Water Activity Of Cheese Research Articles

Analysis of the cheese components’ influence on the dehydration process under reduced pressure

This work is aimed at studying the influence of various components’ content on the process of vacuum dehydration. It was found that with an increase in the proportion of fat in dry matter from 10 to 20 %, the duration of disinfection increases by 4 %. The further grows of the fat proportion from 20 to 50 increases the process duration by 54 %. It was revealed, when cheeses, with the fat proportion equal from 10 to 50 %, a change their fat proportion by 1 %, the duration of dehydration decreases by 4.25 minutes, and the drying rate grows by 0.0065 %/min. It has been discovered that with an increase in the table salt concentration with the same mass fraction of cheese moisture 53–55 %, a decrease in the rate of dehydration is observed as well. In the period with a constant drying rate at a concentration of sodium chloride of 1 %, the drying speed is 0.98 %/min; 2 % – 0.8 %/min; 3 % – 0.72 %/min; 4 % – 0.54 %/min. The amount of water activity in cheeses was investigated. It was established that with an increase in the concentration of table salt from 1 to 4 %, the water activity of cheese before drying changes by 0.131; after drying – by 0.174.

Effects of moisture and salt migration on cheese firmness in cheese-in-sausage products

Moisture and salt migration are responsible for the softening of cheese, called cold melt, found in cheese-in-sausage products. By characterizing the rate of moisture and salt migration in model cheese-in-sausage systems, diffusion coefficients for water and salt in cheese were obtained. As expected, the rate of moisture migration was greater when the initial driving force (difference in water activities of cheese and sausage) were greatest. These conditions also led to most rapid softening of the cheese. An edible barrier was found to reduce but not completely inhibit moisture migration and softening, whereas formulation to match water and salt activity of sausage and cheese virtually eliminated moisture migration and softening.

Modeling of Camembert-Type Cheese Mass Loss in a Ripening Chamber: Main Biological and Physical Phenomena

A model of the mass loss of Camembert-type cheese was established with data obtained from 2 experimental ripening trials carried out in 2 pilot ripening chambers. During these experiments, a cheese was continuously weighed and the relative humidity, temperature, oxygen, and carbon dioxide concentrations in the ripening chamber were recorded online. The aim was to establish a simple but accurate model that would predict cheese mass changes according to available online measurements. The main hypotheses were that 1) the cheese water activity was constant during ripening, 2) the respiratory activity of the microflora played a major role by inducing heat production, combined with important water evaporation, 3) the temperature gradient existing inside the cheese was negligible, and the limiting phenomenon was the convective transfer. The water activity and the specific heat of the cheeses were assessed by offline measurements. The others parameters in the model were obtained from the literature. This dynamic model was built with 2 state variables: the cheese mass and the surface temperature of the cheese. In this way, only the heat transfer coefficient had to be fitted, and it was strongly determined by the airflow characteristics close to the cheeses. Model efficiency was illustrated by comparing the estimated and measured mass and the mass loss rate for the 2 studied runs; the relative errors were less than 1.9 and 3.2% for the mass loss and the mass loss rate, respectively. The dynamic effects of special events, such as room defrosting or changes in chamber relative humidity, were well described by the model, especially in terms of kinetics (mass loss rates).

Effect of Cheese Water Activity and Carbohydrate Content on the Barotolerance of Listeria monocytogenes Scott A

High-pressure processing is an appropriate technique for improving the microbiological safety of packaged ready-to-eat foods. The effect of high-pressure treatment on Listeria monocytogenes Scott A inoculated into fresh Hispánico-type cheese and ripe Mahón cheese was investigated. A 3.8-log reduction in the counts of L. monocytogenes Scott A in fresh cheese was recorded after 3 min at 400 MPa and 12°C, whereas 18 min under the same conditions was required to obtain a 1-log reduction in ripe cheese. Dry matter values were 48.96% for fresh cheese and 58.79% for ripe cheese, and water activity (aw) values were 0.983 and 0.922, respectively. In dehydrated fresh cheese (58.20% dry matter) in which 5% NaCl was added to achieve a 0.904 aw value, L. monocytogenes Scott A counts were lowered by only 0.4 log after treatment for 10 min at 400 MPa. On the other hand, in a 60:40 mixture of ripe cheese:distilled water with a 0.976 aw value, the reduction under the same conditions was 3.9 log. Within the aw range of 0.945 to 0.965, L. monocytogenes Scott A barotolerance was significantly higher in fresh cheese than in ripe cheese for equivalent aw values. Carbohydrate content was higher in fresh cheese than in ripe cheese. The addition of lactose at a concentration of 5 mg/g to an 85:15 mixture of ripe cheese:distilled water did not influence L. monocytogenes Scott A barotolerance during treatment for 10 min at 400 MPa. Galactose at a concentration of 5 mg/g had a protective effect during high-pressure treatment, and glucose at a concentration of 5 mg/g favored L. monocytogenes Scott A survival during refrigerated storage of pressurized samples at 8°C for 5 days.

