LIPIDS | Cholesterol, Factors Determining Levels in Blood

S.M. Grundy , in Encyclopedia of Dairy Sciences, 2002

Saturated fatty acids

The saturated fatty acids are derived from both animal fats and plant oils. Rich sources of dietary saturated fatty acids include butterfat, meat fat and tropical oils (palm oil, coconut oil and palm kernel oil). Saturated fatty acids are straight-chain, organic acids with an even number of carbon atoms ( Table 2 ). All saturated fatty acids that have from eight to 16 carbon atoms raise the serum LDL cholesterol concentration when they are consumed in the diet. In the United States and much of Europe, saturated fatty acids make up 12–15% of total nutrient energy intake.

The mechanisms whereby saturated fatty acids raise LDL cholesterol levels are not known, although available data suggest that they suppress the expression of LDL receptors. The predominant saturated fatty acid in most diets is palmitic acid (C16:0); it is cholesterol-raising when compared with cis-monounsaturated fatty acids, specifically oleic acid (C18:cis1n-9), which is considered to be 'neutral' with respect to serum cholesterol concentrations. In other words, oleic acid is considered by most investigators to have no effect on serum cholesterol or lipoproteins. Another saturated fatty acid, myristic acid (C14:0), apparently raises LDL cholesterol concentrations somewhat more than does palmitic acid, whereas other saturates – lauric (C12:0), capric (C10:0) and caprylic (C8:0) acids – have a somewhat lesser cholesterol-raising effect. On average, for every 1% of total energy consumed as cholesterol-raising saturated, fatty acids, compared with oleic acid, the serum LDL cholesterol level is raised about 2   mg   dl−1 (0.025   mmol   l−1).

One saturated fatty acid, stearic acid (C18:0), does not raise serum LDL cholesterol concentrations. The main sources of this fatty acid are beef tallow and cocoa butter. The reason for its failure to raise LDL cholesterol concentrations is uncertain, but may be the result of its rapid conversion into oleic acid in the body.

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Cholesterol: Factors Determining Blood Levels

S.M. Grundy , in Encyclopedia of Human Nutrition (Third Edition), 2013

Saturated Fatty Acids

The saturated fatty acids are derived from both animal fats and plant oils. Rich sources of dietary saturated fatty acids include butter fat, meat fat, and tropical oils (palm oil, coconut oil, and palm kernel oil). Saturated fatty acids are straight-chain organic acids with an even number of carbon atoms (Table 2). All saturated fatty acids that have from eight to 16 carbon atoms increase the serum LDL cholesterol concentration when they are consumed in the diet. In the USA and much of Europe, saturated fatty acids make up 12–15% of the total nutrient energy intake.

The mechanisms by which saturated fatty acids increase LDL cholesterol levels are not known, although available data suggest that they suppress the expression of LDL receptors. The predominant saturated fatty acid in most diets is palmitic acid (C16:0); it is cholesterol-increasing when compared with cis-monounsaturated fatty acids, specifically oleic acid (C18:cis1, n-9), which is considered to be 'neutral' with respect to serum cholesterol concentrations. In other words, oleic acid is considered by most investigators to have no effect on serum cholesterol or lipoproteins. Another saturated fatty acid, myristic acid (C14:0), apparently increases LDL cholesterol concentrations somewhat more than does palmitic acid, whereas other saturates – lauric (C12:0), caproic (C10:0), and caprylic (C8:0) acids – have a somewhat lesser cholesterol-increasing effect. On average, for every 1% of total energy consumed as cholesterol-increasing saturated fatty acids, compared with oleic acid, the serum LDL cholesterol level is increased approximately 2   mg   dl−1 (0.025   mmol   l−1).

One saturated fatty acid, stearic acid (C18:0), does not increase serum LDL cholesterol concentrations. The main sources of this fatty acid are beef tallow and cocoa butter. The reason for its failure to increase LDL cholesterol concentrations is uncertain, but may be the result of its rapid conversion into oleic acid in the body.

