Formation of Free Fatty Acids by Enzymes in Human Saliva
Dr. Bryan G. Splawn, Department of Chemistry
Living overweight or obese can lead to serious
health problems such as asthma, osteoarthritis,
hypertension, diabetes mellitus, and heart disease. These
adverse health effects are known by most individuals.
Plus, most understand that overweight and obesity can be
treated or prevented by reducing dietary fat in-take and
getting enough physical exercise. So, why do we continue
to eat so much fat?
Reasons could be socioeconomic, genetic, cultural,
or behavioral. Our behavior towards something is
influenced by our senses of touch, taste, and smell. Fat
does have a distinctive texture (oily) and odor (light burnt
smell), but does fat have a taste or flavor? If so, does fat
taste good? Most would agree that the sweet taste of sugar
is good, but could we be developing a preference for fat in
fatty foods like donuts, cookies, and French fries, just to
name a few? The answer to this question could help
explain the rising rate of overweight and obese people in America and elsewhere.
pH
Determining whether or not
humans can taste fat is an area of
research that has received much attention
in the psychological and behavioral
sciences. Thus far, studies with rats have
shown that lingual lipase (enzyme)
A common free fatty acid (FFA) is oleic acid (C18H34O2).
excreted in the oral cavity is capable of
breaking down triglycerides (fat) into free fatty acids (FFAs) 1. Additionally, other studies have
shown that rats can distinguish
between salts solutions with and
Acid/Base Titration of Olive Oil/Saliva Sample
without FFAs by avoiding salt
12.00
solutions with FFAs 2. The
conclusion of this study strongly
14% v/v Olive Oil in Saliva
11.00
suggests that rats can detect the
10.00
presence or perhaps the taste of free
fatty acids. Furthermore, rats have
9.00
Equivalence point: 775 uL
shown an increased preference for
FFA concentration: 0.00401 M
sweet solutions mixed with fatty
8.00
acids as opposed to sweet solutions
Or, 0.11% if all was oleic acid
7.00
without free fatty acids 3. The
conclusion of this research suggests
6.00
0
200
400
600
800 1000 1200 1400 1600
that perhaps FFAs can enhance the
Volume (microliters)
palatability of sweet tasting
products. Overall, most fat taste studies are
conducted with rats, and it is not clear to what
degree humans can detect fat. Moreover, there is
little evidence, if any, on the source, quantities,
and nature of oral free fatty acids in humans.
The goal of this research was to
determine whether free fatty acids can be
generated from complex fats broken down by
enzymes in human saliva. Olive oil was used as
a surrogate fat sample because it is composed
primarily of unsaturated fat. A specified amount
Tuning gas chromatograph-mass spectrometer.
of olive oil was swirled in the mouth for a period
of time while saliva and salivary enzymes were secreted. Free fatty acids were detected in
human saliva by acid/base titration and gas chromatography-mass spectrometry (GC-MS). An
average of 4.94 ± 0.70 mM of total free fatty acids was measured by titration after swirling olive
oil for 150 seconds (n = 4). Lastly, oleic acid was positively detected by GC-MS after swirling
olive oil in the oral cavity for 1200 seconds.
Positive Oleic acid Fingerprint
1200 sec Saliva/Olive
Oil Sample
Oleic acid
1. Kawai, T. and Fushiki T., Importance of Lipolysis in Oral Cavity for Orosensory
Detection of Fat, Am. J. Physiol. Regul. Integr. Comp. Physiol, 285:R447-R454 (2003).
2. McCormack, D.N., Clyburn V.L. and Pittman D.W., Detection of Free Fatty Acids
Following a Conditioned Taste Aversion in Rats, Phys. Behavior, 87:582-594 (2006).
3. Pittman, D.W., Labban, C.E., Anderson, A.A., and O’Connor, H.E., Linoleic and Oleic
Acids Alter the Licking Responses to Sweet, Salt, Sour, and Bitter Tastants in Rats,
Chem. Senses, 31: 835–843 (2006).