Laboratory of the Research Group Food Metabolome Chemistry at the Leibniz Institute for Food Systems Biology at the Technical University of Munich. Credit: J. Krpelan / Leibniz Institute for Food Systems Biology at the Technical University of Munich
Solvent-assisted flavor evaporation (SAFE) is a well-established, standard procedure for isolating volatile compounds from food matrices, and is particularly important for the extraction of food aroma compounds, also known as odorants. While SAFE has been used in food labs for more than 20 years as a relatively easy and effective way to isolate aroma compounds, while limiting the loss of thermally labile odorants and generation of thermal artifacts, the manual procedure still involves the risk of contamination due to human error, and can show decreased yields of high-boiling point compounds, or when isolating from lipid-rich food extracts. A research team from the Leibniz Institute for Food Systems Biology (LSB) at the Technical University of Munich has recently developed a new automated SAFE method (aSAFE) that both increases yield and reduces contamination risk through the use of an electronically-controlled pneumatic valve.
The team found that the greatest drawbacks from working with the manual SAFE system came from the manual operation of the valve on the dropping funnel of the apparatus, according to LSB section and working group leader Martin Steinhaus. Not only did this aspect make the process labor-intensive, but the researchers suspected that yield may vary depending on the operator, the size of the extract portions introduced into the apparatus through the funnel, and the time span between the portions. Automating the function of the valve could allow for more consistent and optimized portion sizes and timing, and reduce the risk of human error in terms of both valve operation and introduction of contaminants. The team modified a conventional SAFE system to include a pneumatic valve connected to a corresponding electronic control unit with which they could set specific valve open and close times that the system would automatically follow. Additionally, the researchers added an automatic liquid nitrogen refill system and an endpoint detection and shutdown system to further automate the process.
The researchers tested the aSAFE system with both pre-prepared model mixtures and with beer and chocolate products purchased from a supermarket. They found that for odorants with boiling points between 120-220°C that were included in a nonfat model mixture, yields of about 100% were achieved for both the manual and automated methods. However, for aroma compounds with boiling points at or above 254°C, such as eugenol and methyl cinnamate, aSAFE consistently produced higher yields than the manual method. The automated method also achieved consistently higher yields of isolated odorants in low-fat and high-fat model mixtures, where overall yield was reduced for both methods due to the presence of lipids. Similar results were seen when both methods were used for non-fat beer and high-fat chocolate. This study was published in European Food Research and Technology.
Steinhaus said that the aSAFE method has completely replaced the manual version in his laboratory, and that other academic and industrial research groups have also shown interest in switching to the automated method. The authors noted that a fully automated system including automatic liquid nitrogen refill, endpoint detection and shutdown did not show significant differences in isolate quality from the version using only an automatic valve, and that labs can consider the costs and benefits of a partially versus fully automated system.