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Phytosterols: physiological functions and therapeutic applications

Suryamani , ... Inderbir Singh , in Bioactive Food Components Activity in Mechanistic Approach, 2022

10.1.4 Phytosterol contents in foods

Sterols account for the greatest proportion of the unsaponifiable lipid fraction. Plant fats and oils contain naturally phytosterols occurring elements. Oils and margarines are the most important natural sources of plant sterols in human diets, though they can also be found in a variety of seeds, legumes, vegetables, and unrefined vegetable oils ( Phillips et al., 2005). Cereal products are an essential source of plant sterols, whose quality, expressed in terms of fresh weight, is higher than that of vegetables (Piironen et al., 2000). 4-demethylsterols such as sitosterol, campesterol, stigmasterol, and avenasterol are the most abundant sterols in the plants. Sitosterol (90%) is the sterol that predominates. Usually, other sterols, such as saturated stanols and sterols synthesized earlier in the pathway of biosynthesis, exist in smaller concentrations, such as 4-monomethyl and 4,4-dimethyl sterols. Plant sterols occur, with substitutions at C3, in foods such as free sterols, fatty acyl esters, glycosides, and fatty acyl glycosides. Consequently, the total sterol content is determined by the quantity of both of them, whereas cholesterol occurs either as free alcoholic sterol or as a cholesterol ester (Akihisa et al., 1991).

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Fats, oils, and emulsifiers

Mohammed Nazrim Marikkar , Yanty Noorzianna Abdul Manaf , in Preparation and Processing of Religious and Cultural Foods, 2018

12.3 Plant substitutes for LD

In recent times, considerable amount of work has been dedicated towards novel halal shortenings using plant oils and fats as replacement for LD in cookies. The main impetus for this initiative was a recent study, which showed the presence of LD in some commercial biscuit formulations (Yanty et al., 2014a). A screening of a series of plant fats, namely avocado butter, cocoa butter, palm oil, and mee fat, showed that use of single fat as replacement for LD may not be feasible (Yanty et al., 2012). It was due to the fact that their physicochemical and thermal properties were considerably different when compared to those of LD. It has been suggested that fat mixtures formulated using lipids such as palm oil (PO), palm stearin (PS), cocoa butter (CB), soybean oil (SBO), and mee fat could be an alternative option. MF being a semisolid fat is an ideal raw material for preparing shortening and other fat derivatives (Marikkar et al., 2017). Yanty et al. (2014a,b) noticed that SFC profile of MF as measured by NMR was quite similar to those of LD at certain temperatures, with some deviations at certain other temperatures (Fig. 12.1). The observed deviations in SFC profile of MF could be minimized possibly through blending with a suitable fat. Yanty et al. (2014a,b) evaluated binary mixture formulations composed of MF and PS at different ratios as a substitute for LD. Of the three binary mixtures formulated, MF:PS (99:1) showed closest compatibility to LD despite differences in their FA and TAG compositions. In terms of the SFC profile, MF:PS (99:1) showed the least difference to LD throughout the temperature range of 0–40°C (Fig. 12.2). There were also similar studies by other researchers using exotic plant fats such as engkabang fat, which is derived from the seeds of Shorea macrophyilla. Nur Illiyin et al. (2013) evaluated binary mixtures formulated by mixing engkabang fat and canola oil at different ratios as replacement for LD. The results of SFC and melting point data, as well as polymorphic form and hardness analyses showed that the blending of EF with CaO within the range of 30%–35% would help produce a fat blend that has closer compatibility to LD.

Fig. 12.1

Fig. 12.1. SFC profile of lard and Mee fat. SFC, solid fat content.

Fig. 12.2

Fig. 12.2. SFC profiles of LD and binary mixtures of plant fats. LD, lard; MF, mee fat; PS, palm stearin; SFC, solid fat content.

Blending of Avo, PS, and CB in different ratios to produce ternary mixtures was another initiative of producing a fat mixture to mimic the thermal properties of LD. A previous report showed that Avo displayed SFC values that were always lower than those of LD throughout the temperature range (Yanty et al., 2011). It was hypothesized that incorporation of hard fat components like PS and CB into Avo could enhance the SFC to a level comparable to the SFC values of LD. After evaluating three different ternary mixtures of these fats, Yanty et al. (2017a) found that Avo:PS:CB (84:7:9) was the closest in similarity to LD in terms of some physical properties. The SFC of this mixture and LD showed the least differences throughout the temperatures that include 0, 5, 20, 25, 35, and 40°C (Fig. 12.3). In a separate study, the possibility of producing a fat mixture to LD was attempted using three different quaternary blends composed of PO, PS, SBO, and CB. Out of the three quaternary mixtures formulated, PO:PS:SBO:CB (38:5:52:5) was found to display the closest similarity to LD in terms of some compositional parameters and SFC behavior. The SFC of this fat mixture and LD showed the least differences throughout the tested temperatures that include 0, 5, and 25°C (Fig. 12.4).

Fig. 12.3

Fig. 12.3. SFC profiles of LD and ternary mixtures of plant fats. LD, lard; Avo, avocado fat; PS, palm stearin; CB, cocoa butter; SFC, solid fat content.

