David Kilcast

Sensory perception of creaminess and its relationship with food structure

Practical difficulties are frequently encountered in understanding the meaning of creaminess as used as a sensory attribute, and in the compositional and physical characteristics of foods that give rise to creaminess. Selected factors have been investigated in this project. The size of dispersed particles (solid, liquid and gaseous) on the perceived creaminess was of particular interest during the course of the work, and this was varied using appropriate changes in processing, during production of samples for analysis. Additional factors investigated included the presence of an added cream flavour in artificial creams, fat content in artificial creams and air content in chocolate mousses. Sensory characterisation of samples was carried out using sensory profiling, while physical characterisation of the samples was by means of particle size measurements, microscopy and rheology. The results show that perceived creaminess is a complex attribute in multi-phase food systems, being dependent on both flavour and textural characteristics of products, with different dependencies on these characteristics, depending on the product type concerned. The project demonstrated the value of manipulating processing and formulation variables as a means of generating a range of food structures for the investigation of creaminess. It is evident, however, that the concept of creaminess might differ between different structural types, limiting opportunities for devising general rules governing the factors controlling creaminess. Further studies should focus on specific structural types that are open to manipulation, and further research is in progress to investigate systematic changes to a mousse structure.

Consumer perception of crispness and crunchiness in fruits and vegetables

Abstract Crispy and crunchy textures are desirable qualities and contribute to our enjoyment of foods, and this is particularly true in the case of fruits and vegetables. However, most of the literature on crispness and crunchiness focuses on dry foods, and little work has been carried out on wet foods such as fruits and vegetables. The study presented here was designed to address two main issues: firstly, to gain a better understanding of consumer terminology relevant to the textural characteristics of fruits and vegetables, with particular emphasis on crispy and crunchy terms; secondly, to investigate the relationship between the vocabularies used by trained panels and consumers. Products were selected to give a wide range of textural characteristics. Free choice profiling was carried out with a small number of naive consumers, as well as with trained panellists. Both sets of data were analysed using generalised Procrustes analysis (GPA), which allowed comparison of the two sets of vocabularies generated. GPA maps showed that sensory perceptions expressed by a trained panel correlated well with consumer terminology. The study also reinforced the idea that crispness and crunchiness are complex concepts that combine a wide range of perceptions such as fracture characteristics, sound, density and geometry. Results showed a better agreement on the meaning and use of crunchy terms by consumers and panellists alike. On the other hand, crispness was less well understood, showing a much wider conceptual space.

Flavour release and perception in reduced-fat foods

Abstract This study has focused on evaluating the suitability of a time-intensity technique for the quantitative assessment of flavour release and perception in reduced- and full-fat versions of selected foods (hard cheeses and salad creams), which varied primarily in their fat contents only. Both sensory profiling and time-intensity techniques showed that reducing the fat content of hard cheeses and salad creams caused an increase in the intensity of basic gustatory sensations, with the exception of saltiness. Moreover, the time-intensity technique revealed that the total persistence time and rate of flavour release were greater in the reduced-fat foods. This demonstrates that lowering the fat content gives rise to flavour imbalance, which can be monitored by a temporal method.

Psychophysical characterization of new sweeteners of commercial importance for the EC food industry

Quantitative psychophysical information on the perceptual characteristics of sucrose (as reference), sodium cyclamate, aspartame, neohesperidin dihydrochalcone (NHDHC) and maltitol were established through the determination and the modelling of their concentration-response (C-R) functions according to linear, Beidler or Hill equations, the recording of the time-intensity (T-I) curves with the determination of the T-I parameters for each sweetener, and the establishment of the sensory profile of the sweetener solutions by the QDA technique. Bulk and intense sweeteners present dissimilar C-R functions. The C-R function observed for maltitol is linear while aspartame, cyclamate and NHDHC exhibit a saturation plateau around 10–13% sucrose equivalent. Temporal characteristics of aspartame and cyclamate are comparable to those of sucrose and maltitol, whereas the T-I characteristics of NHDHC contrast with those of the other sweeteners, essentially because of its long onset and persistence times. Bitter taste and bitter aftertaste are attributes that differentiate maltitol and sucrose from artificial sweeteners. Bitter and metallic are non-sweet aftertastes characteristic of cyclamate, while NHDHC is mainly defined by a liquorice-like and cooling/ menthol flavour. Caramel flavour is associated with nutritive sweeteners, and burnt sugar flavour is related to synthetic sweeteners, except cyclamate, which is characterized by both flavours.

Descriptive profiles of synergistic mixtures of bulk and intense sweeteners

Abstract The descriptive profiles of three bulk and intense sweetener blends (maltitol-cyclamate, maltitol-acesulfam-K, and sucrose-cyclamate) were established with reference to a 10% sucrose solution. These blends were chosen because they had been demonstrated in a previous study (Hutteau et al. , 1998) as having a significant level of synergy. The descriptive profiles were established by a quantitative descriptive analysis-(QDA) type technique and the results were analysed by analysis of variance and by principal component analysis to examine the overall relationships among single solutions and mixtures of sweeteners. A significant reduction of the non-sweet tastes and aftertastes usually associated with acesulfam-K and cyclamate was observed.

A study of the solution properties of selected binary mixtures of bulk and intense sweeteners in relation to their psychophysical characteristics

The solution properties of binary mixtures of two bulk sweeteners (sucrose and maltitol) and three intense sweeteners (acesulfame K, aspartame and sodium cyclamate) were studied. The parameters measured were apparent specific volumes, isentropic compressibilities and compressibility hydration numbers. An attempt has been made to correlate the solution properties of some of the mixtures with their sweetness responses. Both specific volume and isentropic compressibility data have been used to interpret the possibility of synergism or suppression in the mixtures in terms of the affinity of the solutes for the surrounding solvent structure, and hence the effectiveness of transport of the molecules to their appropriate receptor sites. However, an understanding of the nature and stereochemistry of the individual components in the mixtures is necessary for predicting the packing characteristics of molecules in water and their accession to receptor sites. The intense sweeteners seem to play an important role in modifying the structure of water in solution. Although there is no clear proof of how this affects perception, fine differences in solution behaviour can be observed with isentropic apparent specific compressibility measurements. The study supports the idea that receptors lie at different depths in the lingual epithelium, and also that in two-component systems, one species may alter the packing efficiency of the other in solution sufficiently to effect a change in taste quality or intensity.

Sweetness of bulk sweeteners in aqueous solution in the presence of salts

Abstract The perceived effect of adding salts on the sweetness of bulk sweeteners (sucrose, glucose, fructose, sorbitol and xylitol) depends on the sweetener type and concentration and on the type of salt. Sodium chloride enhances the sweetness of all the sweeteners to some degree. Potassium chloride has little effect on any sweetener other than sorbitol, which shows sweetness enhancement at low sorbitol concentrations and suppression at high sorbitol concentrations. Magnesium chloride additions tend to enhance sweetness, particularly of sucrose and glucose. The effects observed can not be ascribed to any inherent sweetness of the salts themselves, suggesting that the observed effects are a result of interactions between the salts and sweeteners in the aqueous medium.