Food flavor enhancement, preservation, and bio-functionality of ginger (Zingiber officinale): a review

ABSTRACT

Ginger (Zingiber officinale) is a spice widely used across the world due to its nutritional and bio-functional properties. This review presents the various uses of ginger for maintaining food quality and the roles of its bioactive compounds in human health. The key components of ginger for adding food value and its bio-functional properties include shogaols, zingerones and gingerols. Ginger facilitates the bioavailability of nutrients and imparts aroma and flavor to foods. It is a natural preservative that improves the organoleptic properties and creates the visual appeal of food. Ginger contains various bioactive phytochemicals such as flavonoids, phenolic acid, terpenes, lipids, organic acids, vitamins, and fiber. These compounds are responsible for the diverse biological activities of ginger, such as antioxidant properties, anti-inflammatory, antimicrobial, anticancer, neuroprotective, cardiovascular, respiratory protection, anti-obesity, antidiabetic, antinausea and antiemetic activities. Future studies should focus on investigating the effectiveness of using ginger in promoting human health through collaborative research activities of experts from different disciplines.

KEYWORDS:

• Bioactivity
• nutritional value
• ginger
• utilization
• human health

Introduction

Ginger (Zingiber officinale) belongs to the Zingiberaceae family and is native to East and South Asia. Worldwide, it consists of 53 genera and 1300 species, 80–90 of which are Zingibers. ^[1] Ginger cultivation dates back to around 3000 years ago and is associated with many integral parts of many well-known dishes of various cuisines.^[2] Ginger is produced in different agroclimatic conditions in many parts of the world. According to FAO’s 2016 statistics, the top 5 ginger producing countries were India (6.55 × 105 tons), China (4.51 × 105 tons), Nepal (2.76 × 105 tons), Indonesia (2.66 × 105 tons) and Thailand (1.61 × 105 tons).^[3] Agroclimatic conditions can affect nutrient content and bioactivity.^[4] Ginger has scientifically proven anti-inflammatory, antioxidant, immunomodulatory, and antimicrobial effects, and other beneficial properties. These perceived benefits drive its production increase worldwide and its consumer acceptance.^[5] Culinary uses of ginger focus on its food flavoring, coloring, and preservation properties. The bioactivity properties of ginger are employed mainly in medicinal and pharmaceutical applications, as well as in the inhibition of oxidation and food pathogenic microorganisms.

Ginger, as food enhancer and traditional medicine, have been used around the world since ancient times.^[6] Ginger imparts aroma and flavor to food products during processing for consumption. Its acceptance by consumers is increasing due to its potential to improve the taste of ready-to-eat foods. The health-promoting properties of ginger are due to the presence of gingerols, volatile oils, shogaols and high antioxidant compounds.^[7] Ginger is a popular single-rhizome flowering plant that is commonly used as a culinary and folk medicine.^[8] The versatile benefits of ginger known to the world today are due to the rapid development of fractionation and detection technology in the field of ginger research.

Ginger has various functional components such as shogaols, zingerones and gingerols that have different medicinal and nutritional functions.^[9] Ginger contains phytochemicals such as phenylpropanoids, terpenes, flavonoids, and anthocyanins, which makes it so versatile in terms of food value enhancement and medicine.^[10] Ginger’s bioactive compounds make it popular for use in foods, pharmaceuticals, and cosmetics. Its bioactive compounds such as gingerol, paradol, shogaols, zingerone, cerumbone, terpenoids, flavonoids and phenols are used to reduce free radicals.^[11] Various types of studies on the antioxidant properties and bioactivities of ginger have been conducted.^[9] Due to its aroma, and flavor potential, ginger is also consumed in the food, beverage, and confectionery industries worldwide. Ginger is an ingredient in products such as jam, pickles, chutney, ginger beer, ginger wine, liqueurs, and other baked goods.^[12]

In Ethiopian, ginger is commonly used as an essential ingredient in main dishes, as a spice and in traditional medicines. Ginger is added as a spice in spicy dishes such as shiro stew, a spicy hot red pepper known locally as berbere, spiced chili pastes, ginger tea, and in food processing with other spices and herbs.^[13] The use of ginger makes Ethiopian cuisine popular in other countries due to its added flavor.^[14] Ginger facilitates the bioavailability of nutrients and imparts flavor and aroma. Natural food preservatives stimulate appetite and create visual appeal for consumers.^[15] Biologically, active compounds in ginger can be used to make nutrients easily accessible. Thus, it improves food value biologically with various medicinal benefits.^[16] Ginger is used during the development of new food products to improve the products’ organoleptic properties and to facilitate the absorption of nutrients.

Ginger is one of the most popular and valued spices and it is well known in human communities worldwide for enhancing food value.^[17] Ginger’s enhancement of the value of food products that use it as an ingredient makes it a very exciting and economically important crop for farmers, consumers, and stakeholders. Nowadays consumers are demanding the use of foods enriched with naturally occurring spices such as ginger, to replace synthetic preservatives with some health concerns. Although the use of ginger in fresh, dried, or extracted form increases food value by supporting recommended intakes of nutrients and encouraging new food product selection, the technological applications of using ginger for nutritional and biological benefits are rare in most ginger-growing regions.

More and more communities are using ginger in appetizers from easily accessible home gardens. According to the Transparency Market Research report, ginger is among the vegetable raw materials with significant economic value.^[18] However, the biological application and use of ginger in the food industry, medicine, cosmetics, perfumery, and dietary supplements needs further investigation, especially in ginger-producing countries. The data published so far on the increase in value of ginger are insufficient. The evaluation of food quality, efficacy and safety based on ginger supplements and use in traditional medicines also needs further investigation. Ginger has known bioactive compounds such as gingerol, paradol, shogaol and zingerone, and may have antimicrobial properties with other biological activities. An antimicrobial potential against pathogens has been certified for the ethanolic ginger extract.^[19,20]

Therefore, this review aimed to justify the use of ginger in food systems and its value in terms of bioactivity potentials while enhancing food value and health benefits. It is possible to predict the future of ginger-fortified novel foods and medicines through further research. Additionally, the use of ginger to add food value is limited to research and review papers. This paper reviews over ten years of investigations on the use of ginger to improve food value and its biological activities. This review highlights the benefits of ginger’s bioactive compounds for food value improvement; and its biological activities in developing countries such as Ethiopia have not been extensively studied apart from some adaptation and agronomic data.^[21] Most reviews were conducted in secondary markets that did not pay attention to the nutritional and medicinal aspects of ginger. Evidence from several documents has shown that most uses of ginger are still medicinal and food-enhancing to a limited extent. Public awareness of the benefits of ginger-enriched food products and their health benefits is low; however, this review aims to close the gaps.

Enhancing nutritional value of Ginger

Around the world, numerous natural sources of nutritional enhancers, including ginger, have been shown to have beneficial effects on human health by preventing disease.^[22] There is an increasing consumer demand for healthy foods with no additives that can be filled by consuming flavorings such as ginger spice. Researchers are evaluating the protective effects of various natural resources and are looking for innovative insights.^[21] The demand for ginger in the food and pharmaceutical industries is constantly increasing.^[23] Ginger has essential oils and various identified bioactive compounds with active compounds associated with specific functional properties and the potential to increase food value.^[24] Ginger is a flavoring agent in soft drinks, baked goods, pickles, confectionery, and sauces.^[25] In addition to adding value to food, its essential oil also has preservative effects.

