Just Noticeable Differences and Weber Fraction of Oral Thickness Perception of Model Beverages

Rheological properties of beverages contribute considerably to texture perception. When developing new beverages, it is important to have knowledge on the smallest differences of viscosity which a consumer can discriminate. Thickness is the sensory attribute most commonly used to describe the viscosity of beverages. The aim of this study was to determine the Just Noticeable Differences (JNDs) of oral thickness perception and the Weber fraction (K) of Newtonian model stimuli (maltodextrin solutions). JNDs were determined using the method of constant stimuli with 5 reference stimuli ranging in viscosity from 10 to 100 mPa⋅s. JNDs increased with increasing viscosity of the reference stimulus. The Weber fraction (K) for oral thickness perception of model beverages was K = 0.26 for the studied viscosity range. The Weber fraction for oral thickness perception is comparable to Weber fractions reported in literature for perception of kinesthetic food firmness and spreadability, creaminess, sourness, and bitterness perception. This demonstrates that the human sensitivity towards oral discrimination of thickness of liquid stimuli is comparable to the human sensitivity towards discrimination of specific texture properties and specific taste stimuli.

PRACTICAL APPLICATION

Changes in the viscosity of beverages can cause changes in thickness perception. The changes in thickness perception can be accompanied by differences in other sensory properties such as sweetness and creaminess which might be undesirable when reformulating beverages or developing new products. Knowledge on the differences by which viscosity of beverages can be modified to create a difference in sensory perception is currently lacking. This study quantified the Just Noticeable Difference (the minimal difference that can be detected between 2 stimuli) for thickness perception of beverages. This knowledge helps food industry to reformulate beverages while maintaining sensory properties.

Influence of choice on vegetable intake in children: an in-home study

Children's vegetable consumption is still far below that recommended, and stimulating their intake is a challenge for caregivers. The objective of this study was to investigate whether choice-offering is an effective strategy to increase children's vegetable intake in an in-home situation. Seventy children (mean age 3.7; SD 1) randomly assigned to a choice or a no-choice condition, were exposed 12 times to six familiar target vegetables at home during dinner. In the choice group, two selected vegetables were offered each time, whereas the no-choice group only received one vegetable. Vegetable intake was measured by weighing children's plates before and after dinner. A mixed linear model with age, gender, and baseline vegetable liking as covariates was used to compare intake between the choice and the no-choice group. Mixed linear model analysis yielded estimated means for vegetable intake of 48.5 g +/- 30 in the no-choice group and 57.7 g +/- 31 for the choice group (P = 0.09). In addition, baseline vegetable liking (P <0.001) and age (P = 0.06) predicted vegetable intake to be higher when the child liked vegetables better and with older age. These findings suggest that choice-offering has some, but hardly robust, effect on increasing vegetable intake in children. Other factors such as age and liking of vegetables also mediate the effect of offering a choice.

Longer oral exposure with modified sham feeding does not slow down gastric emptying of low- and high-energy-dense gastric loads in healthy young men

BACKGROUND

A long oral exposure to food and a high-energy density of food have been shown to increase satiety feelings. The effect of energy density is predominantly caused by an inhibition of gastric emptying. It is hypothesized that prolonging oral exposure may have an additional effect on this inhibition of gastric emptying. However, little human data are available to support this hypothesis.

OBJECTIVE

The objective was to assess the effect of the duration of oral exposure to food on gastric emptying rate of gastric loads (GLs) low and high in energy density and on satiety feelings.

METHODS

Twenty-six healthy men [mean ± SD age: 22 ± 3 y; BMI (in kg/m(2)): 23 ± 1] participated in a randomized crossover trial with 4 treatments and a control. Treatments consisted of either 1- or 8-min modified sham feeding (MSF) of cake, and a GL of either 100 or 700 kcal infused in the stomach via a nasogastric tube (500 mL, 62.5 mL/min). The control consisted of no MSF and a GL of 500 mL of water. Gastric emptying rate was assessed with a (13)C breath test. Breath samples and satiety feelings were collected at fixed time points until 90 min after start of the treatment.

