A review of the progress in enzymatic concentration and microencapsulation of omega-3 rich oil from fish and microbial sources

Technology continues to evolve for the concentration and stabilisation of omega-3 fatty acids for delivery into food and beverage products. The use of lipases for selective concentration of EPA and DHA, or for re-esterification reactions, is important in the production of omega-3 concentrates. Enzymatic strategies require robust enzymes that can be immobilised and multiply re-used. Novel and mild processing methods are particularly important for providing oils with good sensory properties, which are required for successful use as functional food ingredients. Although in some cases good quality oils can be used directly in some foods, such as margarine, many foods require that microencapsulated and stabilised omega-3 oils be used. This is particularly important when the oils are preconcentrated. There are a number of industrially used microencapsulation methods, but the most widely used are complex coacervates and spray dried emulsions. Fish oil is still the most widely used source of long-chain omega-3 fatty acids for addition to food, although algal oil is the primary source of DHA for infant formula use in North America. Algal oil is still significantly more expensive than fish oil for most applications, although many groups are improving both the cost and quality of omega-3 oil from algal sources. In particular, Thraustochytrid and Schizochytrid strains are a promising source of both DHA and EPA, and with further improvement could be used to provide varying ratios of these omega-3 fats. In this short review we will describe some of the current research in omega-3 fat concentration and microencapsulation, with particular emphasis on the use of lipases for concentration and complex coacervation for microencapsulation.     

How does high DHA fish oil affect health? A systematic review of evidence

The health benefits of fish oil, and its omega-3 long chain polyunsaturated fatty acid content, have attracted much scientific attention in the last four decades. Fish oils that contain higher amounts of eicosapentaenoic acid (EPA; 20:5n-3) than docosahexaenoic acid (DHA; 22:6n-3), in a distinctive ratio of 18/12, are typically the most abundantly available and are commonly studied. Although the two fatty acids have traditionally been considered together, as though they were one entity, different physiological effects of EPA and DHA have recently been reported. New oils containing a higher quantity of DHA compared with EPA, such as fractionated and concentrated fish oil, tuna oil, calamari oil and microalgae oil, are increasingly becoming available on the market, and other oils, including those extracted from genetically modified oilseed crops, soon to come. This systematic review focuses on the effects of high DHA fish oils on various human health conditions, such as the heart and cardiovascular system, the brain and visual function, inflammation and immune function and growth/Body Mass Index. Although inconclusive results were reported in several instances, and inconsistent outcomes observed in others, current data provides substantiated evidence in support of DHA being a beneficial bioactive compound for heart, cardiovascular and brain function, with different, and at times complementary, effects compared with EPA. DHA has also been reported to be effective in slowing the rate of cognitive decline, while its possible effects on depression disorders are still unclear. Interestingly, gender- and age- specific divergent roles for DHA have also been reported. This review provides a comprehensive collection of evidence and a critical summary of the documented physiological effects of high DHA fish oils for human health.     

海洋鱼油的生产与应用

全面回顾了国内外海洋鱼油生产与应用的历史与现状,指出海洋鱼油作为二十碳五烯酸(EPA)、二十二碳六烯酸(DHA)等ω-3多不饱和脂肪酸的重要来源,正在饲料、食品以及药品等领域展示其良好的应用前景.     

反式EPA/DHA的来源、检测技术与生理功能研究进展

反式脂肪酸是脂肪酸链上至少含有1个非共轭反式双键的不饱和脂肪酸异构体。反式脂肪酸（C18）会提高血液胆固醇水平,增加心血管疾病的风险,给人体造成不利的影响。EPA/DHA是重要的长链多不饱和脂肪酸,具有多种生物活性,对维持人体健康具有重要意义。EPA/DHA在精炼加工过程中会发生反式异构化。与全顺式EPA/DHA相比,反式EPA/DHA的生理功能发生了显著变化。从反式EPA/DHA的来源、检测技术、生理功能等方面进行了综述,以期为EPA/DHA的综合开发利用提供科学依据和理论基础。     

Different specificity of two types of Pseudomonas lipases for C20 fatty acids with a Delta5 unsaturated double bond and their application for selective concentration of fatty acids

