Sweet Perception Research Articles

The Bamboo-Eating Giant Panda (Ailuropoda melanoleuca) Has a Sweet Tooth: Behavioral and Molecular Responses to Compounds That Taste Sweet to Humans

A growing body of behavioral and genetic information indicates that taste perception and food sources are highly coordinated across many animal species. For example, sweet taste perception is thought to serve to detect and motivate consumption of simple sugars in plants that provide calories. Supporting this is the observation that most plant-eating mammals examined exhibit functional sweet perception, whereas many obligate carnivores have independently lost function of their sweet taste receptors and exhibit no avidity for simple sugars that humans describe as tasting sweet. As part of a larger effort to compare taste structure/function among species, we examined both the behavioral and the molecular nature of sweet taste in a plant-eating animal that does not consume plants with abundant simple sugars, the giant panda (Ailuropoda melanoleuca). We evaluated two competing hypotheses: as plant-eating mammals, they should have a well-developed sweet taste system; however, as animals that do not normally consume plants with simple sugars, they may have lost sweet taste function, as has occurred in strict carnivores. In behavioral tests, giant pandas avidly consumed most natural sugars and some but not all artificial sweeteners. Cell-based assays revealed similar patterns of sweet receptor responses toward many of the sweeteners. Using mixed pairs of human and giant panda sweet taste receptor units (hT1R2+gpT1R3 and gpT1R2+hT1R3) we identified regions of the sweet receptor that may account for behavioral differences in giant pandas versus humans toward various sugars and artificial sweeteners. Thus, despite the fact that the giant panda's main food, bamboo, is very low in simple sugars, the species has a marked preference for several compounds that taste sweet to humans. We consider possible explanations for retained sweet perception in this species, including the potential extra-oral functions of sweet taste receptors that may be required for animals that consume plants.

The impact of sugar and fat reduction on perception and liking of biscuits

Reducing the fat and/or sugar content in biscuits can be a way to improve their nutritional composition. Seventy-nine consumers of biscuits were recruited to study the impact of these reductions on liking and perception. Four categories of products were selected from a wide range of biscuits available at the French market. Three to six variants of each type of biscuit were produced based on reduced content of sugar, fat or both. Consumers tested the samples under laboratory conditions (6 sessions), recording their liking during initial sessions and crispiness, sweetness and fat perception during latter sessions.Sugar-reduced biscuits were perceived as less sweet than standard biscuits at low reduction levels, whereas fat-reduced biscuits were perceived as less fatty than standard biscuits at higher reduction levels (except for one biscuit among the three biscuits studied). A reduction in the sugar content had no effect on perception of fat, whereas a reduction in the fat content sometimes induced a reduced sweetness perception. For most of the biscuits studied, the least appreciated variants were those perceived as (1) less sweet, (2) less sweet and less fatty or (3) less sweet and less crispy than standard biscuits. Moreover, the variants only perceived as less fatty were not significantly disliked. These results suggest that from a sensory point of view, it is more acceptable to reduce the fat than the sugar content in biscuits, at least when products are not perceived as being less sweet.

Eating quality and health-promoting properties of two sweet cherry (Prunus avium L.) cultivars stored in passive modified atmosphere

Two sweet cherry cultivars ('New Star' and 'Sweet Heart') were chosen to explore the impact of passive modified atmosphere packaging on the eating quality and health-promoting properties of fruit. Packaged and unpackaged fruits were stored at 0 ℃ for 15 or 30 days, followed by zero or three days at 20 ℃, after which the analyses were undertaken. In most cases, modified atmosphere packaging helped preserving higher firmness values and reducing the incidence of alterations and decay in both cultivars, but the effects on other physicochemical attributes were different for each cultivar. Partial least squares regression procedures were used to reveal relationships among the different variables assessed. Generally, fruits displaying higher antioxidant capacity were also characterised by higher values for firmness and titratable acidity, in turn related to better acceptability scores in both cultivars. However, the attributes contributing most to acceptability were different in each case. In 'New Star' fruit, acceptability was closely related to the perception of cherry flavour. In this cultivar, acetaldehyde content was related to the perception of off-flavours, while ethanol content was found to associate to soluble solids and to the perception of sweetness. In contrast, acceptability of 'Sweet Heart' fruit was related mainly to the perception of firmness and, to a lower extent, of sweetness.

