An effect of peppermint herb (Mentha piperita L.) pressing on physico-chemical parameters of the resulting product

- The highest amount of essential oils was found in the herb fraction of 2.5-5 mm.
- Similar composition of essential oil was noted in loose and agglomerated herb.
- Herb compaction caused an increase in total polyphenols and ABTS content.
- Pressure agglomeration during storage prevents the loss of active compounds.

The aim of the study was to evaluate the effect of peppermint herb pressure agglomeration process on biologically active compounds' content, antioxidant activity, resulting product compaction, and color of the new form of mint tea infusions. The separated fractions of mint herb with particles dimensions of 0.5-2.5 mm and 2.5-5 mm were compacted at a pressure of 50, 100, 150, and 200 MPa. Agglomerate abrasion resistance, and essential oils' content were analyzed using hydrodistillation method in a Clevenger type apparatus. Chemical composition of the essential oils was determined using gas chromatography coupled to mass spectrometry (GC-MS). Also, the antioxidant activity was analyzed by determining the ability to neutralize the free radical 2,2′-azino-bis(3-ethylbenzothiazoline-6-sulphonic acid) (ABTS) with simultaneous measurement of phenolic compounds' content. The color of infusions obtained was analyzed using a spectrophotometer. All experiments were carried out either directly after agglomerate manufacturing or after 3 months of storage. The agglomerate prepared under a pressure of 50 MPa was characterized by the highest susceptibility to abrasion. Immediately after agglomerate formation, the highest amount of essential oils was found in herb fraction of 2.5-5 mm in an uncompressed state and agglomerate obtained using pressure of 50 MPa. After the storage period, higher loss of oils was found in the loose herb. There were no major differences in the chemical composition of essential oils derived from the herb subjected to pressure agglomeration process and loose. The major components in all samples were menthol and menthone. Herb compaction to the form the agglomerate caused an increase in the content of polyphenols and ABTS both immediately after preparation and after storage. The color of obtained infusions was red-yellow. Darker infusions were obtained from pressed herb.