Fig. 12.4

Fig. 12.4. SFC profiles of LD and quaternary mixtures of plant fats. LD, lard; PO, palm oil; PS, palm stearin; SBO, soybean oil; CB, cocoa butter.

As mentioned earlier, binary mixture of MP:PS (99:1), ternary mixture of Avo:PS:CB (84:7:9), and quaternary mixture of PO:PS:SBO:CB (38:5:52:5) were emerged as potential candidates to formulate a replacement for LD based on their chemical composition and SFC profiles. These three plant-based fat mixtures were processed into shortening and subsequently evaluated their functional properties in terms of hardness, consistency, microstructure, and polymorphism. According to Yanty et al. (2017b), hardness and consistency values of the three plant-based shortenings were comparably similar to those of LD shortening. This could probably be due to the solid content of these fats that are almost similar at 25°C (working temperature). The consistencies of formulated plant-based shortenings and LD shortenings were categorized as plastic fats and spreadable; hence, they were suitable to use in the production of cookies. Despite this, the microscopic analysis showed that the number and size of crystals in the formulated plant-based shortenings were dissimilar to those of LD shortening (Fig. 12.5). These differences in crystals behavior could be due to the different chemical composition of LD shortening and formulated plant-based shortenings. However, the differences in crystals behavior would not affect the polymorphism of shortenings. All the formulated plant-based shortenings and LD shortening displayed a mixture of β′ and β-form polymorphs, of which the β′ form was the predominant polymorph (Fig. 12.6). These results showed that formulated plant-based shortenings could be suitable as a LD substitute. Good shortenings with β′ crystals are desired for a better product with a smooth mouthfeel and a better entrapment of liquid oil because of the spherulitic nature formed (deMan et al., 1989; Borwanker et al., 1992).

Fig. 12.5

Fig. 12.5. Crystal distributions of (A) lard, (B) binary mixture, (C) ternary mixture, and (D) quaternary mixture shortenings at magnification of 10   ×   10.

Fig. 12.6

Fig. 12.6. Diffractogram of lard (LD) and three formulated plant-based shortenings.

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FATTY ACIDS | Dietary Importance

C.J. Field , in Encyclopedia of Food Sciences and Nutrition (Second Edition), 2003

Sources of Fat in the Diet

The quantities and types of fatty acids ingested vary greatly, depending on the dietary source (Table 1). Animal fats contain about 40–60% saturated fatty acids. Some plant oils also contain SFA (i.e., palm oil, palm kernel oil, and coconut oil), which are widely used in processed foods. MUFA are found in animal fats and plant oils, with olive oil being a rich source. Plant oils like corn, soybean, cottonseed, sunflower, and safflower generally have more than 50% of their fatty acids as linoleic acid and are considered excellent sources of PUFA. Poultry and game also contain a small amount of linoleic acid. Linolenic acid, which comprises the majority of most people's n-3 fatty acid intake, is found in high amounts in several plant oils (e.g., canola and flax) and, to a lesser extent, in other plant oils, green leafy vegetables, soybeans, and nuts. The more polyunsaturated long-chain n-3 fatty acids, eicosapentaenoic acid (EPA) and docosahexaenoic acid (DHA), comprise 20–30% of the fatty acids in cold water fish (particularly fatty fish such as herring, mackerel, fresh tuna, sardines, salmon, eel), other marine animals, and in oils extracted from the livers of fish which live in warmer waters (e.g., cod). There are new sources of EPA and DHA, made from single cell organisms, which are available to the food industry to supplement food. Most natural fats contain fatty acids in the cis form, but a small number of trans fatty acids also occur naturally, principally in meat and dairy products. The majority of the trans fatty acids in the diet come from foods made with hydrogenated vegetable oils. Generally, most fruits and vegetables contribute insignificant amounts or no fat to our diets.

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Understanding the nutritional and biological constraints of ingredients to optimize their application in aquaculture feeds

Brett Glencross , in Aquafeed Formulation, 2016

3.5.2 Terrestrial animal oils

Terrestrial animal oils (like beef tallow, pork lard, and poultry oil) are another oil resource with potential for use as replacers of fish oil in diets for fish. Similar to rendered protein meals, these products are produced as a by-product from the production of other meat sources. As these oils are derived from other fed animals, the composition of these oil sources also tends to reflect the composition of what those animals are fed. In contrast to most plant oils though, terrestrial animal oils are typified by higher levels of saturates.

