NUTRITIONAL AND SENSORY SURVEY OF CITRUS SINENSIS (L.) CULTIVARS GROWN AT THE MOST NORTHERN LIMIT OF THE MEDITERRANEAN LATITUDE

ABSTRACT

This report describes Citrus sinensis fruit grown in the Lake Maggiore area (Italy), the upmost Northern distribution range of the genus Citrus in Europe. Total ascorbic acid (TAA), bioflavonoids, total polyphenol content (TPC), antioxidant activity, total soluble solid, total acidity and sensory characteristics were evaluated on oranges harvested during the 2009–2010 season. The range of values detected was as follows: TAA from 36.89 to 67.34 mg/100 mL, hesperidin from 18.97 to 31.87 mg/100 mL, narirutin from 17.30 to 29.28 mg/100 mL and rutin from 4.39 to 5.36 mg/100 mL; antioxidant activity (ferric reducing antioxidant power assay) from 8.62 to 17.00 mmol Fe²⁺/kg, fresh fruit weight; TPC (Folin–Ciocalteu method) from 87.16 to 135.16 mg GAE/100 g. This first attempt to characterize cultivars grown in the Piedmont region showed that these oranges had acceptable nutritional components and sensory quality, if compared with bibliographic data about cultivars grown in the subtropical and Mediterranean area.

PRACTICAL APPLICATIONS

The identification, characterization and valorization of old cultivars are essential to avoid loss of potentially useful germplasm. The reduction of biodiversity of cultivars found in agriculture could lead to problems such as higher susceptibility to widespread outbreaks of plant diseases and pests, and at the same time, the loss of precious source of nutrients. This survey was carried out to characterize a germplasm that could also be used in breeding programs to obtain new cold‐tolerant varieties.     

CO2-Catalyzed Surface Area and Porosity Changes in High-Surface-Area CaO Aggregates

The changes in surface area and mesoporosity in aggregates of ∼0.01 μm cross-section CaO particles when heated in CO₂at 686°C were determined from N₂ adsorption isotherms. Initially, the surface area decreases rapidly with little change in porosity. When the surface area has decreased below ∼90 m²/g, surface area and porosity variations become consistent with expectations for coarsening by grain-boundary or bulk diffusion. The initial rapid decrease in surface area must result from CO₂-catalyzed surface diffusion, but the data suggest that surface diffusion is not rate-limiting. The rate-limiting step may be reaction of CO₂ to form surface CO₃^2- ions or decomposition of these ions to O^2- ions and CO₂ gas.     

Effect of LiCl on the Rate of Calcite Decomposition

The rate of decomposition of calcite powder in vacuum was measured by the Langmuir and Knudsen methods. Measured pressures in effusion cells in the absence of additives approach the equilibrium value. The Langmuir experiments gave an apparent equilibrium CO₂ pressure of =3×10⁻⁴ times the known pressure for the reaction. It is suggested that the CO₂ is in equilibrium with the calcite but the CaO is not. In Langmuir experiments, 10 wt% LiCl does not increase the initial decomposition rate. In the Knudsen cells, 10 wt% LiCl can increase the initial rate by >2 times. LiCl reduces the surface area of the product CaO under either condition from ≥30 to ∼1 m²/g. Probably an LiCl-CaO eutectic provides a solution path for CaO recrystallization and, at high CO₂ pressures, also for CaCO₃ decomposition.     

Vapor-Phase Hydration of Submicrometer CaO Particles

Reaction of water vapor at 25°CC with CaO powder of either high or low surface area yields Ca(OH)₂ with broad XRD peaks. Relative rates of reaction of these hydroxides with CO₂ at 250°CC depend mainly on the sample surface areas per unit weight. SEM observations show that the exterior shapes of porous 1 to 30 μ m particles of CaO formed by decomposition in vacuum of CaCO₃(sr-CaO) or Ca(OH)₂ (h-CaO) are only slightly changed when they are converted to Ca(OH)₂, except for surface roughening, which increases with time of exposure to water vapor. The N₂ adsorption-desorption isotherms of h-CaO and sr-CaO, and of their hydration products, are used to calculate the average particle expansion, the probable pore shapes, and the changes in pore-size distributions that accompany the reaction. These data show that the reaction causes expansion perpendicular to ulterior surfaces of the porous powder particles. A possible mechanism is suggested. Both h-CaO and sr-CaO dissolve in liquid water to yield Ca(OH)₂ by subsequent precipitation.     

SIMPLIFIED FREQUENCY-DEPENDENT MODEL FOR INDUCTION MACHINES

ABSTRACT

The purpose of the present paper is the representation of the behaviour of induction motors, in the presence of harmonics in the power supply, by using a simplified frequency-dependent model. The model is the end product of statistical processing, which leads to the definition of “typical“ parameter values as a function of the frequency. This model is intended primarily for the study of harmonic power flow by means of computer programs. It has also been validated on a test network on which experimental results are available

Better rotating load models at harmonic frequencies can improve the studies of power quality in the design of the future electric power systems.     