RESULTS

Gastric emptying rate and satiety feelings were not affected by duration of MSF (P ≥ 0.27). However, the 700-kcal GL treatments slowed gastric emptying [41% lower area under the curve (AUC)] and increased satiety feelings (22-31% higher AUC) compared with the 100-kcal GL treatments (P < 0.001). No interaction between MSF duration and energy density of GL was found (P ≥ 0.44).

CONCLUSIONS

Higher gastric energy density inhibited gastric emptying and increased satiety feelings in healthy young men. However, prolonging oral exposure to food did not have an additional effect. This study provides more insight in satiety regulation. This trial was registered at trialregister.nl as NTR3601.

That's why I take my ONS. Means-end chain as a novel approach to elucidate the personally relevant factors driving ONS consumption in nutritionally frail elderly users

Oral nutritional supplements (ONS) are a recommended form of nutritional intervention for older malnourished persons when a 'food first' approach and/or food fortification prove ineffective. The efficacy of ONS will depend on, amongst other factors, whether persons do, or do not, consume their prescribed amount. Factors influencing ONS consumption can be product, context, or person related. Whereas product and context have received some attention, little is known about the person factors driving ONS consumption. In addition, the relative importance of the product, context, and person factors to ONS consumption is not known. Using the means-end chain (MEC) method, the current study elucidated personally relevant factors (product, context, and person factors) related to ONS consumption in two groups of older nutritionally frail ONS users: community-dwelling persons and care home residents with mainly somatic disorders. To our knowledge, the current work is the first to apply the MEC method to study older nutritionally frail ONS users. Forty ONS users (n = 20 per group) were recruited via healthcare professionals. The level of frailty was assessed using the FRAIL scale. Both groups were interviewed for 30 to 45 minutes using the soft laddering technique. The laddering data were analysed using LadderUX software™. The MEC method appeared to work well in both groups. The majority of the participants took ONS on their doctor's or dietician's prescription as they trusted their advice. The community-dwelling group took ONS to prolong their independence, whereas the care home group reported values that related more to small improvements in quality of life. In addition, care home residents perceived themselves as dependent on their caregiver for their ONS arrangements, whereas this dependence was not reported by community-dwelling persons. Key insights from this work will enable doctors and dieticians to customize their nutritional interventions to ONS users' personal needs and thus positively impact health outcomes.

It is not just a meal, it is an emotional experience - a segmentation of older persons based on the emotions that they associate with mealtimes

Worldwide, the group of older persons is growing fast. To aid this important group in their food and meal requirements, a deeper insight into the expectations and experiences of these persons regarding their mealtimes and snack times is needed. In the current study, we aim to identify consumer segments within the group of vital community-dwelling older persons on the basis of the emotions they associate with their mealtimes and snack times (from now on referred to as mealtimes). Participants (n = 392, mean age 65.8 (years) ± 5.9 (SD)) completed an online survey. The survey consisted of three questionnaires: emotions associated with mealtimes, functionality of mealtimes, and psychographic characteristics (health and taste attitudes, food fussiness, and food neophobia). Consumer segments were identified and characterised based on the emotions that the respondents reported to experience at mealtimes, using a hierarchical cluster analysis. Clusters were described using variables previously not included in the cluster analysis, such as functionality of mealtimes and psychographic characteristics. Four consumer segments were identified: Pleasurable averages, Adventurous arousals, Convivial indulgers, and Indifferent restrictives. These segments differed significantly in their emotional associations with mealtimes both in valence and level of arousal. The present study provides actionable insights for the development of products and communication strategies tailored to the needs of vital community-dwelling older persons.

Human protein status modulates brain reward responses to food cues

BACKGROUND

Protein is indispensable in the human diet, and its intake appears tightly regulated. The role of sensory attributes of foods in protein intake regulation is far from clear.

