Particle Size Effects on the Diffuse Reflectance of a Sucrose-Caramel Admixture

Decreasing the particle size of homogeneous colorant (caramel) from 68 to 28 microns increased lightness as predicted by the Kubelka-Munk theory. The presence of diluent (sucrose) reversed particle size effects, i.e., reduced caramel particle size decreased mixture lightness. Decreasing the particle size of the diluent, however, substantially increased the diffuse reflectance of the admixture, lowering its color intensity. The degree of color masking was determined mainly by the particle size of sucrose and to a much lesser extent by that of caramel. The dilution ratio and particle size of both colorant and diluent could be used to control the color of many food systems.     

Kinetics of Solids Leaching During Rehydration of Particulate Dry Vegetables

ABSTRACT: Air-dried and freeze-dried carrots were rehydrated in a computerized mixing system, and the medium was analyzed for sugar content with high-performance liquid chromatography (HPLC) and for total organic carbon (TOC). Leaching of solids was significant at very short rehydration time. Understanding the mechanism of the leaching process could provide information required for simulation. TOC values were significantly higher than those derived by HPLC, indicating that other organic components were extracted. The difference between TOC and HPLC values varied with time, indicating the existence of a different mass transfer rate. Sugars and TOC values followed an exponential behavior. Quantifying solids leaching is important for modeling and simulation of the rehydration process and for product optimization.     

Oil Uptake in Deep Fat Frying as Affected by Porosity

The porosity of a restructured potato product ranged from 0.089 to 0.168 after fluctuating subfreezing storage temperatures. A linear relation was found between oil uptake during frying and porosity prior to frying. Bulk and particle density, and porosity were monitored for up to 5 min during deep-fat frying. Particle density increased gradually, bulk density decreased and porosity increased noticeably. After an initial short period, oil uptake correlated linearly with porosity of the fried product. A new term, “net porosity” which excluded the void volume occupied by oil was developed for describing the oil uptake mechanism.     

A Simplified Method for Determination of Browning in Dairy Powders

An improved method for the determination of nonenzymatic browning in dehydrated dairy powders is described. The method involves liberation of the brown pigments from the protein molecules by means of a proteolytic enzyme, pronase. For complete proteolysis, the pronase mixture (2.53 mg enzyme/U.lg dry powder) was incubated at 45°C for 2 hr. After clarification, the browning index (defined as the optical density difference measured at 420 nm and 550 nm) was determined spectrophotometrically. The suggested method proved to be straightforward, easy to employ, and showed high accuracy and reproducibility. The procedure is suitable for routine laboratory analyses and its repeatability, as expressed by the coefficient of variation, was below 3%.     

USE OF PUMPED-HYDRO AS PEAK-LOAD MANAGEMENT PLANT IN OPTIMAL SCHEDULING OF POWER SYSTEMS

ABSTRACT

The system demand, during some intervals of a day, may exceed the available system generation (excluding the pumped-hydro generation). A pumped-hydro plant may then, be used as a peak-load management unit to safeguard the power system by minimizing the power blackout in order to avoid large deviation in system frequency. In this paper, an algorithm is presented to obtain the optimal schedule for hydro, thermal plants including the pumped-hydro unit by proper selection of initial feasible trajectory for the pumped-hydro plant. An additional constraint is introduced to ensure the power balance in each time interval during the perturbation of water storage trajectory. The proposed method decomposes the problem into hydro and thermal subproblems and solves them alternately. The hydro subproblem is solved using a search procedure namely, the local variation method and the thermal subproblem is solved using a judicious combination of participation factors/linear programming method. Optimal scheduling was conducted on a 9-bus system and a 66-bus Utility system. The results obtained for the above two systems demonstrate the effectiveness of the algorithm proposed.     

Constraints to Quality Optimization in Aseptic Processing

The optimization incorporated constraints, such as health requirements to destroy pathogens, spoilage-causing microorganisms and enzymes inactivation. Simultaneously, the optimal process had to maximize chemical and sensory attributes, nutrients retention and overall quality. Linear programming was utilized to conform with all the aforementioned constraints and to derive the optimal processing time and temperature. The method offered a straight forward procedure for the optimization of aseptic processing and could be utilized in the implementation of optimal high temperature-short time processes.