Food value enhancement and the bioactivity of different ginger cultivars can be influenced by agroclimatic conditions and cultivar types.^[26] Ginger production can be improved through better cultivation. Therefore, increasing the level of knowledge for the sustainable production and use of ginger to fortify food and its medicinal benefits, and the value-chain knowhow from production to processing is vital.^[27,28] Since the value-added and medicinal uses of ginger are important to a country’s foreign exchange earnings, its whole value-chain needs to be transformed. Agricultural plans need to go further than just promoting the selling of ginger products in local markets for local consumption.^[29] Ginger oil, oleoresin, ginger candy, ginger puree, ginger powder, ginger beer, and ginger paste are some of the value-added ginger products used in various food products.^[30,31]

Ginger is useful for culinary purposes and can sweeten soft drinks, puddings, apple pies, cakes, breads, and sweets.^[32] Ginger is also used in savory dishes such as soups, sauces, stews, savory puddings, grilled dishes, and roasts. It enhances the taste of the products.^[32] Ginger is a preferred spice for fortifying foods during cooking due to its heat-resistant hypoglycemic component. Ginger effectively improves diet-related metabolic abnormalities with its medicinal benefits.^[33] It can be used in a form of fresh, green, powdered, semi-dry extracts, and essential oil. However, storage method may affect its different forms during use, since fresh ginger may suffer from weight loss, shrinkage, germination, and rot during storage for three to four weeks after harvest. Therefore, processing fresh ginger into value-added products can overcome product quality loses.^[30]

Ginger can be more convenient for flavoring food, product edibility, safety, and shelf life after it is processed. However, processing causes a significant change in its bioactivity.^[34] Ginger processing affects its bioactive compounds such as polyphenols, levels of carotene and dietary fiber.^[35] Essential oils and oleoresins from ginger are preferred as flavorings in the food industry because they are more stable, cleaner, free of contaminants and can be standardized by blending oils from different sources. Ginger essential oils are also used in the production of soft drinks, ginger beer, and in the preparation of high value food products. For example, ginger contains chemical food flavorings such as gingerol, eugenol, apiol, safranal, vanillin, piperine, beta-caryophyllene, -pinene, carvacrol, thymol, sabinene, cinnamaldehyde and others.^[36]

Ginger essential oil has a pleasant and spicy aroma with a penetrating and acrid taste due to the presence of antiseptic compounds. Ginger flavoring can be used in the production of gingerbread, confectionery, ginger ale, curry powders, certain curried meats, table sauces, in pickles, drinks such as liqueurs, ginger cocktails and carbonated drinks.^[37] Food processors use ginger to osmotically process appetizer flakes by blanching lime juice, dipping in 70% sugar syrup for four hours, and rolling flakes in a 2.0% appetizing mix. Nowadays, novel ginger products such as ginger bars, appetizer flakes, essential oils, paste, starch, ginger candy, salted ginger, and crystallized ginger are being produced.^[38] Ginger has aromas, which yield phenylpropanoids, monoterpenes, and other phenolic chemicals. Its volatile oils, zingiber, zingiberene, phellandrene, and linalool, produce improved new food products.^[39] Table 1 shows a summary of food value improvement using ginger and its mechanisms with reference to previous studies. The value-added properties and potential of ginger foods to add aroma, flavor, and color to processed foods containing appetizing spices are presented.

Table 1. Mechanisms for increasing the food value of ginger.

Value-added food	Mechanism	Reference
Appetizing main courses. Facilitates the digestion of many foods.	Imparts food value by concentrating (1.0–1.25%) sensory attributes. It makes main courses tastier and improves digestion by providing access to bio-accessibility and bioavailability of nutrients.	^[Citation40] ^[Citation13]
Flavoring gives flavor and aroma to foods. Improvement in texture.	Products like tea, soft drinks and local drinks can be flavored by including ginger as an ingredient. It can be mixed in spices used in Ethiopian cuisine when preparing berbere. Adds flavor and spiciness to foods as well as attractive color, and increases consumer acceptance.	^[Citation41] ^[Citation42] ^[Citation43]
Increases shelf life due to its terpenoids, flavonoids and phenolic compounds.	Inhibits cyclooxygenase and lipoxygenase, enzymes involved in the prostaglandin and leukotriene biosynthetic pathway. Reduces lipid oxidation by preventing food spoilage and microbial deterioration.	^[Citation41] ^[Citation44]
Processed food flavor and generation of spicy feeling.	Stew processed by adding ginger gives a good taste in the mouth while eating. It is one of the main ingredients in Ethiopian cuisine to flavor the stew and similar products.	^[Citation45] ^[Citation40]
Its bioactive compounds confer nutritional value and nutraceuticals.	Enriches food products such as spices with beneficial nutrients and health potential. Improves nutritional value and medicinal functionality.	^[Citation46] ^[Citation47]
Maintaining the quality of food products and increasing aesthetic acceptability.	Used to preserve the original properties of the product without deteriorating during processing techniques. During the storage of perishable products such as vegetable and meat dishes, ginger keep the product quality due to its aromaticity.	^[Citation48] ^[Citation49]
Preserving processed products.	It can be added to jams, cakes, syrups, sweets (crystallized ginger) and confectionery during food processing. Used for preserving foods used for domestic culinary purposes while processing confectionery, pickles, and sauces.	^[Citation50] ^[Citation51]
Improving food products’ texture and organoleptic properties.	Ginger is used for texturizing and tenderizing products such as meat products in the meat industry. Mixed with food additives, it improves the organoleptic properties.	^[Citation52] ^[Citation53]
Essential oil flavor properties.	Used to add flavor and aroma to baked goods and to preserve seasonings in confectionery, pickles, sauces and meals.	^[Citation54]
Condiments and appetizers are the main dishes during processing of puddings, grills, etc.	Used to mask the bad taste of some foods, preserving color, and adding aroma and flavor. Used for culinary purposes, dishes such as beverages, puddings, apple pie, cakes, breads, and sweets, as well as savory foods such as soups, sauces, and stews.	^[Citation55] ^[Citation56]
Ginger oleoresins is used.	Its composition, such as proteins, lipids, carbohydrates, vitamins and minerals, gives characteristic nutrients.	^[Citation57]
Processing of food products enhances the growth of the food industry.	Improving the food value chain by linking the value of food producers to consumers from the basic level of food production to processed food through agricultural products.	^[Citation58,Citation59]
In nutraceuticals and functional foods.	Enhancing organoleptic properties in the kitchen for their potential health benefits, stimulates appetite and creating visual stimuli for food. By having pharmacological and medicinal properties in addition to their sensory properties.	^[Citation13,Citation59]

Ginger increases the value of food by preventing spoilage and increasing product shelf life. In addition to maintaining food quality through preservation, ginger provides benefit by texturing and imparting organoleptic properties to products during food processing. Ginger has natural coloring properties and is used as an alternative to synthetic colorings. Ginger is one of the most common spices related to a specific flavor bestowed for culinary purposes worldwide. Ginger brings flavor to each food style and culinary identity of different countries.^[59] Therefore, ginger is used to add value to food products to meet consumer’s demand.