OBJECTIVE

We investigated the effect of human protein status on neural responses to different food cues with the use of functional magnetic resonance imaging (fMRI). The food cues varied by taste category (sweet compared with savory) and protein content (low compared with high). In addition, food preferences and intakes were measured.

DESIGN

We used a randomized crossover design whereby 23 healthy women [mean ± SD age: 22 ± 2 y; mean ± SD body mass index (in kg/m(2)): 22.5 ± 1.8] followed two 16-d fully controlled dietary interventions involving consumption of either a low-protein diet (0.6 g protein · kg body weight(-1) · d(-1), ~7% of energy derived from protein, approximately half the normal protein intake) or a high-protein diet (2.2 g protein · kg body weight(-1) · d(-1), ~25% of energy, approximately twice the normal intake). On the last day of the interventions, blood oxygen level-dependent (BOLD) responses to odor and visual food cues were measured by using fMRI. The 2 interventions were followed by a 1-d ad libitum phase, during which a large array of food items was available and preference and intake were measured.

RESULTS

When exposed to food cues (relative to the control condition), the BOLD response was higher in reward-related areas (orbitofrontal cortex, striatum) in a low-protein state than in a high-protein state. Specifically, BOLD was higher in the inferior orbitofrontal cortex in response to savory food cues. In contrast, the protein content of the food cues did not modulate the BOLD response. A low protein state also increased preferences for savory food cues and increased protein intake in the ad libitum phase as compared with a high-protein state.

CONCLUSIONS

Protein status modulates brain responses in reward regions to savory food cues. These novel findings suggest that dietary protein status affects taste category preferences, which could play an important role in the regulation of protein intake in humans. This trial was registered at www.trialregister.nl/trialreg/admin/rctview.asp?TC=3288 as NTR3288.

A systematic review and meta-analysis examining the effect of eating rate on energy intake and hunger

BACKGROUND

Reductions in eating rate are recommended to prevent and treat obesity; yet, the relation between eating rate and energy intake has not been systematically reviewed, with studies producing mixed results.

OBJECTIVE

Our main objective was to examine how experimentally manipulated differences in eating rate influence concurrent energy intake and subjective hunger ratings.

DESIGN

We systematically reviewed studies that experimentally manipulated eating rate and measured concurrent food intake, self-reported hunger, or both. We combined effect estimates from studies by using inverse variance meta-analysis, calculating the standardized mean difference (SMD) in food intake between fast and slow eating rate conditions.

RESULTS

Twenty-two studies were eligible for inclusion. Evidence indicated that a slower eating rate was associated with lower energy intake in comparison to a faster eating rate (random-effects SMD: 0.45; 95% CI: 0.25, 0.65; P < 0.0001). Subgroup analysis indicated that the effect was consistent regardless of the type of manipulation used to alter eating rate, although there was a large amount of heterogeneity between studies. There was no significant relation between eating rate and hunger at the end of the meal or up to 3.5 h later.

CONCLUSIONS

Evidence to date supports the notion that eating rate affects energy intake. Research is needed to identify effective interventions to reduce eating rate that can be adopted in everyday life to help limit excess consumption.

ANS responses and facial expressions differentiate between the taste of commercial breakfast drinks

The high failure rate of new market introductions, despite initial successful testing with traditional sensory and consumer tests, necessitates the development of other tests. This study explored the ability of selected physiological and behavioral measures of the autonomic nervous system (ANS) to distinguish between repeated exposures to foods from a single category (breakfast drinks) and with similar liking ratings. In this within-subject study 19 healthy young adults sipped from five breakfast drinks, each presented five times, while ANS responses (heart rate, skin conductance response and skin temperature), facial expressions, liking, and intensities were recorded. The results showed that liking was associated with increased heart rate and skin temperature, and more neutral facial expressions. Intensity was associated with reduced heart rate and skin temperature, more neutral expressions and more negative expressions of sadness, anger and surprise. Strongest associations with liking were found after 1 second of tasting, whereas strongest associations with intensity were found after 2 seconds of tasting. Future studies should verify the contribution of the additional information to the prediction of market success.

