Current recommendations call for daily intakes of at least five servings of fruit and vegetables, but surveys have shown that the public is falling short. Vegetable consumption has been linked to taste, texture and appearance, as well as cost and availability.
This is the first study to examine how bitterness and sweetness are negative and positive predictors of vegetable preference and intake, and how both contribute to explaining dietary behaviors, wrote lead researcher Valerie Duffy from the University of Connecticut.
The implications of this study for the food industry are obvious. If more attention is paid to taste and sensory qualities, say the researchers, then the intake of vegetables can be improved, along with the associated health benefits and protection from chronic diseases.
The study, published in the journal Physiology and Behavior (vol. 87, pp. 304-313), assessed 110 volunteers (71 women and 39 men) sampling different vegetables (asparagus, Brussels sprouts and kale) and sweets (milk chocolate and marshmallow). The participants were asked to rate the tastes according to liking/disliking, sweetness, sourness, saltiness, and bitterness.
Vegetable intake for the participants was measured from answers from a validated food frequency questionnaire.
The ability to taste bitterness is known to be genetic and is sensed by G protein-coupled receptors (GPCR) (as is sweetness). The researchers quantified the participants ability to taste bitterness using 6-n-propylthiouracil (PROP) and quinine solutions.
Those who tastes PROP as most bitter also tasted more bitterness from sampled vegetables, independent of age and sex, and more sweetness from sampled sweet foods, said Duffy.
Previous studies have linked PROP bitterness to lower acceptance of cruciferous vegetables like broccoli and cauliflower, spinach, soy products and green tea.
Increased consumption of these foods have been linked to a variety of health benefits, ranging from lower risks of cancer to reduced risks of cardiovascular disease.
Diminishing bitterness of vegetables through horticultural techniques and minimizing flavor changes during storage and processing may promote optimal sweetness in vegetables from naturally occurring sugars, concluded the researchers.
The findings are also applicable to food formulators, as it is clear that bitterness affects acceptability and intake. The same principles can be extended for all food.