Greene and Selivonchek (1990) evaluated a range of plant and animal oils and fats when included in diets fed to rainbow trout. Included in their study were salmon oil, soybean oil, linseed oil, poultry oil, pork lard, and beef tallow. In this study growth of the fish was greatest from the fish fed the pork lard and lowest by those fed the beef tallow, however there were no significant differences in growth among any of the treatments. Similarly, feed utilization efficiency was also unaffected by oil/fat type used. None of the different lipids resulted in any significant differences in the proximate composition of the whole fish, though lipid content of fillets from the soybean–oil-fed treatment was significantly higher than that of any of the other treatments. As expected, the fatty acid composition of the fish was a reflection of that of their respective diets and in most cases there was a concomitant decrease in the levels of the LC-PUFA, such as EPA and DHA, with increasing use of different oils and fats.

More recently, Emery et al. (2014) replaced poultry by-product oil with beef tallow at increments up to 50% of the added oil in diets fed to Atlantic salmon. At the end of the study the authors observed no impact on growth performance or feed conversion. However, tallow inclusion did reduce lipid and fatty acid apparent digestibilities and had a significant effect on the fatty acid composition of the fish, with a decrease in n-6 fatty acid content in tissues and an increase in the n-3:n-6 fatty acid ratio in fillet.

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Plant breeding to change lipid composition for use in food

D.J. Murphy , in Modifying Lipids for Use in Food, 2006

12.2.3 Markets for plant lipids

Despite recent increases in the global consumption of animal products, for most people, plants are still the major source of dietary fats, although they are often unaware of exactly how much and what type of lipid they are consuming (this is especially true for 'invisible' fats). Plant lipids are normally obtained in the form of liquid vegetable oils either from oilseed crops like soy or rape, or from oil-rich fruits like oil palm or olive. In 2005, the ten most important commercial oil crops produced a total of 107 million tonnes of oil with a value of about $70 billion (Oil World, 2005 ). Therefore, plant sources supply about 80 % of the total global demand for traded fats and oils – the non-plant fats and oils are mainly obtained from animal, fish and dairy sources. Plant-derived oils tend to have relatively narrow fatty acid profiles, being mainly dominated by C16 and C18 saturates, and by the C18 mono-, di-, and tri- unsaturates. Such a profile has suited the treatment of plant lipids as generic commodity oils, to be produced and transported in bulk and to be blended and/or hydrogenated as necessary to fit a particular end use. This is especially apparent in the processed food sector where most plant lipids are used. Hence, different plant oils may be blended in different proportions to produce the various types of solid fat that are used in products such as spreads and shortenings.

Since the 1980s, there has been an increasing segmentation of the plant oils market as food producers seek to highlight oils from particular crops, which may have special attributes that can add value to an end product. For example, high linoleate sunflower oil is favoured for certain 'high polyunsaturate' margarines, while cold-pressed, unprocessed 'virgin' olive oil is favoured for its organoleptic qualities. In contrast, other plant oils, such as soy and rape, have tended to remain as generic commodity products. In the case of rape oil, this is rather odd because the oil has a very high oleic acid content, which makes it suitable to be branded as 'high in monounsaturates'. There are also varieties of oilseed rape that have less than 4 % linolenic acid, which avoids the need for hydrogenation and potentially allows the oil to be marketed as 'low in trans-fatty acids'. Despite these favourable attributes, however, rape oil still tends to be treated as a low-cost commodity, rather than as a higher value, segmented-market product like olive oil.

This brings us to an important point about the reasons for the manipulation of plant lipid composition. Since the early 1990s, many new types of plant oil crop have been developed, and many more are in the pipeline. However, many of these new plant oils have not been taken up by the market, or have not been exploited to their full potential. Part of the reason for this is that many of the modifications of plant lipid composition, especially by genetic engineering, have been technology-driven, rather than being market-led. This means that markets may be unprepared, unaware or simply unwilling to take on the new products.

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Oxidative Stability and Shelf Life of Low-Moisture Foods

Min Hu , in Oxidative Stability and Shelf Life of Foods Containing Oils and Fats, 2016