Two kinds of lipases, AK-lipase and HU-lipase, produced by two different Pseudomonas fluorescens strains, AK102 and HU380, respectively, were evaluated as to fatty acid hydrolysis specificity using six types of oil containing higher amounts of C20 fatty acids such as arachidonic acid (5,8,11,14-eicosatetraenoic acid, AA, or 20:4omega6), dihomo-gamma-linolenic acid (8,11,14-eicosatrienoic acid, DGLA, or 20:3omega6), 5,8,11,14,17-eicosapentaenoic acid (EPA or 20:5omega3), mead acid (5,8,11-eicosatrienoic acid, MA, or 20:3omega9), 8,11-eicosadienoic acid (20:2omega9) and 8,11,14,17-eicosatetraenoic acid (20:4omega3). Although HU-lipase did not show any specificity for C20 fatty acids with respect to the presence or absence of a Delta5 unsaturated bond, it exhibited comparatively low reactivity for 4,7,10,13,16,19-docosahexaenoic acid (DHA or 22:6omega3). In contrast, AK-lipase was less reactive for C20 fatty acids with a Delta5 unsaturated bond. However, the specificity of hydrolysis of AK-lipase gradually decreased as the reaction proceeded. Utilizing this fatty acid specificity, we concentrated either EPA or DHA from fish oils containing both EPA and DHA by means of lipase-catalyzed hydrolysis and urea adduction. Hydrolysis and urea adduction of refined cod oil including 12.2% EPA and 6.9% DHA with HU-lipase provided free fatty acids with 43.1% EPA and 7% DHA, respectively. The resulting yield of concentrated total fatty acids comprised 2.6% of the fatty acids from the cod oil. Thus, EPA was particularly concentrated in the fatty acids derived from refined cod oil on partial hydrolysis with HU-lipase followed by urea adduction. On the other hand, hydrolysis of cuttlefish oil with AK-lipase followed by urea adduction increase slightly the EPA composition from 14.2% to 16.8%, and markedly enhanced the composition of DHA from 16.3% to 44.6% in the hydrolyzed fatty acids. The yield of purified total fatty acids by urea concentrate was 9.4% of the fatty acids from the cuttlefish oil. Thus, DHA was particularly concentrated in the fatty acids derived from on partial hydrolysis with AK-lipase followed by urea adduction. We concluded that EPA and DHA concentrates can be easily and inexpensively obtained using HU-lipase and AK-lipase, respectively. Furthermore, it might be possible to separate and concentrate C20 polyunsaturated fatty acids (PUFAs) with or without a Delta5 double bond from PUFAs rich oils including both fatty acids.     

Bioavailability and Potential Uses of Vegetarian Sources of Omega-3 Fatty Acids: A Review of the Literature

Presently alpha-linolenic acid (ALA) is the most widely used vegetarian LC3PUFA, but only marginal amounts are converted into eicosapentaenoic (EPA) and docosahexaenoic acid (DHA); both of which are strongly related to human health. Currently, fish oils represent the most prominent dietary sources of EPA and DHA; however, these are unsuitable for vegetarians. Alternative sources include flaxseed, echium, walnut, and algal oil but their conversion to EPA and DHA must be considered. The present systematic review sets out to collate information from intervention studies examining the bioavailability of alternative vegetarian long chain omega-3 (n-3) polyunsaturated fatty acids (LC3PUFA) sources. Ten key papers published over the last 10 years were identified with seven intervention studies reporting that ALA from nut and seed oils was not converted to DHA at all. Three studies showed that ingestion of micro-algae oil led to significant increases in blood erythrocyte and plasma DHA. Further work is now needed to identify optimal doses of alternative vegetarian LC3PUFAs and how these can be integrated within daily diets. The potential role of algal oils appears to be particularly promising and an area in which further research is warranted.     

PUFAs in Fish: Extraction,Fractionation, Importance in Health

ABSTRACT: Polyunsaturated fatty acids (PUFAs), especially eicosapentaenoic acid (EPA) and docosahexaenoic acid (DHA), are currently in demand in the pure form and actively being studied to understand their potential roles in human health. Arachidonic acid, 20:4 (n‐6), and DHA, 22:6 (n‐3), are important in normal neurodevelopment and visual function. Infants fed formula often have low blood lipid 20:4 (n‐6) and 22:6 (n‐3). Consumption of fish oils may increase the 20:5 (n‐3) (EPA) and 22:6 (n‐3) (DHA) in human blood. Some marine fish oils contain higher amounts of arachidonic acid, EPA, and DHA. PUFA contents in different marine fishes and methods for their extraction and fractionation, in terms of fatty acid constituents in the form of methyl esters, are covered in this review. Emphasis is given to the fractionations of EPA and DHA by means of supercritical fluid extractions (SFE). The advantages of SFE compared to conventional methods are discussed in this review. PUFAs are usually extracted at about 10 to 30 MPa and at 40 to 80 °C. SFE is a promising and currently the best technique to extract PUFAs, especially EPA and DHA, from marine and freshwater fish.     

