Aspectos físico-químicos e microbianos do queijo maturado por mofo obtido da coagulação mista com leite de cabra congelado e coalhada congelada

Milk goats are indicated as an economic alternative for small farmers and cheese making could improve their profits. Goat's milk has a seasonal production characteristic and shows periods of abundance and others of scarcity. The use of frozen milk or frozen curd to make cheese can be used to solve the problem. The aim of this work was to evaluate the preparation of cheese made from mixed curd and ripened by Penicillium candidum mould using slow frozen milk (in a domestic freezer) or fast frozen milk (by liquid nitrogen). The slow frozen curd and fast frozen curd without whey were used. It was observed that the cheese from the slow and fast frozen milk and from the slow and fast frozen curd did not differ from the control cheese for the yield, chemicophysical characteristics, chemical composition, extention ripened rate, depth ripened rate and microbiological aspects, even when it was expressed as a dry matter content of cheeses.

Effect of milk treatment on acidification, physicochemical characteristics, and probiotic cell counts in low fat yogurt

The effect of milk treatment (heat, high hydrostatic pressure - HHP, or combined heat and HHP) on acidification, physicochemical characteristics, and probiotic cell counts in low fat yogurt was studied. All samples were analyzed for fermentation time, pH, titratable acidity, total solids, water-holding capacity, syneresis, Hunter L*, a*, and b* values, Streptococcus thermophilus, Lactobacillus delbrueckii ssp bulgaricus, L. acidophilus, and Bifidobacterium longum. The application of HHP combined with thermal treatment resulted in yogurt gels with attractive physicochemical characteristics and high water-holding capacity. In addition to this, the milk treatment did not affect the probiotic bacteria growth. The balance of strains in the starter culture and level of inoculation influenced the yogurt fermentation and properties. The use of combined heat and HHP to treat milk before yogurt fermentation could be an alternative process for obtaining high quality, additive-free healthy products.

Grinding of hardened steels using optimized cooling

Grinding - the final machining process of a workpiece - requires large amounts of cutting fluids for the lubrication, cooling and removal of chips. These fluids are highly aggressive to the environment. With the technological advances of recent years, the worldwide trend is to produce increasingly sophisticated components with very strict geometric and dimensional tolerances, good surface finish, at low costs, and particularly without damaging the environment. The latter requirement can be achieved by recycling cutting fluids, which is a costly solution, or by drastically reducing the amount of cutting fluids employed in the grinding process. This alternative was investigated here by varying the plunge velocity in the plunge cylindrical grinding of ABNT D6 steel, rationalizing the application of two cutting fluids and using a superabrasive CBN (cubic boron nitride) grinding wheel with vitrified binder to evaluate the output parameters of tangential cutting force, acoustic emission, roughness, roundness, tool wear, residual stress and surface integrity, using scanning electron microscopy (SEM) to examine the test specimens. The performance of the cutting fluid, grinding wheel and plunge velocity were analyzed to identify the best machining conditions which allowed for a reduction of the cutting fluid volume, reducing the machining time without impairing the geometric and dimensional parameters, and the surface finish and integrity of the machined components.

Power losses analysis and cooling system design of three topologies of multilevel inverters

This paper presents the comparison of three topologies of multilevel inverters applied to drive an induction motor of 500 kVA/4.16 kV. The multilevel inverters analyzed are: a neutral point clamped inverter, a symmetrical cascaded multilevel inverter and a hybrid asymmetrical cascaded multilevel inverter. The performance indexes used in the comparison are total harmonic distortion, first order distortion factor, semiconductors power losses distribution and heat-sink volume. The comparison is developed with the purpose of finding the efficiency and the heat-sink volume where the three systems present the same output filter. ©2008 IEEE.