Slow food: sustained impact of harder foods on the reduction in energy intake over the course of the day

BACKGROUND

Previous research has shown that oral processing characteristics like bite size and oral residence duration are related to the satiating efficiency of foods. Oral processing characteristics are influenced by food texture. Very little research has been done on the effect of food texture within solid foods on energy intake.

OBJECTIVES

The first objective was to investigate the effect of hardness of food on energy intake at lunch, and to link this effect to differences in food oral processing characteristics. The second objective was to investigate whether the reduction in energy intake at lunch will be compensated for in the subsequent dinner.

DESIGN

Fifty subjects (11 male, BMI: 21±2 kg/m2, age: 24±2 y) participated in a cross-over study in which they consumed ad libitum from a lunch with soft foods or hard foods on two separate days. Oral processing characteristics at lunch were assessed by coding video records. Later on the same days, subjects consumed dinner ad libitum.

RESULTS

Hard foods led to a ∼13% lower energy intake at lunch compared to soft foods (P<0.001). Hard foods were consumed with smaller bites, longer oral duration per gram food, and more chewing per gram food compared to the soft foods (P<0.05). Energy intake at dinner did not differ after both lunches (P = 0.16).

CONCLUSIONS

Hard foods led to reduced energy intake compared to soft foods, and this reduction in energy intake was sustained over the next meal. We argue that the differences in oral processing characteristics produced by the hardness of the foods explain the effect on intake. The sustained reduction in energy intake suggests that changes in food texture can be a helpful tool in reducing the overall daily energy intake.

Dynamics of autonomic nervous system responses and facial expressions to odors

Why we like or dislike certain products may be better captured by physiological and behavioral measures of the autonomic nervous system (ANS) than by conscious or classical sensory tests. Responses to pleasant and unpleasant food odors presented in varying concentrations were assessed continuously using facial expressions and responses of the ANS. Results of 26 young and healthy female participants showed that the unpleasant fish odor triggered higher heart rates and skin conductance responses, lower skin temperature, fewer neutral facial expressions and more disgusted and angry expressions (p < 0.05). Neutral facial expressions differentiated between odors within 100 ms, after the start of the odor presentation followed by expressions of disgust (180 ms), anger (500 ms), surprised (580 ms), sadness (820 ms), scared (1020 ms), and happy (1780 ms) (all p-values < 0.05). Heart rate differentiated between odors after 400 ms, whereas skin conductance responses differentiated between odors after 3920 ms. At shorter intervals (between 520 and 1000 ms and between 2690 and 3880 ms) skin temperature for fish was higher than that for orange, but became considerable lower after 5440 ms. This temporal unfolding of emotions in reactions to odors, as seen in facial expressions and physiological measurements supports sequential appraisal theories.

Effect of replacing sugar with non-caloric sweeteners in beverages on the reward value after repeated exposure

BACKGROUND

The reward value of food is partly dependent on learned associations. It is not yet known whether replacing sugar with non-caloric sweeteners in food is affecting long-term acceptance.

OBJECTIVE

To determine the effect of replacing sugar with non-caloric sweeteners in a nutrient-empty drink (soft drink) versus nutrient-rich drink (yoghurt drink) on reward value after repeated exposure.

DESIGN

We used a randomized crossover design whereby forty subjects (15 men, 25 women) with a mean ± SD age of 21 ± 2 y and BMI of 21.5 ± 1.7 kg/m(2) consumed a fixed portion of a non-caloric sweetened (NS) and sugar sweetened (SS) versions of either a soft drink or a yoghurt drink (counterbalanced) for breakfast which were distinguishable by means of colored labels. Each version of a drink was offered 10 times in semi-random order. Before and after conditioning the reward value of the drinks was assessed using behavioral tasks on wanting, liking, and expected satiety. In a subgroup (n=18) fMRI was performed to assess brain reward responses to the drinks.

