The selection of the parameters that determine the FQI depends on the intended use of the fat being evaluated; the most important concern is meeting the requirements for the use of fats for human consumption, either in pharmaceuticals or as food. Based on this criterion, the parameters required by the regulations for lard, cocoa butter, palm oil, butter, and margarine were analyzed.
It is known that the applicable regulations were drafted with the participation of several experts, companies, and institutions from each country. This panel of experts pooled their experience and knowledge from different countries and incorporated the idiosyncrasies of each country and region in Latin America.
The fat quality index scale ranges from 0 to 100, and represents the quality of the fat as a food product. Five intervals of fat quality are identified: 91 to 100 is classified as excellent, 71 to 90 is considered good, average quality ranges from 51 to 70, poor quality is from 26 to 50, and very poor quality ranges between 0 and 25.
The quality index value is determined by the sum of the product of the sub-indices and the weight that is set for each parameter.
To determine the value of the Fat Quality Index, an equation incorporating the weighed arithmetic average of each parameter was used:
Where
In the construction of the FQI, only those parameters intrinsic to fats were considered, without considering additive compounds such as colors or antioxidants, which are added during the formulation and packaging processes and, therefore, cannot be considered main components of the fats.
Fat quality parameters set by the regulations
| Parameter | Symbol | Weight | Fat | Regulation applied | |||
|---|---|---|---|---|---|---|---|
|
|
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| B | CF | VL | L | ||||
| Humidity% | H | 4 | A | A | A | A | 1, 2, 3, 4, 5, 6, 11, 14, 15, 18, 21, 22, 23, 25, 26 |
| Melting point | MP | 4 | A | A | A | A | 1, 5, 9, 14, 15, 17,18, 21, 22, 23, 24, 25, 26 |
| Solidification point of fatty acids in °C | SP | 4 | NA | NA | NA | A | 18 |
| Specific gravity of 40/25 °C | ρ | 4 | NA | NA | A | A | 17, 18, 20 |
| Refractive Index 313 K (40 °C) | η | 4 | A | NA | A | A | 1, 2,3, 16,17,18, 19, 20, 22 |
| Saponification Index | Sap | 5 | A | NA | A | A | 1, 2, 3, 14, 1, 5, 16,17,18, 20, 21, 22 |
| Unsaponifiable materials (g/kg fat) | USap | 4 | NA | NA | NA | A | 14, 18, 20, 21, 23, 24, 25 |
| Iodine Index (Hanus) | I | 5 | A | NA | NA | A | 1, 2, 3, 17,18, 19, 20, 21, 22 |
| Acidity expressed in lactic acid% (m/m) | A | 4 | A | NA | NA | NA | 3 |
| Free acidity (%) as lauric acid% | A | NA | NA | NA | A | 17, 18 | |
| Free acidity (%) as oleic acid | A | NA | A | A | A | 8,11,14,15, 16,18, 23, 24, 25 | |
| Peroxide Index (meq. of O2·kg−1 fat) | P | 5 | A | A | NA | A | 4, 10, 14,18, 21, 23 |
| Fat% (m/m) | F | 5 | A | A | NA | NA | 2,3,4,5,7, 11, 24 |
| Reichert- Meisst index | Re | 4 | A | NA | NA | NA | 1, 2 |
| Polenske Index | Po | A | NA | NA | NA | 1, 2 | |
| Kirchner index | Ki | A | NA | NA | NA | 1 | |
| Böemer Index | Bo | 4 | NA | NA | NA | A | 18 |
| Suspended solids | Ss | 4 | NA | NA | NA | A | 18, 19 |
| Rancidity | R | 5 | NA | NA | NA | A | 18 |
| Sodium soap | sso | 4 | NA | NA | NA | A | 20 |
| Unsolvable material | UM | 4 | NA | NA | NA | A | 16, 18, 19, 23, 24 |
| Iron | Fe | 5 | NA | A | A | A | 6, 16, 19, 20, 23, 24, 26, 27 |
| Copper | Cu | NA | A | A | A | 5, 16, 20, 23, 24, 26, 27, 28 | |
| Plumbum | Pb | NA | A | A | A | 5, 16, 19, 20, 23, 26, 29 | |
| Arsenic | As | NA | A | A | A | 5, 16, 19, 20, 23, 24, 26, 28, 29, 30 | |
| Nickel | Ni | NA | A | NA | A | 5, 19, 23, 24, 25, 28, 29, | |
| Yellow | Y | 4 | A | A | A | A | 1, 15, 19, 20, 24, 25 |
| Red | R | NA | A | NA | A | 18, 19, 23, 25, | |
| Blue | B | NA | A | NA | A | 18, 23, 25, | |
| Unsaturated/saturated |
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5 | NA | NA | NA | A | 18, 19,31 |
| Smell and taste | ST | 5 | NA | A | A | A | 5, 13, 16, 18, 19, 20, 24, 28, 31, 31, |
| Texture | T | 4 | NA | A | A | A | 5, 14, 18, 19, 24, 31 |
| Appearance | A | 4 | NA | A | A | A | 1, 5, 14, 19, 24, 31 |
| Fat | Butter (B), Composed and hydrogenated fat (CF), vegetable lard (VL) and Lard (L) | ||||||
| Regulations | 1) NMX-F-010, |
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This study considered the physicochemical parameters present in all regulations and omitted parameters that only apply specifically to margarine and butter, such as pH, phosphatase, stability, and dry matter content, which are not considered in the proposed index because they only found in the regulations for a single type of fat. Among these parameters can be found non-fat solids, phosphatase, linoleic acid, casein, fat acidity, conservatives, and sodium chloride type I and II.
