What Are the Uses of Ginger Oil?

Ginger (Zingiber officinale Rosc.) is a herbaceous plant in the family Zingiberaceae, widely cultivated in many tropical and subtropical regions. The part used is the spicy rhizome. As a spice, ginger is widely used in Asian cooking and is also a common herb in traditional Chinese medicine. In addition, ginger is also the most important root spice in international trade today. By the beginning of the 20th century, China had not only become one of the world's leading producers of ginger, but also one of the major exporters. However, to this day, the main focus of ginger trade is still dried ginger, with an annual global trade volume of over 20,000 tons. With the advancement of food processing technology, ginger essential oil and ginger oleoresin, which are processed products extracted from ginger using modern processing techniques, are increasingly being valued by the food processing industry as high-quality, high-value trade products. This has led to in-depth research on ginger as a raw material and comprehensive development of the many useful ingredients it contains, such as the extraction of ginger protease from the processing by-products of ginger oil. This will open up unlimited prospects for the use of ginger resources.

1 The concept of ginger essential oil and oleoresins

Ginger essential oil and oleoresins are currently the two main deep-processed products of ginger. Both are trace amounts of concentrated, high-value substances extracted from ginger and are vegetable oils and fats. Ginger essential oil is the volatile oil obtained from the ginger rhizome by steam distillation. It contains almost no high-boiling components and has a strong aromatic scent. It is mainly used for flavoring and seasoning food and beverages, and is also a highly priced flavoring and medicinal ingredient in demand on the domestic and international markets. Ginger oleoresin is a viscous semi-fluid substance that is obtained by extracting the ginger rhizome with an organic solvent and then recovering the organic solvent. It contains both the volatile components of a small amount of essential oil and non-volatile fatty components that essential oil does not contain. Therefore, ginger oleoresin has an aromatic, spicy taste and contains all the flavor of ginger as a spice. The non-volatile components have a realistic effect on the aroma and act as a natural fixative for the volatile essential oil. Therefore, the high boiling point and non-volatility of ginger oleoresin make it particularly suitable for foods that require high-temperature processing. It is a high-quality seasoning and food ingredient.

2 Advantages of ginger essential oil and oleoresin

Essential oils and oleoresins have been used in the food industry abroad for 50 years. Initially there were only one or two products, but now there are more than 30 varieties, and in particular oleoresins have become one of the main ingredients in the food industry. They have all the aroma and flavour of the original spice, but also have advantages that traditional spices cannot match. Therefore, the application of oleoresins has developed rapidly and has great potential. Specifically, essential oils and oleoresins have many advantages over traditional spices.

2.1 Hygiene

Traditional spice raw materials and their powders are easily contaminated by microorganisms, especially moulds, which not only affects the quality of the spices but may also cause the product to spoil. Therefore, the sterilisation and disinfection of spice powders has become a major problem. However, essential oils and oleoresins obtained by extracting spices do not contain water (3%) and no live bacteria have been detected.

2.2 Economy

Most traditional spice ingredients are processed and ground for consumer use. The main ingredient is lignocellulose, and the essential oils and oleoresins that actually have a flavoring effect cannot be fully utilized. Oleoresins are extracted using an extraction process, in which the solvent can penetrate into the cells of the plant to obtain the complete flavor components. 100% of the flavor components can be utilized.

2.3 Stable and resistant to storage

Essential oils and oleoresins are more stable than spice raw materials, are small in size, have a low water activity and are easy to transport and store.

2.4 Quick, clean and easy to use

Compared to raw materials, it greatly simplifies HACCPs operating procedures and records, avoiding the inconvenience, cost and time involved in storing and using raw materials.

2.5 Uniformity of flavor

Essential oils and oleoresins do not exhibit different thresholds or irregular usage amounts due to the origin, variety, time, or storage of natural spices. Therefore, they are conducive to the standardization of seasoning components and quantification in use.

2.6 Versatile and highly malleable

Essential oils and oleoresins are instant and residue-free seasonings that can be used in all forms of cooking. They overcome the disadvantages of traditional spices in terms of uneven seasoning, insoluble particles and other factors that affect the sensory quality of the product.

