MEASUREMENT OF FIRMNESS OF STIRRED YOGURT IN ROUTINE QUALITY CONTROL

The objectives of the present work were to evaluate the potential use of the vane method and penetration tests as a tool to measure the variability in firmness of stirred yogurt in routine quality control, and to evaluate the effect of distribution on yogurt firmness. Twelve batches of plain stirred yogurt of a commercial brand were studied, acquired both from a manufacturing plant and three retail stores. Both vane method and penetration tests allowed the detection of changes in the firmness of yogurts, confirming that they could be useful in routine quality control to characterize the firmness of yogurt. The yield stress of samples from the manufacturing plant varied within a range of 250 Pa. This important variation was partially explained by variations in the final acidity during fermentation, showing the importance of a standardized production in order to obtain a uniform texture. The yield stress of yogurts from the manufacturing plant was significantly higher than that of samples from the different retail stores. Averaged values being considered, the yogurts lost 53 Pa of their original yield stress during distribution and handling inside retail stores, probably due to mechanical damage. This mechanical damage also caused the occurrence of syneresis.     

OXIDOREDUCTASES FROM TOMATO FRUIT: INHIBITORY EFFECT OF A FUNGAL GLUCOSE OXIDASE

Glucose oxidase (GOD) produced by a strain of Penicillium (Penicillium variabile P16) was employed, in a model system, to control the activities of tomato lipoxygenase (LPO), polyphenoloxidase (PPO), and peroxidase (POD). GOD in-hibited all three enzymes, at the typical pH of tomato fruit (4.3), i.e., the LPO was inhibited up to ca. 88%, the PPO up to ca. 63% and the POD up to ca. 50%. GOD also prevented β-carotene bleaching caused by these enzymes.     

Size and Strategy of Italian Industrial Enterprises (1907-1940): Empirical Evidence and Some Conjectures

Conventional wisdom concerning Italian industry does not fitwell into the general scheme of the Second Industrial Revolutionas constituted by the growth and diffusion of large-size enterprises.This wisdom held that Italian industry was dominated by a smallgroup of large enterprises as a direct consequence of the country'sbackwardness. These enterprises were weak giants, unable toattain the dynamic advantages usually reaped by such organizations.Such interpretations have been generally based on qualitativeevidence because the quantitative evidence is very scanty. Theolder studies suggest a very high concentration, while recentstudies stress the evidence of scale economies and market imperfections.Neither result is convincing for technical reasons. This papertherefore aims at a reassessment based on a newly constructeddatabase of Italian joint stock companies. This evidence doesnot support the traditional view. Rather, it indicated thatconcentration indices are fairly low and that they do not growover the period, the bulk of the firms being of medium sizeand the giant companies few. Although such a situation couldbe attributed to Italian backwardness, the paper concludes thatthis view is too simplistic. It concludes by showing how successfulItalian companies have been able to take advantage of theirsize by means of flexible strategies.     

A study of chlorophyll-like and phycobilin pigments in the C endosymbiont of the apple- snail <i>Pomacea canaliculata</i>

Pigments present in the brown-greenish C morph of an intracellular endosymbiont of Pomacea canaliculata were investigated. Acetone extracts of the endosymbiotic corpuscles showed an absorption spectrum similar to that of chlorophylls. Three fractions obtained from silica gel column chromatography of the acetone extracts (C_I , C_II and C_III ), were studied by positive ion fast atom bombardment-mass spectrometry (FAB–MS) and hydrogen-nuclear magnetic resonance (H-NMR). Results indicated the presence of (1) a sterol in the yellow colored C_I fraction; (2) a mixture of pheophorbides a and b in the major green fraction, C_II; and (3) a modified pheophorbide a in the smaller green fraction, C_III . Aqueous extracts of the C endosymbiont did not show evidence of the occurrence of C-phycocyanin, allophycocyanin or phycoerithrin (light absorption, fluorescence emission, and electrophoresis of the protein moieties) while cyanobacterial cells (Nostoc sp.) showed evidence of C-phycocyanin and allophycocyanin. The possible phylogenetic and functional significance of the pigments present in the C endosymbiont is discussed.     

ON THE LYAPUNOV APPROACH TO ROBUST STABILIZATION OF UNCERTAIN NONLINEAR SYSTEMS

In the Lyapunov approach employed in this paper, known in the literature as Lyapunov control, or min-max control, robust, global uniform asymptotic stability is achieved by a discontinuous control law which ensures that the Lyapunov derivative is negative despite bounded uncertainty. For that, it is assumed that the uncertainties satisfy certain matching conditions, and that a Lyapunov function for the nominal plant is available. To obtain lower control magnitudes, this paper develops control laws which counter the uncertainties on a component-wise basis, rather than the usual normic one. Both the basic discontinuous control law, which is proved to provide robust global uniform asymptotic stability, and a continuous app roximation, which is proved to ensure global uniform ultimate boundedness, are derived. Application to model following is given. We adapt recent results on robust quadratic stabilization of nominally linear time-invariant plants subjected to nonlinear, bo unded and unmatched uncertain perturbations, to extend our results to this important class of systems; this is illustrated by two examples.     