Dairy-Based Emulsions: Viscosity Affects Fat Difference Thresholds and Sweetness Perception.

In complex emulsions, viscosity or viscosity-associated sensory attributes such as creaminess are important for quality assessment and product differentiation. Two sets of emulsions with fat or locust bean gum content being varied at seven levels were developed; the two emulsions at each level had similar apparent viscosity. Additionally, sugar concentration was kept constant either with respect to total emulsion, or with respect to the aqueous phase. Series of two-alternative forced choice tests were performed with one constant stimulus, and just noticeable differences were calculated using probability regression. The results show that, when viscosity was not compensated, it was easy for the subjects to (a) distinguish emulsions with different fat content when the fat content was addressed in the question, and to (b) distinguish emulsions with different fat or locust bean gum content when creaminess was addressed. For the latter descriptor, it is of minor importance whether viscosity is altered by fat content or a thickener. Weber fractions that were calculated for viscosity were approximately 0.20. The quantitative effects of viscosity on sweetness, however, depend on how product rheology was modified.

Impact of apple procyanidins on sensory perception in model cider (part 1): Polymerisation degree and concentration

The impact of the degree of polymerization and of the concentration of procyanidins in a model solution of French cider was investigated. Four purified fractions of procyanidins at three concentrations were added in a solution containing water, ethanol, fructose and malic acid. The four studied sensory characteristics (bitterness, astringency, sweetness and sourness) were modified according to the concentration of procyanidins. The degree of polymerization (DP) of procyanidins influenced only bitterness and astringency but this impact was not the same for all concentrations. Despite the fact that pH, fructose and malic acid concentrations were the same in all samples, the perception of sweetness and sourness were modified according to the concentration of procyanidins.

Aspartame: safety and stability in kalakand.

Aspartame was used in the manufacture of kalakand instead of sucrose. Sensory evaluation revealed that aspartame when used in the preparation of kalakand at a level of 0.065% scored the highest in terms of sweetness perception and resembled control. Aspartame sweetened kalakand possessed the same desirable sweetness, colour, body and texture/consistency and mouthfeel even after 7days of storage at 6-8°C. Significant increase in titratable acidity of control as well as aspartame sweetened kalakand was observed during storage. However, only a slight drop in pH was observed in all samples on storage. The titratable acidity was higher in aspartame sweetened products than the corresponding control samples. Lightness (L*) was less in control samples with sucrose than the aspartame sweetened kalakand during storage. Total plate counts were higher in aspartame sweetened kalakand than its corresponding control throughout the storage period. Total plate counts increased linearly for both aspartame sweetened kalakand and control. A solid phase extraction method was standardized for the isolation of aspartame in kalakand. HPLC analytical conditions were standardized for separation of aspartame and its degradation products diketopiperazine and L-phenylalanine. HPLC analysis revealed that aspartame did not degrade in kalakand during storage establishing its stability in these products.

MODELLING PH AND TITRATABLE ACIDITY IN BANANA FRUIT BASED ON ACID AND MINERAL COMPOSITION

pH and titratable acidity are important indicators of banana fruit quality, since they are involved in the perception of sourness and sweetness. To understand which chemical components drive these parameters of acidity in banana pulp, they were modelled by solving a set of equations (conservation, dissociation, and ionic balance) representing acid/base reactions. The weak acids used in the model were malic, citric, oxalic, isocitric and phosphoric acids. Mineral cations taken into account were potassium and magnesium. The mineral anion chloride was taken into account as it neutralizes cations. The pH and titratable acidity were calculated based on the known acid and mineral composition of the 46 banana samples from 17 cultivars. The model was validated by comparing observed and calculated pH. The prediction of pH and titratable acidity by taking organic acids (malic, citric, oxalic, and isocitric acids), phosphoric acids, potassium, magnesium and chloride was insufficient. Adding a weak acid at a content of 1.5 meq 100 g-1 of fresh weight in the model considerably improved the prediction. The titratable acidity was best predicted with the same input data when titration endpoint was at a pH of 6.5 rather than at a pH of 8.1. (Resume d'auteur)

