Bio valorization and industrial applications of ginger waste: a review

ABSTRACT The rapid increase in agricultural waste is rising across the globe and is a big environmental challenge. The utilization of ginger waste as a valuable product is very limited. The up-cycling of ginger waste is an effective approach for valorization. Ginger waste contains many bio-active compounds. These bioactive compounds possess various functional and bio-active properties. The literature has indicated that ginger and its waste is a rich source of shogaol zingerone and gingerols, these bioactive components contribute to pungency and aroma characteristics These compounds have a wide range of antimicrobial, antioxidant, and anti-inflammatory properties. Furthermore, these have a key role in skin health and the digestive system. The current review consolidates the compositional, functional, medicinal, bioactive, and health-endorsing attributes of ginger waste. The use of ginger wastes for the development of various functional and nutraceutical products is also in the limelight of this paper.


Introduction
Ginger, also known as Zingiber officinale L., is a member of the Zingiberaceae family and is widely used in a variety of foods and medicines in both traditional Indian and Chinese medicine. [1]Ginger was first documented in Chinese herbals, and Greek doctors were also familiar with it between 40 and 90 AD (Anno Domini). [2]The majority of the world's ginger (Zingiber Officinale) is produced in India.In India, ginger is produced more than 275,000 million tons a year [3] Numerous studies have been conducted recently to fully comprehend the potential of this herb.Among other biologically active compounds found in ginger waste, gingerols, shogaols, and zingerone are primarily accountable for certain biological actions.The anticancer and antioxidant qualities of ginger waste are just a couple of the advantages it can provide. [4]Numerous studies have been conducted on the potential health benefits of ginger waste, including its potential anti-inflammatory and anti-cancer effects. [5]These studies have typically focused on nonvolatile constituents known as gingerols and shogaols.Other less significant substances, such as 6-paradol and zingerone, have recently displayed intriguing bioactivity profiles as well. [6]urthermore, it has recently been discovered that the main (and active) metabolites formed by the administration of 6-gingerol to numerous human cancer cell lines are 6-gingerols, the diols that were officially derived by the stereoselective reduction of 6-gingerol. [7]This is but one illustration of the various compounds that might be produced from leftover biomass from ginger.
The production of wasted ginger waste is large (by weight), especially in the companies that produce medicines or beverages. [8]Usually, this garbage is burned or disposed of in dumps, [9] or processed into ginger waste meal, a low-quality animal feed. [10]One of the alternate uses for ginger waste that has been mentioned is as an absorber for the treatment of waste water. [11]lobally, there is an increase in the utilization of ginger waste in industrial processes like oleoresin and essential oil extraction.There hasn't been much research done on the bioactive substances in agrifood waste that might still have medicinal potential.We are aware of very limited research on gingerollike compounds that can be recovered or processed chemically from the ginger residue. [12]ndoubtedly, the rare chemicals found in some ginger oils present a tremendous opportunity for valorizing ginger wastes as part of a partial biorefinery concept, it has been suggested that ginger waste could be used to extract residual ginger oils, which could then be converted into defibrillated celluloses through individual processing. [13]hen added to the diet of animals like rabbits and broilers, ginger waste meal is particularly beneficial.The performance of rabbits was unaffected when maize was completely replaced with GWM (ginger waste meal) in their diet. [14]This review's objectives are to examine recent developments in the extraction of essential oils from ginger waste, investigate the appropriate extraction methods, assess the viability of the techniques for industrial use, and evaluate the bioactive potential of the trash.Ginger waste oil is utilized in extraction, including soxhlet extraction, SC-CO 2 extraction, subcritical water extraction, and many more.The food industry uses the extracted oil extensively. [15]inger waste also gives an incredible possibility for valorization because of some of the special chemicals found in ginger oils.High-value oleoresins found in ginger extractives have special antiinflammatory, antibacterial, antioxidant, and anticoagulant activities. [16]nger waste: background The term "ginger waste," which describes the waste created during the processing of ginger, has also gained popularity recently.According to research, ginger waste has the potential to be a source of bioactive substances, such as essential oils and phenolic compounds with antimicrobial as well as antioxidant properties.Moreover, ginger waste can be used as a source of biogas, soil conditioner, and animal feed. [17]Peel from ginger (Zingiber officinale), a by-product of processing ginger, is frequently thrown away as waste.Yet, the ginger peel has several physicochemical qualities that can be used in food, medicine, and cosmetics, among other things.People squander ginger peel in a variety of ways (including the food industry and household cooking), which causes environmental pollution by releasing greenhouse gases. [18]Methane is the main greenhouse gas produced from biowaste.It is released when organic waste decomposes in landfills.Many scientific investigations have shown that ginger peels include a variety of active compounds that give ginger its anti-inflammatory, anti-cancer, anti-inflammatory, spasmolytic, and diuretic qualities.These possible health advantages are mostly attributable to the accumulation of specific polyphenols (such as flavonoid, phenolic acids, terpenoids, and others) and their derivatives. [1]