In addition to the commonalities of the essential oils and resins of the above spices, ginger essential oil and oleoresin have both a flavoring effect and a health-promoting function because ginger is a medicinal plant and ginger extract contains its main medicinal ingredients, which exhibit good biological activity. In addition, experiments have shown that ginger oleoresin has strong antioxidant properties and preservative and antibacterial effects, so it is a good resource for the research and development of natural spice-based food antioxidants and natural antibacterial agents.

3 Research progress of ginger essential oil and ginger oil resin at home and abroad

3.1 Research progress of ginger essential oil

3.1.1 Components of ginger essential oil

More than 100 components have been found in ginger oil today, the main components being sesquiterpene hydrocarbons 50%-66%, oxidized sesquiterpenes 17%, and the rest mainly being monoterpene hydrocarbons and oxidized monoterpenes. Among the sesquiterpene hydrocarbons, α-gingerene is the main component (15% to 30%), followed by β-elemene (6% to 12%), ar-turmerone (5% to 19%), α-farnesene (3% to 10%), and β-phellandrene (7% to 10%). Except for nerolidol, the content of low-boiling monoterpenes is generally low, at about 2%. Among these, 1,8-cineole, linalool, citronellyl acetate, borneol, geranial and geraniol are the main aroma components of fresh ginger aroma.

3.1.2 Extraction of ginger essential oil and its physical and chemical properties

To date, the method of extracting volatile essential oils from ginger has been mainly steam distillation. The yield is 1.5% to 2.5%. This method is easy to operate and requires little investment, but the disadvantages are long distillation times and low oil yields. In recent years, new high-tech methods have been developed – supercritical fluid technology and short-path molecular distillation – which can efficiently separate and extract target components under mild conditions. The extraction of ginger essential oil is theoretically superior to traditional methods and is well worth trying in practice.

The ginger essential oil obtained by steam distillation is a transparent, light yellow to orange liquid that is a complex mixture. It has a refractive index of 1.4880-1.4940, a specific rotation of -45°, and a density of 0.871-0.882. The physical parameters of ginger essential oil obtained by steam distillation are roughly the same for ginger with different storage periods. However, some compounds in the ginger essential oil are chemically unstable. Therefore, ginger essential oil exposed to light and air for a long time will increase its viscosity, form non-volatile polymerized residues, and reduce its optical rotation. When the temperature exceeds 90 °C, the composition, odor, and flavor of ginger essential oil will undergo harmful changes.

3.1.3 Functional properties of ginger essential oil and its development and application potential

3.1.3.1 Cosmetics

Ginger essential oil has a strong, warm, spicy aroma with a slight lemon note and floral characteristics. The aroma components and their type of attribution are of reference value for the development and application of ginger essential oil in cosmetics. In fact, ginger essential oil is an ideal fragrance for cosmetics, especially men's perfumes.

3.1.3.2 Food

Ginger essential oil has a warm, spicy, pleasant aroma, and is not pungent. It is mainly used to flavor and season foods, beverages, non-alcoholic refreshing drinks and special sweet wines, and is a natural food flavoring.

3.1.3.3 Medicinal

Ginger essential oil has a long history of medicinal use. It can expel cold and dampness, dispel wind and relieve pain, warm the channels and collaterals, prevent and treat motion sickness in cars, boats, planes, etc., and has anti-aging effects. Recent studies have shown that the terpene compounds in ginger essential oil have protective effects on the gastric mucosa and anti-ulcer effects; ginger essential oil has an inhibitory effect on the central nervous system; ginger essential oil also has a good anti-inflammatory effect. Therefore, ginger essential oil has high medicinal value.

3.2 Research progress on gingerol and its products, ginger oleoresin

3.2.1 Components of gingerol

Seven main pungent components have been found in ginger: [6]-gingerol, [8]-gingerol, [10]-gingerol, [6]-shogaol, [8]-shogaol, [10]-shogaol and [6]-gingerone. It can be predicted that with the continuous invention of new and advanced analytical instruments, the analysis technology of gingerol will continue to improve, and the analysis of its components will become more accurate.

