Leaf blade anatomy and ultrastructure of six <i>Simira</i> species (Rubiaceae) from the Atlantic Rain Forest,Brazil

Simira is a predominantly woody Neotropical genus comprising 41 taxa, 16 of which occur in Brazil and eight of them in the southeastern region of Brazil. Leaf blades of Simira eliezeriana Peixoto, S. glaziovii (K. Schum.) Steyerm., S. grazielae Peixoto, S. pikia (K. Schum.) Steyerm., S. rubra (Mart.) Steyerm., S. sampaioana (Standl.) Steyerm. were collected in the southeastern region of Brazil and fixed according to usual methods for light and electron microscopy. The leaf blades show typical characteristics of the Rubiaceae family as dorsiventral mesophyll and paracytic stomata. The presence of two bundle sheaths that extend to the upper epidermal layer, prismatic crystal and crystal-sand, alkaloids in the mesophyll and the organization micromorphological of the outer periclinal wall are considered characteristics representative for the genus. This study also demonstrates some leaf blade characteristics that can be used to Simira species identification (leaf surface, domatia types, epicuticular wax types and patterns of epidermis anticlinal cell walls).     

Quantitative Determination of Ascorbic Acid in Potatoes and Potato Products by High Performance Liquid Chromatography

A simple, rapid and accurate method for the quantitative determination of ascorbic acid in potatoes and potato products has been developed. The system is based on the reverse-phase, ion-pairing concept of high-performance liquid chromatography. Sample preparation is minimal and involves a one-step extraction followed by filtration and/or centrifugation. Recoveries were near the 100% level. As low as 0.02 mcg ascorbic acid could be determined.     

DIET-MEDIATED INTER-COLONIAL AGGRESSION IN THE FORMOSAN SUBTERRANEAN TERMITE <Emphasis Type="Italic">Coptotermes formosanus</Emphasis>

In most social insects, intercolonial and interspecific aggression are expressions of territoriality. In termites, cuticular hydrocarbons (CHCs) have been extensively studied for their role in nestmate recognition and aggressive discrimination of nonnest-mates. More recently, molecular genetic techniques have made it possible to determine relatedness between colonies and to investigate the influence of genetics on aggression. In the Formosan subterranean termite, Coptotermes formosanus, however, the role of CHCs and genetic relatedness in inter-colony aggression has been ambiguous, suggesting the involvement of additional factors in nest-mate recognition. In this study we assess the range of aggression in this termite species and characterize the influence of genetic relatedness, CHC profiles and diet on aggression levels. We collected four colonies of C. formosanus, feeding either on bald cypress or birch, from three locations in Louisiana. Inter-colony aggression ranged from low to high. Differences in CHC profiles, as well as genetic distances between colonies determined by using microsatellite DNA markers, showed no significant correlation with aggression. However, termite diet (host tree) played a significant role in determining the level of aggression. Thus, two distantly related colonies, each feeding on different diets, showed high aggression that significantly diminished if they were fed on the same wood in the laboratory (spruce). Using headspace solid phase microextraction, we found three compounds from workers fed on birch that were absent in workers fed on spruce. Such diet-derived chemicals may be involved in the complex determination of nest-mate recognition in C. formosanus.     

OPTIMAL ROBUST DESIGN OF NOVEL MATERIALS: PROBLEMS OF STABILITY AND VIBRATIONS

A numerical method for the optimal design of thin anisotropic laminates is presented, layer thicknesses and lamination angles being the design variables. An optimal solution is pursued with respect to frequency domain objectives, e.g. fundamental frequency and Euler critical load. A special feature of the method is the semi-analytical second order design sensitivity that is computed with the aid of a Rayleigh-Ritz analysis approach. A modified sequential quadratic programming scheme is then introduced, where standard quasi-Newton approximations are avoided by an exact calculation of the Hessian matrix. Furthermore, the robustness of the method with respect to scatter in material properties such as mass density and elastic moduli is assessed. A stochastic extension of the Rayleigh-Ritz approach is developed on this purpose that allows the location of those regions in the design space that are most sensitive to physical parameter randomness. This allows the use of a modified objective function that penalizes sensitive solution.     

SENSORY QUALITY OF GALA APPLES AS INFLUENCED BY CONTROLLED AND REGULAR ATMOSPHERE STORAGE

The sensory quality of Gala apples stored for up to 4 months in delayed controlled atmosphere (CA), regular atmosphere (RA), and a combination of sequential CA and RA storage (CR) was evaluated. Sensory analysis included difference and acceptance testing. Firmness, soluble solids and titratable acidity contents, and volatile flavor profiles were measured analytically. Acceptability decreased with storage time. Apples stored in RA were more acceptable than apples stored in CA or CR; the differences between storage treatment were not significant after 4 months of storage. Firmness decreased with storage time, but was not affected by storage treatment. Soluble solids and titratable acidity contents were not affected by storage treatment or time. Storage treatment, storage time, and lot had a significant effect on the volatile flavor profiles. CA storage and extended storage contributed to decreases in the content of volatile flavor compounds.     

TRANSGLUTAMINASE IN DAIRY PRODUCTS: CHEMISTRY, PHYSICS, APPLICATIONS

Literature on the effects of microbial transglutaminase on various dairy‐based systems is discussed. Beginning with a short synopsis on the development of microbial transglutaminase as a functional tool for modifying foods, the principles of reactions catalyzed by transglutaminase and their structural implications, as well as the mechanisms of formation and cleavage of isopeptide bonds are reviewed. After summarizing the present knowledge on the specificity of microbial transglutaminase towards milk proteins, including reactions determined by individual lysine and glutamine residues, emphasis is placed on the effects of enzymatic cross‐linking on physicochemical properties in foods and, particularly, dairy‐based systems. Discussed are implications of cross‐linking on acidified milk gels including yogurt and effects on single milk protein fractions, with respect to several physicochemical properties including rheology and mechanical properties of these systems, but also syneresis, and emulsification behaviour.