Compositional analysis
Ginger peel contains various bioactive compounds, such as phenolic acids, flavonoids, and terpenoids.These compounds exhibit phytochemical properties. [19]Ginger peel is a rich source of dietary fiber, minerals, and vitamins.It contains high levels of calcium, iron, potassium, magnesium, and vitamin C. [20] The ginger peel contains essential oil, which is rich in gingerols and shogaols.These compounds contribute to the characteristic aroma and flavor of ginger and exhibit antioxidant and anti-inflammatory activities. [21]Ginger peel has a high water-holding capacity, which makes it suitable for use as a thickening agent in food formulations."Gingerwaste" can also include the ginger peel, stems, and leaves in an industrial processing context, depending on where the ginger is sourced.Ginger stems and leaves (GSL) are composed of proteins and complex carbs like hemicellulose and lignin but are often trash with negligible industrial importance illustrates the components of the ginger waste produced at the farm (stem and leaves) and during enhanced processing.For this reason, the extraction of oleoresin [22] Ginger peel has a yellowish-brown color and a fibrous texture, which can be utilized in food formulations to enhance the color and texture of the final product.
The nutritional contents of spent ginger waste and meal is discussed in the above Table 1.Spent ginger waste (SGW) is the primary material by-product of the ginger oleoresin business.Spent ginger waste is derived from the subsequent extraction of ginger oleoresin at a rate of about 90%.SGW consists of macronutrients, free sugars, surplus volatile oils, and oleoresins. [9]he outer skin, or peel, of ginger, is frequently discarded or used sparingly.Yet, new research has indicated that ginger peel includes several minerals and bioactive substances that may be healthy.Based on the available references, the nutritional makeup of ginger peel is listed below.
• Macronutrients: Carbohydrates, dietary fiber, protein, and fat are all present in ginger peel.The variety of ginger used and the manner of preparation, the precise amounts may change.
According to one study, dried ginger peel, for instance, has about 63% carbs, 12% protein, and 2% fat. [24] Bioactive Compounds: The peel of ginger includes several bioactive substances, such as zingerone, shogaols, and gingerols.The anti-inflammatory, antioxidant, and antibacterial effects of these substances have been demonstrated. [25]e ginger peel contains a variety of phytochemicals, including zingerone, gingerols, shogaols, and other oil components. [15]Owing to their ability to fight inflammation and free radicals, zingerone is significant therapeutically.Zingerones are a prominent component of ginger and are formed during its heat breakdown.Its medicinal value is attributed to the active ingredients gingerol, shogals, and zingerone. [26]Its pharmacodynamic characteristics [27] are varied including anti-oxidant, [28] antiinflammatory, [29] anti-cancer, [30] antimicrobial activities. [9]and anti-diabetic of zingerone have gained importance in recent studies.In particular, it contains antioxidant qualities and activity to lower hydrogen peroxide and super-oxide radicals. [31]Given that zingerone is generally safe and harmless, we anticipated that it would enhance kidney functioning.The sensory and organoleptic qualities of ginger peel are greatly influenced by gingerols and shogaol derivatives.It necessitates taking into account the volatile chemicals found in ginger.In this study, 98 samples of dried ginger peel were analyzed using high-performance liquid chromatography (HPLC) to measure the amounts of phytochemicals.With varied heat treatments, the gingeroldehydration reaction may be employed to modify the gingerol and shogaol contents of ginger.His work ended with a significant degree of diversity in gingerol.Only poorly connected with the concentration of 6-shogaol was the 6-gingerol content, which was substantially correlated with the 8-gingerol content and moderately correlated with the 6-gingerol content.Since the level of change in 6-shogaol concentration was lower than that seen in gingerol content, it was hypothesized that this observation may be explained by zeroth-order reaction kinetics occurring under mild dehydration conditions.For altering batches of ginger through blending procedures or different heat treatments, further knowledge of the gingerol shogaol is helpful.

