Erminio Monteleone

Saliva Characteristics and Individual Sensitivity to Phenolic Astringent Stimuli

Astringency sensation is due to interactions between salivary proteins and phenols and is based on an increased-friction mechanism. Modifications to the profile of salivary proteins and their concentration could affect tannin/protein reactions and hence the intensity of perceived astringency. Salivary characteristics of 65 subjects were compared after abstention from phenol-containing food and immediately after ingestion of tannic acid. The effect of stimulation on saliva characteristics was expressed in terms of D value, computed as the arithmetic difference between values found in saliva samples from the 2 conditions. Based on D values, subjects were clustered in two groups. Cluster 1 (Cl1, 53 cases) was characterized by low D values thus indicating that the basal saliva condition was quickly restored in these subjects. Cluster 2 (Cl2) was composed of 12 subjects whose basal salivary condition was not quickly restored, particularly in terms of salivary protein concentration and profile and saliva haze-forming capacity. Sensory data showed that subjects capable of maintaining constant saliva characteristics were less sensitive to astringent stimuli than subjects in which the same stimulations induced significant saliva modifications. The results suggest that a large proportion of the population are able to maintain their salivary protein concentration and simultaneously intercept and inactivate dietary tannins.

Individual astringency responsiveness affects the acceptance of phenol-rich foods.

Sensory responses greatly vary between individuals, and individual sensory experiences influence eating behaviour. Three groups responding differently to phenolic astringent stimuli (Low Responding, LR, n=20, Medium Responding, MR, n=37 and High Responding, HR, n=20) were identified from a population of 77 subjects, based on the maintenance vs fluctuation of salivary characteristics after repeated stimulation of the masticatory and taste/somatosensory systems. The effect of LR, MR and HR status on perceived astringency and liking for phenol-containing apple, grape and carrot juices spiked with increasing tannic acid (TA) concentrations was examined. TA induced a greater increase of perceived astringency in HR, compared to MR and LR subjects. A decrease in liking for spiked juices was found in HR and to a lesser extent in MR and LR subjects. No significant differences were found comparing MR and LR groups for both astringency intensity and liking data. Liking for and familiarity with 37 food items, as well as preference for 14 phenol-rich foods and beverages, each paired with a less astringent counter-product, were also examined. An internal preference map was computed on liking scores and product subgroups were identified. An effect of LR/HR status was found for two food subgroups consisting of coffee without sugar, tea without sugar, raw chicory and milk chocolate, tea with sugar, coffee with sugar. LR subjects rated the products with the most astringency higher and those with the least astringency lower than did HR subjects. LR subjects also rated their familiarity with highly astringent products higher than did HR subjects. Thus, individual differences related to the physiological salivatory response to oral stimulations affect responses to astringent stimuli and can influence the overall acceptability of phenol-rich food items.

Sensory evaluation of young goat meat

Loins from 12 young goats (three extensively reared-entire males, EE; three extensively reared-castrated males, EC; three intensively reared-entire males, IE; four intensively reared-castrated males, IC) were assessed by a trained panel of eight assessors for odour, flavour and texture using 100 mm unstructured scales. Procrustes analysis was used to produce the spatial configuration of the samples. The first principal axis explained 44.9% of the variation and was mainly based on textural attributes. The second principal axis accounted for 21.3% of the variation and was mainly related to odour and flavour. Samples obtained from groups EE and EC were more tender and juicy, whereas, IE animals produced a more cohesive meat. Groups IE and IC produced a more stringy meat, with a higher meaty odour and flavour. The rearing system affected texture more than odour and flavour, whereas sex had little effect on textural attributes compared with odour and flavour.

