This festive season of the year is for many the season for baking cookies and biscuits. Butter. Sugar. Flour. Mixer. Rolling Pin. Cookie Cutter. But then, we have to decide: parchment paper or silicone baking mat?
Many prefer the silicone baking mat due to its non-stick backing surface made of food-grade silicone and the fact that it is reusable ‒ unlike parchment paper, which is a single-use item.
Silicones or silicone rubbers belong to the class of cross-linked polymers. The backbone of any silicone is based on alternating silicon (Si) and oxygen (O) atoms. Two organic groups are bound to each Si atom and the most common silicone is polydimethylsiloxane (PDMS). Depending on their molecular structure and crosslinking density, they range in physical form from rigid to flexible. They have many great properties that make them suitable for a variety of technical applications, however, their excellent heat resistance of up to 260°C ‒ and some grades even above 300°C ‒ make them a great choice for baking molds, mats and spatulas.
However, are these silicon mats at all safe to use, many of our customers as well as the experts in the NETZSCH application laboratories are asking.
During vulcanization, cyclic and linear siloxane oligomers are common by-products. Therefore, it is useful to study if any of the processing aids or by-products are released during the baking process as well as to detect potentially hazardous outgassing during heating, e.g., release of plasticizers or toxic pyrolysis products, which may be transferred to the baked goods.
Thermal Analysis is suitable to determine product safety
Thermal analysis can be used to detect the release of substances during the baking process. By means of TGA-FT-IR analysis, it is possible to identify the type and temperature of release.
To answer this question, our TGA-FTIR specialists cut a silicone baking mat and silicone-coated parchment paper into pieces and put several pieces of each material into the crucible. The measurements were performed with a PERSEUS® TGA 209 F1 Libra® at a temperature of 230°C, typical for baking.
Table 1: Measurement conditions
|Sample mass||~ 130 mg (both samples)|
|Temperature program||RT-230 °C, held constant for 60 min|
|Heating rate||10 K/min|
Determining the mass loss of both samples
The silicone baking mat (green) loses 0.4 % of its mass during the heating cycle. The parchment paper (red), on the other hand, loses 5.1 % of its initial mass during heating and a further 4.3 % during isothermal treatment. In both cases, the mass loss is not completed after 60 min.
Analyzing the evolved gases of the silicone baking mat
The escaping gases are identified by means of Fourier Transform Infrared Spectrometer (FT-IR). In the case of the silicone mat (spectrum at 230°C in red), the release of CO2 (blue) and traces of the degradation products of silicone rubber (green) were found, which could also be oligomer by-products from production. More details about the individual components released could be provided by GC-MS coupling.
Analyzing the evolved gases of the parchment paper
Parchment paper only releases water, which occurs in the temperature range up to 150°C. Figure 3 shows the measured spectrum at 100°C in red in comparison with the database spectrum of water (blue).
The spectrum of parchment paper (red) at 230°C shows the release of CO (orange), CO2 (green) and small traces of methanol (black) and formic acid (blue). These decomposition products are presumably produced by the thermal decomposition of the paper. After the measurement, a brown discoloration of the paper can be observed.
Outgassing of water, CO and CO2 is harmless as they leave the oven in gaseous form. The amount of contained methanol and formic acid is likely very small. In addition, the silicone degradation products are probably also insignificant since they are harmless. Nevertheless, heating the silicone baking mat without baking goods before first use is certainly useful.
We here at NETZSCH Analyzing & Testing hope these insights will help you enjoy your freshly baked cookies even more this holiday season. We certainly do now!