What factors influence our choice to eat insects as food?

The article entitled “Insects as food: Exploring cultural exposure and individual experience as determinants of acceptance” was published in 2015 by Tan et al. and looks at the cultural, social and individual factors that influence the choice to eat insects as food. There are many factors explored in the article that range from predisposed perceptions to sensory evaluations.

The article compared four distinct groups of individuals based on their previous experiences with insect consumption, and their cultural background. The groups include Thai insect eaters, Thai insect non-eaters, Dutch insect eaters and Dutch insect non-eaters. The reason these two cultures were chosen was because Thailand is a culture that includes insects as food regularly, while insects are rarely included in diets found in The Netherlands. A cross-cultural comparison was formulated in this article that compared these two cultures.

The study looked at individual experiences and knowledge on insects as food; reasons to eat or not eat insects; evaluation of images of insect species and products; and optional tasting and evaluation of insect-based products. One of the main findings of the study was that insect consumption was susceptible to the context of the foods, e.g., if an insect was seen as being savoury, people were less willing to try it if it was prepared in a sweet dish. Also, cultural exposure to insects, and trying insects as children significantly increased a person’s likelihood to be willing to try insects as an adult.

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Figure 1: A range of images of edible insect species used for perceived liking in the article.
Source: Tan HSG, Fischer ARH, Tinchanc P, Stiegera M, Steenbekkersa LPA, van Trijp HCM, 2015. Insects as food: Exploring cultural exposure and individual experience as determinants of acceptance. Food quality and Preference. Vol 42, pp 80.

Some of the differences seen between the two cultures was that the Dutch participants were more interested in eating insects as a novelty or as a sustainable replacement for meat. However, the main motivators for Thai participants to consume insects was for taste and cultural traditions.
Another difference between the two cultures was that the Dutch participants were more willing to eat the worm-shaped or small-sized insects as large insects were perceived to taste negatively. Contrarily, the Thai participants were more willing to eat the large insects, and saw the worm-shaped insects as negative as they had a perceived association with death.

The study overall gave some insight on some factors that influence individual consumption of insects in these two contrasting cultures, but further studies on societal perception and marketing insects as food are necessary if insects as eventually introduced as a sustainable replacement for meat.

Tan HSG, Fischer ARH, Tinchanc P, Stiegera M, Steenbekkersa LPA, van Trijp HCM, 2015. Insects as food: Exploring cultural exposure and individual experience as determinants of acceptance. Food quality and Preference. Vol 42, pp 78-89.

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Fat is the sixth taste

The role of the sense of taste is to act as gatekeeper of ingestion, if a potential food is deemed suitable for consumption it may be swallowed, if not rejected.  To guide the decision making we have five taste qualities: sweet, sour, salty, bitter and umami.  Sweet, salty and umami are all appetitive and signal the food contains essential nutrient, while excessive sour and bitter signal aversion and potential harm.

Over the past few years there has been considerable attention given to fat as an additional taste; it seems logical given that we have taste responses to the breakdown products of carbohydrate (sugars) that elicit sweet, and protein (amino acid) that elicit umami.

For fat to be considered a taste a chain of events must take place.  There must be a class of stimuli (fats or the breakdown products fatty acids) that activate receptors on taste cells that are specific to the stimuli.  A signal must be sent from the taste cell to taste processing regions of the brain.  The signal that is decoded as a perception must be independent of the other tastes (not a combination of sweet and salt or any other possible combinations).

The first evidence of a fat taste came out of a rat model in 1998, with Dr Timothy Gilbertson from Utah University showing a taste response to fatty acids.  Professor Richard Mattes from Purdue showed similar receptors may occur in humans when he looked at sham feeding butter or non-fat butter substitute in humans, and seeing that butter caused an increase in blood triglycerides.  The implication being that the fatty acids were activating a taste receptor system and preparing the body for fat digestion.

The concentrations of fatty acid required to activate fat taste is very low, and in the range found in common fatty foods.  In addition, we also have lingual lipase that can cleave fatty acids from triacylglycerols, albeit with low activity.  But taken together human limits of detection for fatty acids are well within the range we find in common foods.

Various researchers have identified fatty acid receptors on taste cells with the most likely candidates for fat taste being CD36 and GPR120.  Further evidence supporting fat taste was the discovery of fat sensitive neurons in taste processing region of the brain.  Finally, using our taste methodology we have established perceptual independence from the other tastes at detection threshold level.

