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| DETERMINATION OF ACID VALUE IN FATS AND OILS USING FOODLAB |
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The acid content in a alimentary fat or oil is given by the quantity of free fatty acids deriving from the hydrolytic going rancid of the triglycerides. This alteration occurs under unsuitable conditions of treatment and preservation of the fats and thus the acidity represents a basic indicator of the genuineness of the product. Substances with high water content, such as butter, are more subject to hydrolysis of the fats, and they can alter more easily, assuming the typical unpleasant smell and taste. Even olive oil can reach a high free acid content when the olives have not been gathered and processed correctly. Furthermore In dried fruit bad storage as, for example, in a damp place causes the hydrolysis of the fats increasing the concentration of non esterified acids and therefore total acidity.
With the FoodLab system it is possible to determine in just a few seconds the acid value of alimentary fats and oils using micro quantities of sample. Oil can be used directly raw, while solid fat must be melted at a temperature of approx. 60°C.
Furthermore CDR has also designed an innovative system for the cold extraction by means of pressure of the oil contained in dried fruit. The system is practical, fast and uses small quantities of dried fruit given the micro quantities required for analysis, without using solvents to extract the oil.
The reagents are composed exclusively of "low toxicity substances", easily disposable, which allow the test to be carried out in any environment. The method's reliability and precision are guaranteed by a calibration system that allows alignment of the instrument using known standards. |
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| MATERIALS AND CORRELATION METHODS |
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The FoodLab method is based on a colorimetric reaction in which fatty acids, under conditions of pH < 7.0, react with a chromogenous compound, developing a color whose optical density, measured at 630nm, is proportional to the acid concentration of the fat, expressed as a % of oleic acid.
Fat and oil samples were analyzed with the NGD system and with FoodLab, at the same time, in the reference laboratory. |
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| RESULTS AND DISCUSSION |
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The values obtained with the NGD system and with FoodLab on oil and fat samples are shown in Fig.1. The regression line correlation coefficient (r>0.99) indicates that the FoodLab system is perfectly aligned with the reference method.
Some repeatability tests carried out on the FoodLab system with oil and fat samples are shown in the Tab.1. The tests were carried out in the CDR laboratories.
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| Fig.1: Correlation between FoodLab and NGD methods |
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| Tab.1: Repeatability tests. |
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Ref
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Olio¹ |
Olio¹ |
Grasso² |
Grasso² |
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0,073 |
0,126 |
0,085 |
1,42 |
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0,075 |
0,123 |
0,090 |
1,38 |
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0,07 |
0,124 |
0,092 |
1,46 |
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0,074 |
0,126 |
0,086 |
1,45 |
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0,074 |
0,125 |
0,090 |
1,42 |
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MEAN |
0,073 |
0,125 |
0,088 |
1,42 |
SD |
0,002 |
0,001 |
0,003 |
0,03 |
CV,% |
2,35% |
1,18% |
3,09% |
2,02% |
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1 raw oil
2 fat melted at 60°C in a double boiler |
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| SHORT TABLE |
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Linearity |
Accuracy |
Repeat. |
R2 |
Sensitivity |
Total
analysis
time |
Test/hour |
20% |
± 5% |
CV < 2% |
r > 0,99 |
0,01% ac.oleico |
3 - 6 min |
80 |
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