Saturday, March 30, 2013

Bitterness and Supertasting

Excessive bitterness turns people off consuming those foods. For example, if I eat a food and experience excessive or lingering bitterness from it, I am unlikely to consume the food again. To some people that statement may appear illogical because there are many excessively bitter foods common in the food supply; think about beer or coffee.  An important factor in this discussion is individual differences in perception and what I experience as excessively bitter, a second person may experience little to no bitterness.  In such a situation I reject the food, while the other person finds the food perfectly acceptable. Part of the diversity is due to complex biology underpinning bitter taste – we have at least 25 receptors for bitter taste, some receptors are responsive to multiple compounds, others only one or two compounds. 
Individual differences are the norm, we all have our own flavour worlds and bitter taste is particularly variable among the population. One concept common in discussions about bitterness and individual variation is the ‘supertaster’. The term is applied to a person who is sensitive, or experiences extreme bitterness from the compounds PROP (n-6-propylthiouracil) or PTC (Phenylthiocarbamide); both of these compounds activate the same narrowly tuned bitter taste receptor (meaning only a few compounds activate the receptor).  Some studies have shown that supertasters are more sensitive generally to bitterness of foods, meaning they experience a higher intensity of bitterness not just to PROP or PTC, but all bitterness.  Some studies suggest supertasters are more sensitive to all sensory stimuli.  Operationally this is not true, the term supertaster merely means an individual is more sensitive to a specific bitter compound, and may mean no more than that.  When an individual is generally more sensitive to food chemicals the heightened sensitivity to PROP / PTC may be a defacto marker of increased papillae. Given the thought that more papillae means more taste receptors, and the more receptors the greater the taste signal from the papillae. 
In the same paradigm, people who cannot taste bitterness in PROP / PTC are termed ‘non-tasters’.  This is not because they have no papillae, but because the bitter taste receptor has a minor variation in sequence compared to the receptor in supertasters.  When researchers have looked at supertasters and non-tasters as groups, some differences in food consumption are apparent in some studies – for example supertasters find broccoli and alcohol bitter and consume less of them than non tasters; other studies find no differences in consumption between the groups.
The relevance of sensitivity to PROP / PTC to food consumption is debatable because of the large individual variation to bitterness – just because I am sensitive to PROP or PTC does not mean I am sensitive to the bitterness of caffeine or myriad other bitter chemicals in the food supply. You commonly have the situation where an individual may not eat grapefruit because they find it too bitter, but have no problem consuming black unsweetened coffee. Some others may find both or neither bitter.  It can be confusing, but that is a function of the complex biology and perceptual processes involved.   
Dr John Hayes and I recently published a paper reconceptualising the supertaster terminology (1).


Friday, February 15, 2013

Food Quality. What is it?

In terms of how we think about a food, the quality aspect is a perceptual process, Food Quality Perception
Food is described as any solid material that is eaten, or taken into the body for nourishment. It includes all unprocessed, semi-processed, or processed items which are intended for use as food or drinks including any ingredients incorporated into food or drink, and any substances that come into contact with food during production, processing or treatment.
Quality is a theoretical construct, a thought, idea, pattern or notion. It is not a physical entity with a fixed time or position. Quality can be defined in many ways and from many different perspectives. In food science, quality concerns a products ‘fitness for consumption’. A product is considered quality, if it satisfies all the needs and requirements relating to characteristics of food, as determined by the producer, manufacturer or consumer.
Perception is the process in which information is selected, organised and interpreted through input from our sensory systems.  Perception is shaped by cognitive processes, understandings, and experiences.  Perception is individual and influenced by memories, personality, mood, knowledge and expectations.
Quality at the retail level is based on how quickly a product disappears from the shelf, and is based on consumer demand. Whilst this may be considered a good measure of food quality, it is not always the most purchased item that is the best quality. Consider the popularity of white bread which is mass produced and sold, yet its quality merits probably lie with its versatility (can be used for toast, sandwiches) and price (it’s cheap). Most people would argue that home-baked or freshly baked breads from smaller outlets are higher quality, but at the same time are not suitable for all occasions. The quality-to-price ratio is partially responsible for differences between market performance and true quality.
What we see as quality is subjective, foods are considered quality if they meet all our desires and requirements. Personal preferences for food products based on these requirements occur as we take in and interpret information surrounding a product. We assess determinants of quality based on personal needs, knowledge, beliefs and prior experiences. Quality perception is evaluated through cues prior to purchase; after consumption quality can be re-assessed by experience. 
We use both sensory and non-sensory dimensions such as convenience and health to form quality perceptions. Information regarding food products can be evaluated both prior to purchase by touching, smelling, inspecting foods or studying labels, health claims and brands, as well as after preparation and consumption by sensations and other postingestional outcomes or convenience dimensions experienced during preparation.
Attributes of specific foods are considered desirable for different occasions, at different times and as our knowledge and exposure to food increases so does our perception of quality. Food which is chosen for a picnic would not necessarily be served at a high class restaurant, yet both could be considered quality for each occasion. Similarly food which needs to be eaten ‘on the go’ will differ dramatically from food which can be consumed when seated.  Also components of foods may convey quality specific to a food group; fat is an important quality to look for in meat cuts, but is redundant when choosing fruit or vegetables.
With each new food or flavour experience quality perception changes and may affect previous and future expectations and experiences. A beer from a large multinational brewer may taste great, but after consumption of fine hand-pulled ale from a small local producer your tastes and expectations evolve.  In most cases more than one exposure to novel foods and flavours are required for appreciation.  New flavours, methods of cooking or preparation and increased knowledge concerning food products, ingredients and health claims can also alter perception.
Emerging food trends such as lowered fat products are viewed as quality by some, yet despised by others who perceive quality not through fat content but prefer foods embedded within traditions and taste. Food quality perception is a subjective experience which is definable, only by the individual. What rates high on one’s quality list, will not appear on another’s.  The subjectivity and argue-ability of the quality of a food makes the topic inherently interesting. 

The above words are adapted from a Chapter I wrote titled ‘Food Quality Perception’ in Processing Effects on Safety and Quality of Foods, Editor Ortega-Rivas. Publisher Taylor and Francis
Grunert, KG. 1997. What's in a steak? A cross-cultural study on the quality perception of beef. Food Quality and Preference 8 (3):157-174.
———. 2002. Current issues in the understanding of consumer food choice. Trends in Food Science and Technology 13:275-285.
Grunert, KG, K Bredahl, and K Brunso. 2003. Consumer perception of meat quality and implication for product development in the meat sector - a review. Meat Science 66:259-272.
Holm, L, and H Kildevang. 1996. Consumers' views on food quality. A qualitative interview study. Appetite 27 (1):1-14.
Hyde, RJ, and SA Witherly. 1993. Dynamic contrast: a sensory contribution to palatability. Appetite 21:1-16.
Jaeger, SR. 2006. Non-sensory factors in sensory science research. Food Quality and Preference 17:132-144.
Prescott, J. 1999. Flavour as a psychological construct: implications for perceiving and measuring the sensory qualities of foods. Food Quality and Preference 10:349-356.
Stefani, G, D Romano, and A Cavicchi. 2006. Consumer expectations, liking and willingness to pay for speciality foods: Do sensory characteristics tell the whole story? Food Quality and Preference 17:53-62.