Glucose utilization rates regulate intake levels of artificial sweeteners

It is well established that animals including humans attribute greater reinforcing value to glucose-containing sugars compared to their non-caloric counterparts, generally termed 'artificial sweeteners'. However, much remains to be determined regarding the physiological signals and brain systems mediating the attribution of greater reinforcing value to sweet solutions that contain glucose. Here we show that disruption of glucose utilization in mice produces an enduring inhibitory effect on artificial sweetener intake, an effect that did not depend on sweetness perception or aversion. Indeed, such an effect was not observed in mice presented with a less palatable, yet caloric, glucose solution. Consistently, hungry mice shifted their preferences away from artificial sweeteners and in favour of glucose after experiencing glucose in a hungry state. Glucose intake was found to produce significantly greater levels of dopamine efflux compared to artificial sweetener in dorsal striatum, whereas disrupting glucose oxidation suppressed dorsal striatum dopamine efflux. Conversely, inhibiting striatal dopamine receptor signalling during glucose intake in sweet-naïve animals resulted in reduced, artificial sweetener-like intake of glucose during subsequent gluco-deprivation. Our results demonstrate that glucose oxidation controls intake levels of sweet tastants by modulating extracellular dopamine levels in dorsal striatum, and suggest that glucose utilization is one critical physiological signal involved in the control of goal-directed sweetener intake.

Brining Effects on Flavor and Moisture Uptake and Retention in Turkey Meat

Turkey breasts were brined under two salt concentrations for 24 hours (4°C). Moisture uptake during brining and loss after roasting (177°C) was measured. Seventy-eight culinary students evaluated juiciness, saltiness, sweetness, turkey flavor, and overall liking. Moisture uptake was greater in the normal salt brine (7.2% of initial weight) compared to the low salt brine (6.0%) and water (2.3%). Turkey brined in high salt lost less water during cooking compared to control and water soaked samples. Brined turkey breast, regardless of the salt content of the brine, had higher scores for liking and the perception of saltiness, sweetness, juiciness, and turkey flavor compared to control samples. Turkey soaked in higher salt brine was more liked, had more turkey flavor, and was perceived to be saltier than turkey in a lower salt brine. The use of experiments such as this as teaching tools in culinary and food science classes is also discussed.

The effect of delaying harvest date on fruit quality and storage of late highbush blueberry cultivars (Vaccinium corymbosum L.)

The effect of delaying harvest on fruit quality and storage life was measured for the late-season highbush blueberry cultivars ‘Aurora’, ‘Elliott’ and ‘Liberty’. In all three cultivars as fruit ripened, there was a steady decline in TA while SS remained stable, indicating that the fruit were becoming sweeter. This was supported by taste panel perceptions of greater sweetness associated with later harvested fruit. There was also a significant overall reduction in fruit firmness and storage life as the percentage of blue fruit at harvest increased; however, a significant interaction for storage life between crop ripeness and cultivar was observed, indicating that the fruit of some cultivars were less influenced by overall crop ripeness than others. The storage life of ‘Elliott’ was significantly affected negatively by crop ripeness, while ‘Aurora’ and ‘Liberty’ were not. ‘Liberty’ produced the highest percentage of sound fruit of the three cultivars and its fruit stored the longest, suggesting that ‘Liberty’ and ‘Aurora’ fruit can be left longer on the bush before harvesting than ‘Elliott’ without significantly damaging storage life. This would allow ‘Aurora’ to develop a sweeter flavor before shipping. The physicochemical and sensory evaluations were highly correlated, suggesting that TA, SS and firmness can be used as predictors of consumer preferences.