海洋鱼油深加工技术研究进展

海洋鱼油深加工技术可以更加合理、有效地利用其中的EPA和DHA等多不饱和脂肪酸,提升鱼油的利用价值.介绍了以海洋鱼油为原料的EPA/DHA产品的深加工技术,主要包括鱼油脱腥、多不饱和脂肪酸的富集纯化,新型EPA/DHA产品的开发与应用以及产品稳定性的研究.对海洋鱼油多不饱和脂肪酸深加工技术进行了分析与展望,认为含有高纯度EPA、DHA等多不饱和脂肪酸的鱼油产品仍是市场的主流需要.     

Past and Present Insights on Alpha-linolenic Acid and the Omega-3 Fatty Acid Family

Alpha-linolenic acid (ALA) is the parent essential fatty acid of the omega-3 family. This family includes docosahexaenoic acid (DHA), which has been conserved in neural signaling systems in the cephalopods, fish, amphibian, reptiles, birds, mammals, primates, and humans. This extreme conservation, in spite of wide genomic changes of over 500 million years, testifies to the uniqueness of this molecule in the brain and affirms the importance of omega-3 fatty acids. While DHA and its close precursor, eicosapentaenoic acids (EPA), have received much attention by the research community, ALA, as the precursor of both, has been considered of little interest. There are many papers on ALA requirements in experimental animals. Unlike humans, rats and mice can readily convert ALA to EPA and DHA, so it is unclear whether the effect is solely due to the conversion products or to ALA itself. The intrinsic role of ALA has yet to be defined. This paper will discuss both recent and historical findings related to this distinctive group of fatty acids, and will highlight the physiological significance of the omega-3 family.     

Actual ratios of triacylglycerol positional isomers consisting of saturated and highly unsaturated fatty acids in fishes and marine mammals

The distribution of fatty acid species at the (sn-1, 3) position or the (sn-2) position of triacylglycerol (TAG) in natural fats and oils has already been analysed by many researchers and several interesting results have been reported. However, most of these reports only focused on the distribution of fatty acids at the or positions in TAG, and did not take account of the combination of fatty acids in the TAG, i.e., the TAG positional isomers. In this study, the actual ratios of TAG positional isomer pairs, consisting of palmitic acid and highly unsaturated fatty acid (HUFA) such as DHA or EPA, in fish and marine mammals were investigated using a high-performance liquid chromatography/atmospheric pressure chemical ionisation-mass spectrometry (HPLC/APCI-MS) system equipped with tandem jointed non-endcapped polymeric ODS columns. The results show that for combinations of DHA or EPA with two palmitic acids in the TAG of marine mammals, binding was almost all at the α position. In contrast, binding of DHA or EPA was mainly at the β position in fish. The preferred DHA and EPA positions in TAG were the same in the same marine mammal or fish. The binding position tendency of HUFA in TAG positional isomers consisting of two HUFAs and one palmitic acid was the same as that for combinations of one HUFA and two palmitic acids. These results were interpreted as showing that the preferred fatty acid species of sn-glycerol-3-phosphate acyltransferase and 1-acyl-sn-glycerol-3-phosphate acyltransferase in marine mammals are different to those in fish and other animals, or that diacylglycerol acyltransferase in marine mammals favours 1,2-dipalmitoyl-sn-glycerol formed from 1,2-dipalmitoyl-sn-glycerol-3-phosphatidate if HUFA is the reaction substrate.     

水产品中EPA和DHA的研究进展

EPA和DHA是人体中重要的不饱和脂肪酸,具有许多重要的生理功能,对人类和动物的生长发育和健康起着重要的作用,本文简要介绍了EPA和DHA的生理功能,分离提取方法及水产来源的EPA和DHA研究现状,并对其发展前景进行了展望.     

