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Encapsulation has become an important technology in the recent years. Both Food and pharmaceutical industries are utilizing this technique for a wide range of applications. Encapsulation is done mainly to protect the molecules from the environmental interactions ( 1). It was reported that anti-oxidants, flavors and lipid-based compounds can be encapsulated in a variety of wall material made up of starches, gums, gelatins, polymers etc (1). Spray drying is the most common technique used for encapsulation in which hot air is used for drying of fine liquid droplets (2). It was reported that more than 90% of microencapsulated omega-3 oil are produced by spray drying (3). Emulsification plays an important role in optimizing the encapsulation efficiency of food flavors and oils (4). Properties of wall and core materials, emulsion characteristics and various drying conditions are the factors which can affect the efficiency of encapsulation (5). Fish oil contains omega-3 PUFA, which has got an high degree of unsaturation. Omega-3 PUFA's have a common carbon-carbon double bond in the n−3 position, which is highly inclined to oxidation. (6).
The oxidation leads to the development of rancid off-flavor and degradation of nutrients in turn affecting the sensory qualities, nutritional qualities and shelf-life of fish oil-enriched foods, it was reported that even oxidation induces the formation of toxic compounds which makes it difficult for human consumption (7, 8, 9). This ill effects created a major technological barrier for developing fish oil-enriched processed foods (10, 11) Microencapsulation is a technology that has been developed as a means for incorporating fish oil into the foods, which protects the fish oil from oxidation during processing and storage, also to mask the fishy taste and odour in the food products (10). It was reported that using microencapsulation the storage life of the lipid compounds could be increased to more than 2 years (12). Therefore, the main objective of this paper is to review the significances and major advances in the encapsulation of lipids with recent advances in the encapsulation of omega 3 fatty acids.
Omega 3 fatty acids
Omega-3 fatty acids are essential polyunsaturated fatty acids (PUFA) found in some food items. Omega-3 PUFA's cannot be synthesized in the body; it must be obtained from food sources (13).
α-linolenic acid (ALA), eicosapentaenoic acid (EPA), and docosahexaenoic acid (DHA) are considered to be the nutritionally essential n−3 fatty acids. ALA is mainly obtained from the plant sources while EPA and DHA are obtained from marine sources. Percentage of omega-3 fatty acid in various marine and plant sources are shown in Table 1 and Table 2 respectively.
Marine fish is considered to be a good source of omega 3 fatty acids specially eicosapentaenoic acid (EPA) and docosahexaenoic acid (DHA). Fish oil is obtained in the human body by eating oily fish, such as herring, mackerel, salmon, albacore tuna, and sardines, or by consuming fish oil supplements. Among the various health benefits interest in the protective effects of omega-3s in cardiovascular disease (CVD) began with studies of the Greenland Eskimos who were found to have a low risk of CVD despite a diet that was high in fat and cholesterol (14). Since 1970's the evidence from animal-experimental, observational, and clinical research studies has enhanced the credibility of the protective effect of fish consumption on the risk of CHD death (15).
It was reported by world health organization in 2007 that, cardiovascular diseases are the world's largest killers, claiming 17.1 million lives a year (16). Cardiovascular diseases in US in 2009 are projected to cost more than $304.6 billion, including health care services, medications, and lost productivity (17).
Sunflower or safflower oil
Wheat germ oil
Egg with enhanced omega 3
Table: 1 Percentage of omega-3 fatty acid in various plant sources (18)
Tuna, light canned, drained,
Tuna, white, canned in
Salmon, pink, canned
Salmon, Chinook, raw
Salmon, Atlantic wild, raw
Salmon, Atlantic farmed, raw
Table: 2 Percentage of omega-3 fatty acid in various marine sources (18)
Encapsulation is a technology of packing solid, liquid or gaseous materials in small sealed capsules (19). It is a means of isolating a substance from the reactions of the surrounding matter. After encapsulation the entropy of the segregate decreases, potency increases and in some cases the segregate achieves new properties (20). The major advantages of lipid encapsulation are (20, 21, 22)
Oxidation of lipids is reduced
To control the release of active ingredients
Protect ingredients from the environment
Less flavor loss during the product storage
Increases the ingredient bioavailability and efficacy
Also the unpleasant taste of substances may be shielded by encapsulating the lipid (20). Encapsulated lipids can function as carriers for lipid-soluble physiologically active substances, which protects the substances against enzyme hydrolysis, during its transport from mouth to the intestinal tract (20).
