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Hard solid foods encompass a large variety of dry products as well as products with high water content. Most of these foods have a cellular structure, which is generally characterized by connected fairly rigid cell walls, enclosing a fluid material that may be liquid-like (fruit and vegetables) or a gas (mainly manufactured cellular foods). Typical for many hard solid products is their brittle fracture behavior, mostly accompanied by acoustic emission. The latter characteristic is essential for their crispy or crunchy character. Other main texture attributes are hardness and brittleness and for fruits and vegetables juiciness. The latter requires that the liquid content of the cells is released during mastication. Aspects of fracture behavior of cellular food products, oral processing of these products, and the interplay between product characteristics and perception of some main texture attributes (hardness and crispness) will be discussed. PRACTICAL APPLICATIONS It has become more and more clear that texture perception by consumers of hard solid (brittle) foods is based on the interplay between product structure, fracture behavior, oral processing and final grading by the brain. Better understanding of the relations between these aspects is essential for the production of healthy, tasteful food that is liked by consumers. This article focus on the interplay between physical properties of hard solid foods and oral processing in relation to the perception of selected texture attributes (hardness and crispness)

The perception of complex textures in food is strongly related to the way food is processed during eating, and is modulated by other basic characteristics, such as taste and aroma. An understanding at the colloidal level of the basic processes in the mouth is essential in order to link the composition and structure of food products to more complicated texture attributes.

A batter is provided comprising flour, water and optionally starch, wherein the batter comprises glutenin particles having a volume surface averaged particle size smaller than 10 [mu]m. A batter according to the invention comprises flour and optionally starch, and optionally baking powder and salt. At least 95 vol. % of all particles comprised in the batter have a particle size of 100 [mu]m or less. It appears that such a batter provides very crispy coatings to (deep-)fried products.

Glutens were isolated from flour of three European wheat cultivars which perform differently in cereal products. The rheological and fracture properties of gluten-water doughs were determined in uniaxial and biaxial extension at large deformations and small angle sinusoidal oscillation tests and compared with the mechanical properties of the parental flour doughs. At 25 °C the linear region was in the same range as that of flour dough, while at a higher temperature (45 °C) the linear region was more than an order of magnitude higher. At 45 °C the storage modulus and tan were lower than at 25 °C. Variation in moduli between cultivars was much more pronounced for gluten than for flour doughs. Similarly to flour dough in both uniaxial and biaxial extension the stress () increased more than proportionally with the strain, a phenomenon called strain hardening. The stress at a set strain and strain hardening depended much more strongly on the type of deformation for gluten than for flour dough: was higher in biaxial extension for gluten than for flour dough, but was much higher in uniaxial extension. This indicates that orientational effects in elongational flow are of even larger importance for the mechanical properties of gluten than of flour dough. It is likely that it is the glutenin fraction that, because of its large size, confers these direction dependent properties to gluten and flour doughs. Fracture stresses were much higher for gluten than for flour dough, while fracture strains were in the same range or higher. For gluten dough fracture strains increased less strongly with increasing strain rate than for flour dough. Glutens exhibiting a higher stress at a certain strain had a smaller fracture strain. Our findings confirm the conviction that the large deformation properties of flour dough are mainly governed by the gluten fraction. However, there are also differences. Compared to flour dough gluten dough exhibits (i) a stronger strain hardening, (ii) a larger difference in between uniaxial and biaxial extension and (iii) a smaller strain rate dependency of the fracture strain.

Literature on the crispy/crunchy behavior of cellular solid foods with a crust is discussed. The emphasis is on products with a dry crispy or crunchy crust as bread and various snacks and especially on mesoscopic and macroscopic aspects. Successively, the sensory sensations involved, the mechanical and fracture behavior of crispy/crunchy products, morphological aspects, and the relation between crispy and crunchy behavior and mobility of the macro-molecules and plasticizer (primarily water) involved, are discussed. Finally, some ideas for an integrated approach of crispy/crunchy behavior of cellular solid foods with a dry crust will be discussed.

A novel experimental configuration was used to investigate depletion-flocculated oil-in-water (o/w) emulsions. In this configuration oscillatory shear can be applied to a system, which is monitored by Diffusing Wave Spectroscopy (DWS) and Confacal Scanning Laser Microscopy (CSLM) simultaneously. This combination allows probing of the motion of the oil droplets at length scales between 10-9 and 10-4 m.

Brownian dynamics (BD) simulations have been performed on the aggregation dynamics of colloidal particles within the context of a ball-and-string model. Particles are treated as hard spheres that can bind irreversibly through a string attached to their surface. The model is set up to mimic some aspects of the aggregation of casein micelles in renneted milk. In this study we test the model of Smoluchowski by comparing it with our BD simulation model. Aggregation kinetics was studied by models in a range of volume fractions from =4x10-6 to 0.20. We found aggregation rates close to the Smoluchowski rates at low volume fractions, increasing sharply at higher concentrations. Simulations for simpler models also give rates slightly above theoretical values, but only at very high dilution. We show that only when a large fraction of the particles have already clustered is the quasi-stationary solution used in Smoluchowski theory attained. This partially explains the increase in rate with volume fraction. The steep increase in rate with volume fraction also explains why fractal aggregation, in which the effective volume fraction of the clusters increases with cluster size, leads to gelation.

Veranderingen in de structuur van amylopectine uit de zetmeelkorrels maken het brood oudbakken. Door de Landbouwuniversiteit Wageningen werd onderzoek gedaan naar de rol van het zetmeel in het verouderingsproces

Soja-eiwitten als toepassing in de levensmiddelenindustrie om de textuur van produkten te verbeteren

Het geven van een gewenste consistentie of van een bepaalde vaste vorm aan eiwitbevattende mengsels komt in het algemeen neer op het doen geleren van het eiwit. De vraag welke soorten reologische eigenschappen dan nodig zijn wordt kort besproken. Daarna komen de drie voornaamste typen eiwitgelen aan de orde, te weten gelatine, deeltjesgelen (bijvoorbeeld van caseïnedeeltjes) en gelen gevormd als gevolg van hittedenaturatie van globulaire eiwitten (bijvoorbeeld van ovalbumine, ß-lactoglobuline, sommige vleeseiwitten). Deze typen verschillen nogal in vormingswijze en in eigenschappen