Food Waste and Catering Waste; Focus on Valorisation of Used Cooking Oil and Recovered Triglycerides - The Economic Utilisation of Food Co-Products - page 92

Determination of acidity, which is a key parameter for the usability of
UCO. There are several methods used to determine the acidity, either
using wet acid-base titration with KOH or NaOH classical titration 31 or
potentiometric methods 32 as common methodologies. The latter has the
advantage of determining endpoints more accurately than the classical
methods, making it nondependent on colour change.
Viscosity, which is measured by a number of rheological techniques.
Measuring viscosity can be an inexpensive and simple method to
determine the shelf-life and degree of deterioration/ quality of the oil in
comparison with other highly technical methods. 33 Viscosity is especially
important for the use of UCO and others in lubrication and applications
involving the mechanical performance.
Free fatty acid profile and saponifiable materials/eluteables: to quality,
purity and aptitude for an oil/fat to be employed in certain application. A
common technique employed is Gas Chromatography (GC), widely used
both in feed and technical uses such as biodiesel (Figure 6.4). 34
Polar component: Total polar material (TPM) evaluation in oils and fats
may be another good indication of the degree of degradation of the
product. Some polar components are naturally present in fats and oils
(tocopherols, sterols, glycosides and phospoholipds primarily), whereas
others such as oxidised triglycerides and fatty acids and their polymers
form during frying and exposure to air. Methods such as size exclusion
chromatography, TLC and others can be employed to elucidate this
analysis both qualitatively and quantitatively. 35
Iodine value (IV), related to the degree of unsaturation in the oil. This is
defined as the amount in grams of iodine reacting with 100 g of oil/fat, being
halogens readily reactive with double bonds in the side chain from the fatty
acids in triglycerides. The iodine value is a parameter that correlates both
with oxidative stability and other properties such as viscosity and lubricity.
Oxidative stability, consisting generally of the evaluation of the
performance of the material under accelerated thermal oxidation of oils/
fats in the presence of air (Rancimat method). 36 Resistance to stability
generally will increase for fats and oils with decreasing IV, and therefore
with the right balance of monounsaturated and saturates present in
addition to the presence of natural or added antioxidants in the oil, 37 and
will decrease with the length of use of the oil. 38

d n 9 r 3 n g | 0

d y y f n n 3 .

Figure 6.4 Typical GC free fatty acid profile for an UCO.