Health beneficial long chain omega-3 fatty acid levels in Australian lamb managed under extensive finishing systems

The variation in levels of the health claimable long chain omega-3 fatty acids, eicosapentaenoic acid (EPA, 20:5n-3) plus docosahexaenoic acid (DHA, 22:6n-3) across production regions of Australia was studied in 5726 lambs over 3 years completed in 87 slaughter groups. The median level of EPA plus DHA differed dramatically between locations and sometimes between slaughters from the same location. The ratio of EPA plus DHA from lambs with high values (97.5% quantile) to lambs with low values (2.5% quantile) also differed dramatically between locations, and between slaughters from the same location. Consistency between years, at a location, was less for the high to low value ratio of EPA plus DHA than for the median value of EPA plus DHA. To consistently obtain high levels of omega-3 fatty acids in Australian lamb, there must be a focus on lamb finishing diets which are likely to need a supply of α-linolenic acid (18:3n-3), the precursor for EPA and DHA.     

Encapsulation of vegetable oils as source of omega-3 fatty acids for enriched functional foods

Polyunsaturated omega-3 fatty acids (PUFAs), a functional component present in vegetable oils, are generally recognized as being beneficial to health. Omega-3 PUFAs are rich in double bonds and unsaturated in nature; this attribute makes them highly susceptible to lipid oxidation and unfit for incorporation into long shelf life foods. The microencapsulation of oils in a polymeric matrix (mainly polysaccharides) offers the possibility of controlled release of the lipophilic functional ingredient and can be useful for the supplementation of foods with PUFAs. The present paper provides a literature review of different vegetable sources of omega-3 fatty acids, the functional effects of omega-3 fatty acids, different microencapsulation methods that can possibly be used for the encapsulation of oils, the properties of vegetable oil microcapsules, the effect of encapsulation on oxidation stability and fatty acid composition of vegetable oils, and the incorporation of long-chain omega-3 polyunsaturated fatty acids in foods.     

裂殖壶菌合成二十二碳六烯酸机理研究进展

二十二碳六烯酸(DHA)属于ω-3不饱和脂肪酸,是保持人体健康的重要营养成分之一,具有重要的医药应用和营养价值。与植物和动物来源相比,裂殖壶菌合成DHA的工业应用前景广阔。研究表明,过表达聚酮合成酶(Polyketide synthase,PKS)和脂肪酸合成酶(Fatty acid synthase,FAS)途径中的关键作用酶基因与改变培养条件(如碳源、氮源、温度、无机盐、微量元素、前体物质及生物促进剂等),均可显著提高DHA产量。此外,不同限制条件下的裂殖壶菌基因组及转录组的测序分析,揭示了DHA合成过程种不饱和双键形成、信号传导、脂质转运及代谢的分子机制。     

Long-chain n-3 fatty acids and classical cardiovascular disease risk factors among the Catalan population

The protective cardiovascular effect of long-chain n-3 fatty acids has been firmly established in populations with high fish consumption, like those from Mediterranean countries. The current fish consumption in a representative sample from Catalonia, a Mediterranean region, and its relationship with plasma concentrations of eicosapentaenoic (EPA) and docosahexaenoic (DHA) and some classical cardiovascular disease risk factors was evaluated. Mean fish and seafood intake was 78.5 ± 51.4 g/day. Mean plasma concentrations of EPA and DHA were respectively 0.48% and 1.99% of total fatty acids. Consumption of marine foods among the Catalan population, the main source of n-3 fatty acids, appears to beneficially affect some cardiovascular disease risk factors. Our results show that both EPA and DHA are negatively associated with triacylglycerol (TG) concentrations and the ratio of total cholesterol (TC) to HDL-cholesterol. Furthermore, EPA but not DHA has a beneficial effect on plasma HDL-cholesterol among the Catalan population. There were no significant associations between long-chain n-3 fatty acids and LDL-cholesterol, TC, glucose, insulin or blood pressure. Oily fish intake, which is richest in EPA and DHA, is currently at an order of only 1 serving per week in the Catalan population and its increase should therefore be promoted.     

