Journal of Food Engineering 52 (2002) 99-119. doi:10.1016/S0260-8774(01)00106-6Received by publisher: 2000-12-14Harvest Date: 2016-01-04 12:21:51DOI: 10.1016/S0260-8774(01)00106-6Page Range: 99-11

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Preheating potatoes at 50 to 80 degrees C has a firming effect on the cooked potato tissue. This effect is particularly pronounced at a preheating temperature of 60 to 70 degrees C followed by cooling. Several theories have been presented in the literature to explain this firming effect: retrogradation of starch, leaching of amylose, stabilization of the middle lamellae and cell walls by the activation of the pectin methylesterase (PME) enzyme, and by the release of calcium from gelatinized starch and the formation of calcium bridges between pectin molecules. Most probably, none of these theories alone can explain the phenomenon and more than one mechanism seems to be involved. Some of these mechanisms seem to be interdependent. As an example, calcium could be considered as a link all the way through release after starch gelatinization to cross-linking pectin substances in the cell wall and the middle lamellae, which has been demethylated by the PME enzyme. More research and "clear cut" experiments are needed in order to elucidate the role of each mechanism, especially which of them is the main contributor to the process of firming. Most probably, the calcium-pectin-PME mechanism plays a secondary role, that is, it only retards the collapse of the tissue structure that would otherwise occur during the final heating without preheating, and it is not the main factor of firmness.

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Protein concentrates of some Nigerian underused legume seed flours, lima bean (Phaseolus lunatus L.) and pigeon pea (Cajanus cajan), were prepared by alkaline extraction followed by acid precipitation, whereas that of African yam bean (Sphenotilis sternocarpa) was prepared by acid extraction followed by alkaline precipitation. Simple and objective means that allowed precise determination of the inversion point were used in investigating the capacity of the protein concentrates to emulsify fat. Their relative efficiencies as emulsion stabilizers were also investigated. The results revealed that the emulsifying capacities of these protein concentrates decreased with increasing protein concentration and emulsifying speed. However, emulsifying capacities increased with increasing initial aliquot size, whereas variation of speed of oil addition did not have any significant influence. The capacity of the protein concentrates to emulsify fat decreased in the order pigeon pea protein concentrate > lima bean protein concentrate > African yam bean protein concentrate. But for emulsion stability, the protein concentrates were in the opposite rank order.

The optimum experimental design for determining the kinetic parameters of the model resulting from the Weibull probability density junction was studied, by defining the sampling conditions that lead to a minimum confidence region of the estimates, for a number of observations equal to the number of parameters. It was found that for one single isothermal experiment the optimum sampling times corresponded always to fractional concentrations that are irrational numbers (approximately 0.70 and 0.19) whose product is exactly l/e'. The experimental determination of the equilibtium conversion (for growth kinetics) is vety important, but in some situations this is not possible, e.g. due to product degradation over the length of time required. Sampling times leading to a maximum precision were determined as a function of the maximum conversion (or yield) attainable. For studies of kinetic parameters over a range of temperatures, performed with a minimum of three isothermal experiments, it was proved that the optimum design consists of two experiments at one limit temperature with two sampling times (those corresponding to fractional concentrations of approximate[v 0.70 and 0.19) and another at the other limit temperature for a sampling time such that the fractional concentration is lie. Case studies are included for clarijication of the concepts and procedures.

A escassez de profissionais de saúde em áreas remotas e vulneráveis é um importante obstáculo para a universalização do acesso à saúde em diversos países. Este artigo examina as políticas de provimento de profissionais de saúde na Austrália, nos Estados Unidos da América e no Brasil. Apesar do sucesso parcial de iniciativas anteriores, foi apenas com o Programa Mais Médicos que a provisão de médicos em áreas vulneráveis teve a magnitude e a resposta em tempo adequado para atender a demanda dos municípios brasileiros. Estão em curso, no país, mudanças quantitativas e qualitativas na formação médica, que buscam garantir não apenas a universalidade, mas, também, a integralidade e sustentabilidade do Sistema Único de Saúde. O êxito dessas iniciativas dependerão da continuidade da articulação interfederativa, de políticas regulatórias de estado, bem como, do constante monitoramento e aprimoramento do programa.

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