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Miracle fruit improves sweetness of a low-calorie dessert without subsequent energy compensation

Janine M. Wong *, Mark Kern

School of Exercise and Nutritional Sciences, San Diego State University, 5500 Campanile Drive, San Diego, CA 92182, United States

INTRODUCTION

Many alternative sweeteners have been extensively researched for their efficacy in decreasing sugar and energy intake. There is some evidence that the perception of sweetness may stimulate appetite and the desire increase to eat which in effect, could negate any energy savings from non-caloric alternative sweeteners. Other studies have illuminated the complexity as the potential appetite stimulating effects of sweetness appear to vary by multiple factors including gender, the concentration of Sweetener, the form of the food they are consumed in (food or beverages), and habituation to artificial sweeteners.

A sweetness enhancer that is currently being developed is found in miracle fruit (MF) or miraculin. MF is a berry native to West Africa, named for its unique ability to cause acidic (sour) foods to taste sweet. The active compound is miraculin, a glycoprotein that binds adjacently to sweet receptor cells on the tongue, activating them in response to a low pH. Miraculin has no taste itself, but stimulates a sweet taste estimated to be 400,000 times sweeter than sucrose on a molar basis. Researchers are developing miraculin as an alternative sweetener, and have engineered other plants to produce miraculin.

METHODS

1. Subjects

10 subjects were necessary to detect a difference in food consumption of 50 50 g at 80% power and a p-value of 0.05. To ensure adequate power, and protect against subject attrition. 15 subjects were recruited.

2. Protocol

Testing was conducted on four non-consecutive trial days within 2 weeks. Standardized foods were provided to the subjects to consume for the entire trial day. This was done to control for the variability in the different satiating effects of foods with different macronutrient contents, energy densities, and food form. During the weighed food intake portion of trial days, subjects were provided with the same foods, but were allowed to consume as much or as little as desired.

On each trial day, subjects were provided a standardized breakfast of milk and cereal to consume at home. When subjects arrived at the lab, a lunch was provided. Lunch was followed by one of four dessert conditions: a regular dessert, another regular dessert preceded by MF, a diet dessert, or a diet dessert preceded by MF. Conditions were completed in a randomized order.

The desserts were lemon juice based popsicles including a small amount of honey (2 T per 750 ml), that were either sweetened by sucrose (REG: 854 J) or unsweetened (DIET: 142 J). MF was administered in a freeze-dried pill form. Subjects were instructed to dissolve the tablet on their tongue. MF was administered separately from the popsicles, and not as an ingredient in the popsicles because the sweetness enhancing effects of MF occur only after the tongue has been coated with miraculin. It was determined during pilot testing of the popsicles that direct incorporation of MF into the popsicles greatly limits its sweetness enhancing effects. The energy contribution of the MF was negligible.

Before subjects left the lab, they were provided with preweighed standardized snacks and dinner. More food was provided than was anticipated that subjects could consume for the remainder of the day. Subjects returned their leftover food in the original containers during the next trial day. Leftover food was weighed and energy consumption was calculated. Subjects were allowed to consume water ad libitum but were instructed not to eat or drink anything other than what was provided by the investigators for the remainder of the day. Subjects were also asked to keep their physical activity levels the same on each trial day. Muffins for the weighed food intake were made from scratch, and their energy content was calculated using Nutritional Software Library. Energy contents of all of the other food provided was calculated from the Nutrition Facts labels on the food packages.

DECEPTION

Subjects were blinded to the true purpose of the study in order to prevent bias in the sensory and energy measurements. Subjects were told that they were participating in a study investigating the structure-function claims made on a mixed berry dietary supplement. They were not formally informed of what the fictitious claims were, but were led to believe that investigators were measuring their cognitive abilities and energy intake. In order to maintain this deception, subjects completed a mirror tracing activity before consuming the dessert to ‘‘measure’’ cognitive abilities during each trial. To prevent bias in the sensory measures, subjects were told that the investigators were pilot testing the popsicles for another research project and that the popsicles were nutritionally identical to one another and would not affect results in the current study. At the completion of data collection, all subjects were debriefed regarding the true intent of the study, and the sweetness enhancing effects of MF.

RESULTS

15 women participated in the study, of which 13 completed all parts of the study. Two subjects were only able to complete three trials. They were all provided with food from breakfast, lunch and dinner with different kinds of desserts.

This study indicates that fullness is not affected by replacing sucrose energy with non-nutritive alternative sweeteners. As to the MF, it did not affect overall preference for the desserts, even though subjects rated the desserts as sweeter when preceded by MF.

Texture was also found that might have affected the food enhancement. In this experiment, subjects were given desserts which includes honey in both popsicles to enhance overall sensory properties, the difference in sucrose content led to a substantial distinction in the texture of the frozen products.Many subjects subjectively reported that the normal popsicle was ‘‘softer’’ with a more ‘‘pleasing’’ texture, and the low sugar popsicle was ‘‘icy’’ and ‘‘hard’’. Future research evaluating hedonic preferences of foods enhanced for sweetness with MF should be designed to take texture into consideration.

ENERGY INTAKE

It cannot be concluded that MF causes a decrease in subsequent energy consumption as energy intake without the popsicles was the same across trial days. However, compared to a MF sweetened popsicle, a conventionally sweetened popsicle containing sucrose does not promote greater satiety.

CONCLUSIONS

Miracle fruit can successfully improve the sweetness of a low sugar popsicle to a magnitude that is similar to a sugar sweetened popsicle, without subsequent energy compensation for the lacking calories.



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