Bitterness enhancement induced by cut grass odorant (cis-3-hexen-1-ol) in a model olive oil

Abstract In the present study the taste–smell interaction between bitterness and cut grass odour was studied in a model olive oil. Investigating the extent to which the green aroma affects the perception of bitterness in virgin olive oil may affect the identification of new strategies for optimising the sensory properties of the product. The study was organised in four stages: a pre-testing stage verified the suitability of the tastant (quinine dihydrochloride) and the odorant ( cis -3-hexen-1-ol) and to select a moderate concentration of the cut grass odour and a spread of different concentrations of the bitter compound ranging from weak to strong. A second stage studied the effect of the cut grass odour on the intensity of bitterness perceived in the oil and on the oils pleasantness (experiment 1). A third stage studied the influence of the cut grass odour on the dynamic process of the perception of bitterness (experiment 2). A fourth stage, to stimulate a nose-occlusion control condition, verified the sensory nature of the interaction between the odorant and tastant (experiment 3). The results show that the green odour note has a positive significant effect on the perception of bitterness. The presence of cut grass odour enhances the bitterness perception. New strategies in controlling the perceived intensity of bitterness in virgin olive oil may be defined.

Spectrophotometric assay using o-phtaldialdehyde for the determination of transglutaminase activity on casein

In this work, the possibility of using a simple and quick method was tested for determining transglutaminase activity on casein using a spectrophotometric assay. The enzyme activity was estimated on the basis of the decrease of o-phthaldialdehyde reactive e-amino groups of lysine following the formation of isopeptide bonds. The lysine residues involved in the formation of isopeptide bonds when the reaction reaches its plateau are equal to 0.126 μmol per mg of casein. This value results as equal to 0.205 μmol per mg of casein when N-carbobenzoxy-glutaminyl-glycine is added to the reaction medium as a small size acyl group donor. The electrophoretic analysis of the reaction products emphasised a different kinetic formation of casein polymers with the two substrate solutions used. This proposed method has resulted as accurate, with a mean coefficient of variation of 4.6%.

Individual differences in starchy food consumption: The application of preference mapping

Abstract In this study, we applied the technique of Internal preference mapping to examine the individual UK consumer intentions to eat each of 12 common starchy food dishes, and consider how individual opinions varied or clustered into similar groups. The results showed that subjects overall tend to ‘prefer’ (measured as reported frequency of consumption) the most familiar starchy foods, but it was also possible to identify two subject sub-groups, characterised by a different ‘preference’ for these foods. Subjects with traditional food habits prefer potatoes more than any different starchy food and in particular they prefer roast and chipped potatoes. In contrast there is another group composed with subjects who are interested in the health properties of starchy food, who prefer a varied intake of many kinds of starchy products (potato, rice and pasta). The ‘traditional’ group seems to be associated with greater degree of overweight and, to some extent, males more than females, but were no consistent group associations with age or measures of socio-economic status. The existence of these two consumer sub-groups may help to explain the finding of previous research on consumer perceptions of starchy foods, which shows that consumers hold divergent views about the importance and desirability of increasing starchy foods consumption, and about the role of these foods in weight control. This has implications for the communication of dietary recommendations to increase consumption of starchy food rich in complex carbohydrates (for example, boiled potatoes or boiled rice) rather than focusing on generic starchy food.

Optimisation of extra virgin Olive Oil quality

This study investigated the correlation between total polyphenol content and the stability (ie induction time by Rancimat) of oil samples according to different regions, cultivars, extraction technologies and ripening times of raw material. Results indicate a correlation of oil stability with total polyphenols, (r=0·88), a chemical variable easy to determine. We have set up an oil quality index as a measure of desirability including legal parameters, especially the Council Olive Oil International score (COI Score), stability (phenol content) and process yield into account. The study of the effects of olive ripening and storage prior to processing and olive paste mixing times and temperatures on the quality index using an experimental factorial design (24) were investigated. The process variables selected in the experimental factorial design were studied and the main effects on desirability were identified. Based on this information, the extraction process was optimised for quality index in relation to fruit ripening and olive paste mixing time using a response contour to identify optimal experimental conditions. This innovative procedure shows that process conditions can be optimised as a function of Dtot, evaluated according to scientific determinations.

