Determination and Comparison of the Lipid Profile and Sodium Content of Gluten-Free and Gluten-Containing Breads from the Spanish Market

The objective is to verify if gluten-free (GF) and gluten-containing (G) breads differ in their sodium content and lipid profile. Samples of GF (n = 20) and G (n = 14) sliced white sandwich bread of commercial brands most frequently consumed in Spain were collected. The fatty acid (FA) composition and the contents of sodium, fat, cholesterol and phytosterols were determined. Sodium, fat and cholesterol contents were significantly higher in GF bread. The FA composition also differed, while G breads declared in most instances the use of sunflower oil as fat ingredient and presented a higher polyunsaturated FA percentage; GF breads declared a wide variety of fats and oils as ingredients (coconut, palm, olive, sunflower, etc.) which was reflected in their FA profile. Cholesterol content was higher in GF bread because five samples declared the use of whole egg, while G samples did not include any egg product in their formulas. Phytosterol content was higher in G bread but its variability was greater in GF bread. In conclusion, nutritional quality of GF bread varied depending on the ingredients used and might be lower than that of G bread. However, these differences in composition could be reduced or eliminated through changes in the formulation of GF bread. Moreover, the comparison of the results obtained in our laboratory for fat and salt content with the declared contents on the labels showed a much higher deviation for GF samples and it can be concluded that the quality of the nutritional information declared was lower in GF samples. Electronic supplementary material The online version of this article (10.1007/s11130-020-00828-w) contains supplementary material, which is available to authorized users.


Sampling representativeness
According to the last data available from 2012 and 2013, the market share in Spain for sliced sandwich bread (calculated from the tons sold) was respectively 26. 2  nya-CESCE-2017.pdf). In total, it is estimated that the market share covered by the sampling for gluten-containing sliced sandwich bread was between 85-90%, depending on the data used for its calculation.
Regarding the sampling of the gluten-free sliced sandwich bread, it was designed by the Coeliac Association of Catalonia and is estimated to cover the 87% of the market share. The design was based on the deep knowledge of the Spanish market that the association has through the biannual preparation for their associates of the list of gluten-free foods available.

Analytical determinations
All analytical determinations were carried out in duplicate.
• Determination of moisture was carried according to the 925.10 AOAC method [1] in an air recirculation oven at 130 °C.
• Determination of the sodium content was conducted by inductively coupled plasma optical emission spectroscopy (ICP-OES) in a Perkin Elmer Optima 8300. The calibration was done with five standards prepared from certified standard solutions traceable to NIST. The samples (0.1 g) were previously digested with HNO3 and H2O2 in a Teflon reactor heated in an oven at 90 °C.
• Determination of fat content was carried using an adaptation the 922.06 AOAC method [1]. The adaptation consisted in using 50 mL screw-capped centrifuge tubes for acid hydrolysis and fat extraction of samples. Extraction was repeated 5 times with petroleum ether (20 mL x 2 and 15 mL x 3). The results obtained by using this method were compared with the results obtained by using the Soxtec method with petroleum ether (AOAC 2003.06) [1] without acid hydrolysis. It was observed that the method that extracted the fat after the acid hydrolysis gave higher percentages of fat, particularly in breads with low fat content, and therefore we decided to use this method to determine fat content in all the samples.
• Determination of the composition in fatty acids (FA) was carried by gas-chromatography after the extraction of the lipid fraction from 2 grams of bread with hexane: isopropanol (3:2, v/v) three times (20 mL x 1 and 10 mL x 2) using a high-speed homogenizer. Determination was conducted according to a modification of the method described by Guardiola et al. [2]. This method uses double methylation in methanolic medium, first with sodium methoxide and then with borontrifluoride. This 2-step procedure (base and acid catalyzed methylation) allows the complete methylation of free FA. The fatty acid methyl esters (FAME) were analyzed on an Agilent 4890D model (Waldbronn, Germany) gas chromatograph equipped with a flame-ionization detector (FID) and a split-splitless injector, set at 300 and 270 °C, respectively. The split ratio was 1:30.    In yellow the value of humidity that slightly exceeds the limit established until July 2019 for gluten-free bread (45%) [3,4]. For abbreviations see Table S1.