Rapid Discrimination and Determination of Polyunsaturated Fatty Acid Composition in Marine Oils by FTIR Spectroscopy and Multivariate Data Analysis

A rapid analytical approach for discrimination and quantitative determination of polyunsaturated fatty acid (PUFA) contents, particularly eicosapentaenoic acid (EPA) and docosahexaenoic acid (DHA), in a range of oils extracted from marine resources has been developed by using attenuated total reflection Fourier transform infrared spectroscopy and multivariate data analysis. The spectral data were collected without any sample preparation; thus, no chemical preparation was involved, but data were rather processed directly using the developed spectral analysis platform, making it fast, very cost effective, and suitable for routine use in various biotechnological and food research and related industries. Unsupervised pattern recognition techniques, including principal component analysis and unsupervised hierarchical cluster analysis, discriminated the marine oils into groups by correlating similarities and differences in their fatty acid (FA) compositions that corresponded well to the FA profiles obtained from traditional lipid analysis based on gas chromatography (GC). Furthermore, quantitative determination of unsaturated fatty acids, PUFAs, EPA and DHA, by partial least square regression analysis through which calibration models were optimized specifically for each targeted FA, was performed in both known marine oils and totally independent unknown n???3 oil samples obtained from an actual commercial product in order to provide prospective testing of the developed models towards actual applications. The resultant predicted FAs were achieved at a good accuracy compared to their reference GC values as evidenced through (1) low root mean square error of prediction, (2) good coefficient of determination close to 1 (i.e., R ²≥ 0.96), and (3) the residual predictive deviation values that indicated the predictive power at good and higher levels for all the target FAs.     

Physical and nutritional properties of baby food containing menhaden oil (Brevoortia tyrannus) and microencapsulated menhaden oil

Purified menhaden oil (PMO) was characterized and microencapsulated. Baby foods containing PMO and microencapsulated purified menhaden oil (MPMO) were evaluated and compared. PMO had higher total omega-3, total saturated, total monounsaturated, DHA, and EPA contents than MPMO. Emulsion containing PMO (EPMO) exhibited viscoelastic characteristic and droplet size of EPMO was around 2-10 μm. The DHA and EPA in the PMO were reduced in MPMO. All baby-food samples with added fish oils had similar FFA values and color. DHA and EPA of baby food were significantly increased by adding PMO and/or MPMO. Total percent values for omega-3 fatty acids of extracted fat from commercial baby food (CB), commercial baby food containing PMO (BPMO), and commercial baby food containing MPMO (BMPMO) were 4.5, 9.8 and 10.1%, respectively.     

Lipid profiles of oil from trout (Oncorhynchus mykiss) heads,spines and viscera: Trout by-products as a possible source of omega-3 lipids?

Lipid profiles of fish oil extracted from trout heads, spines and viscera using supercritical carbon dioxide and Randall extraction with hexane were measured. The amount of unsaturated fatty acids (as a percentage of total fatty acids) was within the range of 72.6–75.3% in all the substrates. A significant presence of the most important omega-3 fatty acids was detected. Eicosapentaenoic acid (EPA) and docosahexaenoic acid (DHA) content in oil from spines, heads and viscera resulted to be 8.7% and 7.3%, 7.9% and 6.3%, and 6.4% and 6.0%, respectively. A low (≈3%), but worth noting, presence of lipids with omega-1 polyunsaturated fatty chains was observed in all the oils. Finally, significant differences were noticed in the relative amounts of triacylglycerides (TAG), diacylglycerides (DAG) and free fatty acids (FFA). Whereas oil from heads and spines was essentially composed of TAG (≈98%), in viscera oil the molar distribution ratio became TAG:DAG:FFA = 87:8:5.     

Physiological Effects of Eicosapentaenoic Acid (EPA) and Docosahexaenoic Acid (DHA)—A Review

Marine lipids have long been documented to be the major source of polyunsaturated fatty acids (PUFAs), especially n-3 fatty acids such as eicosapentaenoic acid (EPA; 20:5 n-3) and docosahexaenoic acid (DHA; 22:6 n-3). Both EPA and DHA have been documented to have significant influence on biochemical and physiological changes in the body. Although these long chain PUFA exert positive influences on human nutrition and health, there are also some controversies pertaining to the functioning of these n-3 PUFAs including the extent of their requirement by the body. As marine lipids have been thoroughly reviewed often, the present review mainly focuses on works related to physiological effects of EPA and DHA.