Quantitative Crack Surface Morphology of Bone Cements in Relation to Propagation Rate

Morphology of the crack surface of surgical bone cements has seldom been studied in the past despite the clinical relevance of cement failure. Previous studies on a specific cement type suggest that crack morphology depends on crack propagation rate. The objectives of this work were: (i) to develop a quantitative indicator for describing crack morphology; and (ii) to assess if dependency on crack‐propagation rate is affected by cement formulation. Known crack surfaces were obtained from specimens under controlled loading conditions. Crack surface roughness was measured for different crack‐propagation rates, and compared against the amount of cleaved pre‐cured beads (measured with a semi‐automated procedure based on micrographs). Such indicators were extremely robust, operator‐independent, highly correlated, and sensitive to the type of fracture. Moreover, it was found that crack surface morphology heavily depends upon cement composition. Thus, crack surface roughness is proposed as a method for quantitatively identifying crack morphology, and finally classifying fracture type.     

Cover Application of the NOAA-AVHRR images to the study of the large forest fires in Spain in the summer of 1994.

Ozone vertical profiles derived from Umkehr observations by the Dobson spectrophotometer at Belsk (52.50° N, 20.47° E) and from ozone soundings carried out at the nearest aerological station, Legionowo (52.24° N, 20.58° E), have been compared with those measured by the MLS instrument on board the Aura spacecraft during the sites' overpasses for the period 2004–2005. It is assumed that the satellite station distance should be less than 2° and less than 4° for the latitudinal and longitudinal difference, respectively. The bias, RMS error, and the correlation coefficients between the ozone content in the Umkehr layers have been calculated using Dobson/sonde/MLS data. The ozone mixing ratio at selected levels in the lower and mid‐stratosphere (from 215 hPa up to 6.8 hPa) have been compared using the sonde/MLS data. The number of analysed daily values was ～40 (Dobson/MLS), 60 (sonde/MLS), and 60 (Dobson/sonde) since August 2004. The comparisons show a good correspondence (bias ～±5%, RMS <10%, correlation coefficient >0.5) between the ozone content in Umkehr layers 4–8 and ozone mixing ratio at pressures <50 hPa. At lower stratosphere (Umkehr layer 3) and upper stratosphere (Umkehr layer 9), there is also statistically significant relationship between the data, but the biases and RMS are ～2 times larger, while the correlation coefficients are still high (>0.7).     

SURVIVAL OF LISTERIA INNOCUA IN APPLE JUICE AS AFFECTED BY VANILLIN OR POTASSIUM SORBATE

Survival of stationary phase Listeria innocua ( as surrogate microorganism for L. monocytogenes) inoculated in apple juice (pH 3.3 or 3.8) supplemented with vanillin (1,500 ppm or 3,000 ppm) or potassium sorbate (500 ppm or 1,000 ppm) and stored at room temperature was studied. L. innocua survived in apple juice without the preservatives at pH 3.3 or 3.8, with minimal population reductions. In the juices with the incorporation of potassium sorbate or vanillin , L. innocua behavior depended on the pH value, the type of antimicrobial and its concentration. At pH 3.3, the presence of vanillin (3,000 ppm) or potassium sorbate (1,000 ppm or 500 ppm) decreased L. innocua counts, with population reductions ranging from 4 to 5 log cycles after a 4 h – 8 h exposure at 30C. However, at pH 3.8 , L. innocua showed sensitivity only to 3,000 ppm vanillin. Survival curves were successfully fitted using a Weibull type distribution of resistances.
The results suggest that the use of potassium sorbate or vanillin could prevent the survival of L. innocua in contaminated unpasteurized and pasteurized apple juice. Vanillin, a natural antimicrobial, would be particularly suitable as an antilisterial additive for less acidic apple juice.     

EFFECT OF DIFFERENT STORAGE CONDITIONS ON THE LIPID FRACTION OF A VEGETABLE CREAM

Fatty acids (free and esterified), diglycerides, peroxides and total sterols were determined in a vegetable cream. Cream samples were analyzed when fresh and after storage for 3 and 6 months at 4, 15, 30C and room temperature (10–25C). The product showed a higher amount of unsaturated fatty acids ( ≈ 50% of total fatty acids) with respect to milk fat and a low level of cholesterol ( < 0.01%). The phytosterol content ( ≈ 14 mg/100 g of cream) was not high enough to contribute to a decrease in cholesterolemia. Lipid oxidation remained low during storage (peroxides: 2.0–3.0 meq O₂/kg of fat), but a small increase was observed at room temperature after 6 months (about 6.0 meq O₂/kg of fat). Free fatty acids never exceeded 0.3% of fat. Storage at 4C and 15C delayed lipolysis in comparison to storage at 30C and room temperature.

PRACTICAL APPLICATIONS

The analysis of a vegetable cream demonstrated that it was a shelf-stable product, showing a high stability toward lipid oxidation and lipolysis. Such a product might be employed as vehicle for healthy fat compounds like long-chain polyunsaturated fatty acids, phytosterols and fat-soluble vitamins.