Development of a GC-FID method for the quantitative determination of polyglycerol polyricinoleate (PGPR) in foods

Abstract

Polyglycerol polyricinoleate (PGPR) is a powerful lipophilic emulsifier used in low-fat spreads and chocolate. It should be used at the lowest level at which the desired technological effect is achieved, not exceeding the specified maxima according to Annexe II to Regulation (EC) No 1333/2008. A gas chromatography-flame ionisation detection (GC-FID) method was developed for quantification of PGPR. This method is based on estimating the content of ricinoleic acid using 12-hydroxyoctadecanoic acid as an internal standard, from which the PGPR concentration was deduced. The method involved saponification, methylation, a two-step solid phase extraction (SPE) separation of the fatty acid methyl esters (FAMEs), silylation, and GC-FID analysis. The limits of detection and quantification of ricinoleic acid were 2.2 and 6.7 μg/mL, respectively, at 0.1 µL injection volume. Considering the average content of ricinoleic acid in PGPR (i.e. 86.63 ± 2.0 wt%) and the amount of food product that is used in the proposed protocol (i.e. 20 mg), this resulted in a LOD and LOQ of 0.76 and 2.32 μg PGPR per mg of food product, respectively. The developed method was validated by determining PGPR recovery from a high oleic sunflower oil (HOSO) solution, from chocolate spiked with a commercially available PGPR, and from commercially available low fat spreads with a known PGPR content. The actual recovery was more than 95% for all matrices, indicating the accuracy of the developed analytical technique. Moreover, the method proved to be very reproducible, with RSD < 4% for concentrations ranging from 0.2 to 5 wt%. The results showed that our proposed GC-FID method enables the reliable and quantitative determination of the PGPR concentration in commercial food products with various fat contents.

Impact of Nonthermal Plasma on Lipid Oxidation from the Perspective of Plasma Treatment Parameters and Plasma Species: Identification of Key Reactive Species

“…A weight of 20.0 mg of FAMEs were weighed in a glass test tube containing around 3 mg of methyl C19:0 as the internal standard (IS). Next, 3 mL of iso-octane was added into the test tube and the mixture was vortexed for 30 s. The mixture was then diluted 40 times with isooctane and the FAME composition was analyzed according to the procedure described by Su et al 28 The stripped linseed oil methylesters comprised 5.4, 4.1, 19.1, 14.2, and 49.1% of C16:0, C18:0, C18:1, C18:2, and C18:3 (in wt %), respectively. The stripped methyl oleate comprised 3.7, 1.4, 71.1, and 9.7% of C16:0, C18:0, C18:1, and C18:2 (in wt %), respectively.…”

Analytics and applications of polyglycerol polyricinoleate (PGPR)—Current research progress

“…PGPR typically consists of a complex mixture of various esters with a varying polymerisation degree (both on the level of glycerol and ricinoleic acid) and a varying esterification degree (Bastida‐Rodríguez et al., 2013; Mortensen et al., 2017; Su et al., 2021). As a synthetic food additive, a comprehensive analysis of the molecular species composition of PGPR is crucial.…”

“…Recently, a method was proposed to analyze the composition and content of all fatty acids in PGPR by gas chromatography‐flame ionization detector (GC‐FID) (Figure 2). This method consists of a saponification of the PGPR sample with methanolic NaOH, followed by a methylation of the fatty acids with boron trifluoride‐methanol, after which the non‐OH‐fatty acid methyl esters were separated from methyl ricinoleate via a two‐step solid phase extraction (SPE) and the OH‐fraction was silylated (Su et al., 2021). For quantitative analysis, 12‐hydroxyoctadecanoic acid and nonadecanoic acid were used as internal standards for hydroxyl‐fatty acids and non‐hydroxyl‐fatty acids, respectively.…”

“…Scheme for the total fatty acid determination of polyglycerol polyricinoleate (PGPR); for more detailed experimental conditions, please refer to Su et al. (2021). …”

“…Due to the complexity of PGPR's composition, it is not possible to measure the individual PGPR species present and account the sum of them as total PGPR content. Currently, only a few indirect methods are reported that enable PGPR quantitation in relevant food matrices (Mortensen et al., 2017; Su et al., 2021; Younes et al., 2022).…”