Virtual Thermocouple: A Non-Invasive Multipoint Product Temperature Measurement for Lyophilization

Monitoring product temperature during lyophilization is of critical importance, especially during the process development stage, as the final product may be jeopardized if its process temperature exceeds a threshold value. While conventional thermocouples can track product temperature, they are invasive and can significantly alter the freezing and drying behavior. In this work, a new methodology for non-invasive product temperature monitoring and drying behavior during the entire lyophilization process is proposed and experimentally validated. The method is based on a new flexible wireless multi-point temperature sensing probe that is attached to the outside of the vial. Combining the wirelessly-collected data with advanced multi-physics simulations allows the accurate extraction of the product temperature non-invasively.

NUMERICAL SEARCH OF MATHEMATICAL MODEL PARAMETERS OF FOOD PRODUCTS FROM HYDROBIONTS FOR PASTEURIZATION PPROCESS

The article highlights the numerical search for the mathematical model parameters of food products from hydrobionts put into hermetically sealed canning containers. The mathematical description of the canned products was given as transfer functions. The input value is a retort short-term temperature-time dependence and the output value is the product temperature dynamics. The search for the transfer function coefficients was performed by the numerical optimization method based on the plant response. The product temperature response data was obtained experimentally with thermologgers of the “iButton Data Loggers” series during canned food pasteurization. The numerical search for the mathematical model parameters of food products was carried out using the software AutoCont Lite: SeekerC developed by the author at the Automation and Computer Engineering Department of Murmansk State Technical University. A first-order factor was chosen as a candidate for a product model in a tin can, and for a product in a glass container there was chosen a third-order factor. To solve the problem of numerical search for model parameters the integral estimate was employed as an optimization criterion. It is calculated as the square deviation between the output values of the model and the plant over the investigation period. The research resulted in mathematical models of fishery-canned products obtained in the transfer function form. The obtained result was applied for modeling and subsequent automatic control system implementation for the industrial autoclave ASCAMAT-230 during the canned food pasteurization.

Cycle Development in a Mini-Freeze Dryer: Evaluation of Manometric Temperature Measurement in Small-Scale Equipment

The objective of this research was to assess the applicability of manometric temperature measurement (MTM) and SMART™ for cycle development and monitoring of critical product and process parameters in a mini-freeze dryer using a small set of seven vials. Freeze drying cycles were developed using SMART™ which automatically defines and adapts process parameters based on input data and MTM feedback information. The freeze drying behavior and product characteristics of an amorphous model system were studied at varying wall temperature control settings of the cylindrical wall surrounding the shelf in the mini-freeze dryer. Calculated product temperature profiles were similar for all different wall temperature settings during the MTM-SMART™ runs and in good agreement with the temperatures measured by thermocouples. Product resistance profiles showed uniformity in all of the runs conducted in the mini-freeze dryer, but absolute values were slightly lower compared to values determined by MTM in a LyoStar™ pilot-scale freeze dryer. The resulting cakes exhibited comparable residual moisture content and optical appearance to the products obtained in the larger freeze dryer. An increase in intra-vial heterogeneity was found for the pore morphology in the cycle with deactivated wall temperature control in the mini-freeze dryer. SMART™ cycle design and product attributes were reproducible and a minimum load of seven 10R vials was identified for more accurate MTM values. MTM-SMART™ runs suggested, that in case of the wall temperature following the product temperature of the center vial, product temperatures differ only slightly from those in the LyoStar™ freeze dryer.