Ginger has unique benefits in adding value to food, ranging from main course preparation at home to the food industry level.^[60] In addition, ginger is used in food preservation techniques because food preservatives retard or inhibit lipid oxidation. Ginger inhibits oxidation reactions and can improve food quality during processing and preservation (Table 1).^[61] Currently, artificial antioxidants such as butylated hydroxytoluene (BHT) and butylated hydroxyanisole (BHA) are widely used in various food industries to prevent food spoilage.^[62] However, ginger can replace these chemical preservatives during food preservation for consumers who prefer natural preservatives. Synthetic preservatives such as nitrates, benzoates, sulfites, sorbates BHA and BHT could pose risks for consumers in large quantities.^[62]

Ginger in maintaining food quality

Most foods are perishable due to nutrient composition, unsaturated lipids, and water content. Ginger can be added as an ingredient during food processing and preservation to maintain food quality.^[63] Furthermore, the uptake of oxygen in food production during industrial food processing contributes to an increase in lipid oxidation and microbial load.^[1] These problems can be solved by using ginger as an alternative preservative during food processing and preservation, which has the potential to minimize food spoilage and to eliminate shelf life reducing factors.^[40] Ginger’s antioxidant potential, and phenolic and flavonoid ingredients are safe and are used more frequently than other similar food grade products.^[64]

Several research directions are emerging, with many focused on extracting natural antioxidants that add quality to food products to replace synthetic additives.^[65] Ginger is preferred to synthetic additives because it imparts a pleasing taste and color.^[66] The benefits of ginger in maintaining food quality are imparting sensory properties (taste, smell, texture, and appearance), nutritional profile and other attributes related to product acceptance. Changes in color, appearance, nutritional content, and microbial count often affect food quality and consumer acceptance.^[67]

Currently, preserving the quality of processed foods using naturally occurring spices and herbs is receiving more attention by consumers than using chemical and synthetic food preservatives. Therefore, using ginger and similar spices has the potential to preserve food quality and convey medicinal benefits to consumers. Many researchers are working to reduce the negative effect of factors on food quality by using naturally occurring additives during food processing and preservation, particularly regarding concerns about carcinogenicity and teratogenicity due to the residual toxicity of inorganic chemicals used in food preservation. Radiation technology used to protect food from pathogenic microorganisms also raises doubts about the possible side effects.^[68]

Currently, nutritional trends are changing around the world based on food availability and consumer demands. Therefore, approaches to food availability and utilization can affect diet quality and consumer health. Ginger may become a key player in improving the quality of commercially processed foods.^[69] Some studies have shown that inhibition of alpha-amylase, alpha-glycosidase, and lipase enzymes might occur during drying. After drying the volatile oil and fiber content, the level of pungency, aroma and taste should be evaluated to give quality assurance of the dried ginger. To improve the status of ginger production and processing, paying more attention is needed to product diversification and market expansion, as well as branding of the quality standards of the products. In many parts of the world, food is stored indoors for emergencies, even if the food has a limited shelf life. A little attention to basic processing steps such as cleaning, grading, and packing can create additional benefits in maintaining ginger quality in production.

During food processing and preservation, enzymatic browning reaction affects the shelf life of food and its eating quality. Storing perishable foods can inhibit natural aging and lead to discoloration. Therefore, natural or processed foods become inedible if they are not handled properly. However, storing foods with dried ginger or extracts used to extend shelf life can impact the quality of processed and preserved foods.^[70]

Processing ginger to maintain food quality

Ginger processing requires careful selection of rootstock and harvest time based on the nature of the products being processed. Factors such as the maturity of the rhizomes, processing methods, types of solvents used during extraction, and preservation methods have been influenced by the need to use ginger to maintain food quality. A combination of chemicals is used during ginger processing. The bioactive compounds in ginger, used to add flavor and color to foods, can be obtained during ginger processing. The essential oil and oleoresin contents in ginger extracts significantly affect food quality through their coloring, flavoring and preserving properties.^[71] The antioxidant activity of ginger was evaluated in vitro and showed better performance for dried ginger compared to fresh ginger. This fact is mainly related to the concentration of polyphenols which is higher in dried ginger, likely due to the temperatures applied during processing, which could convert gingerols into shogaols, resulting in an increase in antioxidant capacity.^[72] Food quality can be affected by microorganisms and during storage in different areas. Processing to limit or delay both biological and chemical spoilage of food can be done either synthetically or with natural preservatives. The antioxidant and antimicrobial properties of spices such as ginger can be harnessed to prevent natural deterioration. In natural and processed foods, the oxidation of unsaturated fatty acids, particularly polyunsaturated fatty acids (PUFA), produces unacceptable rancid flavors and odors and can produce harmful secondary oxidation products,^[73] by preventing the autoxidation of pigments, flavors, lipids, and vitamins.^[74] Ginger in food processing increases food safety and nutritional value by minimizing oxidation in which food is processed.

During food processing, food lipids, proteins, vitamins and pigments are prone to oxidative reactions unless quality-preserving ingredients are used. The antioxidants in naturally occurring spices can significantly prevent or inhibit lipid oxidation in food and inhibit autoxidation of pigments, flavors, proteins, and vitamins. They intervene both directly to trap Reactive Oxygen Species (ROS) and indirectly to inhibit their production. They can also scavenge free radicals and generate a new stable radical upon further oxidation through intermolecular hydrogen bonding.^[75]

Antioxidants help to maintain food quality by scavenging radicals or stopping the generation of autoxidation chain reaction. The hydroperoxide destroyers convert hydroperoxides into stable products, and metal chelators bind metal pro-oxidants and form stable compounds. The singlet oxygen quenchers remove oxygen singlets and enzymatic antioxidants. Primary antioxidants donate electrons or hydrogen atoms to the unpaired electron of the lipid free radical and convert it into a resonance stabilized radical. Antioxidants, ascorbic acid, and alpha-tocopherols have a synergistic effect in the photo-oxidation and autoxidation of lipids.^[76] Therefore, due to its antioxidant properties, ginger can be used to preserve vitamins in processed foods without altering its sensory properties.^[77] It is rich in natural antioxidants and is one of the most important polyphenolic compounds derived from the secondary metabolism of plants.

Ginger’s property of maintaining food quality is due to its bioactive compounds such as flavonoids, coumarins, lignins, xanthones, hydroxybenzoic acids and hydroxycinnamic acids.^[77] The carotenoid compounds in ginger are used both as antioxidants and as coloring agents. The most commonly used compounds in maintaining food quality are lycopene, lutein, and beta-carotene. The quality of foods such as meat, fish, fruits, grain products, pastries, dairy products and others can be maintained by using ginger as an ingredient.^[77] Ginger protects food from fungal contamination, toxic aflatoxin B1 (AFB1) and lipid peroxidation, as its essential oil contains terpinen-4-ol, which is a significant preservative encapsulated in chitosan nanoemulsion.^[78] Ginger’s bioactive encapsulated compounds can also be an excellent antifungal to extend food shelf life during preservation by maintaining food quality.