We started our research in 2007 and published our first paper in 2010 showing a link between fat taste and BMI, with subjects who were insensitive to fat having a higher BMI.  Since then we have published papers on method development, reliability of fat taste measures, links with overweight and obesity, links with gastrointestinal tract sensing of fat, and mechanisms that link fat taste with overconsumption of fatty foods.

The one characteristic of fat taste that is different from the other 5 tastes is a conscious quality.  For example, we place sucrose on our tongue and experience sweetness, or NaCl on our tongue and experience saltiness.  For fat taste we present 3 solutions, one of which contains a fatty acid.  The task is to identify which solution contains the fatty acid.   If the subject is incorrect the concentration of fatty acid is increased and the test rerun. This continues until the correct solution is identified multiple times.  Participants can correctly identify the fatty acid solution but cannot provide an adjective that describes any taste; they know it is different but cannot articulate why.

Questions will remain. Does no taste quality exclude fat from being classified as a taste?  Or is there a piece of information that would exclude fat from being a taste?  However, with the advances in scientific techniques, our growing understanding of the taste system and its role as the first part of the alimentary canal, emerging evidence for Kokumi and other non-traditional tastes on the horizon, it may be time to broaden the scope of how we define taste.

-Professor Russell Keast (PhD)
Head of the Centre for Advanced Sensory Science
Deakin University

Keast, R. and A. Costanzo (2015). “Is fat the sixth taste? Evidence and implications.” Flavour 4(5). doi:10.1186/2044-7248-4-5

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Sensory phenotype and salt: what is the link?

The article entitled ‘Explaining variability in sodium intake through oral sensory phenotype, salt sensation and liking’ was published in 2010 by Hayes, Sullivan and Duffy, and focuses on the relationship between sensory phenotype, liking of saltiness and sensitivity to saltiness. The term ‘sensory phenotype’ in this case refers to differences between individuals regarding their sensitivity to a particular bitter compound (PROP) and the amount of taste buds on an individual’s tongue.

This article investigates these relationships with the view to further understand the issues surrounding salt intake and associated health implications. As discussed on the blog before, there are a number of health issues that are associated with high levels of dietary sodium, and as such it is important to investigate any potential causes of heightened consumption.

Participants were tested for sensitivity to salt and their liking in two ways;

  1. Salt solutions

Participants were asked to rate the intensity of the sensations and their liking of a salt and water solution.

  1. Chicken broth

Participants were asked to provide intensity and liking ratings for seven chicken broth samples with differing levels of sodium.

This study found that both PROP sensitivity and number of taste buds were associated with greater sensitivity to salt in salt/water solutions. It was found that individuals who found PROP more bitter also found the sodium solutions more salty. Higher levels of perceived saltiness was also found to be associated with lower liking ratings.

Conversely, the testing using a chicken broth base found that while there was a relationship between PROP sensitivity and sodium sensitivity, there was no relationship between taste bud density and any outcomes. This is contrary to previous research that has been done in relation to the number of taste buds an individual has.

Overall, this study suggests that PROP sensitivity and papillae density are linked with intake through liking and sensation rather than directly affecting intake itself. The main finding of this study relates to PROP sensitivity, which is shown below in figure 1. Papillae density appears to be linked with lower liking of high fat and salt foods, and therefore lower intake.salt1

As a final note, the authors suggested that as individuals who are more sensitive to both PROP and salt have been shown to add less salt to their food at the table, it may be that they are able to taste enough saltiness and therefore don’t need to add any additional discretionary salt, whereas individuals who are less sensitive may need to add salt to get the same level of sensation.

 

 

Reference:

Hayes, J., Sullivan, B., Duffy, V. (2010). Explaining variability in sodium intake through oral sensory phenotype, salt sensation and liking. Physiology and Behavior, 100, 369-380.

Posted in bitterness, broth, chicken, flavour, health, hypertension, intensity, liking, obesity, overweight, papillae, phenotype, PROP, saline, Salt, saltiness, sensitivity, sensory phenotype, sodium, solutions, stroke, taste, taste buds, Uncategorized, variability | Leave a comment

The anti-inflammatory effects of oleocanthal and ibuprofen

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A significant part of the quality (perceived and health) of virgin olive oil is assessed based on the bitterness and pungency as these qualities indicate a high phenolic content in the oil. It is the phenolic compounds contained in virgin olive oil that are believed to contribute to the the low incidence of chronic inflammatory disease observed in Mediterranean populations.

