Vanillin as an Antimicrobial for Producing Shelf-stable Strawberry Puree

The utilization of vanillin was studied as a natural antimicrobial in a combined technology for producing a shelf-stable strawberry purée. Mild heat treatment (blanching) was combined with addition of 3,000 ppm vanillin and 500 ppm ascorbic acid and adjustment of water activity (a_w) to 0.95 and pH to 3.0. This prevented growth of both native and inoculated flora for ≥60 days storage at room temperature.     

Microbial characterisation and stability of a farmhouse natural fermented milk from Spain

This work reports the microbial characterisation of a farmhouse natural fermented milk (NFM) with good sensorial properties produced in Spain. Culturing and denaturing gradient gel electrophoresis (DGGE) analyses showed thatLactococcus lactissubsp.lactis and L. lactissubsp.cremoris(approximate levels of 10⁹ cfu/mL) were dominant in this NFM, whileLactobacillus plantarumappeared at a lower level (10⁶–10⁷ cfu/mL). Repetitive extragenic palindromic (REP)‐PCR typing of the isolates identified single strains each ofLc. lactissubsp.lactis, Lc. lactissubsp.cremorisandLb. plantarum. These three strains formed a stable microbial association which has been maintained for at least some decades.     

Comparison of free amino acids and volatile components in three fermented milks

Free amino acids (FAAs) and volatile components were analysed in commercial samples of yoghurt and Actimel^® drink as well as laboratory‐made kefir. The lysine and cysteine were the principal amino acids and accounted for about 70% of the total FAAs in all the samples. However, the amino acid profiles in the different fermented milk products differed: on the whole values for most of the amino acids were observed to be significantly higher in the Actimel^® samples. A total of 50 volatile components were identified. The largest number of volatiles were found in the kefir. Ethanol, 2,3‐ butanodione and 3‐hidroxybutan‐2‐one were the most prevalent volatile components, with ethanol significantly higher in the kefir samples.     

CHANGES IN EQUILIBRIUM MODULUS AND αsl-CASEIN BREAKDOWN DURING THE RIPENING OF PORT SALUT ARGENTINO CHEESE AS AFFECTED BY FROZEN STORAGE

The effect of the freezing, frozen storage and thawing on textural parameters and α_sl-casein breakdown during the ripening of Port Salut Argentino cheese was studied. Moisture content, salt concentration, casein profiles and asymptotic equilibrium modulus were monitored in control cheeses ripened at 5C and in cheeses, stored at -22C for 30 days, thawed and ripened at 5C, for different ripening times (1, 6, 13, 27 and 56 days) and two sampling zones (central and external). The freezing process significantly increased the rate of α_sl-casein and α_sl-I-casein hydrolysis. This process may affect the susceptibility of α_sl-casein to chymosin attack and also the availability of hydrolytic enzymes released by damaged microorganisms, which may contribute to the faster hydrolysis of α_sl-I-casein. The freezing process did not significantly affect the decay rates of asymptotic equilibrium modulus. First order kinetics constants for decay of the asymptotic equilibrium modulus were 3.71 10^-2day^-1 (control cheeses, central zone), 8.48 10^-2 day^-1 (control cheeses, external zone), 4.52 10^-2 day^-1 (frozen cheeses, central zone), and 11.43 10^-2 day^-1 (frozen cheeses, external zone). Significant differences in the decay rates of asymptotic equilibrium modulus were found between central and external zones in control and frozen cheeses primarily due to differences in moisture contents of the sampling zones.     

Average NaCl Concentration in Cheese for Different Volume Ratios of Brine and Solid during Salting

Fick's second law for unsteady-state, one-dimensional diffusion in solid media from a well stirred solution of limited volume was used to develop mathematical equations for modeling the mass transfer of NaCl in cheeses during salting. A computational method was employed to solve the equations and analyze the suitable conditions for salt penetration in finite cylindrical cheeses. Various volume ratios of solution and solid were considered to determine the variation of NaCl concentration in cheeses. Experimental results were predicted by the proposed mathematical model with less than 10% error.     

RHEOLOGICAL PROPERTIES OF MOZZARELLA CHEESE DETERMINED BY CREEP/RECOVERY TESTS: EFFECT OF SAMPLING DIRECTION, TEST TEMPERATURE AND RIPENING TIME

The viscoelastic properties of mozzarella cheese using a creep/recovery test considering different sampling directions (parallel and perpendicular to protein fiber orientation), test temperatures (20, 30 and 40C) and ripening times (1, 8, 15, 29 and 36 days) were studied. Creep data were interpreted by a Burger model of four parameters. A semiempirical approach was proposed to obtain the contribution of each main compliance to the total deformation of the system. Creep tests at different temperatures allowed gaining a better understanding of changes that occur in the cheese matrix during heating and ripening. Sampling direction did not affect any of the parameters studied. Finally, it was clearly observed that cheese matrix behaves as a quite different physicochemical system depending on temperature. Therefore, it is recommended to carry out the rheological tests at different temperatures to evaluate appropriately the viscoelastic properties of mozzarella cheese.

PRACTICAL APPLICATIONS

Mozzarella cheese must have certain characteristics to be used on pizzas and on other prepared foods that use the cheese in melted state. The protein chains in the mozzarella curds coalesce into large strands that are oriented in the direction of stretching. For this reason, mozzarella cheese has an anisotropic structure. Therefore, it is relevant to determine the effect of protein fiber orientation on the rheological properties. Valuable information may be obtained through the creep/recovery test of mozzarella cheese samples to study its rheological properties and to explain molecular mechanisms that occur during ripening or melting processes considering sampling direction.