Chemical and nutritional composition of ginger

Ginger contains over 400 bioactive chemical compounds. Bioactive ginger compounds such as diarylheptanoids, gingerol analogues, phenylalkaloids, sulfonates, monoterpenoid glycosides, steroids and terpenes are found more frequently than others.^[79] The high levels of chemical components and nutrients in ginger are essential for many physiological and biochemical processes in the human body. Ginger’s chemical compounds show promise in relieving, treating, and preventing disease. In addition, ginger is rich in carbohydrates, lipids, terpenes and phenolic compounds. Due to its chemical composition, ginger has been used for brain disorders such as paralysis from ischemic stroke and as a nerve relaxant.^[80] There is clinical evidence that ginger has been used to treat diseases such as cancer, emesis, bone disease, metabolic disorders, and vascular disease.^[2]

Several chemical constituents in ginger provide pharmacological effects and health benefits through their bioactivity. Diarylheptanoids, sesquiterpenes, and phenolic compounds are the main bioactive components of ginger.^[81] Several studies have shown that gingerols and shogaols possess certain distinct health benefits and food value-enhancing properties.^[6,7,9] Due to its chemical composition, ginger is in greater demand from consumers and is grown sustainably in the food industry. The nutritionally superior ginger is essential for the development of novel food products and medicinal compounds. Ginger is used to increase food value in order to reduce unpleasant flavors when mixing and or using new products. The nutritional compositions of ginger have been used for their anticarcinogenic, antioxidant, antimicrobial, anti-inflammatory, antidiabetic, anti-fatty, anti-gastric ulcer and antiallergic effects.^[81]

The chemical and nutritional composition of ginger is associated with enriched nutrition and it has growth-promoting, immune-stimulating, and digestive properties, and can improve protein and lipid metabolism.^[82] It has antioxidant, antihyperglycemic, antiviral, antimicrobial, and antiparasitic properties.^[83] According to the Food and Drug Administration (FDA), ginger has a significant flavoring and nutritional function in whole, crushed, and ground foods.^[23] Most Ethiopians use ginger by combining it with garlic in their commonly used dishes at home and in restaurant-level food preparations. They are often used in small amounts as food additives to flavor or preserve foods and to stimulate appetite by increasing gastric juice flow and improving the taste of foods.^[84] Ginger is considered safe to use it as a herbal medicine with minimal and insignificant adverse effects on humans and livestock.^[85]

Ginger can inhibit certain types of cancer, degenerative diseases (arthritis, rheumatism, and Alzheimer’s disease), cardiovascular diseases (atherosclerosis and high blood pressure), vomiting and diabetes mellitus.^[86,87] Ginger has been reported to contain bioactive compounds with potent potential to combat a range of bacterial, viral, fungal, and parasitic diseases.^[88] Ginger is nutritionally rich in fiber, carbohydrates, fat, sugars, protein, gum, ash, and essential oils. Thus, it increases food value through its nutritional composition and its powerful antioxidant and antimicrobial properties.^[14] Because of its potential to impart flavors, aromas and visuals, ginger-infused foods can increase consumer acceptance. An inexpensive, environment friendly fiber has been extracted from ginger and used for transparent cellulose films. Ginger fiber from agricultural waste has antimicrobial activity that can be used for food packaging and food safety applications in addition to its nutritional benefits.^[89]

Mineral composition and their reactivity

The mineral composition of different varieties of ginger can vary depending on agronomic conditions, curing, drying methods, storage conditions and reactions.^[90] The presence of minerals in ginger with their various phytochemicals and vitamins benefits consumers from a nutritional, medicinal, pharmacological, and epidemiological point of view. Its use is beneficial for improving appetite and the palatability of food. Furthermore, it is used to facilitate nutrient absorption and enhanced flow of gastric enzymes.^[91] Ginger minerals reduce harmful microorganisms and oxidation during food preservation and processing. The minerals in ginger also contribute to the acid-base balance and the maintenance of body fluids, in the movement of gases between tissues.

Table 2 shows that the predominant elements found in ginger are potassium, phosphorus, magnesium and calcium, while iron, manganese, sodium and zinc are found in low concentrations. However, all of them are important and are required by the body for proper functioning.^[93] Potassium is used to synthesize protein, maintain fluid balance, nerve and muscle function, and for the uptake of glucose and glycogen. It is also used to maintain normal blood pressure. Calcium, together with phosphorus, is mainly responsible for the hardness of bones and teeth and is essential for all tissues during their reaction mechanisms. It plays a crucial role in blood clotting, nerve sensitivity and the body’s acid-base balance.^[93]

Table 2. Mineral composition of ginger.

Mineral	Ground ginger rhizome (mg/100 g)^[Citation45]	Raw ginger rhizome (mg/100 g)^[Citation45]	Dried ginger rhizome (mg/100 g)^[Citation92]
Calcium	114	16	16
Iron	19.8	0.6	60
Magnesium	214	43	43
Manganese	33.3	ND	229
Phosphorus	168	34	34
Potassium	1320	415	415
Sodium	27	13	13
Zinc	3.64	0.34	0.04

ND - Not detected

Calcium is important for bone health and aids in blood clotting, nerve transmission, and even the absorption of vitamin B12. Therefore, ginger is a significant source of both macro and micro elements, along with several vitamins such as thiamine, ascorbic acid, niacin and riboflavin. The chemical composition of various parts of ginger, such as the rhizome, leaves and flowers, varies depending on the variety of ginger, sowing method, agronomic conditions, curing, harvesting, drying and storage.

Ginger rhizome consists of valuable minerals for controlling many physiological processes and health disorders in the human body.^[37] Ginger facilitates nutrient absorption and the flow of gastric enzymes due to its mineral composition.^[94] The use of ginger in diet can inhibit osteoporosis, a condition characterized by brittle bones and increased susceptibility to fractures. Since osteoporosis can be caused by a lack of minerals, especially calcium, a mineral deficiency can cause many health problems, and this can be inhibited by regular intake of ginger. The mineral deficiency of copper causes anemia and disorders of the bones, nervous system, and cardiovascular system.^[95] Iron is necessary for hemoglobin, to carry oxygen through body tissues for internal respiration. Iron is an essential trace metal that plays numerous biochemical roles in the body, including oxygen-binding hemoglobin, and as a key catalytic center in cytochrome enzymes.^[96] Manganese aids in protein metabolism.

The reactive composition of minerals such as phosphorus, zinc and magnesium play a crucial role in cell structure and many biochemical reactions during energy metabolism. The minerals facilitate enzymatic reactions, nucleic acid binders of cell walls, and the breakdown of carbohydrates in various body tissues.^[97] Ginger has been used for food flavoring and its nutritional value through its chemical components. Ginger leaves have been reported to have a moisture content of 80%, followed by 12.3% carbohydrates, 2.4% fats, 2.3% proteins and 1.2% minerals.^[98] The organoleptic and preservative properties of ginger were more commonly used in the past than in modern times. However, recent studies on their medicinal and nutritional properties have opened new areas for nutraceuticals and functional foods.

