Since the last decade, consumers are becoming conscious of the nutritional value and safety of their food and its ingredients. This has considerably increased the demand for appropriate nutritional and health standards. On the other hand, the protection of crops, stored food grains and pest control in the public health sector continues to place heavy reliance upon the use of chemicals.
However, the negative consumer perception of chemical preservatives drives focus towards natural alternatives. Preference for natural foods and food ingredients that are believed to be safer, healthier and less subject to hazards is shifting to their synthetic counterparts. In the face of this challenge, there is a need to look for new sources of ingredients or additives.
Emphasis should also be given on recycling and upgrading of waste to meet the rising costs and decreasing availability of raw materials. One such source may be agro-food co-products. The screening of plant extracts has revealed the potential of higher plants as a source of agents to serve the processing of natural products. Their possible use as natural additives emerged from a growing tendency to replace synthetic agents with natural ones.
Phyto-compounds, which have advantage over synthetic pesticides, can also be obtained from plants and their extracts. Although the fruits have significant economic value for their essential oils due to their aromatic compound, antioxidant activities, antimicrobial activities and ant-insecticidal activities, essential oils have recently been proven to be successful eco-friendly bio-control agent. Like many of the exotic plants oil or extracts that are eco-friendly, citrus oil has been a part of human diet for hundreds of years and has been recognised as safe by the Food and Drug Administration (FDA).
In the citrus industry, along with citrus fruit, its peel has also found significant economic value for its essential oil. Due to unawareness, this highly valuable peel having renowned mass is considered as waste. Essential oil from citrus peel waste is a value-added commodity which is attracting interests of people. If proper recycling of citrus peel is done, valuable peel oil can be extracted from it.
The peel of citrus fruits comprises two layers, coloured outer layer called 'flavedo' and inner white layer 'albedo'. The flavedo layer contains essential oils in the range of 0.5 to 3.0 kg per ton of fruit. Citrus oil is a complex mixture of natural compounds (approximately 400 compounds) whose content depends on the specific citrus cultivar, extraction and separation methods.
This essential oil comprises two main components - terpene hydrocarbons (the major component) and oxygenated terpenoids. The citrus oil generally contains over 90 per cent monoterpencs, about five per cent oxygenated compounds and less than one per cent non volatiles such as wax and pigments.
Citrus plants are rich in naturally-occurring flavonoids which are found in peel oil and can act as antioxidants by many potential pathways such as their ability to reduce free radical-mediated degradation of cells and tissues in an organism, enzyme inhibiting and chelating of metal ions.
Citrus fruit peel oil also has an antimicrobial activity and the isolated coumarines has high activity against micro-organisms. It is found that the total polyphenols contents in citrus peel oil are higher than in other parts, which show its natural antioxidant activity. Antimicrobial, antifungal, antioxidant, anti-insecticidal and radical scavenging properties of peel oil can not be denied.
In biological systems, lipid oxidation can produce toxic compounds and initiate other harmful reactions and variety of disorders, including degenerative disorders of the central nervous system (CNS), such as Alzheimer, cancer, atherosclerosis, diabetes mellitus, hypertension, AIDs and aging.
Citrus peel oil has phenolic compounds which can act as antioxidants by many potential pathways such as free radical-scavenging, oxygen radical absorbance. Citrus peel oil has demonstrated chemo-preventive activity against a variety of chemically induced rodent cancers.
The negative consumer perception or chemical preservatives drives focus towards natural alternatives. One such alternative to these hazards pesticides/insecticides/fungicides is the use of natural plant protectants with pesticidal activity Citrus essential oils have various functions in plants including conferring pest and disease resistance. Microbiocide can also be developed from natural compounds (peel oil & limonene) extracted from citrus flavedo.
This can prevent the development of decay in bacterial/fungal inoculated fruits, and markedly reduced decay in non-inoculated citrus fruits. In baking industry, bread occupies a unique position as compared to other bakery products. The ingredients of bread are supportive to growth of micro-organisms.
This microbial spoilage of bread is troublesome for bakers. Since, bread is an important part of our daily diet, there is a need to increase its shelf-life. This can be done by improving the hygienic conditions of mixing and baking premises and ensuring sterilised environment.
To enhance the shelf-life of bread, several chemical antimicrobial agents have been used but they are considered responsible for many carcinogenic and teratogenic attributes and residual toxicity Due to these reasons, consumers' demand for natural preservatives has increased.
This problem can also be solved with application of citrus peel oil as flavonoids present in it exhibit a wide range of antimicrobial, anti-carcinogenicitv and anti -teratogenic attributes. Citrus oils are also used as flavouring agent in a large number of internationally marketed soft drinks and in beverages, sweets, jams, cookies, and confectioneries. Chewing gum, gelatins and ice cream are among those products in which citrus flavours are commonly used.
Citrus oils is also used in the cosmetics industry to make different kind of perfumes, creams, lotions, eye makeup, hair care products, detergents, after shaves and other personal beauty-care products. Sometimes, simply citrus peel is used as a facial cleanser.
For example the astringent action of lime essential oil helps to increase and improve the tone of the skin and remove oiliness from the skin. These oils provide the fragrance to products in such a perfect way that even modern technology cannot reproduce the exact combinations in them.
Essential oil can be used for making medicines and as a scent in toothpastes, mouthwash, soap, shampoo, washing powder and in several other uses in household hygiene and in reducing contamination with its environment-friendly fragrance. Essential oil is one of the citrus by-products which is generating keen interest among the people due to its friendly effects and attributes. Citrus peel oil has a very strong economic market value.
In Pakistan citrus peel oil is sold for Rs 35,000-40,000 per kg. If concerted effort is made, the annual import of a big quantity of citrus oil worth Rs 300 million can be minimised by establishing our own industry. Public-private and governmental co-operation can play a significant role in the extraction of this valuable neglected product with promising future.
Courtesy: Hortimag