2020 Sep 24.
Thermoviscoelastic and biochemical properties of Afuega'l Pitu cheese blancu (B) and roxu (R), a Spanish acid-curd cheese made from cow's milk, were determined at 3, 15, 30 and 60 days of ripening. The contents of fat (>45 g/100 g total solids, TS) and NaCl (<3 g/100 g TS) were similar between varieties and did not change with ripening. Total solids, pH, nitrogen fractions and fat acidity increased with ripening time in B and R samples. Lactose content was higher in B than in R cheeses at 3 d, was degraded gradually throughout ripening but did not disappear totally in both cheeses at 60 d. Viscoelastic parameters were determined in the linear viscoelastic region (LVER) by stress sweeps (6.3 rad/s, 20 °C): the stress amplitude (σ) and complex modulus (G*) increased, while strain amplitude (γ) decreased up to 60 d. Mechanical spectra were also determined, in the LVER, at 20 °C, 50 °C and 75 °C, showing that all samples behaved as "true gels" (elastic modulus, G' > viscous modulus, G''), irrespective of temperature. The best gel properties (low values of loss factor, tanδ = G''/G', and minor frequency dependence, i.e., low n', n'' exponents), were observed at 20 °C for B30 and R30. The viscoelastic parameters (G and G) increased with ripening time, irrespective of the temperature, and for a fixed ripening time they were lower at higher temperature. At 75 °C, all samples exhibited notable frequency dependence (n'' ≫ n'), resulting in shear-induced gelation at low frequencies (high oscillation times) which was consistent with data in thermal profiles from 70 °C to 90 °C.
测定了西班牙用牛奶制成的阿夫埃加·皮图白奶酪（B）和红奶酪（R）在成熟3、15、30和60天时的热粘弹性和生化特性。各品种间脂肪含量（>45 g/100 g总固形物，TS）和氯化钠含量（<3 g/100 g TS）相似，且不随成熟度变化。B和R样品中的总固形物、pH值、氮组分和脂肪酸度随成熟时间增加。在第3天时，B奶酪中的乳糖含量高于R奶酪，在整个成熟过程中逐渐降解，但在60天时两种奶酪中均未完全消失。通过应力扫描（6.3 rad/s，20℃）在线性粘弹性区域（LVER）测定粘弹性参数：应力幅值（σ）和复数模量（G*）增加，而应变幅值（γ）在60天前降低。还在20℃、50℃和75℃下于LVER测定了机械光谱，结果表明所有样品均表现为“真正的凝胶”（弹性模量G'>粘性模量G''），与温度无关。在20℃时，B30和R30表现出最佳的凝胶特性（损耗因子tanδ = G''/G'值低，频率依赖性小，即n'、n''指数低）。粘弹性参数（G和G）随成熟时间增加，与温度无关，且在固定的成熟时间下，温度越高其值越低。在75℃时，所有样品均表现出显著的频率依赖性（n''≫n'），导致在低频（高振荡时间）下发生剪切诱导凝胶化，这与70℃至90℃热曲线中的数据一致。