Good quality virgin or extra virgin olive oil has a distinct sensory quality which has been attributed to one particular phenolic compound, oleocanthal. This distinct pungency is restricted to the throat which is unusual, as most irritants will stimulate other areas in the mouth, nose, eyes…. Oleocanthal shares this perceptual characteristic with ibuprofen, a non-steroidal anti-inflammatory drug, and also targets the same inflammatory pathway as ibuprofen. Both oleocanthal and ibuprofen inhibit cyclooxygenase enzymes which are inflammatory enzymes.

The throat irritation produced from oleocanthal and ibuprofen is variable amongst individuals and this is attributed to the specificity of these compounds to the Transient receptor potential cation channel, subfamily A, member 1 (TRPA1). It is a protein that in humans is encoded by the TRPA1 gene. TRPA1 is anion channel located on the plasma membrane of many human and animal cells and higher proportions of TRPA1 are located in the throat..

Therefore oleocanthal and ibuprofen produce a localised irritation where as other irritants such as capsaicin (the heat component of chilli peppers) irritate other areas of the oral cavity. Capsaicin is the prototypical TRPV1 agonist. The function of TRPV1 is primarily detection and regulation of body temperature. Additionally, TRPV1 receptor provides sensation of scalding heat and pain (also known as nociception).

A recent study conducted by Bennett and Hayes (2012) aimed to quantify the overall intensity of oleocanthal in olive oil and ibuprofen while also investigating predominant and secondary sub qualities and then compared them to capsaicin. Bennett and Hayes (2012) add to the molecular data with behavioral evidence that olive oil and ibuprofen differ from capsaicin in receptor specificity as capsaicin does not activate TRPA1 receptor. However of interest, although olive oil and ibuprofen differ from capsaicin in intensity of irritation ratings there is a correlation between olive oil and capsaicin in chemesthetic subqualities (e.g., burn, warm, hot). This would indicate that an unknown compound in olive oil is a TRPV1 agonist.

These authors conclude that Ibuprofen and capsaicin had independent sub qualities while olive oil is an intermediate and shares qualities with both ibuprofen (numbing, tickling) and capsaicin (burning, warming). There are a number of limitations when gathering meaningful qualitative data on irritant sensations, as irritant qualities such as tickling, itching etc are hard to characterize. Therefore future studies should focus on suitable descriptive qualities of irritant compounds such as ibuprofen, oleocanthal and capsaicin, that produce these sensations.

 

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Food and Emotions

Dr Herb Mieselman and the members of his team have been conducting research into the relationship between emotion and food. While there has been research done into a circular relationship between emotion and eating (see figure 1), the research Dr Mieselman and his research group have been involved with has focussed on consumer behaviour and the related emotions. This research has been largely devoted to determining what emotions can be elicited via eating, or even by being presented the name of a specific food.

emotions

In 2012 Cardello et al  published the article ‘Measuring emotional responses to foods and food names using questionnaires’ in the journal Food Quality and Preference. This article investigated the relationship between a variety of emotions and foods, and also aimed to determine the reliability of the questionnaires that have been employed. While there are a number of validated questionnaires focussing on emotion, these are largely from the field of clinical psychology and have limited applicability to the consumer research field. This is generally because clinical psychology focusses on negative emotions, whereas consumer food research has a comparatively positive emotional range. As such, consumer research requires significantly more detail regarding positive emotion than is generally included in clinical questionnaires. Further, as this is an emerging field, there are limited consumer specific methodologies that have been adequately validated. As a result, part of this paper focusses on the reliability of the questionnaire used – the EsSense Profile, which was originally developed by King and Mieselman (2010).

Emotional responses to foods and food names

Participants were given 12 food names on separate pieces of paper and asked to rate each emotion on the EsSense Profile after looking at each name. There are 39 emotions addressed by this questionnaire, including joyful, interested, bored, aggressive, eager and good natured. A separate group of participants were then given four samples of different foods, each one with two varieties. For example, they were given potato chips as one of food variety, and were given both plain and barbeque flavours. Liking was measured in addition to emotion.

