Estudo da instantaneização de misturas contendo cacau em po por aglomeração com jato de vapor

AUTOR(ES)
DATA DE PUBLICAÇÃO

2003

RESUMO

The agg1omeration process of dry mixtures containing cocoa powder was considered in order to evaluate the instant properties of the product. A pilot-plant steam jet agg1omerator was developed, composed by a stainless steal tower (diameter: 0.30m; height: 2.15m), a vibrating feeder for the powder supply (up to 65 kg/h), a steam generator, a device to promote a turbulent contaet between steam and the free-falling partic1es, at the bottom of a 1.9 cm (ID) cylindrical Teflon® duet, and an air supply and exhausting system. The composition and physical characteristics of the raw material were determined, complemented by microscopic and X-rays difractograms observations. Cocoa powder is amorphous, has a bimodal size distribution (average diameter: 19J.1II1), is insoluble and hardly dispersible in water. The pH and the cocoa butter content influenced the wettability and the dispersability in water. The sorption isotherm followed the GAB model. Crystal sugar with good wetting abilities was used in the formulations. A statistical planning was applied considering the significant effects on four dependent variables: the wettability, the size of the agg1omerates, the bulk density and the final moisture content of the product. An L8 Taguchi s orthogonal array method was used, twice, for the initial screening of the factors of significant effect. A detailed analysis using a central composite, non-factorial, surface design based on 29 experiments was then performed. The wettability, considered the most appropriate attribute in instant properties quantification is influenced by lecithin content, proportion of sugar and of fines, steam pressure, and drying air temperature, in this order of importance. The quadratic model exhibited the best fitting to the experimental results. The size of the agg1omerates is affected by steam flow rate and lecithin content. The most important effects on the density of the agg1omerates were the content of fines and the drying air temperature. The moisture content of the product was mainly affected by the mixture formulation and the steam flow rate. The excellent solubility of sucrose and the plasticization of the surface of the crystals in the agglomeration zone, confirmed through microscopic and X-rays observations, control the process kinetics

ASSUNTO(S)

cacau aglomeração metodo de (controle de qualidade) chocolate planejamento experimental superficies de reposta (estatistica) taguchi

ACESSO AO ARTIGO

Documentos Relacionados