Vivaldo Silveira Junior

Improving transport container design to reduce broiler chicken PSE (pale, soft, exudative) meat in Brazil

Throughout the chicken production chain, transport from farm to the commercial abattoir is one of the most critical sources of stress, particularly heat stress. The aim of this work was to describe the performance of a new prototype truck container designed to improve the microenvironment and reduce the incidence of pale, soft and exudative (PSE) meat and dead on arrival (DOA) occurrences. Experiments were carried out for four different conditions: regular and prototype truck, both with and without wetting loaded cages at the farm (for bird thermal stress relief) just before transporting. While there was no difference in the DOA index (P ≥ 0.05), the prototype truck caused a reduction (P < 0.05) in the occurrence of PSE meat by 66.3% and 49.6% with and without wetting, respectively. The results of this experiment clearly revealed a low-cost solution for transporting chickens that yields better animal welfare conditions and improves meat quality.

Avaliação de temperaturas em câmaras frigoríficas de transporte urbano de alimentos resfriados e congelados

The objective of this work was to monitor the operational conditions of the transport of chilled and frozen foods during delivery within cities and to evaluate the impact of the door openings on the alteration of the internal temperature of the refrigerated environment. Several temperature and pressure sensors were used in a refrigerated container with two compartments and they were installed in the refrigeration system unit and on the internal and external surfaces of the container. After the monitoring tests, it was verified that door openings during deliveries resulted in a disturbance that raised the internal temperature of the refrigerated container above values recommended for adequate conservation of the products transported. Moreover, increasing the number of door openings promoted a cumulative effect on the internal temperature, mainly in the chilled food compartment of the container. It was concluded that the refrigeration system unit presented serious limitations with regard to the maintenance of the containers internal temperature during the actual distribution routine, since it does not possess enough instantaneous capacity to restore the temperature set-point between deliveries.

Reologia do açúcar líquido invertido: influência da temperatura na viscosidade

The rheological behavior of invert liquid sucrose with two different percentages of inversion (59.68% and 89.88%) was studied from 17°C to 65°C using a concentric cylinders rheometer. The results showed that the invert liquid sugar exhibits Newtonian behavior within the range of temperature tested. The effect of temperature on viscosity of invert sugar was expressed by the Arrhenius relationship and the fitted models presented correlation coefficients (R2) greater than 0.99. The activation energies calculated for both samples, 59.68% and 89.88% of inversion, were respectively 70.5kJ.mol-1 and 86.5kJ.mol-1.

Influence of secondary packing on the freezing time of chiken meat in air blast freezing tunnels

Freezing of poultry cuts in continuous convective air blast tunnels is normally performed with the products protected by Low Density Polyethylene (LDPE) as a primary packaging and using Corrugated Cardboard Boxes (CCB) as secondary packaging. The objective of this work was to investigate the influence of these secondary packaging on the freezing of poultry cuts in continuous convective air blast tunnels. The study was performed by replacing CCB with Perforated Metal Boxes (PMB) in order to remove the packaging thermal resistance. The assays, performed in a industrial plant, demonstrated that CCB used commercially for meat freezing have a high heat transfer resistance. Their replacement with PMB can lead to shorter freezing times and spatially homogeneous freezing. Reductions of up to 45% in the freezing times were observed using PMB. The plateau of the temperature curve, related to the freezing time of free water, was significantly reduced using PMB, which is accepted to lead to better product quality after thawing. As the products were protected by the LDPE films as primary packaging, their appearance were not affected. The results presented in this work indicate that replacing CBB with PMB can be an excellent alternative to reduce freezing time and improve freezing homogeneity in industrial air blast tunnels, which could also be applied to other products.

FUZZY-PID CONTROLLER APPLIED TO A REFRIGERATION SYSTEM

A refrigeration system exhibits a dynamic behavior on which the variables are interdependent and subjected to oscillation, hence, implicating necessity of changes on operating conditions and undesirable energy expenses. These characteristics ratify the importance of adequate dimensioning and equipment selection to find pre-defined operating conditions such as, the maximum cooling capacity and the evaporating and condensing temperatures. The application of fuzzy control in industrial processes is growing fast in the last decades, mainly in processes whose first principle models require complex methods to be simulated. In these cases, the fuzzy controllers’ capacity of acting correctly based only on expert knowledge and on the capacity of inter-relating all the variables of the process are attractive features. This work presents the experimental development and evaluation of fuzzy-PID controllers for the maintenance of the evaporating temperature in a chiller. The system was submitted to load and set-point disturbances accomplishing an analysis based upon error parameters and transient response. The results showed that fuzzy controllers were adapted satisfactorily.

Processo de congelamento em túnel portátil com convecção forçada por exaustão e insuflação para paletes

The objective of this work is to build an experimental portable forced-air freezing tunnel which creates a low or high pressure region surrounding the product. Comparative studies with air exhausting and blowing were conducted. The tunnel was built and placed inside a freezing product storage chamber, and the objective was to improve the air circulation and the thermal distribution between the product and cold air for a sample batch left inside the chamber. A heat transfer analysis comparing the process and the air distribution around the product was performed. The air evacuation process reduced up to 14% of the freezing time in relation to the blowing system and 10% in relation to the mixed system.

Variation of Transfer Function for Dynamic Behavior of a Vegetable Oil Refrigeration Unit

The knowledge of the dynamic behavior of a process variable is essential for characterizing the process and defining the control logic configuration to be implemented in automated plants. This work aims to characterize the dynamic behavior of a cooling process of vegetable oil under different perturbation, starting from the same initial steady state conditions. The experimental unit is consists of two sectors: 1) modular heating and 2) cooling of the vegetable oil. In the second section there are three cooling modules: 2a) set of serial finned heat exchangers with forced-air; 2b) nebulization system and 2c) plate heat exchanger with chilled water as cold fluid. Both heat exchangers showed a good adjustment to a linear second-order function for each perturbation applied. The processes, however, showed low level nonlinear behavior. In regard to these nonlinearities, the process curves were adjusted to a nonlinear second-order function with parameters – proportional gain, perturbation intensity and time constant – varying with the manipulated variable. It was verified that the proposed model is suitable for the process in the considered operating range of the manipulated variable.