9.3 Methods to Increase Oxidation Stability and Extend Shelf Life of Low-Moisture Foods

Because a number of internal and external factors impact lipid oxidation of low-moisture foods, our main focus should be on effectively controlling these factors to minimize lipid oxidation and extend the shelf life. First, a number of low-moisture foods contain oils or fats to increase flavor and essential fatty acids of the low-moisture foods. Fish, algal, and flaxseed oils contain a large amount of polyunsaturated fatty acids such as DHA, EPA, and ALA (alpha-linolenic acid) that are more readily oxidized than animal fats such as pork and chicken fat and plant oils such as soybean, canola, and corn oils. Thus, blending oils containing n-3 fatty acids with animal fats and/or plant oils may be an effective method to increase the oxidative stability and shelf life of low-moisture foods containing n-3 fatty acids. Blends of fish oil, plant oil, and chicken or pork fat have been used in food and pet food industries. Also mid- and high-oleic vegetable oils can be used to mix with flaxseed oil or algal oil to increase the oxidative stability of the blends containing flaxseed or algal oil. Second, for the dry foods containing both continuous and noncontinuous fat phase such as frying cereal chips and dry kibbles, antioxidant should be added to both continuous and noncontinuous fat phase, or inside of the chips and kibble and the surface of the chips and kibble, in order to manage the lipid oxidation and extend the shelf life.

Second, it is critical to control a w, RH, and glass transition temperature of dried food powders. Milk powders were oxidatively stable at a w between 0.1 and 0.24 (Lloyd et al., 2009a). Spray-dried milk base for baby food was the most oxidatively stable at a w near 0.24 (Roozen and Linssen, 1992). But the highest cholesterol oxidation appeared in egg powders (a w  =   0.17–0.87) with the lowest a w during storage (Obara et al., 2006). Increasing RH (0%, 11%, 33%, 54%, and 75%) improved the oxidative stability of the encapsulated sunflower oil powders. The greatest improvement of the oxidative stability of the encapsulated oil powders was seen in the glass state powders at RH 54% (Damerau et al., 2014a). Dry kibble was oxidative stable at a w 0.35 to 0.55 (unpublished data). Glass transition temperature should be considered in stability prediction for polymeric systems. It is feasible to formulate food powders to bring the powders into glass state and increase the glass transition temperature, so that the oxidative stability of the powders can be increased. Further, it is critical to decrease the temperature and avoid light and inactivate lipid enzymes during processing, shipping, and storage. In addition, it is also essential to order high-quality raw ingredients such as bulk oils/fats and oil/fat-containing ingredients. Food manufacturers need to check the quality of bulk oils/fats and oil/fat-based ingredients and apply high-quality ingredients for production of dry foods. If nonfresh oil/fat-containing ingredients or bulk oils are used to produce dry foods, not only will the shelf life be decreasing but it will also be difficult to understand and predict the oxidative stability and shelf life of the products. Moreover, selecting appropriate antioxidants or antioxidant blends to be applied to dry foods is very important for food companies to produce high-quality oxidatively stable dried food products. An antioxidant may have different efficacy in varying matrices of dry foods. As for dry foods containing both continuous and noncontinuous lipid phase, antioxidant(s) should be added to both phases in order to extend the shelf life of the dry foods. The antioxidants can be either synthetic antioxidants such as BHA, BHT, TBHQ, and PG (propyl gallate) or natural antioxidants such as tocopherols, caffeic acid, catechin, quercetin, green tea, rosemary, and pomegranate extract.

Finally, lipid oxidation needs oxygen in the air. Thus, oxygen absorbents, modified atmosphere, and active packaging are used in food industry. Small bags of oxygen absorbent are usually added to the packaged bags containing dried foods. In the past few years, various modified atmosphere and active packages have drawn a great deal of attention. The modified atmosphere packaging is a technology of modifying the composition of the internal atmosphere of a food package to extend the shelf life of the products. The modification may lower the amount of oxygen from around 21% to 0%, in order to decrease the rate of lipid oxidation. The removed oxygen can be replaced with nitrogen or carbon dioxide; 80% nitrogen, 20% carbon dioxide, or vacuum can be selected for packaging. Active packaging involves the incorporation of antioxidants to food packaging materials and releases the antioxidants by a controlled mechanism of diffusion (Sanches-Siva et al., 2014).

