Traditionally, bitter melon has been used as a vegetable in a variety of ways in Asian cuisine, and as the main ingredient its bitter taste can be overwhelming. Bitter melon-containing food dishes are not popular in the Western world due to its bitterness, which is an acquired taste. We therefore conducted a pilot study to incorporate bitter melon into few popular food dishes regularly consumed in Hawaii.
Our results indicate that chili, soup, and tomato sauce were more palatable compared to the curry dish which was considered unacceptable due to its "bitterness". It is possible that a sampling bias could have existed solely by the use of the term "bitter melon" in the recruitment process. Participants were aware from signs used to advertise the study, that it would be a tasting or acceptability study of bitter melon. Additionally, one of the main attributes singled out for hedonic evaluation was "bitterness" which could have drawn more attention to this potentially negative food trait even before the tasting began. To date, there are no published palatability studies of food dishes prepared with bitter melon. In one related study, hedonic ratings for bitter melon "pleasantness" before exposure to a bittersweet beverage for seven days and post-exposure were 2.9 ± 0.2 and 3.2 ± 0.3 (mean ± SE), respectively . These values were similar to the average "pleasantness" hedonic ratings of bitter melon and another bittersweet beverage of 3.2 ± 0.4 and 3.4 ± 0.5 for low- and high-exposure groups, respectively, reported by Mattes . In our study, the mean hedonic curry scores for "bitterness" (3.27 ± 2.22) and "overall" liking (3.53 ± 2.14) for the curry dish were similar to those previously reported [20, 21]. Furthermore, since 65% of the participants were between the ages of 24 to 35 years, it is highly possible that hedonic score about bitterness could be influenced by age, as older populations are more tolerant to bitter taste due to blunted gustatory sensations.
Although spices in the curry were unable to mask the bitter taste, its low total energy content makes it an attractive therapeutic alternative in Asian countries such as India wherein curry preparation may be culturally preferred and more acceptable. The other three dishes consisted of several other ingredients such as tomatoes, garlic and basil that masked their bitterness. Some traditional Asian recipes remove the bitter flavor from the fruit by adding salt, which extract the bitter juices and is then discarded. Alternatively, a combination of salt and vinegar can also be used to mask the bitter flavor. Besides salt, natural and artificial sweeteners as well as fat or cooking techniques such as pickling, caramelizing, or braising can be effective in reducing bitter taste [[18, 31, 32]]. In our study, increasing fat or sugar content to improve palatability was avoided since the dishes are intended for future clinical trials among diabetic individuals.
Since this was a palatability testing, the variation in calories of different food dishes is not expected to affect the taste. Similarly, bland starches such as rice and pasta are not expected to significantly affect palatability of bitter melon-containing food dishes. Although participants commented on "more rice" or "less rice" to increase palatability, there was no preference for one starch over the other. Moreover, these bitter melon-containing dishes could have been consumed without the starches. However, that may have resulted in a false positive or negative palatability score as these food dishes are generally consumed with starches.
Besides taste, health information also may influence the gradual acceptance and consumption of functional foods with bitter taste . In our study, health information failed to have a significant effect on consumption intentions. This is in contrast to previous study indicating that likelihood of consumption is decreased as bitterness increased, while intentions increased with only certain information on health benefits . Failure to see a change in consumption intentions could be a consequence of age since 35% of our participants were young (below 24 years) and healthy, and therefore may not have had the same health concerns as older populations. Earlier studies by Caltabiano and Shellshear indicated that health was less important in young adults (mean age of 22 years) than taste or palatability when determining food preferences .
Most of the information provided in this study focused on attributes and consequences of bitter melon consumption that would benefit individuals at higher risk for diabetes or CVD. Although diabetes is considered as an old age disease, the prevalence of T2DM is increasing in children and young adults, especially in the Pacific region . Therefore providing bitter melon-associated health information to younger population may be critical in prevention of diabetes. However, statistical analysis indicated that age did not influence the consumption intention in our study (data not shown).
Major strength of our study was identifying ingredients from western diet that are able to effectively mask the bitterness of functional food such as bitter melon. Although the order of samples was not randomized, this study limitation may not necessarily affect the taste of subsequent samples since water and saltine crackers were provided between dishes to cleanse their palates. However, the first food sample was randomized so that each dish would not be influenced by the perceived bitterness of the other dishes. This is exemplified by the fact that the participants at the soup station did not all dislike the chili (the last to be sampled by these participants). Randomizing the first dish was an effort to eliminate any potential cumulative effect on taste and therefore may be perceived as "structured randomization".
Overall, our study demonstrated that incorporating bitter melon in commonly consumed dishes increased acceptability among a mixed-ethnic and variable age group. However, previous exposure and knowledge of its health benefits had no effect on consumption intentions. Although our study was limited in the number of bitter melon-containing dishes that were tested and the age of the population, acceptability of foods with masked bitter taste merits future studies with large number of bitter melon-containing food dishes.
Bitter melon is routinely consumed as a part of many Asian diets and should therefore be expected to have minimal side effects. Well-designed clinical trials are also warranted to verify the dosage, safety, and pharmacokinetics of bitter melon. Results obtained from such studies will be significant since the information can help to develop nutritional regimens that can be incorporated into a daily diet. Developing such dietary alternatives to increase palatability and ultimately consumption of bitter tasting functional foods is expected to positively impact diabetes outcomes. Such intervention strategies would also be valuable to populations where conventional therapy is inaccessible and/or unaffordable, thereby improving diabetes care and management.