Impact of Thermal Processing on the Composition of Secondary Metabolites of Ginger Rhizome—A Review

Abstract

Ginger (Zingiber officinale Rosc.) is both a commonly used spice, and an ingredient of various dietary supplements and medications. Its diverse applications result from the range of health benefits that this plant brings thanks to the presence of active compounds (secondary metabolites) in the matrix. Even if several studies underline a stronger pharmacological activity of fresh ginger rhizomes, the unprocessed plant is relatively rarely used. Ginger rhizomes are subjected to thermal processing, such as boiling, blanching, steam drying and others, at different temperature and time settings. Additionally, freeze-drying of the rhizomes is used as the first step in the preparation of raw material. It was proved that the composition of secondary metabolites of the Zingiber officinale rhizome changes upon the influence of temperature. Therefore, the aim of the review was to put together scientific results on the impact of traditional and unconventional methods of heat treatment on ginger rhizomes and to show the compositional differences that they induce in the plant matrix. Variations in the content and the transformation of some compounds into other metabolites will be also discussed, with particular attention paid to two major groups of secondary metabolites present in the plant, namely, phenolics and terpenes.

Impact of Thermal Processing on the Composition of Curcuma longa Rhizome

“…Plants from the Zingiberaceae family are highly valued for their properties and taste, and they are commonly used as spices and other food additives; therefore, many studies on the influence of thermal processing on the composition and activity of these products have been performed so far. However, the obtained results are very often inconclusive, both in terms of the observed changes in composition and activity [ 45 , 46 ]. Prathapan et al [ 37 ] investigated the effect of time (10–60 min) and temperature (60–100 °C) in the thermal treatment of a fresh turmeric rhizome on the content of curcuminoids, phenols (TPC) and the activity of polyphenol oxidase (PPO), i.e., an oxidizing enzyme responsible for the browning of plant tissues.…”

Postharvest Physiology and Handling of Guava Fruit

“…Microcosmically, HTs disrupt the functioning of several key enzymes, including ethylene-forming enzyme (EFE) (which coverts ACC to C 2 H 4 ), pectin methylesterase (PME), and polygalacturonase (PG) (which initiates the pectin degradation and softening). HT also influences protein synthesis, secondary metabolism, and antioxidant enzyme activity [ 59 , 60 , 61 , 62 ]. Finally, HT is bactericidal and insecticidal [ 63 ].…”

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

“…Among the most common methods of culinary processing, we can distinguish boiling in water, steaming, grilling, stewing, frying, drying, baking or stir-frying, described and characterized by the authors in their previous work [ 14 ]. Having in mind a multitude of processing techniques that can be used for the preparation of foods or herbs for consumption, the aim of the review is to set together the information on their impacts on the biological properties of ginger.…”

“…The presence of thermally unstable components from the group of terpenes and easily dehydrated phenolic components makes it important to study the effect of thermal treatment on their content, which was summarized in the authors’ previous work [ 14 ], but also on their biological properties.…”

“…However, in some studies, the antioxidant activity has increased, which may be due to changes in the intrinsic properties of the product matrix or to the destruction of the cellular wall and thus the increased penetration of the solvent during the extraction process. Changes in the biological activity of ginger as a result of thermal processes are a secondary process to the complicated changes in the composition of the raw material, which were extensively described and discussed in our previous review work [ 14 ]. It is difficult to say unequivocally whether the thermal treatment of the raw material increases or decreases biological activity.…”