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Fats

C.S. Bowen-Forbes , A. Goldson-Barnaby , in Pharmacognosy, 2017

21.2 Classification of Lipids

There are various classifications of lipids that exist in living tissue. One of the more straightforward was developed by Bloor in 1920 [3]. In this classification, lipids are divided into three groups: simple lipids (comprised of fats and waxes), compound lipids (inclusive of phospholipids and glycolipids), and derived lipids (inclusive of fatty acids, glycerol, and sterols, with cholesterol, bile acids, and vitamin D being examples of animal sterols). Upon hydrolysis, simple lipids directly yield two types of products per mole: fatty acids and an alcohol (usually glycerol). Simple lipids are further divided into neutral fats or acylglycerols and waxes. The term neutral fats is generally used to describe fatty acid esters of glycerol. These may be mono-, di-, or triesters of glycerol, the latter being the major ones found in nature. TAGs are also known as triacylglycerides and triglycerides, the latter being the least acceptable term, chemically, though very frequently used in nutrition literature. Animal (and plant) fats and oils are comprised mostly of this group of compounds. They are esters comprised of three fatty acid molecules attached to a glycerol backbone. Compound lipids give rise to at least three types of primary products upon hydrolysis. Phosphatides, sphingolipids, glycolipids, and sulfolipids are included in this group, of which phospholipids are the most abundant [4]. Fatty acids, phospholipids, and cholesterol are discussed further below. Waxes are discussed in Chapter 22, Waxes.

Lipids may be divided into three groups: simple lipids (comprised of fats and waxes), compound lipids (inclusive of phospholipids and glycolipids) and derived lipids (inclusive of fatty acids, glycerol and sterols such as cholesterol, bile acids and vitamin D).

21.2.1 Fatty Acids—Components of Acylglycerols

Fatty acids may be termed, short, medium, long, or very long-chained based on the number of carbons (2–4, 6–10, 12–18, and 20–24 carbon atoms, respectively). No strict convention exists for the classification of fatty acids based on chain lengths, and so several different versions of this classification can be found in the literature [5,6]. Naturally occurring fatty acids generally have an even number of carbons arranged in a straight chain with most having 14–24 carbons present. Fatty acids with odd numbers or branched chains are more characteristically found in microorganisms and dairy fats. Dairy fats and tropical oils possess significant amounts of short-chain fatty acids. Fatty acids may also be described as saturated (having no carbon–carbon double bonds) or unsaturated [7]. Those having one C=C double bond are called monounsaturated (MU), with those possessing two or more being described as polyunsaturated (PU). Double bonds in fatty acids naturally occur in the cis-configuration and are separated by a methylene (i.e., CH2) group. Subsequently, if the position of the first double bond is known, those of all the others may be easily predicted, with the exception of conjugated trans fats such as conjugated linoleic acids (CLA) found in ruminant fats. Double bonds may be numbered starting from the carboxylic acid end or the methyl end (named omega or n- end; Fig. 21.1). Although fatty acids are formally named based on the number of carbons and double bonds present, they are often given common names based on their source.

Figure 21.1. Structure of alpha linolenic acid (18:3n-3; or 18:3Δ9,12,15).

Trans fats are uncommon in nature, with the exception of ruminant fat (including cows and sheep), which contains vaccenic acid as the main trans fatty acid, produced as a result of incomplete biohydrogenation of linoleic and linolenic acids by microorganisms in the rumen. Dairy fat contains 2–9% trans fatty acids. Industrial trans fatty acids are produced by partial hydrogenation of vegetable or fish oils. Trans fatty acids from industrial sources are known to lower high-density lipoprotein cholesterol (HDL-C), raise low-density lipoprotein cholesterol (LDL-C), and increase the risk of coronary heart disease (CHD). The major trans fat in partially hydrogenated vegetable oil products is elaidic acid, whereas trans isomers of C20:1, 20:2, 22:1, and 22:2 are found in partially hydrogenated products from marine origin. Although the effects of trans fatty acids from natural sources are less clear, some research suggest that all trans fats have a similar effect on plasma cholesterol levels. Research in this area is however limited and, in some cases, conflicting [8,9]. Fatty acids commonly found in foods are shown in Table 21.1.

Table 21.1. Fatty Acids Commonly Found in Foods

Common and Numerical Names Systematic Names Food Sources
Saturated
Caprylic (8:0) Octanoic Palm and coconut oil
Capric (10:0) Decanoic Goat and cow butter
Lauric (12:0) Dodecanoic Coconut oil and palm kernel oil
Myristic (14:0) Tetradecanoic Coconut oil, dairy fat
Palmitic (16:0) Hexadecanoic Palm oil, meat, and dairy fats
Stearic (18:0) Octadecanoic Meat, poultry, fish, and grain products
Unsaturated
Monounsaturated Oleic (18:1n-9) cis-9-Octadecenoic Olive, canola, and sunflower oil
Polyunsaturated Linoleic (18:2n-6) all-cis-9,12-Octadecadienoic Corn, safflower, evening primrose, and grape seed oil
α-Linolenic (18:3n-3) all-cis-9,12,15-Octadecatrienoic Canola oil, walnuts, flaxseed, flax oil
Arachidonic (AA) (20:4n-6) all-cis-5,8,11,14-Eicosatetraenoic Chicken, eggs
Eicosapentaenoic (EPA) (22:5n-3) all-cis-5,8,11,14,17-Eicosapentaenoic Marine algae, fish oils
Docosahexaenoic (DHA) (24:6n-3) all-cis-4,7,10,13,16,19-Docosahexaenoic Animal fats as phospholipid component, fish oils, dairy products

Fatty acids may be termed, short, medium, long, or very long-chained based on the number of carbons (2–4, 6–10, 12–18, and 20–24 carbon atoms, respectively), and as saturated (having no carbon-carbon double bonds) or unsaturated (possessing at least one carbon-carbon double bond). Most of these double bonds occur naturally in the cis-configuration.