Rearrangement of Porous CaO Aggregates During Calcite Decomposition in Vacuum

High-resolution SEM photographs, N₂ adsorption isotherms, Hg porosimetry, and micrometer measurements were used to characterize CaO particle shapes and pore-size distributions that result when calcite crystals are decomposed in vacuum at 686°C. The surface area of the CaO produced from large calcite crystals is constant at 116.4 m²/g independent of the extent of reaction. The volume occupied by a CaO aggregate is 98±2% that of the original calcite crystal. The ∼54% total porosity is comprised of 42% pores of ∼5 nm cross section and 12% pores of ∼10 μ m cross section. The duplex pore structure is formed by a diffusionless repacking of CaO particles that initially form with a more uniform distribution of particles and pores.     

Characterization of the Porous CaO Particles Formed by Decomposition of CaCO3 and Ca(OH)2 in Vacuum

The solid products of decomposing CaCO₃ powder in vacuum at 510°C (sr-CaO) and of decomposing Ca(OH)₂ powder at 320°C in vacuum (h-CaO) are particles which have approximately the same exterior dimensions as the parent CaCO₃ or Ca(OH)₂ particles. N₂ adsorption and desorption isotherms show that sr-and h-CaO have high internal surface areas which for sr-CaO have cylindrical symmetry, with the most common diameters being ∼ 10 nm, and for h-CaO are slit-shaped, with the most common slit width being ∼ 2.7 nm. The conclusions reached in earlier investigations, i.e that these decomposition reactions in vacuum initially yield a form of CaO which has the same unit cell dimensions as the parent solid, were in error, probably because water vapor converts much of the CaO to poorly crystalline Ca(OH)₂ before XRD measurements can be completed in air. From the volume of N₂ adsorbed by the porous powders, the porosity of h-CaO is calculated to be 36±5% and of sr-CaO 41.5±5%. These porosities imply that the linear dimensions of the 1 to 20 μm particles of h-CaO and sr-CaO are ∼5% smaller than those of the parent particles. XRD measurements made as a function of time show that particle shrinkage must occur by cooperative, diffusionless movement of crystallites of sr-CaO or h-CaO as they form.     

Effect of Li2CO3 on Reaction Between CaO and CO2

Reaction between CaO powders and CO₂( g ) is often limited by slow diffusion of CO₂ through the CaCO₃ product. Additions of Li₂CO₃ are shown to increase the reaction rate. At temperatures around 940 K, near to the Li₂CO₃-CaCO₃ eutectic temperature, 935 K, complete reaction of the CaO with CO₂ can be achieved when the heating rate and Li₂CO₃ content are optimized. At lower temperatures Li₂CO₃ causes lesser but measurable increases in reaction rates. SEM and surface area observations suggest different reaction paths when Li₂CO₃ is present, when Li₂CO₃ and eutectic are present, and when eutectic alone is present.     

H.V. CABLE TRANSMISSION: A STUDY ON TORSIONAL STABILITY

ABSTRACT

The purpose of this paper is to analyze the torsional stability of a turbogenerator, in a case in which, with a.c. 400 kV cable transmission lines, it is necessary to provide shunted compensation.

The problem is brought into focus from the physical point of view by means of a simplified schematic operating presentation. This simplified analysis is then validated by means of a computer program for the dynamic study of the electromechanical system, applied to an example consisting of a turbine shaft, the alternator, the excitation control system, a step-up transformer, and a cable line with shunt compensation and connected to a prevalent power node. Both the methods of analysis show that, unlike the dual case of the series compensation of overhead lines, in this case conditions of torsional instability do not occur.     

PREDICTIVE MODELING APPLIED TO GROWTH OF SPOILAGE VIRGIBACILLUS PANTOTHENTICUS ON INDUSTRIAL CRÈME CARAMEL

The aim of this work was to identify the spoilage microorganisms in commercially produced crème caramel and to study their growth kinetic in different conservation conditions. Fifty‐four randomly selected strains were isolated from altered crème caramel samples with typical “medicine smell.” In order to detect the strains that cause the smell alterations, an experimental medium (PM) was prepared with crème caramel. Nineteen out of 28 isolated strains of gram‐positive spore‐former bacteria developed “medicine smell” in PM medium. Of the 19 isolated strains, five were identified as Virgibacillus pantothenticus. One was studied in a fermenter in aerobiosis at 4, 12 and 30C and in anaerobiosis at 30C. The modified Gompertz model was applied. In aerobic conditions, the maximum growth rate decreased with the temperature: μ = 1.68 at 30C and μ = 0.28 at 12C; at 4C, there was neither growth nor alteration. In anaerobic conditions, at 30C the maximum growth rate was lower than in aerobiosis (μ = 0.90), and there was no smell alteration. The appearance of these alterations was independent of the maximum growth rate. “Medicine smell” was a result of piperonal alterations. Microbiological spoilage risk could be reduced with tight control of the temperature in the production chain.