Characterization of Siahmazgi cheese, an Iranian ewe's milk variety: Assessment of physico-chemical, textural and rheological specifications during ripening

•Siahmazgi is an Iranian cheese manufactured from mixture of ewe and goat's milk.•Sheepskin was used as a container for ripening of this kind of cheese.•Distinct increase of salt and total solid contents were observed during ripening.•WSN and NPN were the proper indices for the progress in the proteolysis.•Higher values of rheological characteristics were found during ripening.

Siahmazgi cheese is an Iranian locally-made cheese produced from ewe's milk or a mixture of ewe and goat's milks in the suburbs of Rasht in the north of Iran. This kind of cheese is kept in sheepskin for six months under special condition which cause distinct physicochemical and textural characteristics. Therefore, in the present study the effect of ripening time (6 months) on the chemical, physicochemical, rheological and textural characteristics of Siahmazgi cheese (18 samples) was investigated. The rheological and textural properties were determined using rheometer (frequency sweep) and texture analyzer (uniaxial compression). Based on our findings, the measured values including pH, titratable acidity (TA), dry matter, fat, protein, ash, salt content, water soluble nitrogen in total nitrogen, and non-protein-nitrogen in total nitrogen significantly increased during ripening (P < 0.05). Furthermore, the results showed that the six-month ripened Siahmazgi cheese contained high values of dry matter (59.95 ± 0.08 g/100 g), salt (5.65 ± 0.05 g/100 g), and ash (7.24 ± 0.02 g/100 g). Regarding rheological and textural properties, storage modulus (G′), loss modulus (G″), fracture stress (σf) and firmness increased while loss tangent and fracture strain decreased.