No abstract

No abstract

The relevance of initial rheological properties and mechanical and enzymatic structure breakdown in determining selected sensory texture attributes of custards was studied. The so-called structure breakdown cell was used to characterize saliva-induced breakdown, i.e., by monitoring digestion of starch by amylase from saliva. Based on rheological parameters, some attributes could be predicted well, while others more poorly or were not predicted. Predictable attributes were primarily determined by bulk properties; poorly and nonpredictable attributes originated from properties of the outer lowviscosity surface layers or were not related to rheological properties. Both mechanical and enzymatic breakdown were important for creaminess, thickness and melting. Enzymatic breakdown was the dominant mechanism involved in the perception of fattiness, roughness and stickiness but not heterogeneity. Creaminess was the only attribute that was also determined by initial rheological properties and mechanical and enzymatic breakdown. 5 Corresponding Journal of Texture Studies 38 (2007) 42-69. All Rights Reserved. © 2007, The Author(s) Journal compilation © 2007, Blackwell Publishing 42Custards displaying high creaminess ratings had high initial stiffness, the structure broke down at low stress and enzymatic breakdown was slow. Microstructural organization of starch plays a dominating role in defining rheological and breakdown behavior of custards and in this way determines creaminess to a high extent. PRACTICAL APPLICATIONSBreakdown during eating is a complex process. In the work presented, breakdown of a semisolid food system is unravelled and linked to its microstructure and sensory perception. It is demonstrated that it is possible to reasonably predict sensory mouthfeel properties, especially the important attribute, creaminess, based on data from instrumental techniques. The knowledge obtained could be applied to high throughput screening of newly developed food products without the need of involving sensory panels. This will enable the food industry to increase the effectiveness and efficiency of the design and control of sensory attributes throughout the food product development process. KEYWORDSCreaminess, custards, rheology, saliva-induced structure breakdown, sensory, starch microstructure 43 RHEOLOGY AND SENSORY TEXTURE ATTRIBUTES OF CUSTARDS 44 A.M. JANSSEN ET AL.

Characteristics of food products are commonly assessed in series of sensory studies to gain insight which can be used, for instance, for product development. Sensory studies are very timeconsuming and susceptible to large sources of variation. Assessing information about (new) products by means of instrumental measurements would be very beneficial for numerous reasons, including repeatability, reproducibility and, most of all, the fact that instruments do not suffer from fatigue or adaptation. Measurements simulating sensory assessment of product properties can be performed at different stages of consumption and on different types of sensory attributes. In this study the relation between rheological parameters and creamy mouthfeel was investigated. The goal was to discover whether a model using a limited mechanical characterization, namely parameters describing bulk rheological behaviour, would suffice to describe the sensory attribute 'creamy mouthfeel', also called creaminess. The two main reasons for performing this study were (i) to investigate the possibility of using rheological measurements for high-throughput screening of newly developed custard products without the need for involving sensory panels already at an early stage of product development and (ii) to gain knowledge about the correlation between rheological measurements and the multidimensional attribute creamy mouthfeel. The resulting model shows that prediction of creamy mouthfeel by means of rheological measurements is possible only to a certain extent (Q 2 CV ¼ 0.48). Reasons that can be mentioned for deviations between measured creaminess and modelled creaminess are (i) variation in measured creamy mouthfeel scores (variation in y-variable) and (ii) lack of description of surface properties of the food product by the rheological measurements used here. The results show that instrumental measurements are complementary to sensory analysis and can greatly facilitate the task for the practitioner at an early stage of product development, making high-throughput screening of novel products feasible.

Commercial and model mayonnaises varying in fat content and type and amount of thickener were characterized by sensory analysis, rheological measurements and novel instrumental measurements covering other physicochemical properties and/or reflecting changes of food properties during oral processing. Predictions of texture attributes by rheological measurements were analyzed and compared with predictions by rheological measurements combined with novel measurements. Most of the texture attributes were predicted well by rheological parameters alone. Parameters from other instrumental measurements played a small complementary role, except in the predictions of most of the afterfeel attributes. Most important were rheometry at large deformation and in the nonlinear regime of the dynamic stress sweep and two novel measurements reflecting the effect of saliva: turbidity of rinse water and viscosity with added saliva. Tan d at 500% strain, reflecting the 5 Corresponding 82 fluid-like character of the samples during high-strain dynamic flow, relates best to creaminess and other texture attributes. PRACTICAL APPLICATIONSThis article describes how and how well the texture attributes of mayonnaises can be predicted from rheological and novel instrumental measurements. It shows that many texture attributes can be successfully predicted by bulk rheological properties alone, but that for some the quality of the predictions increases slightly when parameters from other instrumental measurements, such as those from turbidity measurements, those from viscosity measurements in the structure breakdown cell with saliva, or those from friction measurements, are added. These results are relevant not only to those investigating the mechanisms involved in the oral perception of texture in semisolids but also to those who want to perform quick screening of new samples without the use of time-consuming and expensive sensory panels. Simulations can be performed using the models to predict how texture attributes are influenced by changes in the rheological characteristics of a product. The results also identify rheological measurements and novel instrumental measurements relevant for texture attributes of mayonnaise. This knowledge may help to improve the efficiency of product development in industry.