3.2.2 Extraction methods and physicochemical properties of gingerol

Gingerol is obtained by extracting ginger with a solvent. The yield, aroma, flavor and pungency of the product are related to the source of the ginger, the harvest period, the solvent and the extraction method. The extraction method is the most active factor. Currently, there are the following main methods for extracting ginger oleoresin:

a. Solvent extraction methods include direct solvent immersion and Soxhlet extraction. Among these, continuous Soxhlet extraction with ethanol can obtain the total oil content of ginger, and in terms of commercial quality, this method can obtain more ginger oleoresin than acetone;

b. The pressing method involves the direct treatment of washed ginger with mechanical means to obtain the ginger oleoresin. The amount of ginger oil obtained by this method is not only related to the quality of the ginger itself, but also to the pre-treatment of the ginger and the operating conditions of the pressing facility.

c. Liquid CO2 extraction and supercritical CO2 extraction. Among these, supercritical CO2 extraction is the most efficient, and its reaction conditions are mild, with no solvent residue and easy to control selectivity. The ginger oleoresin extracted by this method has a high-quality flavor and a subtle aromatic scent produced by light molecular essential oil components. In addition, this process has opened up new functional uses for ginger oleoresin in commercial applications, while its mild operating conditions make further downstream use of its waste corners possible.

Extracted ginger oleoresin is a dark amber to dark brown viscous liquid. It is almost insoluble in water and has low solubility in alcohol. It can produce a granular precipitate after standing. The EOA in the United States defines standard oleoresin as having a volatile oil content of 18 to 35 ml/100 g, a refractive index of 1.488 to 1.498 (20 °C), and optical rotation of -60 ° (20 °C). Ginger oleoresin: The gingerols in gingerols are chemically unstable and can easily lose water or undergo an aldol condensation reaction (Aldol) to form gingerone and corresponding aliphatic aldehydes when heated, treated with acids or alkalis. In addition, the gingerols content of ginger oleoresin will increase during storage.

3.2.3 Functional properties of ginger oleoresin and its potential for application development

3.2.3.1 As a seasoning

Ginger oleoresin contains all the aroma and flavour of ginger. It has a spicy, sweet smell, a pungent, warm taste and a stimulating effect. It can therefore be used as a high-quality concentrated seasoning to replace traditional spices in food processing and cooking. In particular, it contains the main flavor component of ginger, gingerol. The spiciness of the gingerol component is of great significance to the food industry.

3.2.3.2 Developing natural antioxidants

The gingerol in ginger oleoresin contains a guaiacol structure in the molecules of each component substance. It is a viscous liquid at room temperature, has strong antioxidant properties, and is an effective ·OH scavenger. Ginger is a medicinal plant with a long history of use in China. It is safe, reliable and effective, and conforms to consumer eating habits. Extracting substances with strong antioxidant activity from ginger that are highly effective, low in toxicity and economical is an important way to further develop natural, highly effective food antioxidants.

3.2.3.3 Developing natural antibacterial agents

There are examples to show that ginger extract (ginger oleoresin) exhibits strong antibacterial activity against Escherichia coli, brewer's yeast and penicillium, and its activity pH range is wide. Moreover, plant extracts derived from ginger are themselves food, and they combine multiple functions in one, so they can be added directly, serving multiple purposes with one dose, simplifying the processing and reducing production costs. This is of great practical value in today's situation of a shortage of natural preservatives.

3.2.3.4 Medicine and health products

Modern medicine has shown that ginger alcohol extract not only has a pressor and cardiotonic effect on laboratory animals, but also has a hypolipidemic and anti-atherosclerotic effect. Ginger acetone extract 1000mg/kg has an inhibition rate of 97.5% on gastric mucosal damage, and its active ingredient is zingerone. Ginger ether extract has obvious anti-inflammatory and analgesic effects. In addition, because of the better biological activity of ginger oleoresin, it can help prevent modern civilization diseases, making the added food applications “engineered foods” that play a role in human nutrition and health care. Therefore, there is much room for development in this field.

In summary, the comprehensive development, utilization and deep processing research of ginger in China is not only of economic significance, but also of academic significance. With the gradual commercialization of ginger essential oil and oleoresin as industrial raw materials, it will surely drive China's food seasonings and related food processing industries to reach the international level.