A model approach revealed the relationship between banana pulp acidity and composition during growth and post harvest ripening

Titratable acidity and pH are important chemical traits for the organoleptic quality of banana since they are related to the perception of sourness and sweetness. Banana fruit has the particularity of having separate growth and ripening stages, during which pulp acidity changes. A modeling approach was used to understand the mechanisms involved in changes in acidity during pulp growth and post harvest ripening. Changes in pH and titratable acidity were modeled by solving a set of equations representing acid/base reactions. The models were built using data from growth and post harvest ripening of three dessert banana cultivars with contrasting acidity. For each model, calculated values were compared to observed values. These models allowed the prediction of pH (R2=0.34; RMSE=0.75, biais=0.05) and of titratable acidity (R2=0.81, RMSE=2.05, biais=−1.44) during fruit growth and post harvest ripening. The sensitivity analyses showed that among acids, malic, citric and oxalic acids are the main contributors to banana pulp acidity, and that among soluble minerals, potassium also plays an important role. Studying the factors that affect the accumulation of organic acids (citric, malic, and oxalic acids) and potassium in banana pulp could be a relevant area of research with the objective of modifying banana fruit acidity.

Fructose–Maltodextrin Ratio Governs Exogenous and Other CHO Oxidation and Performance

Fructose coingested with glucose in carbohydrate (CHO) drinks increases exogenous-CHO oxidation, gut comfort, and physical performance. This study aimed to determine the effect of different fructose-maltodextrin-glucose ratios on CHO oxidation and fluid absorption while controlling for osmolality and caloricity. In a crossover design, 12 male cyclists rode 2 h at 57% peak power then performed 10 sprints while ingesting artificially sweetened water or three equiosmotic 11.25% CHO-salt drinks at 200 mL·15 min, comprising weighed fructose and maltodextrin-glucose in ratios of 0.5:1 (0.5 ratio), 0.8:1 (0.8 ratio), and 1.25:1 (1.25 ratio). Fluid absorption was traced with D2O, whereas C-fructose and C-maltodextrin-glucose permitted fructose and glucose oxidation rate evaluation. The mean exogenous-fructose and exogenous-glucose oxidation rates were 0.27, 0.39, and 0.46 g·min and 0.65, 0.71, and 0.58 g·min in 0.5, 0.8, and 1.25 ratio drinks, representing mean oxidation efficiencies of 54%, 59%, and 55% and 65%, 85%, and 86% for fructose and glucose, respectively. With the 0.8 ratio drink, total exogenous-CHO oxidation rate was 18% (90% confidence interval, ±5%) and 5.2% (±4.6%) higher relative to 0.5 and 1.25 ratios, respectively, whereas respective differences in total exogenous-CHO oxidation efficiency were 17% (±5%) and 5.3% (±4.8%), associated with 8.6% and 7.8% (±4.2%) higher fructose oxidation efficiency. The effects of CHO ratio on water absorption were inconclusive. Mean sprint power with the 0.8 ratio drink was moderately higher than that with the 0.5 ratio (2.9%; 99% confidence interval, ±2.8%) and 1.25 ratio (3.1%; ±2.7%) drinks, with total- and endogenous-CHO oxidation rate, abdominal cramps, and drink sweetness qualifying as explanatory mechanisms. Enhanced high-intensity endurance performance with a 0.8 ratio fructose-maltodextrin-glucose drink is characterized by higher exogenous-CHO oxidation efficiency and reduced endogenous-CHO oxidation. The gut-hepatic or other physiological site responsible requires further research.

Covering the Cover

Covering the Cover

Rebaudioside A and Rebaudioside D Bitterness do not Covary with Acesulfame-K Bitterness or Polymorphisms in TAS2R9 and TAS2R31