The stability of emulsion is one of the critical factors for developing microcapsules with desired properties and performance, especially for oxidative stability of encapsulated oil (23)
An emulsion ideal for oil encapsulation should have the following properties, such as small size and narrow distribution of oil droplets stable to agglomeration and coalescence, a high solid content for enabling them to form a controlled release of bioactives in foods and nutraceuticals, and a low viscosity which is essential for an easy flow, pump and spray (24).
In some studies, for the encapsulation of fish oil a liquid-liquid dispersion system was studied in solid zein particles. This serves as an alternative to emulsions. It can be an easy method for producing solid sub micrometer particles (25).
Also it was shown that aggregation of maltodextrin with an aqueous emulsion has a good potential for ideal encapsulation. This has got high oxidative stability and has suitable properties of flow ability and wetability (26).
In another study fish oil was encapsulated using double emulsification and subsequent enzymatic gelation method, using microbial transglutaminase (MTGase) cross-linked proteins and isolated soya protein as the wall material. Encapsulated microcapsules exhibited a higher oxidative stability and lower water solubility (27).
Properties of Wall Materials
The wall materials used for encapsulation should have the following properties (5, 28)
High emulsifying activity and stability
The lipids should not get detached from the emulsion during dehydration
Wall must prevent oxygen transfer (to prevent oxidation)
A tendency to form a fine, dense network during drying.
Wall materials should not react with core materials to be encapsulated
Safe for use in foods
Cost is another factor; the wall materials should be easily available and cheap.
The materials and methods that have been used for microencapsulation of fish oils are listed in Table 3
Whey proteins have been reported to be an excellent encapsulating agent for volatiles and lipids (29, 30, 31, 32). Whey proteins are also known to have significant antioxidant properties and provide oxidative stability to oil emulsion stabilized by whey proteins (33, 34, 35 ). Various studies have shown that a wall system consisting of protein in conjunction with carbohydrates is an excellent material for improving the oxidative stability and shelf-life.
Sodium caseinate, maltodextrin
Sodium or calcium caseinate, skim milk
Sand eel oil
Gum arabic, maltodextrin, gelatine
Shark liver oil
Chitosan, lecithin, corn syrup solid, Whey protein isolate or soy protein
isolate, glucose syrup
Egg white protein
Sodium caseinate, lactose, maltodextrin
Sand eel oil
EPA ethyl ester
Shark liver oil
Table 3: The materials and methods that have been used for microencapsulation of fish oils (adapted from 24 )
Encapsulation efficiency analysis (5)
Encapsulation efficiency is defined as the amount of core material encapsulated inside the powder particles. It is given by the formula
Encapsulation efficiency = Lipids on surface/ Total lipid content
Smaller this ratio better will be the encapsulation. Surface oil, else called as free or extractable oil can be quantified using solvent extraction techniques.
Surface oil coverage analysis (5)
Surface composition of the fish oil encapsulated powders can be analyzed using a X-ray photoelectron spectroscopy (XPS).
Analysis of moisture content and water activity of powders (5)
Moisture content of the encapsulated powders was finding out by using oven drying method.
Micro structural properties (5)
Micro structural properties of the encapsulated powders can be analyzed by using A JSM 6400F model scanning electron microscope.
The properties of wall materials, drying criterion and emulsion characteristics are the factors that will affect the quality of the encapsulated product. Since the characteristics of wall materials has a significant role in increasing the efficiency of encapsulation, more research must be carried out to develop high potential wall materials for improving the oxidative stability as well as shelf-life of encapsulated products. Spray drying is a common technique for drying of encapsulated powders, recent studies have been concentrated more onto increase the efficiency of spray drying as well as to develop new technologies for drying of encapsulated powders.