Valorization of ginger peel
The Zingiberaceae family includes ginger (Zingiber officinale) which is primarily used in foods as spices rich in antioxidants. [21]Among the phenolic components of ginger, 6-gingerol is the most abundant in the fresh and dried rhizome and has been associated with antioxidant, anti-inflammatory, anticancer, antidiabetic, and anti-obesity effects. [32]Unpeeled and peeled rhizomes have both had their antioxidant activity investigated in several studies, but none have examined the peels, which are often Agro-food waste.So, the aim of this research is on determining how well ginger peels function as antioxidants according to their phenolic characteristics.The recovery of the primary ginger waste components and their biotransformation to produce a small library of optically enhanced derivatives were studied here as a different valorization technique.A nearby farm's fermented ginger biomass still contained 30% of unmodified chemicals similar to gingerol. [5]

High-value compounds produced from the valorization of ginger waste
The extraction of substances from ginger waste has the potential to be highly valuable. [15],revealed the thermodynamic microwave-induced extraction of levoglucosan, 5-hydroxymethylfurfural (5-HMF), furfural, formic acid, acetic acid, and lactic acid from used industrial ginger waste.The production of small molecules grew as the temperature rose, but the yield of sugars (such as glucose and xylose) declined because of thermal degradation, which turned them into 5-HMF and furfural as the temperature rose. [15]

Diversity and availability of ginger waste
Ginger Cultivar Harvest time, processing technique, and geographical region effect the variety and availability of ginger trash.Ginger is predominantly grown in tropical and subtropical areas, with India, China, and Nepal being the top producer.Due to the enormous production of ginger waste and the strong demand for ginger goods, ginger is predominantly utilized as a spice and traditional medicine in these nations. [33]There are various phases in the processing of ginger, including cleaning, peeling, slicing, and drying.Peels and stems that are produced as byproducts during these processes are normally thrown away as garbage.The processing effectiveness and intended final product quality determine how much ginger waste is produced.For instance, Superior Ginger Goods such as whole ginger roots may produce less waste than inferior products like ginger powder or extract.The various processing technique affects the variety of ginger waste as well.For instance, the ginger plants rhizomes which are typically used as a spice contain distinct bioactive chemicals than the peels and stems. [22]

Bio active properties of ginger waste
Since ginger (Zingiber officinale) contains several bio-actives chemicals including polyphenols, flavonoids, vitamins, and carotene, it is frequently utilized and has health-promoting effects. [21]Numerous scientific studies have demonstrated the presence of a wide range of active chemicals in ginger peels which are responsible for the spice and anti, inflammatory, anti-cancer, spasmolytic, and diuretic properties.The buildup of particular polyphenols (such as flavonoids, phenolic acid, and terpenoids) and others and their derivative is largely responsible for these potential health benefits. [1]For its antiinflammatory, antioxidant, and digestive properties, ginger peel is frequently utilized.It includes benefits, nutrients, and bioactive substances with medical potential. [17]It can be applied for pharmacological or medicinal reasons Different peels are used to extract substances with antimicrobial, antioxidant, and anti-inflammatory properties. [34]This possibility will offer a different way to address the issues surrounding the use of antibiotics as a cost-effective and environmentally friendly method of minimizing pollution caused by the disposal of such agricultural waste. [35]

Antioxidant properties
Antioxidants included in ginger feces can protect the body from oxidative stress and lower the risk of developing chronic illnesses, including cancer, diabetes, and heart diseases, according to our research in the Journal of Food Science.When compared to the root, leaf, and stem of the ginger plant.Ginger peels exhibited the highest antioxidant activity.The study also discovered that ginger peels' antioxidant activity was comparable to that of the well-known antioxidant butylated hyrhydroxytolueneHT) and ascorbic acid. [36]

Anti-inflammatory
According to research ginger waste has anti-inflammatory properties that can lessen pain and inflammation brought on by ailments including arthritis and digestive issues.In a rat model of acute inflammation, a study in the Journal of Natural Medicine discovered that ginger leaf extract showed strong anti-inflammatory effects.DeSantis concluded that ginger leaf extract has utensils to function as a natural anti-inflammatory. [37]

Digestive health
Ginger waste includes digestive enzymes that can help with indigestion, bloating, and nausea symptoms.According to a study in the Journal of Agriculture and Food Chemistry, ginger stem extract contained a considerable amount of amylase, lipase, and protease activity.That is purposed using ginger stem extracts on a natural diuretic. [2,8]

Skin health
The ginger waste's anti-inflammatory and antioxidant characteristics might also be advantageous for skin health.In vitro, tests on human skin cells revealed anti-aging properties of ginger peel extract, according to a study's findings Ginger peel extract can be used as a natural component in skin care products that fight aging. [38]

Antimicrobial properties
Because Ginger nanofibers (GNF) was added to the biopolymer matrices, The 5% GNF Bionanocomposites showed effective bacterial eradication against Bacillus cereus, Escherichia coli, Staphylococcus aureus, and Salmonella Typhimurium. [39]Ginger exhibits strong antimicrobial properties, which have been demonstrated by testing the susceptibility of various bacterial and fungal strains by measuring the zone of inhibition. [40]E.coli 10 • S.auerus 12 • Proteus vulgaris 10 • Lactobacillus 11 • Saccharomyces cerevisiae 20 [41] These findings indicate that ginger waste may offer a variety of health advantages even though Research on its medicinal potential is still in its early stages.it's crucial to remember that additional research is required to completely comprehend the effects of ringer waste on human health and to identify the most efficient application for its medicinal use.