Due to its nutritional value and mineral composition, ginger has a positive impact on the physical and chemical properties of baked goods. Therefore, the presence of minerals in ginger can promote the health of consumers.^[98] In addition to the changing lifestyle of consumers, the emergence and increase of diseases motivates research to focus on effective and healthy diets based on functional nutrients, such as functional foods. The exploitation of new bioactive compounds provides innovative areas where industries can produce products more economically using technically reliable processes. Food designers promote the nutritional, functional and sensory properties of food.^[99]

Bioactivities of ginger

Ginger has been used for centuries in traditional ailments to treat various diseases such as nausea, gastrointestinal diseases, respiratory diseases, atherosclerosis, migraines, stomach ulcers, cholesterol, and others.^[100] It has benefits in relieving pain, rheumatoid arthritis, and has anti-inflammatory and antioxidant effects. The main components of ginger, shogaole, paradole and gingerols, can provide benefits due to their bioactive properties during cooking and after consumption by improving the metabolic and digestive systems.^[101] Several phytochemicals from ginger have been studied for their bioactivity. The health-promoting potential of ginger depends on the concentrations and processing properties of gingerols, shogaols, phenylbutenoids, diarylheptanoids, flavonoids, diterpenoids and sesquiterpenoids.^[102,103] Ginger rhizomes have been administered with an infusion of brown sugar to relieve colds, and scrambled eggs with ginger powder have been taken as a home remedy for coughs.^[31]

Ginger essential oils are used as bioactive compounds and therapeutic agents in health practices. Therefore, it plays a crucial role in the development of scientific evidence for its potential pharmaceutical and food value enhancement.^[47,48] However, its value in home cooking, food value enhancement, food preservation, pharmacy, food processing, and antibiotics has rarely been emphasized. Ginger’s remedy for relieving motion sickness and morning sickness during pregnancy and reducing heart spasms has been studied for its bioactive potential.^[31]

The phenolic compounds of ginger: gingerols, shogaols, and paradols are responsible for the diverse bioactivities of ginger.^[98] Gingerols, shogaol, gingerols, ingenol, paradols, and zingerones are derived from bioactive compounds of ginger with nutraceutical and medicinal benefits. Of these, gingerol and shogaols consist of 6-, 8- and 10-structural analogs, and have the most pharmacologically active components.^[104,105] Because of its potential benefits, ginger is used as an anti-cancer, anti-diabetic, and antimicrobial antioxidant. Anti-neuro-inflammation, chemotherapy-induced nausea and vomiting alleviation have been reported.^[12,106,107] Ginger has shown a protective role against toxicity of drugs such as carbon tetrachloride.^[108]

The aqueous ginger extract could inhibit the intestinal absorption of dietary fat by inhibiting its hydrolysis. Ginger shows activity in liver enzymes by reducing fat absorption, and increasing beta-oxidation of fats and energy expenditure. Therefore, ginger could protect against cancer, atherosclerosis, heart disease, and several other diseases. Experiments with rats showed that ginger protects DNA from lipopolysaccharide-induced oxidative damage.^[104] Moreover, ginger has neuroprotective, gastroprotective, antiemetic, hepatoprotective, antiplatelet, and antihypertensive/cholesterol-lowering properties. Ginger consists of flavonoids, phenolic compounds, sulfur-containing compounds, tannins, alkaloids, phenolic diterpenes and vitamins as its bioactive components.^{[109,110,111]} Thus, ginger imparts flavor, aroma, texture, and color to foods as its primary function.

Ginger has been used to treat atherosclerosis, cancer, diabetes, obesity, inflammation, arthritis, immune deficiency, free radical effects, microbes, aging and mental health issues.^[43] The general health benefits and beneficial effects of bioactive compounds from ginger have potential for the human body and enhance cognition effects.^[49] The polyphenols in ginger are used in various foods for human health and can act as adjuncts in functional food processing. Inhibition of SARS-CoV2 spike protein binding ACE2 using naturally occurring bioactive compounds in ginger is a promising approach to prevent and treat COVID-19 infection.^[55,79].

Table 3 summarizes the bioactivity potentials of ginger and its mechanisms related to its potentials. In these studies, different parts of the ginger, mostly the rhizomes in fresh, dried, and cooked form, were incorporated into different bioactivities. Ginger has an anti-inflammatory, anti-diabetic effect and regulates blood sugar. As shown in Table 3, several authors reported the antimicrobial and antioxidant properties of ginger, as well as its potential to prevent obesity and regulate body weight when consumed in standard amounts on a regular basis.

Table 3. Ginger bioactivity potentials and their mechanisms.

Type of ginger part and form	Health benefit	Mechanism	Reference
Ginger rhizome in fresh or dried powder form.	Has anti-inflammatory effect, and relieves nausea.	By reducing or eliminating the symptoms of hyperemesis gravidarum. Use in patients undergoing laparoscopic cholecystectomy and during surgery to control nausea and vomiting by taking ginger slices. Reducing nausea symptoms in pregnancy, is an effective alternative for women who suffer from nausea and vomiting during pregnancy (NVP).	^[Citation112] ^[Citation113] ^[Citation114]
Infusion of ginger rhizomes.	Treats cold and flu, and relieves asthma.	By treating colds, colic, asthma, cough, palpitations, swelling, dyspepsia, loss of appetite and rheumatism.	^[Citation115]
Either fresh or dried ginger.	Reduces arthritis pain.	To treat Echinococcus granulosus infections and other inflammations in the body.	^[Citation115]
After ten weeks of consuming food products fortified with ginger.	Prevents obesity and body weight gain with regular consumption.	It reduces body weight without inhibiting pancreatic lipase levels by keeping the balance by lowering cholesterol and antihyperlipidemic agent. Influencing the bilirubin concentration with a positive effect on increasing the peroxisomal catalase level and HDL cholesterol. Progressive resistance training (PRT) protects against oxidative stress by counterbalancing obesity through individualized interventions.	^[Citation116] ^[Citation116] ^[Citation117]
Ginger in fresh or powdered form.	Prevents cancer.	Pharmacological effects in cancer treatment, through modulation of molecular mechanisms, inhibition of vascular endothelial growth factor (VEGF) and lipoxygenase.	^[Citation86]
Ginger rhizome powder or fresh (Anthocyanins and Gingerols).	Improves cognition and brain function	Improves memory impairment after cerebral ischemia by improving oxidative stress. The aging process in humans causes an improvement in memory and learning.	^[Citation118] ^[Citation40]
Heated raw ginger.	Relieves muscle pain.	Using raw and heat-treated ginger by 25% and 23% for its anti-inflammatory properties.	^[Citation43]
Boiled fresh or dried in water.	Prevents menstrual cramps	By influence on exert abortive and prophylactic effects in migraine headache without any side effects and anti-ulcerogenic.	^[Citation1]
Ginger in dietary supplement form.	Promotes heart health and treats cardiovascular diseases.	Treatment of hyperemesis gravidarum due the inherent heterogeneity by non-pharmacological option. By preventing hypercholesterolemia in rats fed a high-cholesterol diet through mechanisms of folliculogenesis and implantation.	^[Citation118] ^[Citation119]
Ginger with fixed concentrations of phenolic compounds.	Is used as antioxidants and antihydatic agents.	Protective effects against ferrous sulfate-induced liver and kidney toxicity by reducing lipid peroxidation and chelating iron. Used as an antihydatid effect in vitro, their product protects against host cell death by reducing high levels of nitric oxide (NO). It eliminates disorders caused by oxidative and neuroprotective effects such as analgesic effects.	^[Citation120] ^[Citation121] ^[Citation122]
Essential oil forms of ginger.	Prevents skin infections and detoxifies the body.	Through anti-skin tumor-promoting effects, through inhibition of cellular, biochemical and molecular changes caused by tumor promoters using chemoprotective mechanisms.	^[Citation123]
Ginger, as spice ingredient, and ginger rhizome extract.	Prevents stomach and liver ulcers, and aids in proper digestion.	Improvement of diet-related metabolic abnormalities due to its potential effectiveness on metabolic syndrome related to stomach and liver. Significantly inhibited gastric damage and showed significant anti-ulcerogenic activity in a promising gastro-protective agent.	^[Citation124] ^[Citation125]
Dried ginger powder in a dose of (1g/day).	Has an anti-inflammatory effect.	By activating P53 and inhibiting interleukin, Bcl2 and surviving, cyclooxygenase, IFN-γ. Suppression of TNF & NF-kB and activation of the G0/G1 phase reduce inflammatory markers in patients with knee osteoarthritis and can therefore be recommended as a suitable adjunct for them.	^[Citation49] ^[Citation126,Citation127]
Ginger rhizomes dried powder.	Antidiabetics and regulates blood sugar.	Supplementation significantly lowers blood sugar and HbA1c levels and, when combined with diet and lifestyle measures, can be an effective intervention to treat type 2 diabetes mellitus.	^[Citation128,Citation129]
Cooked ginger extracts.	Has an antimicrobial effect.	When preparing food and against bacteria in the event of an active infection. For the treatment of various bacterial infections, they are used in colic and atonic dyspepsia. By stimulating and nourishing the affected body with set amounts of ginger extracts.	^[Citation130] ^[Citation131] ^[Citation132]

