Desenvolvimento de um sistema de aplicação simultânea de micro-ondas e ultravioleta UV-C para descontaminação de carne bovina

Abstract

The raw meats they are favorable to the growth of microorganisms, whether they come from the microbiota of the flesh or of the production process. The relevance of the use of radiation to the food technology as well as the combination of emerging technologies has been proposed in order to reduce microbiological changes and increase the shelf life of food. In this context, the aim of this study was to evaluate the effects of applying microwave radiation and the optimization of this with ultraviolet radiation in the UV-C decontamination of ground beef in natura. A conventional microwave oven was used (2450 MHz) of 800 W, cadmium an ultraviolet lamp (228 nm), and the feedstock used was purchased at a local premises, food processed in the processing laboratory, kept under cooling to 2 ℃ to both treatments. Preliminary studies were performed to use the microwaves, determining the actual power, the determination of pulsed microwave radiation, the mapping of the microwave with ultrapure water, and thermographic imaging with ultraviolet light. The treatments were named: C or control, which was not subjected to irradiation; M 50 - treatment with pulsed microwave radiation (power 50%); 100 M - continuous treatment with microwave radiation (100% power); MUV 50 - Simultaneous treatment with pulsed microwave radiation and ultraviolet UV-C (50% power); MUV 100 - simultaneous continuous treatment with microwave radiation and ultraviolet UV-C (100% power). After the treatments, the samples were subjected to microbiological analysis of Salmonella spp, Staphylococcus coagulase-positive, aerobic mesophilic, psychrotrophic, thermophilic, molds and yeasts, Enterobacteriaceae, thermotolerant, and the physical and chemical pH, color, water and moisture activity. The results revealed that the adopted microwave oven has 78,4% energy efficiency, focusing on border regions of the turntable and the study of pulsed microwave radiation showed more homogeneous distribution of radiation in the samples. The thermographic images confirmed differences in the distribution of the microwave energy applied to the forms, pulsed and continuous, and greater temperature variation (Δ𝑇� = 31,6 ℃) for the continuous process and consequently higher hots spots, while the images thermographic simultaneous processes of continuous and pulsed showed minor variations in temperature, Δ𝑇� = 19,4 ℃ and Δ𝑇� = 11,5 ℃ respectively. Still, it was done the mapping with ultraviolet light through the mesophilic aerobic counts, which showed no significant difference (p>0,05), and the height and the sample collection site in the cooler. As for microbiological and physico-chemical results of samples submitted to different treatments, all they presented siginificativa difference as compared to the control. However, they stood out simultaneous treatment technologies, as showed better effects on microbial reduction, especially the MUV 100 which reduced significantly (p <0,05) all counts of Staphylococcus coagulase positive, aerobic mesophilic, psychrotrophic, thermophilic and molds and yeast. The physical and chemical results, we emphasize the color of the samples treated by M 100 and 100 MUV which did not differ significantly from the control (p> 0,05) keeping the color of fresh meat. All samples, treated and control, showed no Enterobacteriaceae, thermotolerant and Salmonella spp (at 25 g / sample). The most efficient treatment was the microbiologically MUV 100, which was used to study the shelf life of the product, involving the analysis of aerobic mesophilic, psychrotrophic bacteria and Pseudomonas spp, pH, lipid oxidation (TBARS), total heme pigments, color , moisture and water activity. The study generally showed that it is possible to develop an efficient methodology, safe and with application potential for the conservation of food. The study of microbiológiaca and physico-chemical stability of the meat revealed that the simultaneous application of microwave and ultraviolet ground in fresh beef using the method developed is capable of reducing microbial counts and maintain shelf life storage for two days at 4 ℃ without much interference on the physicochemical characteristics.