RESULTS

Outcomes of both the behavioral tasks and fMRI showed that conditioning did not affect the reward value of the NS and SS versions of the drinks significantly. Overall, subjects preferred the yoghurt drinks to the soft drinks and the ss drinks to the NS drinks. In addition, they expected the yoghurt drinks to be more satiating, they reduced hunger more, and delayed the first eating episode more. Conditioning did not influence these effects.

CONCLUSION

Our study showed that repeated consumption of a non-caloric sweetened beverage, instead of a sugar sweetened version, appears not to result in changes in the reward value. It cannot be ruled out that learned associations between sensory attributes and food satiating capacity which developed preceding the conditioning period, during lifetime, affected the reward value of the drinks.

Consumption with large sip sizes increases food intake and leads to underestimation of the amount consumed

BACKGROUND

A number of studies have shown that bite and sip sizes influence the amount of food intake. Consuming with small sips instead of large sips means relatively more sips for the same amount of food to be consumed; people may believe that intake is higher which leads to faster satiation. This effect may be disturbed when people are distracted.

OBJECTIVE

The objective of the study is to assess the effects of sip size in a focused state and a distracted state on ad libitum intake and on the estimated amount consumed.

DESIGN

In this 3×2 cross-over design, 53 healthy subjects consumed ad libitum soup with small sips (5 g, 60 g/min), large sips (15 g, 60 g/min), and free sips (where sip size was determined by subjects themselves), in both a distracted and focused state. Sips were administered via a pump. There were no visual cues toward consumption. Subjects then estimated how much they had consumed by filling soup in soup bowls.

RESULTS

Intake in the small-sip condition was ∼30% lower than in both the large-sip and free-sip conditions (P<0.001). In addition, subjects underestimated how much they had consumed in the large-sip and free-sip conditions (P<0.03). Distraction led to a general increase in food intake (P = 0.003), independent of sip size. Distraction did not influence sip size or estimations.

CONCLUSIONS

Consumption with large sips led to higher food intake, as expected. Large sips, that were either fixed or chosen by subjects themselves led to underestimations of the amount consumed. This may be a risk factor for over-consumption. Reducing sip or bite sizes may successfully lower food intake, even in a distracted state.

Effects of oral and gastric stimulation on appetite and energy intake

Appetite is regulated by many factors, including oro-sensory and gastric signals. There are many studies on contributions of and possible interaction between sensory and gastric stimulation, but there are few studies in humans using simultaneous oral and gastric stimulation. We investigated the effect of simultaneous, but independently manipulated, oral and gastric stimulation on appetite ratings and energy intake. We hypothesized that compared with no stimulation, oral and gastric stimulation would equally and additively decrease appetite ratings and energy intake. Healthy men (n = 26, 21 ± 2 years, BMI 22 ± 3 kg/m(2)) participated in a randomized crossover trial with four experimental conditions and a control condition. Experimental conditions consisted of oral stimulation, with either 1 or 8 min modified sham feeding (MSF), and gastric stimulation, with either 100 or 800 ml intragastrically infused liquid (isocaloric, 99 kcal, 100 ml/min). The control condition consisted of no oral or gastric stimulation. Outcome measures were energy intake 30 min after the treatment and appetite ratings. Compared with the control condition, energy intake decreased significantly after the 8 min/100 ml (19% lower, P = 0.001) and 8 min/800 ml conditions (15% lower, P = 0.02), but not after the 1 min/100 ml (14% lower, P = 0.06) and 1 min/800 ml conditions (10% lower, P = 0.39). There was no interaction of oral and gastric stimulation on energy intake. Hunger and fullness differed across all conditions (P ≤ 0.01). In conclusion, duration of oral exposure was at least as important in decreasing energy intake as gastric filling volume. Oral and gastric stimulation did not additively decrease energy intake. Longer oro-sensory stimulation, therefore, may be an important contributor to a lower energy intake.