Bioaccessibility and Antioxidant Activity Stability of Phenolic Compounds from Extra-Virgin Olive Oils during in Vitro Digestion

The impact of an in vitro procedure that mimics the physiochemical changes occurring in gastric and small intestinal digestion on the bioaccessibility and antioxidant activity of phenols from 10 extra-virgin olive oil samples was assessed. Extra-virgin olive oil phenols were totally extracted in the aqueous phase, which reproduces gastric fluids during the digestion procedure. A linear bioaccessibility model, based on tyrosol behavior in model oil samples, was used to estimate the bioaccessibility index (BI%) of extra-virgin olive oil phenols. The BI% varied amongst samples from a maximum of 90% to a minimum of 37%, thus indicating that only a fraction of phenols can be considered bioaccessible. The specific antioxidant activity of olive oil phenols proved to be negatively affected by the digestion procedure. By computing a principal component analysis, it was possible to show that differences in the potential bioactive effect of extra-virgin olive oil samples were related to different phenolic profiles.

The impact of individual variations in taste sensitivity on coffee perceptions and preferences

Despite a few relationships between fungiform papillae (FP) density and 6-n-propylthiouracil (PROP) taster status have been reported for sensory qualities within foods, the impact on preferences remains relatively unclear. The present study investigated responses of FP number and PROP taster groups to different bitter compounds and how these affect coffee perception, consumption and liking. Subjects (Ss) with higher FP numbers (HFP) gave higher liking ratings to coffee samples than those with lower FP numbers (LFP), but only for sweetened coffee. Moreover, HFP Ss added more sugar to the samples than LFP Ss. Significant differences between FP groups were also found for the sourness of the coffee samples, but not for bitterness and astringency. However, HFP Ss rated bitter taste stimuli as stronger than did LFP Ss. While coffee liking was unrelated to PROP status, PROP non-tasters (NTs) added more sugar to the coffee samples than did super-tasters (STs). In addition, STs rated sourness, bitterness and astringency as stronger than NTs, both in coffee and standard solutions. These results confirm that FP density and PROP status play a significant role in taste sensitivity for bitter compounds in general and also demonstrate that sugar use is partly a function of fundamental individual differences in physiology.

Methodological approach to evaluate the effects of age at slaughter and storage temperature and time on sensory profile of lamb meat

A methodological approach, that requires the use of an experimental design, the definition of a sensory profile and an appropriate statistic validation of sensory data, was developed, in order to evaluate the effects of some process variables, such as age at slaughter and storage time and temperature, on sensory characteristics of lamb meat. In this study factorial design (2(3)) was used. The first step was the definition of descriptive terms for determining the sensory profile of meat. A vocabulary of 10 descriptive terms of odour, flavour and texture was developed. Therefore, after an appropriate and rigorous training, a panel of 8 assessors evaluated the lamb products in triplicate using a 100 mm unstructured scale. The following step was the statistic validation of data. Sensory data for each attribute were submitted to a fixed analysis of variance. Results showed that even though the panel was trained, judgements differed among assessors, as demonstrated by the significant assessor x sample interaction which was found for most attributes. In order to minimise this effect, the sensory data were submitted to a mixed analysis of variance that allows the determination of panel performance and selection of significant attributes for sample discrimination. Eight attributes were selected. Finally, analysis of variance with age, frozen temperature and storage time as main effects, was performed on mean values of selected attributes. Meaty odour and flavour, cohesiveness and stringiness were negatively influenced by age, whereas tenderness and juiciness were positively influenced by age. Lamb odour and flavour were positively influenced by frozen temperature. At increasing storage time, meaty odour and flavour and juiciness increased. The descriptive analysis allowed an objective description of the products in terms of perceived sensory attributes. The fixed and mixed models of analysis of variance produced different results. A mixed model appeared to be suitable for validation of panel performances and selection of significant attributes for meat samples discrimination.