Chemical, physical and sensory changes of herbal drugs after sturated steam decontamination
The novel saturated steam decontamination method called Lemgo process is based on a short steam treatment, followed by an extremely rapid evacuation of the treatment chamber. This results in the reduction of the bonding forces between the microorganisms and the surface and in a sudden evaporation of the condensate film on the herbal material, and therefore in a mechanical removal of the superficial microorganisms. 2 L of drugs were treated in a ploughshare stirrer for 20 s with saturated steam of 110 degrees C and 125 degrees C, respectively, followed by the evacuation of the stirrer. A double treatment, consisting of a twofold vaporization and evacuation, was examined as well. The process was able to reduce the total plate count and aerobic spore count of the five investigated herbal drugs Linum usitatissimum L. (linseed), Foeniculum vulgare Mill. (fennel), Origanum majorana L. (marjoram), Tropaeolum majus L. (nasturtium) and Allium cepa L. (onion) by up to 4 powers of magnitude, reaching the microbiological detection limit of 100 CFU/g. The steam and vacuum treatments of linseed caused neither a loss of its value-adding ingredient crude fat nor a change of colour. Furthermore, the swelling index and flavour of linseed, determined for assessing the quality, showed no significant changes. In the case of fennel, only 7% of the essential oil was lost, and the treated herbal material did not show remarkable differences in appearance. Marjoram was the only material with a high loss of ingredients (at least 86% of the essential oil). Glucotropaeoline and cysteine sulfoxide as value-added ingredients of nasturtium and onion are usually prone to fast enzymatic degradation. However, due to the decontamination treatment and probably the short heat treatment, there was only a loss of 16% glucotropaeoline and 18% cysteine sulfoxide. Changes in colour of nasturtium were moderate but onion suffers a noticeable embrowning.