In order to reduce calories in foods and beverages, the food industry routinely uses non-nutritive sweeteners. Unfortunately, many are synthetically derived, and many consumers have a strong preference for natural sweeteners, irrespective of the safety data on synthetic non-nutritive sweeteners. Additionally, many non-nutritive sweeteners elicit aversive side tastes such as bitter and metallic in addition to sweetness. Bitterness thresholds of acesulfame-K (AceK) and saccharin are known to vary across bitter taste receptors polymorphisms in TAS2R31. RebA has shown to activate hTAS2R4 and hTAS2R14 in vitro. Here we examined bitterness and sweetness perception of natural and synthetic non-nutritive sweeteners. In a follow-up to a previous gene-association study, participants (n=122) who had been genotyped previously rated sweet, bitter and metallic sensations from rebaudioside A (RebA), rebaudioside D (RebD), aspartame, sucrose and gentiobiose in duplicate in a single session. For comparison, we also present sweet and bitter ratings of AceK collected in the original experiment for the same participants. At similar sweetness levels, aspartame elicited less bitterness than RebD, which was significantly less bitter than RebA. The bitterness of RebA and RebD showed wide variability across individuals, and bitterness ratings for these compounds were correlated. However, RebA and RebD bitterness did not covary with AceK bitterness. Likewise, single nucleotide polymorphisms (SNPs) shown previously to explain variation in the suprathreshold bitterness of AceK (rs3741845 in TAS2R9 and rs10772423 in TAS2R31) did not explain variation in RebA and RebD bitterness. Because RebA activates hT2R4 and hT2R14, a SNP in TAS2R4 previously associated with variation in bitterness perception was included here; there are no known functional SNPs for TAS2R14. In present data, a putatively functional SNP (rs2234001) in TAS2R4 did not explain variation in RebA or RebD bitterness. Collectively, these data indicate the bitterness of RebA and RebD cannot be predicted by AceK bitterness, reinforcing our view that bitterness is not a simple monolithic trait that is high or low in an individual. This also implies consumers who reject AceK may not find RebA and RebD aversive, and vice versa. Finally, RebD may be a superior natural non-nutritive sweetener to RebA, as it elicits significantly less bitterness at similar levels of sweetness.

Differential sweetness of commercial sour liquids elicited by miracle fruit in healthy young adults

Miracle fruit (Synsepalum dulcificum) contains the glycoprotein miraculin which turns a sour taste into a sweet one. Chemical analyses and sensory evaluation experiments were conducted to examine the sweetening effect of miracle fruit with regard to five different commercial sour liquids which were diluted until they were subjectively equally sour. HPLC-based analyses revealed that (1) the predominating acids in two and three of the liquids were citric acid and acetic acid, respectively and (2) all five liquids contained fructose and glucose. Healthy young adults (eight males and 10 females) in the sensory evaluation experiments were asked to chew a miracle fruit and apply their saliva to the oral mucosae. They were asked to score the sweetness elicited by the five liquids relative to a sucrose standard at 0, 15, 25 and 35 min thereafter. The citric acid-based liquids were perceived as being sweeter than the acetic acid-based liquids at all timepoints. Thus, commercial sour liquids that mainly contain citric acid are more effective than acetic acid-based liquids in eliciting a perception of sweetness after the miracle fruit application, while the sugars in the liquids seemed to play a minimal role as determinants of sweetness.

Relation between volatile composition, ellagitannin content and sensory perception of oak wood chips representing different toasting processes

The evolution of both volatile and nonvolatile (ellagitannins) compounds extracted from oak wood chips while being macerated for 3 months in wine model solution with eight different commercial chips [Toasted LT (Light Toast), LT+ (Light plus Toast), MT (Medium Toast), MT+ (Medium plus Toast), HT (Heavy Toast), Noisette, Special) and un-toasted (UN)] was studied. Sensory analysis concerning vanilla, spicy, overall woody, astringency, bitterness and sweetness descriptors was conducted in parallel. A 2-month time is needed for the maximum extraction of ellagitannins and of furfural compound. Relating to other volatile compounds, their concentration increased progressively over time. Spicy, woody and vanilla aromas as well as sweetness perception increased during contact time with oak wood. Additionally to pyrolytic toasting stage, watering process during toasting influences significantly oak wood composition (lactones, vanillin guaiacol compounds and ellagitannins). Correlation analysis between chemical and sensory data demonstrated significant correlations between chemical and sensory parameters and provides some insight into the implication of volatile and nonvolatile composition on the final quality perception of astringency. A predictive model between astringency intensity and ellagitannins, furfural, guaiacol and methyl guaiacol contents was established. Ellagitannins levels explained 45 %, guaiacol and methyl guaiacol contents interpreted 13.20 and 8.86 %, respectively, whereas furfural levels justified 5.66 % of the total astringency variance.

