Texture of a Port Salut Argentino light cheese with milk protein concentrate after 5 months of frozen storage was studied. Behavior of dynamic rheological measurements during ripening time (6, 20, 33, 47 and 68 days) with maturation index was analyzed. At 68 days of ripening, moisture decreased by 11% and total nitrogen content increased by 25% in frozen cheeses with respect to control cheeses. Between 6 and 68 days of ripening, maturation index was higher for frozen (17.8-29.1) than control cheeses (4.4-11.6). G′ was higher than G″ showing that elastic behavior was dominant. During ripening, these parameters decreased in control cheeses, but increased in frozen cheeses. According to power law model parameters, elastic properties were more sensitive to changes with frequency. Coefficient a was significantly affected for both freezing process and ripening time, coefficient b only by freezing process. Long frozen storage period affected significantly the physicochemical and textural characteristics. PRACTICAL APPLICATIONSTexture is important to the consumer to determine the quality and preference of a cheese variety. The effect of freezing on physicochemical and rheological properties of cheeses was widely studied due to its importance over the texture. Freezing can be a useful methodology to transport cheeses to long-distance commercial places without any modifications. This paper focuses on textural changes of Port Salut Argentino light cheese with milk protein concentrate after a long frozen storage period (5 months) and during the ripening time (expressed as maturation index). Relations between the power law parameters obtained from rheological measurements with maturation time were studied. Similar textural characteristics can be obtained during ripening after thawing for increasing commercial demand. The obtained results can be important to obtain equal cheese characteristics after being transported in frozen state.

Thermodynamic studies on phase transformation of biopolymers in solution are useful to understand their nature and to evaluate their technological potentials. Thermodynamic studies should be conducted avoiding time-related phenomena. This condition is not easily achieved in hydrophilic biopolymers. In this contribution, the simultaneous effects of pH, salt concentration, and cooling rate (Cr) on the folding from random coil to triple helical collagen-like structures of gelatin were systematically studied. The phase transformation temperature at the absolute invariant condition of Cr = 0 °C/min (T(T)Cr=0) ) is introduced as a conceptual parameter to study phase transformations in biopolymers under quasi-thermodynamic equilibrium and avoiding interferences coming from time-related phenomena. Experimental phase diagrams obtained at different Cr are presented. The T(T)(Cr=0) compared with pH and TT(Cr=0) compared with [NaCl] diagram allowed to explore the transformation process at Cr = 0 °C/min. The results were explained by electrostatic interactions between the biopolymers and its solvation milieu.

Port Salut Argentino light cheese is a typical variety of soft cheese produced in Argentina made with cow milk, and in this work has the addition of milk protein concentrate (MPC). Aroma and flavor are the most important food quality criteria, in fact it is generally accepted that the volatile profile reflects the image of the smelting and aroma of cheeses. To characterize the profile of volatile compounds, gas chromatography coupled to mass spectrometry is the used method, and the isolation of compounds from cheese matrix, was using headspace solid phase micro-extraction. The methodology allowed the determination of 24 volatile compounds in the Port Salut Argentino Light with MPC at 34 days of maturation: six fatty acids, six ketones, five alcohols, three esters, one aldehyde, two aromatics and one sulphur compound. Some of the metabolic pathways for their biosynthesis are reviewed to indicate the possible origin of the compounds identified.