Storage under pressure of requeijão without refrigeration

• Autor(a) principal: Duarte, Ricardo Valente
• Data de Publicação: 2014
• Tipo de documento: Dissertação
• Idioma: eng
• Título da fonte: Repositório Científico de Acesso Aberto de Portugal (Repositórios Cientìficos)
• Texto Completo: http://hdl.handle.net/10773/13824
• topic: Biotecnologia alimentar; Lacticínios; Conservação dos alimentos - Alta pressão

Storage under mild pressure of Requeijão, the traditional Portuguese whey cheese, a highly perishable dairy food, was evaluated as a possible energy costless alternative to refrigeration. At a laboratorial scale, the whey cheese was stored during 4 and 8 hours, at different pressure levels (0.1, 100, and 150 MPa) and temperatures (25, 30, and 37 ºC), and the results were compared with refrigeration (4 ºC). A experiment in an industrial equipment was conducted, using Requeijão with similar sizes to those commercially available, for longer storage periods, 12 and 24 hours, under 100 MPa at room temperature (≈21 ºC), with the respective control under refrigeration. A post-hyperbaric storage study was performed, in which samples previously stored under refrigeration and at room temperatures under 0.1 and 100 MPa, for 24 hours, were then stored under refrigeration at atmosphere pressure, for three days. Microbial analyses showed that storage for 4 hours at 100 MPa was able to maintain microbial counts similar to refrigeration and initial counts, ≈3 Log10 CFU/g, at all tested temperatures. By increasing the pressure to 150 MPa and the storage time to 8 hours, a microbial inactivation effect was observed for all microorganisms, being the lactic acid bacteria and Enterobacteriaceae reduced to counts below the detection limit. Hyperbaric storage in general maintained pH, water activity and lipid oxidation values, at levels similar to refrigeration, retaining also the colour of Requeijão. The experiment in an industrial equipment obtained similar results to those mentioned above, with a clear microbial growth inhibition and inactivation for all microorganism studied, at 12 and 24 hours of storage, comparatively to refrigeration. The results obtained in this study, shows that the storage under pressure of highly perishable foods, could be a possible energy costless alternative to refrigeration, with economical benefits for industries and ecological advantages.