Food applications
To create oil, leftover ginger trash is used.Starch is available as waste from the commercial usage of ginger.The yield and composition of the ginger oils (as measured by GC-MS) from recovered industrial ginger waste was obtained using Soxhlet extraction techniques.The primary constituents in the used industrial ginger waste were discovered to be zingiberene, curcumin, bisabolene, 6-shogaol, and 6-gingerol.These are generally accepted as the primary components of commercial ginger oil. [42]he chemical phenol Ginger (Zingiber officinale) rhizomes are widely employed in the food, cosmetic, and pharmaceutical industries.The principal pharmacologically energetic component of ginger waste is 6-gingerol.In addition to showing potential applications as a natural antioxidant, preservative, and flavor enhancer, 6-gingerol has also shown a synergistic impact with other substances for preserving the quality and shelf-life of food products. [43]he main items made from spices are oleoresins and spice oils.Finding a method to use industrial waste for food purposes is desirable.Spices are a great source of dietary fiber, protein, vitamins, polyphenols, and key minerals including calcium, iron, magnesium, and zinc that are needed for many metabolic processes in the body.
Low in vitro starch digestibility (45%) and significant gelatinization properties were found in the starch extracted from ginger waste.To stabilize the texture of meals being prepared at high temperatures, the starch extracted from ginger spent may be used.Spent ginger contains a lot of carbohydrates, and Saccharomyces cerevisiae ferments those carbs to produce bioethanol. [9]s antibacterial and antifungal agents, natural oils and materials made from waste are preferable to metals and/or bactericides created from synthetic materials.The development of a bacterial-resistant ginger essential oil-composite palygorskite was described by Lei et al.These researchers discovered that adding 19% ginger essential oil to the GEO-PGS composite improved its thermal, chemical (acid and base), and antibacterial capabilities when compared to a palygorskite (PGS) alone composite.
The antifungal activities of chitosan-carboxymethyl cellulose films were enhanced by the addition of ginger essential oil.In comparison to films infused with cinnamon oil, ginger essential oils provided much better fungus control (Noshirvan et al., 2017).To create protective packaging materials with exceptional thermal durability, Chitosan, sodium carboxymethyl cellulose (CMC), and ginger essential oil have been incorporated in a microencapsulation technique. [44]

Miscellaneous applications
Ginger waste has been used to make porous supports for heterogeneous catalysts.By first carbonizing ginger straw (350°C, 60 min), and then sulfonating the resultant hydrochar (concentrated H2SO4, 105°C), Yu et al. produced a heterogeneous acid catalyst.When it came to esterifying oleic acid, the ginger straw-derived acid catalyst outperformed Amberlyst-15, achieving up to 93% conversion and lingering versatility.
Dangerous Patent Blue VF (PBVF) dye was extracted from an aqueous solution using ginger waste material (GWM) as an adsorbent.In batch adsorption studies, the effects of pH, contact time, dye concentration, adsorbent dose, and temperature were investigated.The maximum adsorption was shown to require the optimal pH of 2.
According to Ahmad and Kumar (2008), the current study used ginger waste material (GWM) as an adsorbent to remove Patent Blue VF in a batch technique.The yield of red ginger oil made from red ginger trash is high.According to [45] red ginger waste has the potential to be used as a raw material to make red ginger essential oil as an option to reduce the waste of red ginger waste.Ginger straw (GS) is a byproduct of ginger cultivation.Notably, there is a significant amount of ginger straw that is commonly discarded as waste in the field, which is harmful to the environment.Waste can potentially be used by using GS as a precursor to making carbons.There haven't been any reports that mention using GS's unique porous carbons as MB (methyl blue) adsorbents, as far as we know.

Conclusion
Ginger is a potential source of biologically active compounds that includes gingerols, shogaols, and zingerone are of prime importance.Ginger waste can be extracted, pyrolyzed, and processed using a hydrothermal microwave to produce bio-based compounds, minerals, and energy.The biologically active compounds are responsible for some biological processes these compounds have some properties like anti-bacterial, anti-oxidant, anti-microbial, etc. Bioactive components are being used in different foods for their value addition and also for pharmaceutical purposes to treat certain diseases.The ginger essential oil is extracted from the waste of industries and is utilized in bio-refinery strategies.The extracted natural oil from waste has much more antibacterial and anti-fungal properties.Moreover, the bioactive components from ginger waste have various food applications in the production of cosmetics and other synthetic products as well.

Disclosure statement
No potential conflict of interest was reported by the author(s).

Table 1 .
Nutritional profile of ginger waste.