|Constituents ||Content/100g fresh weight|
|Energy (Cal)||38 - 76|
|Protein (g)||2.0 - 3.6|
|Fat (g)||0.1 - 0.6|
|Total Carbohydrate (g)||10.5 - 17.6|
|Total Sugar (g)||1.6 - 2.2|
|Inulin (g)||7 - 30|
|Other (g)||0.6 - 4.0|
|Moisture (g)||77 - 87|
|Potassium (mg)||278 -1250|
|Calcium (mg)||28 - 352|
|Iron (mg)||0.5 - 2.0|
Food products that are claimed to be healthier and have functional properties have gained popularity in many fields whether in research or the food industry. Functional foods are products that have health promoting properties beyond their nutritional value. The most recognized functional components of functional foods include soluble dietary fiber, polyunsaturated fatty acids, antioxidants, vitamins, minerals, prebiotics and probiotics.
Jerusalem artichoke tubers contain a number of functional components including inulin, oligofructose and secondary metabolites such as phenolic compounds. Phenolic compounds have positive physiological functions such as antioxidants, antimutagenic and antitumor activities. There are numerous commercial possibilities to use Jerusalem artichokes as a functional ingredient to develop not only prebiotic food products but also low glycemic index products with high antioxidant properties. Due to its prebiotic properties and antioxidant properties, the use of inulin from Jerusalem artichokes can be an innovative way to add value to food products in terms of functionality and profitability for the food industry.
Bioactives - Phenolic compounds
Studies have shown that Jerusalem artichokes (H. tuberosus) contain secondary metabolites like phenolic and polyphenolic compounds such as coumarins, polyacetylenic derivatives and sesquiterpenes. Phenolic compounds are believed to have important health benefits by acting as antioxidant, antimicrobial, antifungal and anticancer agents. Phenolics compounds are widely distributed in plants and may have putative roles in protection against infection by plant pathogens. Antibacterial activities in genus Helianthus have been reported in the early 1980s. Extracts of the aerial parts of H. tuberosus contained sesquiterpene compounds and were found to possess antimicrobial and antifungal activities. Heliangin, a germacrane sesquiterpene lactone isolated from the leaves of the plant, indicated significant activity in vitro against Ehrlich ascites carcinoma cells. Studies have also demonstrated that crude extract of Jerusalem artichoke leaves also possessed antifungal or antimicrobial activities. The main constituents in the leaves of Jerusalem artichokes are chlorogenic and isochlorogenic acids that have good antioxidant properties. Phenolic acids also dominate the phenolic profile of Jerusalem artichoke tubers. Studies have reported chlorogenic, salicylic, caffeic and gallic acids as the major phenolic acids in the tubers. The content of total phenolics in Jerusalem artichoke tubers appears to be dependent on the cultivar and the part of the tuber that was analyzed. The skin of tubers appears to contain 2 to 12 times the total phenolic content compared to the internal flesh. Similar to inulin the phenolic content in tubers depends on the maturity of the tubers at harvest. As the plant grows, the content of phenolic compounds in the tubers rise and reaches a maximum and then decreases at termination of growth. To get all the benefits of the secondary metabolites, the JA tubers harvested in autumn before overwintering in the fields or storage in cold rooms, and should be cooked with the skin on.
Jerusalem artichoke tubers contain on average 80% water, 15% carbohydrate of which 80% is inulin and 1-2% protein. Variations in the nutritional content depend on different cultivars, harvest periods, production conditions, post-harvest storage and processing methods. The nutritional information of raw tubers is seen in Table 1. Tubers contain little or no fat and have a low caloric value. The Jerusalem artichoke tubers are an important source of dietary fiber due to its high inulin content that varies from 7 to 30% of fresh weight (50% of dry weight). The tubers contain all the essential amino acids in favourable proportions. They are also abundant in iron (0.5-2.0 mg/100 g), calcium (28-352 mg/100 g) and potassium (278-1250 mg/100 g). The tubers are also a good source of vitamins, such as vitamin B complex, vitamin C and beta-carotene.
Nutritional and Functional Properties of Jerusalem Artichokes
The Jerusalem artichoke possesses some advantageous characteristics compared to traditional agricultural crops, including high growth rate, adequate tolerance to frost, drought and poor soil, and strong resistance to pest and plant diseases with minimal fertilizer requirements.
The Jerusalem artichoke has been grown for its edible tubers, as a forage crop, for biofuel production and for the extraction of inulin and production of fructose. Jerusalem artichokes are low in fat, rich in minerals and contain inulin as its main carbohydrate reserve in tubers, compared to other plants that store starch. Inulin in the tubers represents a special value for human diet, nutritional and medicinal products as well as animal feed. Tubers and different parts of the Jerusalem artichoke can be used as feed – forage, silage, food pellets or prebiotic feed supplements. The whole plant crude protein content is considered adequate for the maintenance of ruminant animals. In particular, digestible nutrients and protein content compared favourably to forage crops such as corn or maize silage and sugar beet pulp. Moreover, its cultivation may be advantageous in soils and regions where other forage crops are difficult to grow.
Table 1 Nutritional composition of raw Jerusalem artichoke tubers (of different cultivars) per 100 g fresh weight
Jerusalem Artichoke Association of Canada