Joanne Hort

Improved methods for fMRI studies of combined taste and aroma stimuli.

Previous neuroimaging studies of the cortical representation of gustatory and olfactory stimuli have often delivered tastants to the mouth in very small quantities or stimulated olfaction orthonasally. In studies of retro-nasal olfaction, swallowing was generally delayed to reduce head motion artefacts. The present fMRI study aims to improve upon such methodological limitations to allow investigation of the cortical representation of flavour (taste and aroma combination) as it typically occurs during the consumption of liquid foods. For this purpose we used (1) a novel, automated, sprayed stimulus delivery system and a larger volume of liquid sample (containing sweet tastants and banana/pear aroma volatiles) to achieve more extensive stimulation of the oral cavity taste receptors, (2) a pseudo-natural delivery paradigm that included prompt swallowing after each sample delivery to obtain physiological retro-nasal olfactory stimulation, (3) fMRI acquisition with wide brain coverage and double-echo EPI to improve sensitivity. We validated our paradigm for the delivery of volatiles using atmospheric pressure chemical ionisation mass spectrometry. This showed that the main retro-nasal delivery of volatiles in the paradigm occurs immediately after the swallow. Several brain areas were found to be activated, including the insula, frontal operculum, rolandic operculum/parietal lobe, piriform, dorsolateral prefrontal cortex, anterior cingulate cortex, ventro-medial thalamus, hippocampus and medial orbitofrontal cortex.

Developments in the textural and rheological properties of UK Cheddar cheese during ripening

Abstract To achieve the required texture Cheddar cheese must undergo a substantial ripening period. To investigate changes that occur during ripening, the textural attributes of an English Cheddar were evaluated by a trained panel at selected stages during maturation (0, 8, 18, 28, 34, 50 and 64 weeks). Rheological properties were determined using compression and stress relaxation tests carried out on an Instron Universal Testing machine. Panel results indicated changes in most textural attributes, particularly springiness and creaminess and, to a lesser extent, firmness. Variations in the rheological properties also occurred, most notably a decrease in strain at fracture. Progressive changes in the textural and rheological properties could be divided into three distinct stages representing the period prior to retail sale, the stage at which the cheese would be commercially classified as ‘mild’ through to ‘medium’ and a final stage at the end of which it would be labelled ‘Mature’.

The cortical response to the oral perception of fat emulsions and the effect of taster status

The rewarding attributes of foods containing fat are associated with the increase in fat consumption, but little is known of how the complex physical and chemical properties of orally ingested fats are represented and decoded in the brain nor how this impacts feeding behavior within the population. Here, functional MRI (fMRI) is used to assess the brain response to isoviscous, isosweet fat emulsions of increasing fat concentration and to investigate the correlation of behavioral and neuroimaging responses with taster status (TS). Cortical areas activated in response to fat, and those areas positively correlated with fat concentration, were identified. Significant responses that positively correlated with increasing fat concentration were found in the anterior insula, frontal operculum and secondary somatosensory cortex (SII), anterior cingulate cortex, and amygdala. Assessing the effect of TS revealed a strong correlation with self-reported preference of the samples and with cortical response in somatosensory areas [primary somatosensory cortex (SI), SII, and midinsula] and the primary taste area (anterior insula) and a trend in reward areas (amygdala and orbitofrontal cortex). This finding of a strong correlation with TS in somatosensory areas supports the theory of increased mechanosensory trigeminal innervation in high 6-n-propyl-2-thiouracil (PROP) tasters and has been linked to a higher risk of obesity. The interindividual differences in blood oxygenation level-dependent (BOLD) amplitude with TS indicates that segmenting populations by TS will reduce the heterogeneity of BOLD responses, improving signal detection power.

Taste-aroma interactions in a ternary system: a model of fruitiness perception in sucrose/acid solutions.

Cross-modal interactions between aroma, sweetness, and acidity were studied. A series of samples was presented to trained panelists who assessed strawberry flavor intensity using magnitude estimation with a reference modulus. The delivery of aroma stimuli from the different solutions was measured by monitoring exhaled breath using atmospheric pressure chemical ionization-mass spectrometry to determine whether there were any physicochemical effects on volatile release; no significant differences were noted. Three-dimensional predictive models were built to describe perceived strawberry flavor intensity as a function of concentrations of sucrose, acid, and volatiles. Analysis of the data identified two groups of panelists with different responses: For Group 1, increasing sucrose and/or acid levels also increased the perceived flavor intensity. For Group 2, changing sucrose concentrations had little effect, but increasing acid and/or volatile levels did. The results show different effects of organic and inorganic acids on perception, as well as clear interactions between the modalities of taste (sugar and acid) and aroma. The clustering of panelists’ responses suggests that this phenomenon may depend on prior associations between the fruity flavor and the tastants.

Measuring the emotional response to beer and the relative impact of sensory and packaging cues

Recent studies have highlighted that, in todays extremely competitive markets, using hedonic measurement alone is inadequate for evaluating consumer product experience. Measuring emotional response is suggested to provide a richer insight into consumer responses. The objectives of this study were to 1) measure consumer emotional responses to beer, 2) determine whether a relationship exists between sensory and emotional attributes of products, and finally 3) investigate the relative impact of sensory and packaging attributes on the emotional response to beer. Using the EsSense Profile technique, the levels of liking and emotional response to a broad range of 10 commercial lager beers were evaluated by 90 lager consumers under three different conditions: blind (liquid only), pack (packaging only), and informed (liquid plus packaging). Emotional response was shown to discriminate across the beer samples in terms of both pleasantness and engagement level. Packaging cues were more influential on emotional response, but sensory attributes did play a role. Increasing carbonation and familiarity and decreasing sweetness and alcohol content were shown to influence a more pleasant and engaged emotional response in this set of beers. This study highlights the need to evaluate both liquid and packaging characteristics to gain better insights into developing and understanding the emotional signature of beer.

