Estudo de latas eletrossoldadas para acondicionamento de ervilha, extrato de tomate e pessego em calda

AUTOR(ES)
DATA DE PUBLICAÇÃO

1998

RESUMO

The purpose of this study was to evaluate the welding quality and the performance of welded cans relative to the package/food interaction by means of storage tests in the packaging of three types of food products: peas, tomato paste and peaches in syrup. For each kind of product, two package alternatives were analysed as follows: one with the variation of the welding protective lacquer (for peas and tomato paste) and the other with the presence and the absence of the can internal lacquering. The welding quality of the different types of cans was determined through visual evaluation tests (verification of the regularity of the welding overlap before and after welding), tests of mechanical resistance (rip test, test of expansion and partial reversion of the cylinder) and metalographic evaluation of the longitudinal and cross sections (to evaluate fusion and presence of commas and inclusions) of the welded seams. All the test methods to evaluate the welding quality were adapted for this study specifically. Storage tests were conducted during 365 days in three temperature conditions, that is, 23, 30, 35°C, with periodical evaluations at intervals of 90 days relative to the internal visual appearance of the cans, vacuum level, chemical analyses of the product (pH, acidity and soluble solids), composition of the gases in the headspace (O2 and H2) and concentration of iron and tin in the product. The analysed packages were also characterized as to type and coating of the metallic material and of the internal lacquering. The evaluation of the quality of the welded cans revealed that the most effective test to determine the quality was the microstructure evaluation of the longitudinal and cross sections of the welded are a, although the different parameters are complementary. Pea cans had a slight quality alteration, tomato paste cans presented a higher variation with the occurence of several defects and one of the types of peach can presented insufficient fusion condition, whereas the other showed normal quality deviations. The correct distinction between the acceptable condition and the weld limit for each type of package, depending on the final application, was fundamental. Storage tests showed that the low corrosion in the pea can did not permit the differentiation of the two analysed packages. Therefore, it is not necessary to invest in a better protection of the welded seam; in this case, the influence of the storage temperature on the product/package interaction was not relevant. Tomato paste presented intense internal corrosion in the body and in the welded area, resulting in alteration of the internal surface, vacuum loss, swelling and iron and tin dissolution in the product, which were strongly influenced by the storage temperature. The can with epoxy-mina side stripe presented a slightly superior performance than the can with the epoxy-urea lacquer in the welding area. The peach in syrup packaged in a can without lacquer presented high tin dissolution and even alteration of the surface in different parts of the can, which shows that the use of the weld protective lacquer is dispensable in cans for this kind of product. Such cans presented corrosion by the detinning mechanism, which was strongly accelerated by the storage temperature of 35°C, showing that it is necessary to control the environment temperature for the adequate performance of these cans during storage.

ASSUNTO(S)

estabilidade embalagens

ACESSO AO ARTIGO

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