[Synthesis, characterization and application of polyglycerols and polyglycerol fatty acid esters]

Re-evaluation of polyglycerol esters of fatty acids (E 475) as a food additive

The EFSA Panel on Food Additives and Nutrient Sources added to Food (ANS) provides a scientific opinion re-evaluating the safety of polyglycerol esters of fatty acids (PEFA) (E 475) when used as a food additive. In 1978, the Scientific Committee on Food (SCF) endorsed an acceptable daily intake (ADI) of 25 mg/kg body weight (bw) per day previously established by the Joint FAO/WHO Expert Committee on Food Additives (JECFA). Absorption of intact PEFA in the gastrointestinal tract was extremely low. PEFA was rapidly and almost fully hydrolysed to polyglycerols and fatty acids in the gastrointestinal tract. The safety of polyglycerols and specific fatty acids has recently been assessed and no adverse effects were identified in the available studies. No adverse effects of PEFA at any dose have been observed in short-term, subchronic or chronic toxicity studies. A no observed adverse effect level (NOAEL) of 9,000 mg/kg bw per day was identified from subchronic studies and of 2,500 mg/kg bw per day from chronic studies, the highest doses tested. No genotoxic potential of PEFA was identified from the limited information available. The reproductive toxicity studies showed no adverse effects of PEFA but had major limitations. Clinical chemistry and urinalysis, from a clinical study with limited information, did not reveal any adverse effects in volunteers receiving up to 300 mg/kg bw per day for 3 weeks. The highest exposure to PEFA used as a food additive was 2.6 and 6.4 mg/kg bw per day in children at the mean and the 95th percentile, respectively, for the non-brand loyal scenario. Considering all the above, the Panel concluded that the food additive PEFA (E 475) was not of safety concern at the reported uses and use levels and that there was no need for a numerical ADI. The Panel recommended some modifications of the EU specifications for E 475.

Re-evaluation of polyglycerol polyricinoleate (E 476) as a food additive

The Panel on Food Additives and Nutrient Sources added to Food (ANS) provides a scientific opinion re-evaluating the safety of polyglycerol polyricinoleate (PGPR, E 476) used as a food additive. In 1978, the Scientific Committee for Food (SCF) established an acceptable daily intake (ADI) of 7.5 mg/kg body weight (bw) per day for PGPR. PGPR is hydrolysed in the gut resulting in the liberation of free polyglycerols, polyricinoleic acid and ricinoleic acid. Di- and triglycerol are absorbed and excreted unchanged in the urine; long-chain polyglycerols show lower absorption and are mainly excreted unchanged in faeces. Acute oral toxicity of PGPR is low, and short-term and subchronic studies indicate PGPR is tolerated at high doses without adverse effects. PGPR (E 476) is not of concern with regard to genotoxicity or carcinogenicity. The single reproductive toxicity study with PGPR was limited and was not an appropriate study for deriving a health-based guidance value. Human studies with PGPR demonstrated that there is no indication of significant adverse effect. The Panel considered a 2-year combined chronic toxicity/carcinogenicity study for determining a reference point and derived a no observed adverse effect level (NOAEL) for PGPR (E 476) of 2,500 mg/kg bw per day, the only dose tested. Therefore, the Panel concluded that the present data set give reason to revise the ADI of 7.5 mg/kg bw per day allocated by SCF to 25 mg/kg bw per day. Exposure estimates did not exceed the ADI of 25 mg/kg bw per day and a proposed extension of use would not result in an exposure exceeding this ADI. The Panel recommended modification of the EU specifications for PGPR (E 476).

Controlled doping by self-assembled dendrimer-like macromolecules

Doping via self-assembled macromolecules might offer a solution for developing single atom electronics by precisely placing individual dopants at arbitrary location to meet the requirement for circuit design. Here we synthesize dendrimer-like polyglycerol macromolecules with each carrying one phosphorus atom in the core. The macromolecules are immobilized by the coupling reagent onto silicon surfaces that are pre-modified with a monolayer of undecylenic acid. Nuclear magnetic resonance (NMR) and X-ray photoelectron spectroscopy (XPS) are employed to characterize the synthesized macromolecules and the modified silicon surfaces, respectively. After rapid thermal annealing, the phosphorus atoms carried by the macromolecules diffuse into the silicon substrate, forming dopants at a concentration of 1017 cm-3. Low-temperature Hall effect measurements reveal that the ionization process is rather complicated. Unlike the widely reported simple ionization of phosphorus dopants, nitrogen and carbon are also involved in the electronic activities in the monolayer doped silicon.

High Functionality Polyether Polyols Based on Polyglycerol

Polyglycerol (PGL) is a polyhydroxyl compound obtained by selfcondensation of glycerol in the presence of alkaline catalysts. It is a very attractive polyol as a starter for the synthesis of polyether polyols for rigid polyurethane foams. It is liquid, easy to handle and has a very high average functionality of 4—20 (or more) hydroxyl groups/mol. By propoxylation of PGL or PGL—sucrose mixtures, we obtained new polyether polyols with very high functionalities, which are very difficult or impossible to obtain by other methods. A new technology for PGL-based polyether polyols preparation was investigated. In the first step the self-polycondensation of glycerol to PGL in the presence of potassium hydroxide or potassium methoxide as a catalyst was carried out. In the second step, the crude alkaline PGL was alkoxylated with PO without removing the catalyst, followed by purification of the resulting polyether polyols. Rigid polyurethane foams prepared from the synthesized PGL-based polyether polyols and crude MDI displayed good physical and mechanical properties, excellent dimensional stability, and low friability.

Combined liquid and gas chromatographic characterisation of polyglycerol fatty acid esters

In the present study a combined liquid and gas chromatographic technique is described for the analysis of polyglycerol fatty acid esters. Liquid chromatographic fractionation of samples resulted in pure standards of monoesters of di- and triglycerols and diesters of di- and triglycerols. Confirmation of their identity was achieved by LC-MS analysis. Moreover, a chromatographic identification of the mono- and diesters of cyclic diglycerol was proposed. From the isolation of pure esters and their gas chromatographic analysis, it was revealed that co-elution of several compounds occurred. Thus it was shown that prefractionation of the sample using a simplified liquid chromatographic separation, was necessary in order to characterise the esters correctly. In combination with some other chemical analyses, a complete profile of the chemical composition of polyglycerol fatty acid esters can be obtained.