Results

Significant differences in emotions were found in both study one and two after viewing food names and tasting different foods. However, there were no significant differences in emotional responses to the different brands/flavours of food that were tasted. Additionally, higher intensity emotions were recorded after participants were shown the names of foods rather than after tasting them. The authors postulate that this may be because an individual’s memory of a specific food is generally the best version of that food they have experienced, whereas consuming a food product in a laboratory may not be as positive an experience. A positive correlation between liking and emotional responses was also found when food products were tasted.

Reliability of the EsSense Profile

Four food names were given to participants, and their emotional responses were recorded, as in study one. These four names were chocolate, oatmeal, potato chips and carrots, and were chosen as a result of their variability in emotional responses according to the previous two studies. Participants completed the same emotion questionnaire as in the previous studies after reading the food names. Participants were retested one week later to determine reliability of responses

A separate group of participants were given four foods to tasted (chocolate, plain potato chips, coca cola and shortbread), with emotional responses measured after each. Participants were retested one week later.

Results

Some emotions were highly correlated, while some weren’t for both study three and four. For example, words such as guilty, polite, tender, whole and satisfied were highly correlated for food names, while words such as joyful, eager, daring, aggressive and good natured were most correlated for tasted foods. However, the correlation range was between 0.309 to 0.767, with some emotions being less correlated for both names of foods and tasted foods.

Additionally, the 39 emotions that were investigated were correlated to investigate any similarities. This resulted in six groupings of similar emotions;

  1. Glad, good, pleased, happy, satisfied, enthusiastic, joyful, interested, pleasant, eager, energetic, good natured, calm, friendly, merry
  2. Quiet, understanding, tame, steady, tender, polite, warm, secure, whole, peaceful, mild
  3. Adventurous, wild, daring, aggressive, active
  4. Loving, affectionate, merry
  5. Disgusted, guilty, worried
  6. Bored

From this study we can determine that there is indeed a relationship between emotions and food at a consumer level, and that most of the resulting emotions are positive. However, as this field is currently emerging and has limited established methodologies, there are potential validity issues with the questionnaires that are used. Particularly, there is no indication that the EsSense questionnaire is measuring the specific emotions it is designed to. As such, as this field develops further, it will be important to conduct further examinations of the specific tools being used. Additionally, when considering the consumer applications of research such as this, it may be relevant to create more sensitive measures, as the current questionnaires cannot determine any difference between brands or flavours (e.g. plain vs barbeque chips, or varieties of chocolate), which is particularly important for companies looking to succeed in the competitive food marketplace. Further, it may be beneficial in further investigations to include pre-test emotion questionnaires, to get a fuller understanding of the change in emotion following food presentation.

References

Cardello, A., Meiselman, H., Schutz, H., Craig, C., Given, Z., Lesher, L., Eicher, S. (2012). Measuring emotional response to foods and food names using questionnaires. Food Quality and Preference, 24, 243-250.

King, S., & Meiselman, H. L. (2010). Development of a method to measure consumer emotions associated with foods. Food Quality and Preference, 21, 168–177.

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Introducing temporal dominance of sensation

In product research and development in the food industry, it is important to understand the key sensory attributes of a product (aroma, flavour and mouth feel) to guide its development or modification. This may be useful when food companies wish to modify ingredients to develop a healthier product, to alter or eliminate undesirable characteristics, to add or enhance a particular characteristic, or in the initial development of a novel product.

A traditional method used to describe a products sensory attributes is Quantitative Descriptive Analysis (QDA). This method identifies all sensory attributes to describe a given product as well as providing an intensity rating for each attribute identified. Traditionally, a group of expert assessors form a panel and are trained to be able to accurately and repeatedly describe the characteristics present and quantify the intensity of each of the attributes on a line scale. The descriptive language used is devised and defined by the panel members with the guidance of a panel leader so all panel members understand and use the descriptors in the same way.

An example of a product being evaluated using QDA is chocolate. Some of the attributes that may be used to describe the flavour of chocolate are sweet, bitter and nutty. These would be evaluated on line scales like the ones below.

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For some products, such as the freshness of chewing gum, it may be important to include information on both the intensity and duration of each attribute. The intensity is evaluated at various time points to produce a curve of the intensity and duration. However only one or two attributes can be evaluated at a time. The figure below provides an example of an evaluation of chewing gum using the time-intensity method.

