Efeito de embalagens flexíveis na qualidade de leite pasteurizado e na sua aceitabilidade

• Ano de defesa: 2009
• Autor(a) principal: Pinto, Michele da Silva
• Orientador(a): Carvalho, Antônio Fernandes de
• Banca de defesa: Minim, Valéria Paula Rodrigues , Sant ana, Helena Maria Pinheiro , Andrade, Nélio José de
• Tipo de documento: Dissertação
• Tipo de acesso: Acesso aberto
• Idioma: por
• Instituição de defesa: Universidade Federal de Viçosa
• Programa de Pós-Graduação: Mestrado em Ciência e Tecnologia de Alimentos
• Departamento: Ciência de Alimentos; Tecnologia de Alimentos; Engenharia de Alimentos
• País: BR
• Palavras-chave em Português: Leite; Vida de prateleira; Embalagens
• Palavras-chave em Inglês: Milk; Shelf life; Packages; Packaging
• Área do conhecimento CNPq: CNPQ::CIENCIAS AGRARIAS::CIENCIA E TECNOLOGIA DE ALIMENTOS::CIENCIA DE ALIMENTOS
• Link de acesso: http://locus.ufv.br/handle/123456789/2860

This study aimed to evaluate four flexible packagings for pasteurized milk, as well as to evaluate their effects on shelf life of this product. First, films were tested for permeability to oxygen, light transmission, elasticity and traction. The layer number of each packaging and the hydrophobicity and roughness of the surface in contact with the product were also examined. Three multilayer polyethylene packages (Dupont Pouch) were tested: (1) multilayer polyethylene (PE) (SCLAIRFILM - 80E0337W7), (2) multilayer PE (SCLAIRFILM - 90B0324PW) and (3) multilayer PE SCLAIRFILM - 90E0323W7. A monolayer PE packaging (4) commercially used for pasteurized fluid milk was used as control. Based on the mechanical properties, the permeability to oxygen and light barriers, the packaging 1 provided high barrier to oxygen and light, supplying rigidity and resistance to traction, whereas the packaging 2 provided high barrier to oxygen, high tensile strength and high rigidity, but showed low barrier to light. The packaging 3 was very permeable to oxygen and provided high light barrier, low tensile strength and low rigidity. Finally, the package 4 showed low barrier to oxygen, allowed the passage of light, and showed low tensile strength and low rigidity. Microscopy techniques were useful tools for the initial characterization of packagings regarding the layer number and the surface profile sucha as roughness and hydrophobicity, so that, films 1, 2 and 3 had surfaces with lower roughness values . To assess the influence of each packaging on the shelf life of pasteurized milk, 1000 mL milk samples were packaged into the four packagings and stored at 5 ºC for 21 days. Microbiological analysis were carried out by standard plate counts and enumeration of psychrotrophic microorganisms every 3 days of storage, as well as determination of total coliforms, thermotolerant coliforms and Salmonella sp. was performed only on the day of milk packaging. Physicalchemical analyses were performed at time zero, including protein content, dry extract, lactose and fat content, and density and cryoscopy for raw and pasteurized milk. To determine the shelf-life, analyses of pH and acidity for milk of all packages were carried out every 3 days. Nutritional quality was assessed through the vitamin degradation by high performance liquid chromatography and lipid oxidation by the TBA method every 5 days of storage. Finally, consumer acceptance of milk in each of the packagings was tested using the attributes taste, aroma and overall impression with a hedonic scale of nine points. The microbiological quality of the raw material, for both raw milk and shortly after pasteurization, was found to meet the standards of the Brazilian legislation. Packaging did not affect (P > 0.05) mesophilic and psychrotrophic counts during storage. The end of shelf life, with respect to mesophilic count occurred at 12 days for all packagings. With respect to psychrotrophic count, the end of shelf life was at 18 days of storage regardless the packaging used. Regarding physical-chemical characteristics, the raw material was considered of good quality, with no evidence of tampering. All results were within the standards established by legislation for both raw milk and milk shortly after pasteurization. During shelf life, milk pH and acidity were not different (P > 0.05) among packagings, with variation occurring only with time. The Brazilian legislation determines a maximum acidity of 0.18% for milk to be considered as good quality, which was reached only after 18 days of storage. Barriers provided by the packagings had similar effects on lipid oxidation and riboflavin content of milk pasteurized and stored at 5 ºC for 21 days. Mean lipid oxidation found in units of optical density at 532 nm was 0.055 and the average riboflavin content was about 1.37 mg.L-1. There was also no difference (P> 0.05) for acceptability over time among the different packagings for the attributes aroma, flavor and overall impression, with the average scores by the assessors for the samples over the time was 6, lying between the hedonic terms like slightly and like moderately . Barriers provided by the packagings had similar effects on the characteristics of pasteurized milk stored at 5 ºC for 21 days, since during this time no differences were detected between the procedures.