Trans fats are uncommon in nature, with the exception of ruminant fat. Trans fatty acids from industrial sources are known to lower HDL cholesterol, raise LDL cholesterol, and increase the risk of coronary heart disease. Some research suggest that all trans fats have a similar effect on plasma cholesterol levels.

Saturated fatty acids (SFAs) having 10 or more carbon atoms are solids at 25°C and are a more dominant feature in animal fats than plant oils, with unsaturated fats being more prominent in plant oils. Unsaturated fatty acids are liquids, as are all SFAs with less than 10 carbon atoms, and the higher the degree of unsaturation, the lower the melting point of a fatty acid. Long-chain omega-3 fatty acids are characteristically found in large amounts in fish oils compared to fats from terrestrial animals (Tables 21.2 and 21.3). Oleic acid and linoleic acid (LA) are the main fatty acids in most vegetable oils.

Table 21.2. Fatty Acid Composition (% wt) of Fish Oils and Other Marine Sources

Myristic 14:0 Palmitic 16:0 Stearic 18:0 Palmitoleic 16:1 Oleic 18:1 Cetoleic 22:1 Eicosenoic 20:1 EPA 20:5 DPA 22:5 DHA 22:6 SFA MUFA PUFA Omega-3 Omega-6
Fish Oils
Capelin 7 10 NA 10 14 14 17 8 NA 6 17 55 14 14
Norway pout 6 13 NA 5 14 12 11 8 NA 13 19 42 21 21
Mackerel 8 14 NA 7 13 15 12 7 NA 8 22 47 15 15
Sardine/Pilchard 8 16 NA 10 11 3 18 NA 9 26 30 27 27
Horse mackerel 8 18 NA 8 11 8 5 13 NA 10 26 32 23 23
Anchovy 9 19 NA 9 13 2 5 17 NA 9 28 29 26 26
Menhaden a 8 29 4 8 13 2 1 10 1.5 13 41 24 24.5 23 1.5
Blue whale a 5 8 0 1 1 14 22 2.5 1.5 3 13 38 7 5.5 1.5
Seal a 4 7 1 16 28 7 12 5 3 3 12 63 11 8 3
Cod liver b 4 13 3 6 17 8 9 10 1 13 20 45 24 23 1.2
Shark liver b 4 32 9 7 22 0 2 1 2 5 45 31 8 6 2
Fish Oil Capsules c
Enriched fish oil 0 1 1 0 8 NA 4 41 4 33 2 12 78 74 4
Pure fish oil 9 16 3 9 9 NA 2 22 3 16 28 20 41 38 3
Salmon oil 7 24 4 12 8 NA 2 17 3 16 35 22 36 33 3
Cod liver oil 5 19 3 8 14 NA 9 13 2 16 27 31 31 29 2
Krill oil 11 21 5 8 8 NA 3 19 ND 16 37 19 35 35 ND

NA, not analyzed.

a
Belitz, HD, Grosch, W, Schieberle, P. Food Chemistry. 5th ed. Springer, Berlin, 2009.
b
Nunez, GC. Quality and stability of Cuban shark liver oil: comparison with Icelandic cod liver oil [dissertation]. [Iceland]: The United Nations University; 2007.p. 38.
c
Adapted from Raber, G, Laoteng, K, Francesconi, KA. Identification and characterization of fish oil supplements based on fatty acid analysis combined with a hierarchical clustering algorithm. Eur J Lipid Sci Tech 2014;116:795–804 [16].

Table 21.3. Fatty Acid Composition (%wt) of Terrestrial Animal Fats

Myristic 14:0 Palmitic 16:0 Stearic 18:0 Palmitoleic 16:1 Oleic 18:1 Linoleic 18:2 Linolenic (18:3) SFA MUFA PUFA Omega-3
Beef tallow 3 26 20 4 40 5 0 49 44 5 0
Sheep tallow 2 21 28 3 37 4 0 51 40 4 0
Lard 2 24 14 4 43 9 1 40 47 10 1
Goose fat 1 21 7 3 58 10 2 29 61 12 2
Emu fat a 22 8 4 48 11 2 30 52 13 2
a
Abdominal fat.