Leptin Responsiveness to Energy Restriction: Genetic Variation in the Leptin Receptor Gene

Serum leptin concentrations are an important afferent signal in energy balance homeostasis. It has been speculated that the leptin responsiveness to energy restriction is affected by the functionality of the leptin receptor. The purpose of this analysis was to explore the effect of polymorphisms in the LEPR gene on the acute decline in leptin after 4 days of 65% energy restriction. Leptin concentrations of the study group (n = 44; all men) declined by 2.3 +/- 1.5 micro g/L [-39.4% (95% confidence interval: -43.6 to -34.9)]. Leptin responses did not statistically differ between noncarriers and carriers of three mutant variants of the polymorphisms: Lys109/Lys109 (-41.4%) vs. Arg109/+ (-37.0%) (p = 0.33); Gln223/Gln223 (-41.5%) vs. Arg223/+ (-37.8%) (p = 0.40); Lys656/Lys656 (-39.5%) vs. Asn656/+ (-39.3%) (p = 0.96). No effect of the assessed polymorphisms in the LEPR gene on the acute decline in leptin after energy restriction was observed. Power calculations are provided for future studies on the leptin responsiveness to energy restriction.

Texture and satiation: the role of oro-sensory exposure time

One of the characteristics of the current obesogenic food supply is the large availability of foods that can be ingested quickly. Controlled nutrition intervention studies have shown that the ingestion of simple energy containing beverages, which are consumed very quickly, do not lead to a lower compensatory intake of other foods. One of the theories behind this observation is that calories that are ingested quickly are not well sensed by the sense of taste, and do not lead to an adequate satiety response. This idea is confirmed by the results of a series of studies, where we have shown that the low satiation/satiety response of beverages can be largely attributed to their short oral residence time. Prolonging the oro-sensory exposure time to foods leads to earlier meal termination and/or a higher satiety response. The low satiation/satiety response to simple energy containing beverages is congruent with the observation from studies on the cephalic phase response to foods, i.e. the physiological response to sensory signals. Energy containing beverages do not lead to an adequate cephalic phase response. Various recent studies showed that slower eating leads to higher levels of satiety hormones. These results are in line with the idea that the sense of taste is a nutrient sensor which informs the brain and the gut about the inflow of nutrients. The sense of taste has an important contribution to the satiating effect of foods. One of the challenges in future research is to see whether or not these proofs of principles can be applied in longer term studies with regular commercial foods. This may make our obesogenic food supply more satiating, and may lead to a lower energy intake.

Anterior cingulate taste activation predicts ad libitum intake of sweet and savory drinks in healthy, normal-weight men

After food consumption, the motivation to eat (wanting) decreases and associated brain reward responses change. Wanting-related brain responses and how these are affected by consumption of specific foods are ill documented. Moreover, the predictive value of food-induced brain responses for subsequent consumption has not been assessed. We aimed to determine the effects of consumption of sweet and savory foods on taste activation in the brain and to assess how far taste activation can predict subsequent ad libitum intake. Fifteen healthy men (age: 27 ± 2 y, BMI: 22.0 ± 1.5 kg/m2) participated in a randomized crossover trial. After a >3-h fast, participants were scanned with the use of functional MRI before and after consumption of a sweet or savory preload (0.35 L fruit or tomato juice) on two occasions. After the scans, the preload juice was consumed ad libitum. During scanning, participants tasted the juices and rated their pleasantness. Striatal taste activation decreased after juice consumption, independent of pleasantness. Sweet and savory taste activation were not differentially affected by consumption. Anterior cingulate taste activation predicted subsequent ad libitum intake of sweet (r = -0.78; P < 0.001(uncorrected)) as well as savory juice (r = -0.70; P < 0.001(uncorrected)). In conclusion, we showed how taste activation of brain reward areas changes following food consumption. These changes may be associated with the food's physiological relevance. Further, the results suggest that anterior cingulate taste activation reflects food-specific satiety. This extends our understanding of the representation of food specific-appetite in the brain and shows that neuroimaging may provide objective and more accurate measures of food motivation than self-report measures.