Evaluation of proteolytic and physicochemical changes during storage of fresh Panela cheese from Queretaro, Mexico and its impact in texture

Mexican Panela cheeses manufactured with pasteurized cow's milk at a pilot plant scale were analyzed in order to determine the relationship between physicochemical and textural changes during 15-day storage. Changes in hardness, cohesiveness, springiness and chewiness were measured by texture profile analysis (TPA). Moisture, pH (superior and inferior rind and center) and total protein were evaluated with official methods. Proteolytic indexes (acid soluble nitrogen (ASN), non-protein nitrogen and 70% ethanol soluble nitrogen (EtOH-SN)) were obtained by selective precipitation and quantified by Kjeldahl method. Organic acids (lactic (LA), propionic (PA) and butyric acid (BA)) quantitation was done by high performance liquid chromatography. Analysis of variance (ANOVA) showed significant differences for all the physicochemical parameters evaluated, but only cohesiveness and springiness showed significant differences in texture parameters. By principal component analysis (PCA) two groups were separated, one from day 1 to 7 and one from day 9 to 15.