Changing Wheat Bran Structural Properties by Extrusion-Cooking on a Pilot and Industrial Scale: A Comparative Study

Extrusion-cooking can be used to change the techno–functional and nutrition-related properties of wheat bran. In this study, pilot-scale (BC21) and industrial-scale (BC45) twin-screw extrusion-cooking using different types of extrusion (single-pass, double-pass and acid extrusion-cooking) and process parameters (temperature, moisture) were compared for their impact on wheat bran. When applying the same process settings, the higher strong water-binding capacity, extract viscosity and extractability displayed by bran extruded using the industrial set-up reflected a more considerable wheat bran structure degradation compared to pilot-scale extrusion-cooking. This was attributed to the overall higher specific mechanical energy (SME), pressure and product temperature that were reached inside the industrial extruder. When changing the type of extrusion-cooking from single-pass to double-pass and acid extrusion-cooking, wheat bran physicochemical characteristics evolved in the same direction, irrespective of extruder scale. The differences in bran characteristics were, however, smaller on industrial-scale. Results show that the differentiating power of the latter can be increased by decreasing the moisture content and increasing product temperature, beyond what is possible in the pilot-scale extruder. This was confirmed by using a BC72 industrial-scale extruder at low moisture content. In conclusion, the extruder scale mainly determines the SME that can be reached and determines the potential to modify wheat bran.

Modeling the Effects of Product Temperature, Product Moisture, and Process Humidity on Thermal Inactivation of Salmonella in Pistachios during Hot-Air Heating

ABSTRACT Prior efforts to model bacterial thermal inactivation in and on low-moisture foods generally have been based on isothermal and iso-moisture experiments and have rarely included dynamic product and process variables. Therefore, the objective of this study was to test appropriate secondary models to quantify the effect of product temperature, product moisture, and process humidity on thermal inactivation of Salmonella Enteritidis PT30 on pistachios subjected to dynamic dry- or moist-air heating. In-shell pistachios were inoculated with Salmonella Enteritidis PT30, equilibrated in controlled-humidity chambers (to target water activities [aw] of 0.45 or 0.65), and in some cases, subjected to a presoak treatment prior to heating in a laboratory-scale, moist-air convection oven at multiple combinations (in duplicate) of dry bulb (104.4 or 118.3°C) and dew point (∼23.8, 54.4, or 69.4°C) temperatures, with air speed of ∼1.3 m/s. Salmonella survivors, pistachio moisture content, and aw were quantified at six time points for each condition, targeting cumulative lethality of ∼3 to 5 log. The resulting data were used to estimate parameters for five candidate secondary models that included combinations of product temperature, product moisture, aw, and/or process dew point (coupled with a log-linear primary model). A model describing the D-value as a function of temperature and dew point fit the data well (root mean squared error [RMSE] = 0.86 log CFU/g); however, adding a term to account for dynamic product moisture improved the fit (RMSE = 0.83 log CFU/g). In addition, product moisture content yielded better model outcomes, as compared with aw, particularly in the case of the presoaked pistachios. When validated at the pilot scale, the model was conservative, always underpredicting the experimental log reductions. Both dynamic product moisture and process humidity were critical factors in modeling thermal inactivation of Salmonella in a low-moisture product heated in an air-convection system. HIGHLIGHTS

Optimization of Heat and Mass Transfer Process in Single Screw Floating Fish Feed Extruder

To optimize the extrusion conditions of locally developed single screw floating fish feed extruder. A factorial experiment in completely randomized design was employed to study the effect of extrusion variables: feed moisture content (20, 30, and 40% wet basis), screw speed (158.5, 245, 334 rpm), die size (4, 6, 8, mm) while checking for their effect on Product temperature of the feed produced. Product temperature is strongly related to the extrusion process parameters under study. Product temperature decreased with increasing moisture content. Optimum condition was found at 74.11⁰C at the feed section, 80.83⁰C at compression section and 85.15⁰C at metering section, screw speed at 330.5 rpm, feed rate at 0.6 kg/min, die size at 7.47 mm, moisture content at 39.87%, particle size at 1.1., and the coefficient for the final model is 0.93 which indicated that the model is good. The extruder was found to be cost efficient for floating fish feed production. Thus, model-fitting using response surface methodology was performed to examine their effect on product temperature. Quadratic coefficients fit the extrusion data very well, better than linear models. The equations relating the various dependent and independent variables were established to predict the performance of the machine.