Ginger antioxidant properties

Ginger has long been used as a flavoring spice and for its antioxidant potential to treat arthritis, sore throat, indigestion, dementia, and fever.^[101,133] A study by Suman et al.^[134] found about 40 antioxidant compounds in ginger. Gingerol and shogaol in ginger have greater antioxidant potential than other bioactive components and can eliminate disorders caused by oxidative stress.^[135] Studies have shown that phenolic compounds and anthocyanins present, including gingerols, have many neuroprotective effects. Other antioxidant benefits of ginger are analgesic effects as well as enhancing memory and learning caused by the aging process.^[122]

The antioxidant activity of ginger can vary in its different parts (leaves, rhizomes, and flowers) with different potential during functional food development and other health effects.^[106] Ginger’s natural antioxidants delay autoxidation by inhibiting the formation of free radicals. It is used to scavenge free radicals, chelate metal ions, and as an oxygen scavenger. The antioxidant radical formed is stabilized by delocalizing the unpaired electron around the phenol ring to form a stable resonance hybrid.^[136] Due to its antioxidant properties, ginger has several health benefits that protect it from oxidative rancidity through its edible oils and fats. Akinyemi, Ademiluyi and Oboh^[119] evaluated the antioxidant properties of ginger using glycemic indices and carbohydrate hydrolyzing enzyme activities. The bioactive compounds in ginger with beneficial functions are vitamins C and E, carotenoids and phenolic compounds, flavonoids, tannins, and flavones.^[137]

Table 4 shows the antioxidant potential of ginger as a bioactive compound in general detected in in vitro and in vivo studies. The production of ROS in human body can be the cause of many diseases. Many synthetic and naturally occurring sources of antioxidants inhibit ROS in the human body. However, individual health conditions, lifestyle differences, and other dietary factors affect antioxidant bioavailability and accessibility. The bioactive compounds found in ginger are used to boost food value through its antioxidant properties.^[104] Due to its antioxidant property, ginger suppresses the oxidation process by increasing the number of natural antioxidant enzymes.

Table 4. Antioxidant properties of ginger and its mechanisms.

Ginger bioactive ingredient	Application area	Mechanism	Reference
6-shogaol (20 µM).	HCT-116 human colon cancer cells.	Increasing the intracellular GSH/GSSG ratio and decreasing ROS levels enhances the expression of genes involved in glutathione synthesis. Utilizes the catalytic subunit of glutamate cysteine ligase (GCLC) and the subunit of glutamate cysteine ligase (GCLM).	^[Citation87]
6-shogaol (100 mg/kg).	Wild-type and Nrf2−/− C57BL/6J mice.	Upregulation of MT1, HO-1 and GCL expression in its metabolite-activated Nrf2 via alkylation of cysteine residues the goblet-like ECH-associated protein 1.	^[Citation138]
Ginger oleoresin (100 µg/mL).	Human chondrocyte cells.	Decreases ROS levels by translocating Nrf2 to the nucleus and activating gene expression from HO-1. Uses NQO1 (nicotinamide adenine dinucleotide phosphate (NADPH) quinone dehydrogenase 1) mechanisms.	^[Citation139]
Ginger oleoresin (100 µg/mL).	Human cell stress is mediated by interleukin-1β (IL-1β).	Reduction in ROS production; Induction of nuclear factor erythroid 2-related factor 2 (Nrf2) translocation. Antioxidant activity to the nucleus through activation of HO-1 and NQO1 gene expression.	^[Citation52]
Phenylpropanoids (40 µg/mL).	BJ foreskin fibroblasts.	Increasing Nrf2 activity and GSTP1 levels and decreasing H2O2 and MDA levels.	^[Citation140]
6-gingerol-rich fraction (50 and 100 mg/kg).	Female Wistar rats.	Reducing H2O2 and MDA levels by increasing antioxidant enzyme activities and GSH levels increases antioxidant enzyme activity. Increase glutathione with oxidative damage from chlorpyrifos.	^[Citation141] ^[Citation142]
6-gingerol-rich fraction (100 mg/kg).	Male Wistar albino rats.	Reduce MDA levels and prevent depletion of catalase activity and GSH content.	^[Citation143]
Ginger extract (5 and 25 µg/mL).	C28I2 human chondrocyte cells.	Increase gene expression of antioxidant enzymes.	^[Citation2]
Ginger extract (200 & 400 µg/mL).	HT1080 human fibrosarcoma cells.	Reduction of ROS generation by H2O2-induced oxidative stress.	^[Citation144]
Ginger extract (78–313 µg/mL).	Rat-heart homogenates.	The ginger extract decreased levels of malondialdehyde (MDA), which was associated with lipid peroxidation.	^[Citation139]
Ginger polyphenols and flavonoids bio-active compounds.	Increases food value and bestows health while bringing happiness.	Ginger root imparts a yellow color to the food processing quality due to the phytochemicals.	^[Citation145]

