Equipe Physico-Chimie des Systèmes Polyphasés, UMR 8612 du CNRS, 5 rue J. B. Clément, 92296 Châtenay-Malabry, France.
J Agric Food Chem. 2011 Apr 13;59(7):3125-34. doi: 10.1021/jf103641f. Epub 2011 Mar 4.
Both the composition and the thermal kinetics that are applied to processed cheeses can affect their texture. This study investigated the effect of the storage conditions and thermal history on the viscoelastic properties of processed cheese and the physical properties of the fat phase. The microstructure of processed cheese has been characterized. Using a combination of physical techniques such as rheometry, differential scanning calorimetry, and X-ray diffraction, the partial crystallization of fat and the polymorphism of triacylglycerols (TG; main constituents of milk fat) were related to changes in the elastic modulus and tan δ as a function of temperature. In the small emulsion droplets (<1 μm) dispersed in processed cheeses, the solid fat phase was studied at a molecular level and showed differences as a function of the thermal history. Storage of processed cheese at 4 °C and its equilibration at 25 °C lead to partial crystallization of the fat phase, with the formation of a β' 2 L (40.9 Å) structure; on cooling at 2 °C min(-1), the formation of an α 3 L (65.8 Å) structure was characterized. The cooling of processed cheese from 60 to -10 °C leads to the formation of a single type of crystal: α 3 L (72 Å). Structural reorganizations of the solid fat phase characterized on heating allowed the interpretation of the elastic modulus evolution of processed cheese. This study evidenced polymorphism of TG in a complex food product such as processed cheese and allowed a better understanding of the viscoelastic properties as a function of the thermal history.
应用于加工奶酪的组成和热动力学可以影响其质地。本研究探讨了储存条件和热历史对加工奶酪的粘弹性和脂肪相物理性质的影响。加工奶酪的微观结构已被表征。通过流变学、差示扫描量热法和 X 射线衍射等物理技术的组合，脂肪的部分结晶和三酰基甘油（TG；乳脂的主要成分）的多晶型性与弹性模量和 tan δ随温度的变化有关。在加工奶酪中分散的小乳液滴（<1 μm）中，在分子水平上研究了固体脂肪相，并表现出随热历史变化的差异。在 4°C 下储存加工奶酪并在 25°C 下使其达到平衡会导致脂肪相部分结晶，形成β'2L（40.9 Å）结构；以 2°C/min(-1)的速率冷却时，形成α3L（65.8 Å）结构。加工奶酪从 60°C 冷却至-10°C 会导致形成单一类型的晶体：α3L（72 Å）。在加热过程中对固体脂肪相的结构重组进行了表征，这有助于解释加工奶酪弹性模量的演变。该研究证明了 TG 在加工奶酪等复杂食品中的多晶型性，并更好地理解了热历史对粘弹性的影响。
