Histamine and Tyramine in Chihuahua Cheeses during Shelf Life: Association with the Presence of tdc and hdc Genes

Cheese is a product of animal origin with a high nutritional value, and it is one of the most consumed dairy foods in Mexico. In addition, Chihuahua cheese is the most consumed matured cheese in Mexico. In the production process of Chihuahua cheese, maturation is carried out by adding acid lactic microorganisms, mainly of the Lactococcus genus and, in some cases, also the Streptococcus and Lactobacillus genus. As part of the metabolism of fermenting microorganisms, biogenic amines can develop in matured foods, which result from the activity of amino decarboxylase enzymes. In cheeses, histamine and tyramine are the main amines that are formed, and the consumption of these represents a great risk to the health of consumers. In this work, the presence of biogenic amines (histamine and tyramine) was determined by HPLC at different times of the shelf life of Chihuahua cheeses. In addition, the presence of genes hdc and tdc that code for the enzymes responsible for the synthesis of these compounds (histidine and tyrosine decarboxylase, or HDC and TDC) was determined by molecular techniques. A significant correlation was observed between the presence of both histamine and tyramine at the end of shelf life with the presence of genes that code for the enzymes responsible for their synthesis.

Moisture sorption isotherms and thermodynamic properties of mexican mennonite-style cheese

Moisture adsorption isotherms of fresh and ripened Mexican Mennonite-style cheese were investigated using the static gravimetric method at 4, 8, and 12 °C in a water activity range (aw) of 0.08-0.96. These isotherms were modeled using GAB, BET, Oswin and Halsey equations through weighed non-linear regression. All isotherms were sigmoid in shape, showing a type II BET isotherm, and the data were best described by GAB model. GAB model coefficients revealed that water adsorption by cheese matrix is a multilayer process characterized by molecules that are strongly bound in the monolayer and molecules that are slightly structured in a multilayer. Using the GAB model, it was possible to estimate thermodynamic functions (net isosteric heat, differential entropy, integral enthalpy and entropy, and enthalpy-entropy compensation) as function of moisture content. For both samples, the isosteric heat and differential entropy decreased with moisture content in exponential fashion. The integral enthalpy gradually decreased with increasing moisture content after reached a maximum value, while the integral entropy decreased with increasing moisture content after reached a minimum value. A linear compensation was found between integral enthalpy and entropy suggesting enthalpy controlled adsorption. Determination of moisture content and aw relationship yields to important information of controlling the ripening, drying and storage operations as well as understanding of the water state within a cheese matrix.

Mexican Queso Chihuahua: functional properties of aging cheese

Queso Chihuahua, a semi-hard cheese manufactured from raw milk (RM) in northern Mexico, is being replaced by pasteurized milk (PM) versions because of food safety concerns and the desire for longer shelf life. In this study, the functional traits of authentic Mexican Queso Chihuahua made from RM or PM were characterized to identify sources of variation and to determine if pasteurization of the cheese milk resulted in changes to the functional properties. Two brands of RM cheese and 2 brands of PM cheese obtained in 3 seasons of the year from 4 manufacturers in Chihuahua, Mexico, were analyzed after 0, 4, 8, 12, and 16 wk of storage at 4°C. A color measurement spectrophotometer was used to collect color data before and after heating at 232°C for 5 min or 130°C for 75 min. Meltability was measured using the Schreiber Melt Test on samples heated to 232°C for 5 min. Sliceability (the force required to cut through a sample) was measured using a texture analyzer fitted with a wire cutter attachment. Proteolysis was tracked using sodium dodecyl sulfate-PAGE. Compared with PM cheeses, RM cheeses showed less browning upon heating, melted more at 232°C, and initially required a greater cutting force. With aging, cheeses increased in meltability, decreased in whiteness when measured before heating, and required less cutting force to slice. Seasonal variations in the cheesemilk had minimal or no effect on the functional properties. The differences in the functional properties can be attributed, in part, to the mixed microflora present in the RM cheeses compared with the more homogeneous microflora added during the manufacture of PM cheeses. The degree of proteolysis and subsequent integrity of the cheese matrix contribute to melt, slice, and color properties of the RM and PM cheeses. Understanding the functional properties of the authentic RM cheeses will help researchers and cheesemakers develop pasteurized versions that maintain the traditional traits desired in the cheeses.