This fundamental research holds considerable potential for food makers: identifying signals for satiety would lead to new product designs that encompass certain flavours and ingredients that could provide the consumer with a full up trigger.
Over-consumption of food, and therefore having an energy intake that exceeds expenditure, is seen as a major risk factor in the development of obesity. The new study, published in the journal Physiology and Behaviour (Vol. 87, pp. 469-477), appears to suggest that demand for variety and new flavours may be tempting people to eat more.
"Spontaneous intake of a sensorily varied diet can lead to over-consumption and weight-gain, especially with highly refined energy-dense foods. In contrast, monotonous meals may reduce intake and lead to weight loss," said lead author Michael Romer from the Department of Clinical Neurology, AKH, Austria.
Sensory-specific satiety (SSS) is defined as "a decrease in pleasure aroused by a specific food which has just been eaten in contrast to other non-consumed food". It is purely sensory and does not require food to enter the intestinal tract, and is not linked to calories.
The new study reports that a SSS may promote the search for diversity and new foods, and also that SSS for a given food can be reversed simply by seasoning: this last observation has never been reported before, say the researchers.
The scientists preformed three experiments with the help of 180 young volunteers (average age 27, BMI 21.5 kg per sq. m) divided into three groups. The first experiment looked at the effects of pleasure and appetite of one food before and after eating it. The second experiment looked at pleasure and appetite of a second food after eating the first. The third experiment looked at offering the same food as the first after seasoning.
Six foods were used in the experiments, divided into three groups: vegetable (cucumber, tomato), sweet fruits (pineapple, banana), nuts (peanut, pistachio).
After only two minutes of eating the first food, the researchers found that further intake was limited by SSS, due to 'sensory fatigue' of eating the same food. This was shown by an 86 per cent decrease in 'olfactory pleasure' towards the food.
During intake of the first food, the pleasure for the second increased by 39 per cent, while decreasing the pleasure of the first by 79 per cent. When a second (different) food was offered, olfactory pleasure for the first food increased by 12 per cent after eating the second food.
The third experiment showed that seasoning of food renewed the flavour-pleasure of the food, and even surpassed the initial pleasure by about 25 per cent.
"The renewal in flavour-pleasure for the seasoned food was associated with additional food intake (plus 84.2 per cent in weight; 86 per cent in volume and 111.6 per cent in calories)," said Romer.
This research has two important implications, say the researchers, with the phenomena of SSS participating in the induction of a specific feeling of fullness, and therefore the end of eating, and secondly, that SSS may promote the search for new foods during a meal.
Better understanding the human response to such stimuli may help better understand the link between food intake and obesity. The results of this study appear to indicate that increased palatability is linked to increased food intake.
However, research is on-going into how certain flavours and ingredients can decrease food intake by increasing satiety. Last year, the Brussels-backed DiOGenes project was launched to explore the possibility that certain ingredients and flavours may enhance or diminish "full-up", satiety signals in the consumer.
Over 300m adults are obese worldwide, according to latest statistics from the WHO and the International Obesity Task Force. About one-quarter of the US adult population is said to be obese, with rates in Western Europe on the rise although not yet at similar levels.
By Stephen Daniells - productiondaily.com