Impact of Thermal Processing on the Selected Biological Activities of Ginger Rhizome—A Review

Ginger (Zingiber officinale Rosc.) is a spice, medicinal and cosmetic plant that has been
known for centuries. It can be used in dried, fresh, marinated or candied form, and is also an
essential ingredient in well-known curry blends. Ginger rhizomes are often freeze-dried as the
first step in the preparation of the raw material. Many studies have proved that the composition and
biological activity of ginger changes due to thermal processing. Therefore, the aim of the review was
to summarize the scientific results on the impact of traditional and unconventional methods of the
heat treatment of ginger rhizomes and their influence on the antioxidant and other selected biological
activities of the plant. The review of the available scientific data is inconclusive, and it is hard to state
unequivocally whether the thermal treatment of the raw material increases or decreases biological
activity. Based on the presented literature review, it can be concluded that traditional cooking and
microwave processing in general decrease the antioxidant activity of the ginger rhizome, whereas
frying, autoclaving, blanching or traditional drying in the sun mostly lead to a significant increase in
ginger activity. Interesting data were presented in the works describing the freeze-drying process
during which the antioxidant potential of ginger increased.