As depicted in Figure 1, 6-Shogaol leads to translocation of Nrf2 into the nucleus and increases expression of Nrf2 target genes by modifying Keap1 and preventing Nrf2 from proteasomal degradation. Thus, the GSH level increases and the ROS level decreases. The use of ginger is receiving more attention due to its naturally occurring antioxidants and health benefits, ushering in a new era for consumers. Ginger is one of the natural spices which has high antioxidant activity. On this basis, consumer food acceptance is increased due to the bioavailability of essential antioxidants in food processing. Ginger imparts pungency and is also used to improve the organoleptic character of foods by imparting aroma and flavor and changing the appearance of food quality.^[52] Its antioxidant activity was evaluated in vitro by iron-reducing antioxidant potency (FRAP), 2,2-diphenyl-1-picrylhydrazyl (DPPH) and 2,20-azinobis-(3-ethylbenzothiazoline-6-sulfonic acid) (ABTS) -Methods.^[19,142]

Figure 1. Antioxidant mechanisms of ginger.^[146] Nrf2 - nuclear factor erythroid 2-related factor 2; Keap1 - Kelch like ECH-associated protein 1; NQO1 - nicotinamide adenine dinucleotide phosphate (NADPH) quinone dehydrogenase 1; HO-1 - heme oxygenase-1; GCLC - catalytic subunit of glutamate cysteine ligase; GCLM - glutamate cysteine ligase modifier subunit; Trx1 - thioredoxin 1; TrxR1 - thioredoxin reductase 1; AKR1B10 - member B10 of aldo-keto reductase family 1; FTL - Ferritin Light Chain; GGTLA4, -glutamyltransferase-like activity 4; ROS - reactive oxygen species; GSH - glutathione; ARE - Antioxidant Response Element.

Pungent ginger compounds include gingerols, shogaols, paradols, and zingerone, which have the potential to control oxidation problems. It inhibits the overproduction of free radicals such as ROS that cause many chronic diseases. Different antioxidant potentials have also been demonstrated in fresh, dried, fried, and carbonated ginger.^[147] Binti Anzian et al.^[148] emphasized the importance of the antioxidant effects of ginger from naturally occurring bioactive compounds for increasing food value.

Food spoilage microorganisms are the main challenges facing most developing countries. These microorganisms, which produce undesirable taste, texture and appearance of food can affect food value. Contaminated food is unfit for human consumption. Various measures must be taken to reduce or eliminate pathogenic bacteria in food. These measures also increase overall food quality, safety, and shelf life. The antimicrobial activity of ginger was tested against Staphylococcus aureus (SA), Bacillus subtilis (BC), Escherichia coli (EC), Pseudomonas aeruginosa (PA), and Candida albicans (CA) using an agar diffusion method.^[149] Ginger-inhibited foodborne pathogens such as S. aureus, E. coli, and Enterococcus species have also been reported.^[9] Ginger is rich in naturally occurring bioactive compounds and essential oils that suppress the growth of a variety of food spoilage microorganisms. The antimicrobial activity of ginger depends on its concentration and the type of microbial species.

Ginger possesses aromatic and volatile compounds that play an essential role in its antimicrobial properties. Its aromatic properties improve food value and food preservation more favorably than chemical and synthetic food preservatives.^[150] The potential of ginger for microbial inhibition depends on its substrate composition, processing conditions, and storage duration. Ginger stabilizes food from microbial deterioration by progressively slowing and suppressing microbial growth. In addition, it imparts a natural antimicrobial effect to food to prevent natural spoilage by inhibiting microbial growth.^[151] Ginger essential oils of different concentrations can inhibit gram positive and gram-negative bacteria, yeast, and mold. Microbial pathogens are major contributors to food spoilage, leading to foodborne illnesses and affecting its quality.^[9]

Ginger is used to make internationally commercialized products such as essential oil and oleoresin, which are used during food processing to inhibit bacteria and maintain food quality. These products possess the full organoleptic properties of ginger aroma, flavor, and pungency in addition to their antimicrobial activity. The significant antimicrobial activities of ginger essential oil and oleoresins have been mentioned in another study^[152]; and a 10% ethanolic extract showed antimicrobial potential against pathogens.^[153] Recently, many organic compounds, including polymers and biopolymers, have shown potential as antibacterial and antiviral agents to combat infections caused by harmful bacteria and viruses.^[154,155]

In vitro studies have shown that active components of ginger inhibit the proliferation of gastrointestinal bacteria, including Helicobacter pylori. A study found that the higher the concentration of the ginger extracts, the more antimicrobial properties red ginger extracts had and the larger the diameter of the obtained inhibition zones were for bacterial growth. Gingerol has been described as an active inhibitor of Mycobacterium avium and M. tuberculosis in vitro.^[143,156] Ginger has shown antimicrobial activity against E. coli, Salmonella typhi, and Bacillus subtilis, and its ethanolic extract showed the broadest zone of inhibition against Salmonella typhi.^[134] The microbiological property of ginger is one of the physical, chemical and nutritional bases for making it the standard.

The antimicrobial properties of ginger include controlling the mechanisms of release with a specific activity of bioactive chemicals within the resistance of microorganisms. Studies on antimicrobial systems should consider the chemical nature of packaged food, physical and mechanical properties of packaging materials, organoleptic properties, and potential toxicity of additives.^[16] A study on garlic, onion, and turmeric essential oil extracts showed that ginger effectively delays the production and growth of aflatoxin and could combat fungus.^[157] Ginger extracts inhibit various spore and non-spore forming bacteria by inhibiting the microbial load that affects the aesthetic value of food. It extends food shelf life through its antimicrobial, anti-browning, and antioxidant properties.^[158]

Ginger anti-diabetes activities

In recent years, the popularity of spices including ginger has increased in both developing and developed countries due to their health benefits. Most communities believe that natural remedies are more effective and have milder side effects than synthetic drugs to prevent or treat various diseases.^[159,160] As a result, they have wide acceptance in home-made foods, and in the food and pharmaceutical industries. It has been reported that 70–80% of the world’s population rely on the use of complementary and alternative traditional medicines made from spices and herbs (herbal medicine) for important primary health care concerns.^[5,161] Pharmacological and epidemiological studies have attributed various health benefits to ginger, due to its richness in phenolic compounds (gingerols, paradols and shogaols), terpenes, polysaccharides, lipids, organic acids, and crude fibers. One of ginger’s bioactive properties is anti-diabetic activity.^[134]

Aqueous rhizome extracts of ginger between 5 and 40 g/L are said to have anti-diabetic properties by inhibiting glucose diffusion and reducing glycation.^[6] A study by Akinyemi, Ademiluyi and Oboh^[119] also suggested that consumption of drinks formulated with 50% ginger, 10% pineapple, and 40% apple is useful for relieving high blood sugar and for preventing diabetes mellitus.

Ginger Anti-Inflammatory properties

The anti-inflammatory effects of ginger extracts can be detected using an immunohistochemical technique, and extracts have been shown to significantly reduce the expression of transcription factors NF (B) and inflammation marker TNF-. The anti-inflammatory potential of pure 6-shogaol and 6-gingerol on hepatoma cells investigated by Weng et al.^[162] showed that treatment of 13-acetate (PMA)-treated HepG2 and PMA-untreated Hep3B cells with 6-shogaol and 6-gingerol, phorbol 12-myristate, reduced the cell viability in a dose-dependent manner. Their migration and invasion of cells was reduced. After incubation with these compounds, both PMA-treated HepG2 cells and PMA-untreated Hep3B cells showed an increase of matrix metalloproteinase (MMP)-9 activity and the expression of Tissue Inhibitor Metalloproteinase protein (TIMP)-1.

