Effect of dairy by-products as milk replacers on quality attributes of ice cream.

The aim of this study was to evaluate the effect of ricotta whey (RW), cheese whey (CW), and butter whey (BUW) as replacers of whole milk (WM) at different ratios (0:100, 25:75, 50:50, 75:25, and 100:0) in the physicochemical and sensory qualities of ice cream. All formulations, including a commercial sample used as reference, were analyzed for nutritional composition, energy value, pH, titratable acidity (TA), melting behavior, desorption index, instrumental color properties, instrumental hardness, and consumer sensory testing. Overall, the addition of RW, CW, and BUW increased the moisture content, TA, melting rate, and redness (a*) and yellowness (b*) values but decreased the pH, lightness (L*) value, energy value, levels of ash, protein, lipid, and carbohydrate. As exception, CW did not influence the TA, and BUW resulted in lower lipid reduction and in lower hardness changes, and it did not affect the content of ash, protein, and a* and b* values of ice creams. Any ice cream formulation had dietary fibers and a desorption index. Ricotta whey and CW at all ratios and BUW at 25% did not affect overall liking compared with the commercial sample, whereas purchase intention was only decreased by the addition of BUW from 50 to 100%. Ricotta whey at 75 and 100% decreased melting velocity and creaminess, and BUW at 50, 75, and 100% increased hardness, TA, and cream flavor but decreased creaminess, which contributed negatively to overall liking. Therefore, the evaluated dairy by-products, especially RW and CW, have great potential for replacing milk in ice creams.

Slow-release nutrient capsules for microorganism stimulation in oil remediation.

As the concern towards environmental deterioration grows worldwide, new technological achievements become essential for all countries. Among the technologies with great potential of bioremediation is microencapsulation of active material. Several studies have investigated the use of controlled release of active materials as a way of biostimulation and supplying the nutrients necessary for the bioremediation process. In fact, as the use of microorganisms has a great potential in degrading crude oils, this work aims to use that technology and to associate it to produce controlled-release capsules of nitrogen, phosphorus, and potassium (N, P, and K) for bioremediation purposes. For the capsule formulation, polymers of sodium alginate, Capsul®, and the commercial fertilizer NPK from Sempre Verde Inc. were used. Crude oil was the only carbon source and mineral medium for microorganism growth. Controlled-release nutrient capsules, with 4 mm in diameter, made of 3.0 % alginate (w/v) and 4.0 % Capsul® (w/v) were produced. Those capsules were used in association with a microbial consortium, in a liquid phase bioremediation process, having degraded 43.6 % of the total hydrocarbon within 240 h, evidencing thus as a promising tool for hydrocarbon bioremediation.

Cell surface characterization of Yarrowia lipolytica IMUFRJ 50682.

In the present work, the surface characteristics of a wild-type strain of Yarrowia lipolytica (IMUFRJ50682) were investigated. Six different methods to characterize cell surfaces--adhesion to polystyrene; hydrophobic interaction chromatography (HIC); microbial adhesion to solvents (MATS) test; zeta potential; microbial adhesion to hydrocarbons (MATH) test; and contact angle measurement (CAM)--were employed to explain the cell surface behaviour of Y. lipolytica (IMUFRJ50682). This Y. lipolytica strain presents significant differences at the cell surface compared with another Y. lipolytica strain (W29) previously reported in the literature. The main difference is related to the higher cell adhesion to non-polar solvents. The proteins present on the cell wall of Y. lipolytica IMUFRJ50682 seem to play an important role in these particular surface characteristics because of the consistent reduction of this yeast hydrophobic character after the action of pronase on its cell wall.

Morphological analysis of Yarrowia lipolytica under stress conditions through image processing.

Stress conditions (thermal and oxidative) were applied to Yarrowia lipolytica culture. A rearrangement in cell metabolism as well as dimorphism was observed under these conditions. An image analysis procedure was employed for morphology characterization, and a net increase of around 25% on hyphae formation was detected. A significant increment in total hyphal length was detected, compared with the control system. The results obtained lead to the consideration of a possible relationship between dimorphism and a cell response mechanism to stress conditions.

A stable lipase from Candida lipolytica: cultivation conditions and crude enzyme characteristics.

Although lipases have been intensively studied, some aspects of enzyme production like substrate uptake, catabolite repression, and enzyme stability under long storage periods are seldom discussed in the literature. This work deals with the production of lipase by a new selected strain of Candida lipolytica. Concerning nutrition, it was observed that inorganic nitrogen sources were not as effective as peptone, and that oleic acid or triacylglycerides (TAG) were essential carbon sources. Repression by glucose and stimulation by oleic acid and long chain TAG (triolein and olive oil) were observed. Extracellular lipase activity was only observed at high levels at late stationary phase, whereas intracellular lipase levels were constant and almost undetectable during the cultivation period, suggesting that the produced enzyme was attached to the cell wall, mainly at the beginning of cultivation. The crude lipase produced by this yeast strain shows the following optima conditions: pH 8.0-10.0, temperature of 55 degrees C. Moreover, this preparation maintains its full activity for at least 370 d at 5 degrees C.