ImageTo be able to evaluate more than one attribute at a time using intensity and duration, a method was developed by Pascal Schlich and his research group in 2003 termed Temporal Dominance of Sensation (TDS). This method looks at a single eating event and identifies the dominant sensory attribute at any given point in time during the eating process. TDS is a technique whereby the intensity of dominant attributes are evaluated at the time sensations begin, repeatedly until the sensations end. Upon swallowing the product of interest a trained assessor will select the dominant attribute and rate the intensity of that attribute until the dominant attribute changes. The assessor will continue to evaluate the intensity of the dominant attribute until all sensations end. This method may be useful when the product of interest has a lingering after taste or effect, such as with chewing gum or mint flavoured confectionary.

During an evaluation, all attributes will appear simultaneously on a screen for the duration of the analysis. Upon commencing the evaluation, the time that each attribute is selected as dominant will be recorded together with the concurrent recorded intensity. The below figures provide an example of what the screen would look like for assessors evaluating a mint flavoured candy if minty was selected as the first dominant attribute.

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When collating the results obtained via the TDS method a temporal dominance of sensation curve may be established. The below figure illustrates the dominant attributes pertaining to a mint flavoured candy using the TDS method.

ImageThis methodology may be a welcomed addition to quantitative descriptive analysis to provide a more comprehensive picture of the sensations occurring during and following an eating event to assist food companies in product research and development.

References:

Cliff, M., & Heymann, H. (1993). Development and use of time-intensity methodology for sensory evaluation – a review. Food Research International, 26, 375–385.

Labbe, D., Schlich, P., Pineau, N., Gilbert, F., & Martin, N. (2009). Temporal Dominance of Sensations and sensory profiling: A comparative study. Food Quality and Preference, 20, 216–221.

Larson-Powers, M., & Pangborn, R. M. (1978). Paired comparison and time-intensity measurements of the sensory properties of beverages and gelatins containing sucrose or synthetic sweeteners. Journal of Food Science, 43, 41–46.

Pineau, N., Schlich, P., Issanchou, S., Imbert, A., Cordelle, S., Mathonnière, C., et al. (2009). Temporal Dominance of Sensations: Construction of the TDS curves and comparison with time-intensity. Food Quality and Preference, 20, 450–455.

Stone, H., Sidel, J. L., Oliver, S., Woolsey, A., & Singleton, R. C. (1974). Sensory evaluation by quantitative descriptive analysis. Food Technology, 28, 24–33.

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How much do you like strawberries?

One of the current projects that is being run through the Deakin University sensory lab is being run by PhD student Penny Oliver, with help from Horticulture Australia. Penny is a year through her project, and has taken over the lab with strawberries, fruit puree, and a panel of trained participants who gather at least twice a week to talk strawberries.

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The project has been funded by Horticulture Australia in an effort to produce a more flavoursome strawberry variety, that will be bred and produced locally. Most current strawberry varieties are bred for their appearance, longevity and resistance to both cold and pests, but with less regard for flavour. However, Horticulture Australia is taking it upon themselves (and ourselves!) to give the public what they want – more delicious fruit.

Participants were first screened for their tasting ability, with testing of sweet, salty, bitter, sour and umami (savoury) , to ensure that only the best tasters were included. More testing has followed, with participants being tested on identification of flavours.

Penny has been training her participants to improve their tasting palates further by identifying the flavours within specific types of strawberries. These flavours are varied, with descriptors such as ‘honey’ ‘vanilla’ ‘rose’ and ‘green’ being used to describe the properties of these varieties.

Penny has combined pureed strawberries with a number of other products to ensure that participants are all on the same page when they’re describing a strawberry as tasting like ‘plum’ or ‘fruity’.

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And while some products have been more difficult to reach consensus on (I’m looking at you ‘green’!), participants are now in the ‘intensity’ phase of their training. This involves discussing where on a scale the intensity of the flavour falls. For example, if a strawberry had a relatively small ‘citrus’ flavour component, it would be reported as such;citrus1

With the strawberry season coming up rapidly (though not as rapidly as expected given the weather!) Penny is looking forward to providing more varieties for analysis. These varieties will be tasted, smelled, examined and discussed to come up with a specific flavour profile for each. These profiles will then be used in further research to determine which flavour profiles are most preferred by strawberry consumers.

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This ‘liking’ phase of testing is slated to begin in February of 2014, though our original panel of tasters are unfortunately excluded from participation due to their previous involvement.
If you are interested in participating in tasting strawberries and discussing your preferences, please contact Penny Oliver on psol@deakin.edu.au

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