Modifying flavour in food.

Modifying flavour: an introduction Flavouring substances: from chemistry and carriers to legislation Extraction of flavourings from natural sources From fermentation to white biotechnology: how microbial catalysts generate flavours New developments in yeast extracts for use as flavour enhancers Chiral chemistry and food flavourings Formulating low fat food: the challenge of retaining flavour quality New pungent and cooling compounds for use in foods Controlled release of flavour in food products Developments in sweeteners Enhancing umami taste in foods Bitter blockers in foods and pharmaceuticals Masking agents for use in foods Selecting the right flavourings for a food product.

Study of the influence of yeast inoculum concentration (Yarrowia lipolytica and Kluyveromyces lactis) on blue cheese aroma development using microbiological models

Yarrowia lipolytica and Kluyveromyces lactis occur as part of Stilton cheese microflora yet are not controlled during production. This study investigated the influence of their inoculum concentration on aroma production. Models of Y. lipolytica and K. lactis, with Penicillium roqueforti, were analysed using instrumental and sensory analysis. Different concentrations of Y. lipolytica produced important changes in the aroma profiles of microbiological models, analysed by solid-phase microextraction (SPME GC-MS). Sensory analysis with discrimination tests showed differences were detectable via human perception but did not concern the similarity to blue cheese odour. Increasing the inoculum concentration of K. lactis resulted in decreased variation between replicates. Partial least squares (PLS) regression on Flash profile data showed models inoculated with low concentrations of K. lactis exhibited blue cheese-related attributes, associated with increased ketone production. Results suggest that controlling the amount of Y. lipolytica and K. lactis during production offers potential to manipulate blue cheese aroma development.

Colour influences sensory perception and liking of orange juice

BackgroundThis study assesses the effect of slight hue variations in orange juice (reddish to greenish) on perceived flavour intensity, sweetness, and sourness, and on expected and actual liking. A commercial orange juice (COJ) was selected as a control, and colour-modified orange juices were prepared by adding red or green food dyes (ROJ and GOJ) that did not alter the flavour of the juice. A series of paired comparison tests were performed by 30 naive panellists to determine the influence of orange juice colour on flavour intensity, sweetness, and sourness. Then, 100 orange juice consumers were asked to rate expected liking of orange juice samples initially by visual evaluation and subsequently for actual liking upon consumption, using a labelled affective magnitude scale.ResultsResults of pair comparison tests indicated that colour changes did not affect flavour intensity and sweetness, but the greenish hue (GOJ) significantly increased the perceived sourness. Results of the consumers’ study indicated significant differences in expected liking between the orange juice samples, with ROJ having the highest expected liking. However, scores of actual liking after consumption were not significantly different. COJ and GOJ showed a significant increase in actual liking compared to expected liking.ConclusionsThis study shed light on how slight variations in orange juice hue (reddish to greenish hues) affect the perceived flavour intensity, sweetness, and sourness, and the expected and actual liking of orange juice.

Impact of flavour solvent (propylene glycol or triacetin) on vanillin, 5-(hydroxymethyl)furfural, 2,4-decadienal, 2,4-heptadienal, structural parameters and sensory perception of shortcake biscuits over accelerated shelf life testing

The influence of choice of flavour solvent, propylene glycol (PG) or triacetin (TA), was investigated during accelerated shelf life (ASL) testing of shortcake biscuits. Specifically, the differential effect on the stability of added vanillin, the natural baked marker compound 5-(hydroxymethyl)furfural (HMF), specific markers of oxidative rancidity (2,4-decadienal, 2,4-heptadienal), and the structural parameters of hardness and fracturability. Significantly more HMF was formed during baking of biscuits prepared with TA; these biscuits were also more stable to oxidative degradation and loss of vanillin during ageing than biscuits prepared with PG. Fresh TA biscuits were significantly more brittle than fresh PG biscuits. There was no impact of solvent choice on hardness. Sensory evaluation of hardness, vanilla flavour and oily off-note was tested during ASL testing. There was no significant impact of storage on sensory ratings for either the PG or TA biscuits.

Formulating low-fat food: the challenge of retaining flavour quality.

Publisher Summary The term, “fat” can encompass a range of different materials but throughout this chapter, the term, “fat” has been used to refer to the triglyceride molecules present in food that are composed of a glycerol backbone esterified to three fatty acids. Fats form integral elements of cell membranes and contribute to cholesterol transport, blood clotting, immune function, and the manufacture of hormones for reproductive function. Certain fatty acids, linoleic acid and alpha-linolenic acid (essential fatty acids) must also be obtained directly from the diet as they cannot be made in the body. However, there is now little doubt that a diet high in fat is linked to the chronic health problems of Western society: obesity, heart disease, diabetes, and colon cancer. Fat has a higher energy value than protein or carbohydrate but does not appear to reduce hunger or induce satiety to the same extent as these other macronutrients. Diets high in saturated fatty acids and low in unsaturated fatty acids are linked to higher blood cholesterol levels and subsequent complications, such as coronary heart disease.