Food waste, a by-product of various industrial, agricultural, household and other food sector activities, is rising continuously due to increase in such activities. Various studies have indicated that different kind of food wastes obtained from fruits, vegetables, cereal and other food processing industries can be used as potential source of bioactive compounds and nutraceuticals which has significant application in treating various ailments. Different secondary metabolites, minerals and vitamins have been extracted from food waste, using various extraction approaches. In the next few years these approaches could provide an innovative approach to increase the production of specific compounds for use as nutraceuticals or as ingredients in the design of functional foods.
Being health related compounds; bioactive compounds are known to lower the risk of developing various diseases like cancer, Alzheimers, cataracts and Parkinsons, among others. These beneficial effects have been attributed mainly to their antioxidant and radical scavenging activities which can delay or inhibit the oxidation of DNA, proteins and lipids. An imbalance between the production of reactive oxygen species (ROS), and their eradication by defensive mechanisms in our body creates oxidative stress.
Antioxidant systems of our body detoxify the reactive intermediates and result in reduction of oxidative stress. ROS can be divided into free radicals and non-radicals. Molecules containing one or more unpaired electrons are called free radicals whereas non-radical forms are created when two free radicals share their unpaired electrons. The three major ROS of physiological importance are superoxide anion (O2 -.), hydroxyl radical (.OH), and hydrogen peroxide (H2O2).
There should be interaction between free radicals, antioxidants and co-factors for maintaining health and prevention from ageing and age-related diseases. Oxidative stress caused by free radicals is balanced by the endogenous antioxidant systems of our body which get strengthened by the intake of exogenous antioxidants with an input from co-factors. Production of free radicals in excess of the defensive effects of antioxidants and some co-factors causes oxidative damage which gets accumulated during life cycle resulting in ageing, and chronic diseases such as cancer, cardiovascular diseases, neurodegenerative disorders, and other lifestyle diseases.
Free radicals generated in the body during normal metabolic functions affect the vital cellular structures and functions resulting in various degenerative diseases. These free radicals are deactivated by antioxidant enzymes that catalyse oxidation/reduction reactions and serve as redox biomarkers in various human diseases along with controlling the redox state of functional proteins.
Redox regulators with antioxidant properties related to active intermediates, cell organelles, and the neighbouring environments are involved in diseases related to redox imbalance including neurodegenerative diseases, ageing cancer, ischemia/reperfusion injury and other lifestyle diseases.
Nutraceuticals are usually consumed in pharmaceutical preparations such as pills, capsules, tablets, powder, and vials. Single administration of mangiferin or in combination with known anticancer chemicals has shown the potential benefits of this molecule in brain, lung, cervix, breast and prostate cancers, and leukemia besides its antioxidant and anti-inflammatory properties.
Meat industry by-products such as brains, nervous systems and spinal cords are a source of cholesterol, which after extraction are used for the synthesis of vitamin D3. The effect of adding flavonoids and saponins from black bean seed coat to whole wheat bread formulation was resulted in retention of more than 90% of added flavonoids and saponins, and 80% of anthocyanins in bread after baking. Use of such breads rich in these health promoting compounds might have significant health consequences.
In the production of rolled oats, phenolic compounds derived from natural sources such as benzoin, catechin, chlorogenic acid, and ferulic acid, mixed with the other ingredients prior to extrusion might obtain products more resistant to oxidation (retardation of hexanal formation).. It was characterised by the presence of hydroxytyrosol, ß-hydroxyverbascoside, oleoside derivative, luteolin etc., as potential ingredients for nutraceuticals preparations or feed industry.
Conclusion and future prospects
As an indication, various reports of diverse array of bioactive compounds from specific food residues and availability of highly sensitive measurement tools provide a great opportunity to quantify metabolites in different range of food waste materials. Based on higher quantity of specific bioactive components, a food waste by-product could be utilised for its extraction using any of approaches discussed above.
Utility of extraction methods is evident based on various reports and supercritical fluid extraction technology was proved to be very useful. A suitable extraction method could be adopted based on outcome of optimisation process. Development of a bioprocess with better efficiency of bioactive component recovery will not only add value to the food waste but also be useful in reducing cost of formulated products and decreasing the use of synthetic chemicals in such formulations.
With increasing setup of food processing industries and post-harvest losses of fruits and vegetables, the increasing amount of food and agriculture waste is available and its utilisation as a source of bioactive compounds will increase the financial status of farmers and decrease the burden of waste management. Improvement in extraction technology with lesser or no use of solvent will be of great significance towards a sustainable bioprocess.
Moreover, in India, the discarded portion of industrial waste is very high and it creates a serious waste disposal problem. Organic wastes generated from industries are hazardous to the environment and can be used as a potential bioresource for extraction of bioactive components. The present review ascertains how the use of different technologies can result into the extraction of bioactive compounds which can be used as nutraceuticals and dietary supplements. The replacement of environmentally troublesome organic solvents in such extraction techniques, with green and safe solvents such as CO2, ethanol, and water is the main objective of this review.
Steps should be taken to help build a more rational use of our natural resources. A detailed economic analysis of these extraction techniques will help setting up commercial units, thereby establishing a commercial use for such residues. This will help in complete utilisation of the industrial waste thereby providing extra compensation to the industries by sale of residues and will also help in eradicating environmental pollution caused by the poor dumping of industrial food waste.