Modelling of French Emmental cheese water activity during salting and ripening periods

Water sorption isotherms of French Emmental cheese have been determined at various temperatures (between 4 and 28 °C) for core or rind samples taken at various ripening stages during a standard 74 days ripening period. The differences observed between all the experimental isotherms are probably due to the evolution of product composition during the cheese ripening. Experimental data concerning the water activity profiles for industrially processed Emmental cheese have been collected after different brining experiments carried out at usual temperature conditions (4–18 °C) and all along the ripening cycle. The local water activity profiles during the Emmental brining and ripening periods are strongly dependent on the local NaCl concentration distribution. All these profiles vary in relation to the process step and of the process time. For the brining step, a precise correlation was proposed to express the influence of the water content and of the NaCl concentration. For the ripening period, a more general correlation expressing the water activity as a function of the water, NaCl and free NH 2 group concentrations was fitted to our experimental data. This last correlation was able to interpret the activity profiles more precisely during an Emmental ripening cycle in industrial conditions than the physical models of sorption fitted to the water sorption curves.

Improved equation for cryoscopic estimation of water activity in cheese

Cryoscopes employed in dairy plants for routine quality control of milk can be used for the determination of the water activity ( A w of cheese according to the equation: A w=1·0155+0·1068. fp where fp is the freezing point in °C of an aqueous extract of cheese solutes obtained under standard conditions. This linear regression equation was obtained for 139 pairs of A w and fp measurements. The differences between the measured and calculated A w values in the range 1·00–0·90 were only greater than 0·02 A w units in a small number (6·5%) of the samples with the lower A w values. Hence this cryoscopic approach can be applied by the cheese industry as a straightforward quality control technique.

Water sorption by proteins: milk and whey proteins.

The content and physical state of water in foods influence their physical, chemical, quality, safety, and functional behavior. Information concerning the sorption behavior of dairy proteins, in the water activity (Aw) range 0 to 0.9, is collated in this paper. The sorption behavior of proteins in general, the kinetics of absorption, factors affecting water binding, the phenomenon of desorption hysteresis, and the chemical and physical nature of water/protein interactions are reviewed in general terms. This is followed by a discussion of thermodynamic aspects of sorption phenomena and the adequacy of the various equations for describing sorption isotherms of proteins. After a discussion of the methods available for measuring sorption by milk proteins, the sorption behavior of various milk protein preparations, i.e., nonfat dry milk, whey proteins, caseins, and milk powders is summarized. Finally, the water activity of cheese and its relationship to solute mobility and solvent water are discussed. Some of the unique features of protein behavior, i.e., conformational changes, swelling, and solubilization are cited as possible sources of disparities between various reports.

Prediction of Water Activity of San Simón Cheese

In San Simón cheese water activity was highly related to moisture content and, consequently, to the aqueous concentration of many solid components. The following linear regression equations aw = .7662 + .0046g moisture/100g cheese, and aw = 1.0234 - .0070g ash/100g moisture, as well as a simple nomograph based on both chemical parameters, was used to predict water activity of San Simón cheese with an absolute error not greater than±.01 often found in measurements of water activity by different methods.

Nomograph for Predicting Water Activity of Soft Cheese

In soft cheese water activity is determined almost solely by the sodium chloride concentration in the aqueous phase of the cheese, and the water activity can be predicted with reasonably accuracy from percentages of cheese moisture and salt by a simple nomograph. Because the true water activity cannot be higher than that calculated, the nomograph can be useful for routine control of the “upper water activity limit” of soft cheese in the high-water activity range of .96 to 1.00, in which the true water activity is difficult to measure.

Water Activity and Chemical Composition of Cheese

In most cheeses with a moisture content above about 40% a simple and reasonably accurate predictive equation for water activity can be derived from the sodium chloride molality (aw = 1 −.033M). In cheese with a moisture content below about 40% the molality of sodium chloride does not provide a basis for an accurate calculation of cheese water activity because of the additional effect of other solids lowering water activity.