Contribution of oak wood ageing to the sweet perception of dry wines

Background and Aims Winemakers observe a sensory effect of oak ageing in wines, but the phenomenon has never been fully described. The aim of this study was to determine the influence of the ageing container on the sweetness of dry wines and to evaluate the contribution of oak volatile compounds. Methods and Results Both white and red dry wines were produced in various containers, such as stainless steel and oak tanks, and new and used oak barrels. Sensory analysis (with or without use of nose clip) by a panel of experts showed an increase in sweetness when wine was in contact with wood. Oak volatile compounds (vanillin, β-methyl-γ-octalactone and eugenol) were quantified by gas chromatography-mass spectrometry and then added to the wines to obtain the same concentration in all samples. To determine the contribution of the volatiles to the increase in sweetness, the treatments were tasted again after such an ‘oak aroma’ homogenisation. The ranking of the wines remained unchanged. Conclusion These results demonstrate that the sweet perception of dry wines depends on the nature of the ageing container, and that these oak volatiles are not involved in this phenomenon. Significance of the Study This work confirms an empirical observation and establishes for the first time the sweetening effect of oak ageing, strongly suggesting the existence of sweet non-volatile compounds in oak wood.

Learning and retention time effect on memory for sweet taste in children

This study investigated the effect of learning and retention time on memory for fruit purée varying in sweetness among 214 children aged 8–10years. During a first session, all children received a snack including a target fruit purée. Half children tasted the snack without any mention to memory (incidental group), whereas the other children (intentional group) were explicitly asked to taste and remember it. During a second session, children of each learning group were divided in two groups, which were tested for memory after respectively 1day and 1week. Children were confronted with a series of samples consisting of the same target previously tasted and variants of it slightly modified in sweetness. Children performed also a hedonic and a perceptive test. Memory was better under incidental rather than intentional conditions. Recognition was based more on the correct rejection of the distractors rather than on the identification of the target. No clear evidence for a retention time effect on memory was found. The relationship between sweetness perception and memory is discussed.

Developing Supra-Molecular Structures During Freeze-Drying of Food

In this contribution, we discuss a scientific approach to controlling the freeze-drying process in order to obtain products with desired attributes, using two examples. In the first part, the freeze-drying kinetics of a model food are recorded and represented using a state diagram, which was then used to optimize a strategy to preserve the physical structure and minimize the drying time of the product. The second part focuses on the application of freeze drying to produce amorphous sucrose coatings. In this study, model food materials have been coated with a liquid sucrose solution, and freeze-dried on a laboratory scale. The drying kinetics have been measured and plotted on a sucrose state diagram in order to optimize the process conditions and to minimize possible crystallization. Analysis of the physical state of the sucrose (using DSC, NIR, and microscopy) showed that a dominantly amorphous coating was obtained. Compared to a crystalline reference, the amorphous sucrose dissolved more quickly in a liquid, inducing a faster sweetness perception. This result also opens new opportunities for sugar reduction in food due to an enhanced sweetness perception.

Whey protein concentrate gels with different sucrose content: Instrumental texture measurements and sensory perception

Correlations between instrumental texture, sensory texture and sweetness perception were studied in whey protein concentrate (WPC) gels at different pH (4 and 7), sucrose (0–40%, w/w) and whey protein (10–20% w/w) content. The presence of sucrose modified the structure of WPC gels, mainly at pH 4, making the gel structure more homogeneous and with smaller pores. Sucrose also increased the solid behaviour of gels, their water holding capacity, hardness and adhesiveness. Sweetness perception decreased as protein concentration increased, and was higher in gels at pH 4 than in gels at pH 7. A good correlation was obtained between the instrumental and sensory attributes hardness, cohesiveness and elasticity.