Stability of a Rhus coriaria L. tannin extract under different storage conditions

In the past year, vegetable tannin consumption has increased considerably. Having overcome the problems that sumac (Rhus coriaria L.) gave in the past, it is now possible to reintroduce it in tanneries. It would be convenient to present this extract as a liquid. In this work, we have studied by hide powder assay, UV-Vis spectrophotometry and HPLC-DAD the stability of liquid sumac extracts with different tannin contents and that were kept in different storage conditions. If no stabilizer is added, the higher the extract concentration the lower the loss of tanning activity. Low temperatures such as 4°C or -5°C help to maintain the sample's tanning properties for longer periods. Adding small quantities of a stabilizer (80 mg/L SO2) to different liquid extracts helps such samples to maintain their tanning capacity after storage for 9 months at 35°C, this behaviour is similar to the powder control sample.