Fatty acid composition is complex, and the regulations consider over 15 parameters. The fatty acid profile has great importance in the quality of a fat. However, including these parameters in addition to the physicochemical ones would make the calculation of the FQI too complex and would not properly represent the interests of the fatty acid profile.
The use of the ratio of unsaturated/saturated fatty acids, which is the ratio between the sum of unsaturated fatty acids and the sum of saturated fatty acids expressed as a percentage, is proposed. This definition is a representation of the fatty acid profile that groups all the components together (Valenzuela
The maximum and minimum values of the ratio of unsaturated/saturated fatty acids are not established in the regulations, so to define these values, two limiting cases are set considering the values of each fatty acid.
Thus, to determine the minimum allowed value of the unsaturated/saturated ratio, the sum of the percentages of all unsaturated fatty acids at their minimum allowed value divided by the sum of the percentages of all saturated fatty acids at their maximum allowed value is considered. Thus, the first limiting case is obtained as a ratio that represents a fat sample with the smallest allowed amount of unsaturated fatty acids and the maximum of saturated ones. This value can be represented by the following equation:
Likewise, to obtain the maximum allowed value of the unsaturated/saturated ratio, the sum of the percentages of unsaturated fatty acids at their maximum allowed value is divided by the sum of the percentages of all saturated fatty acids at their minimum allowed value. Thus, a sample with a small content of saturated fatty acids and a large content of unsaturated ones is considered:
Finally, the organoleptic characteristics are considered, which are of great importance in the quality of the fat due to its use in foods and can significantly alter the quality of the products.
With the purpose of transforming the variables to a dimensionless scale to then integrate them into the FQI, each type of contribution is determined depending on the characteristics and trends seen in the regulations.
Organoleptic parameters (except color) and the Kreiss reaction are qualitative determinations. Thus, it is not possible to determine the value of the sub-index mathematically, as it only provides nominal values such as negative or positive. Therefore, the use of the value 100 is proposed for those samples that meet the value accepted by the regulations, and a value of three is proposed for samples that do not meet the regulations.
A statistical analysis of the parameters is performed using the computer program
With the analysis and inspection of the statistical results, the most suitable mathematical model is proposed, considering the values of central tendency, kurtosis, and symmetry, in addition to the analysis of the behavior of tens of percentiles. Additionally, the lower and upper confidence limits for 95% of the population of the analyzed data are determined.
The variability and confidence intervals are determined both statistically, according to the standard deviation, and in accordance with the regulations regarding the significant values of each parameter, which are set according to the standard analytical detection method employed. This procedure allows for the use of two significant numbers in the FQI.
Furthermore, the averages were evaluated in chunks corresponding to the main types of fats: animal (e.g., butter fat, butter milk), vegetable (e.g., palm oil, cocoa butter), and mixed (margarine and hydrogenated).
Most of the parameters have sub-indices that are obtained by the method of curves described by mathematical equations and based on the regulations. Using these sub-indices, each parameter is described in an objective manner through the correlation between the actual value of the parameter and the 0–100 sub-index scale of each parameter; this method is the most widely accepted (Samboni-Ruiz
The values of the lower and upper confidence limits or ranges of statistical acceptance of the data extracted from the regulations for each parameter are considered to determine the necessary minimum value to be labelled a fat with acceptable quality, which in this case is considered to be a value of 71.
Furthermore, depending on the type of tendency the parameter shows, the mathematical model chosen is the one that shows the best fit to the expected behavior and to the results of the statistical analysis. To determine the model, the tens of percentiles of the FQI statistical analysis are correlated with the values of 71 and 100 for a fat that meets the quality criteria.
To establish the parameters, linear, exponential, potential, and non-linear mathematical models were used. Adjustments were made using the computer programs
However, some parameters display more complex tendencies, so it was necessary to consider multiple models that describe multiple parameters with a single index. Thus, the metals and Lovibond parameters are expressed as the algebraic sum of each parameter in an equation with multiple variables. Similarly, the Reichert-Meissl, Polenske, and Kirchner values are integrated into a single parameter that represents volatile fatty acids.