Caterina Dinnella

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.

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%.

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.

Preparation and properties of an immobilized soluble-insoluble pectinlyase

Abstract An endo-pectinlyase present in a commercial mixture was immobilized on EUDRAGIT L100-55, a polymer which is reversibly soluble-insoluble depending on the pH of the medium. The enzymic activities of biocatalytic matrices, obtained by pre-activating the polymer either with water-soluble carbodiimide or by simple adsorption, were compared. The biocatalyst obtained by adsorption showed an enzymic activity higher (500 E.U. g −1 ) than that obtained using the activated polymer (50 E.U. g −1 ). Moreover, the activating agent did not seem to be necessary in order to stabilize the interaction between carrier and protein. In fact about 80% of the initial activity was detectable on both matrices after repeated washings with NaCl 0.2 m . The immobilization procedure did not alter the main biochemical parameters of the immobilized enzyme with respect to its native form and appreciably enhanced its stability in the temperature range 25-45°C.

Core-shell functional microspheres by dispersion polymerization: 2. Synthesis and characterization

Abstract Polystyrene microspheres ranging in diameter from 3 to 10 μm were prepared in alcoholic media by dispersion polymerization of styrene in the presence of a methacrylic acid/ethyl acrylate 1:1 statistical copolymer (Eudragit) as the stabilizer precursor. The effects of the initial Eudragit and free radical initiator concentrations on the microsphere dimensions, the microsphere size distribution and surface functionality were investigated. The particle dimensions were found to increase with increasing initiator concentration and decrease with increasing steric stabilizer precursor concentration. The percentage Eudragit in the microspheres was found to increase with the stabilizer precursor concentration and decrease with the initiator concentration. The resulting double-shell microspheres, with specific surface functionalities, are promising as tailor-made supports for biocatalysts.

Pectolytic enzymes co-immobilization on γ-alumina spheres via organophosphate compounds

Abstract Endopectinlyase (EC 4.2.2.10), endopolygalacturonase (EC 3.2.1.15) and pectinesterase (EC 3.1.1.11) present in a commercial mixture were co-immobilized on γ-alumina spheres activated with organophosphate compounds. Staining of the alumina-enzyme complexes with a dye specific for protein showed that only the carrier external surface was available for protein binding. When confined in a packed bed reactor, the activity of the co-immobilized enzymes brought about a viscosity decrease of 70–90% in pectin and polygalacturonic acid solutions, respectively. Sixty per cent of the initial activity was retained from the immobilized enzymes after the sixth utilization cycle on both the substrates used. The immobilized enzymes were also active against fresh apple juice producing a 90% reduction in viscosity in the first five cycles of utilization.

Inclusion of Hermetia illucens larvae meal on rainbow trout (Oncorhynchus mykiss) feed: effect on sensory profile according to static and dynamic evaluations

BACKGROUND Diet implementation with insect meal has aroused increased attention in aquaculture considering the advantages of this new protein source. The effect of Hermetia illucens meal (HI) inclusion in diets on rainbow trout physical-chemical and sensory properties was evaluated. Three diets were prepared: HI0, HI25, HI50, with 0, 25 and 50% of HI replacing fish meal, respectively. Fillet sensory profiles were described by descriptive analysis and temporal dominance of sensation methods. Cooking loss, Warner-Bratzler shear force, proximate analysis, and fatty acid composition were also determined. RESULTS Diets significantly affected fillets sensory profile. Descriptive analysis indicated significant changes in perceived intensity of aroma, flavour and texture descriptors as a function of diet composition. Temporal dominance of sensation evaluations provided information on dominance and evolution of sensations perceived in fillets from different diets. The first sensations perceived as dominant were related to texture attributes, followed by flavours. Dominance of fibrousnesses decreased with the increase of HI in the diet. Boiled fish, algae flavours and umami taste clearly dominated the HI0 dynamic profile. The onset of metallic flavour dominance characterised HI25 and HI50. No differences in physical parameters were detected. Principal component analysis highlighted the relationship between sensory attributes and physico-chemical parameters. CONCLUSION The sensory description of fillets indicated that HI inclusion induces significant differences in the perceived profile.

Comparison of three nudge interventions (priming, default option, and perceived variety) to promote vegetable consumption in a self-service buffet setting

Background Dietary choices in out-of-home eating are key for individual as well as for public health. These dietary choices are caused by a wide array of determinants, one of which is automatic decision-making. Nudging is attracting considerable interest due to its understanding and application of heuristic biases among consumers. The aim of this study is to test and compare three nudges in promoting vegetable consumption among test persons in a food lab-based experiment. Methods The initial sample consisted of 88 participants recruited in Copenhagen, Denmark. Each study participant was randomly assigned to one of the three experiments: priming, default and perceived variety. The priming arm of the experiment consisted of creating a leafy environment with green plants and an odour of herbs. In the default arm of the experiment, the salad was pre-portioned into a bowl containing 200g of vegetables. The third experiment divided the pre-mixed salad into each of its components, to increase the visual variety of vegetables, yet not providing an actual increase in items. Each individual was partaking twice thus serving as her/his own control, randomly assigned to start with control or experimental setting. Results The default experiment successfully increased the energy intake from vegetables among the study participants (124 kcal vs. 90 kcal in control, p<0.01). Both the priming condition and perceived variety reduced the total energy intake among the study participants (169 kcal, p<0.01 and 124 kcal, p<0.01, respectively), mainly through a decrease in the meat-based meal component. Conclusions Considerable progress has been made with regard to understanding the use of nudging in promoting a healthier meal composition, including increasing vegetable intake. This study suggests that the nature of a nudge-based intervention can have different effects, whether it is increasing intake of healthy components, or limiting intake of unhealthy meal components. This work has demonstrated that consumer behaviour can be influenced without restricting or providing incentives for behaviour change. The present findings have promising application to the foodservice sector.