Pure 6-shogaol and 6-gingerol were used to effectively inhibit invasion and metastasis of hepatocellular carcinoma through various molecular mechanisms. Inhibition of MAPK and PI3k/Akt signaling pathways and NF-B and STAT3 activities suppressed MMP-2/-9 and uPA expression and blocked angiogenesis.^[162] Naderi et al.^[163] stated that ginger powder supplementation of 1 g/day can reduce inflammatory effects.

Benefits in inhibiting coronavirus (COVID-19)

Infectious diseases that can be transmitted from person to person lead to significant morbidity and mortality worldwide.^[156] The recent coronavirus pandemic (SARS-CoV2 virus or COVID-19) is associated with a highly infectious viral pathogen and the emergence of new strains that are often resistant to current treatment, and the virus has been associated with a higher fatality rate than previous coronavirus infections.^[164] The death rate from respiratory syndrome associated with the 2002 coronavirus epidemic (MERS-CoV) in the Middle East was around 10%. In 2012, the severe acute respiratory syndrome coronavirus (SARS-CoV) emerged, with a mortality rate of 35%.^[156]

Complications from a COVID-19 infection can cause pneumonia, severe acute respiratory syndrome, kidney failure and even death in severe cases. People with weak immune systems and with certain conditions like diabetes, cardiovascular disease, kidney disease, asthma, lung disease etc. are more susceptible to complications. Therefore, a healthy physical immune system supports the host in treating and defending against some pathogenic diseases associated with COVID-19. Scientific reports mentioned that respiratory syndrome, fever, cough, fatigue, shortness of breath and dyspnea are common symptoms of COVID-19. Therefore, the use of ginger for the treatment of respiratory diseases is compatible with other measures.^[40]

Different varieties of ginger contain different bioactive compounds such as flavonoids, terpenoids, lignans, sulfides, polyphenols, carotenoids, coumarins, saponins, plant sterols, curcumins and phthalides. These phytochemicals may inhibit various viruses (including COVID-19) and prevent disease.^[165] Various COVID-19 protection measures have been aligned to promote public health, including regular hand washing, lockdown, social distancing measures and safe food practices.^[156] However, efficient preventive therapeutics against COVID-19 are urgently needed.

Ginger’s antiviral properties can be linked to immune-stimulating properties and its biologically active compounds against several health complications such as COVID-19. Recent studies have shown that ginger phenolic compounds such as 8-gingerol and 10-gingerol are significantly active against COVID-19.^[166] The potential inhibitory activity of ginger phytochemicals against SARS-Cov-2 have been assessed through their binding affinities. A study by Hemalatha et al.^[167] on 8-gingerol and 10-gingerol showed high Glidescores (5.88 and 5.72 kcal/mol, respectively) and therefore high binding affinities toward the studied receptor compared to hydroxychloroquine (5.47 kcal/mol) and other ginger components. The inhibitory potential of a methanolic ginger extract also showed antiviral activity against COVID-19 with IC₅₀ value of 0.034 g/ml.^[168]

Post-harvest handling of ginger

Ginger requires optimal processing methods, storage types and mechanisms for the domestic and the export markets. Due to its different active ingredients, ginger is considered a safe medicinal plant with few significant side effects.^[169] However, the traditional processing methods and storage pose challenges to ginger production and use. In processing, drying is the most widely used technique to preserve ginger, since fresh ginger contains a high-water content (80–95%) that can lead to microbial spoilage. Poor post-harvest handling and storage of fresh ginger results in reduced shelf life and significant post-harvest losses. These problems challenge ginger producers and processors in developing countries who may not have access to up-to-date methods.

Ginger needs lots of attention during drying to preserve the overall quality of the end product as well as the sensory and physico-chemical properties.^[76] Most ginger producers store ginger of different sizes in one place in traditional packaging and ship it to markets using inferior containers. Ginger transportation materials and storage containers are often not well ventilated, which can damage the rhizomes. For the domestic market, the use of plastic bags, nets, and wooden boxes that provide better protection is rare.

Throughout the world, the food value chain is linked to long-term interactions between human societies, our ancestral agroecological landscapes, and various trading systems. In developing countries like Ethiopia, small-scale ginger farmers face many challenges in using ginger to enhance food value or to derive a benefit from its bioactive components.^[170] Companies that carry out activities to increase the value of a product from primary ginger production through processing and marketing to the final product for consumers play a vital role. Processing ginger to the minimum microbial activity level is used to prevent degradation. It also facilitates the transportation of ginger-based food and provides the dried product regardless of the season.^[171] However, most developing countries use sun-air drying methods to dehydrate ginger and other crops, which can be nutritionally and biologically challenging. The long drying time of this technique (15 days and more) results in severe degradation of the color and nutritional quality of the final product.^[172]

Adequate processing is required to realize the full potential of ginger. However, some operations are very expensive in comparison to traditional processing. Based on some studies, improved processing methods can enhance its nutritional, antioxidant, physico-chemical, sensory and structural properties.^[135,173] Ginger that is not well processed can be exposed to biological and chemical contamination during the post-harvest period. This can result in the production of toxic substances such as aflatoxins.^[174]

Reduced access to appropriate processing, storage, and transport facilities are also influencing factors, often cited as challenges in developing countries.^[175] The use of ginger as a food additive must therefore begin with cultivation and processing using innovative practices and techniques. The lack of an organized market information service for the different players in the ginger farm-to-market can affect the whole value chain. The fewer channels for ginger products to enter the international market through market promotion and creation of market links are mostly controlled by the world’s largest producers and consumers of ginger.^[136] The use of ginger in food processing could be used for strengthening buyer-producer relationships. To do this in the food supply chain and to take greater advantage of its health benefits the process must start with small farmers, go through the processors and end with the consumers.

Conclusion

The use of natural products to add value to food and promote human health is receiving increasing attention from the scientific community and other sectors. Ginger has a long history as a flavoring ingredient in cuisines and natural remedies to promote human health. Ginger extracts have found applications from adding visual appeal to meals, stimulating appetite, adding flavor and texture to food, imparting distinct aroma and flavor during food processing, to extending food shelf life by preventing spoilage from microorganisms and inhibiting food pathogens. Monoterpenoid hydrocarbons, sesquiterpene volatile components, gingerols, shogaols, paradols and zingerone are bioactive compounds that have been identified in ginger. These bioactive components of ginger exhibit various therapeutic properties including anti-inflammatory, antimicrobial, anti-cancer, neuroprotective, cardiovascular, respiratory, anti-diabetic, anti-obesity, anti-nausea and anti-emetic activities, among others. This evidence suggests that ginger is a good choice for the nutraceutical, functional food, and biopharmaceutical industries. It should be noted that results from previous studies reporting the benefits of ginger were conducted mainly in cell and animal models. However, human clinical studies demonstrating therapeutic effects in various chronic diseases are lacking. Therefore, there is a need for joint studies by researchers from different fields such as clinicians, chemists, nutritionists, epidemiologists, and other experts to further investigate the effectiveness of ginger in human health promotion and to obtain reliable information about the effectiveness of ginger.

Disclosure statement

No potential conflict of interest was reported by the authors.