Source: Wang, YW, Sunwoo, H, Sim, JS, Cherian, G. Lipid characteristics of emu meat and tissues. J Food Lipids 2000;7:71–82 [30]. Adapted from Belitz, HD, Grosch, W, Schieberle, P. Food chemistry. 5th ed. Springer, Berlin, 2009.)

Palmitic, stearic, and oleic acids are dominant in terrestrial animal fats, while palmitic, oleic, eicosapentaenoic (EPA), and docosahexaenoic (DHA) acids are among the dominant fatty acids in marine oils. Oleic and LAs are the main fatty acids in most vegetable oils.

Phospholipids are the most abundant type of lipid constituents in cell membranes, their chief role involving structural integrity of the membrane bilayer. They are glycerol esters in which (most of the times) two of the glyceride OH groups are linked to fatty acids while the other is attached to a phosphate group. The phosphate is then linked to a simple, polar organic molecule. The majority of phospholipids are comprised of a diacylglycerol, a phosphate group, and a simple organic molecule, such as ethanolamine or choline. As they possess an abundance of LA, phospholipids are susceptible to autooxidation [10]. Palmitic acid is also commonly present.

Phosphatidylcholine (PC), which is often referred to as lecithin, is the most abundant class of lipids in animal cell membranes, accounting for nearly half of the total. Similarly they are the major components of plant membranes. Lecithin serves as a surface-active agent in the production of emulsions. Commercially, egg yolk is the most important animal source of lecithin (with soy being the most important plant source). PC is the main plasma phospholipid and an important component of lipoproteins, especially HDL. It strongly influences the circulation of different classes of lipoprotein, more so the very-low-density lipoproteins (VLDL). PC is the biosynthetic precursor of phosphatidic acid, lysophosphatidylcholine platelet-activating factor, and phosphatidylserine. Additionally, it provides the choline for sphingomyelin (one of many sphingolipids) biosynthesis. Phosphatidylserine, phosphatidylethanolamine, and lysophosphatidylcholine are among the more abundant phospholipids. Table 21.4 provides information on their various functions, as well as those of sphingolipids [4].

Table 21.4. Phospholipids and Sphingolipids and their Functional Properties

Phospholipid Locale Function Sources
Phosphatidylcholine Cell membrane Structural element of biological membranes Egg yolk
Pulmonary surfactant Cell signaling Soybean
Biosynthetic precursor of sphingomyelin
Phosphatidylserine Cell membrane Component of cellular membranes Bovine brain
Precursor for other phospholipids Cabbage
Essential cofactor that binds to and activates a large number of proteins Soybean
Blood coagulation process in platelets
Regulation of apoptosis
Key component of the lipid-calcium-phosphate complexes that initiate mineral deposition during bone formation
Lysophosphatidylcholine

Cell membrane

Blood plasma

Proinflammatory properties

Cell signaling

 Oats, egg yolk, soybean
Phosphatidylethanolamine Sarcolemmal membranes, nerve tissue

Membrane fusion

Secretion of lipoproteins

 Egg yolk
Sphingolipids Biological membranes

Signal transmission

Cell recognition

 Dairy, eggs, soybean

Source: Jing L, Xuling W, Ting Z, Chunling W, Zhenjun H, Xiang L, et al. A review on phospholipids and their main applications in drug delivery systems. Asian J Pharm Sci. 2015;10:81–98.

Phospholipids are the most abundant type of lipid constituents in cell membranes, with PC (which is often referred to as lecithin) being the most abundant class. Commercially, egg yolk is the most important animal source of lecithin, with soy being the most important plant source.

21.2.2 Cholesterol

Cholesterol is the most dominant sterol in animal fats and oils, being present in vegetable oils in negligible amounts [5]. In addition to synthesis by the body (within the liver), it may also be obtained from the diet via the consumption of animal foods. Cholesterol has a number of important biological roles and is required for human life and health. It resides mainly in membranes, the brain being the most concentrated source of cholesterol among animal organs. Due to its water insolubility, cholesterol has to be combined with water-soluble proteins in order to be transported in the body, thereby forming lipoproteins [5]. These lipoproteins (e.g., HDL and LDL) have been associated with much controversy as it relates to their relationship with cardiac health. High levels of cholesterol in the blood can lead to the development of atherosclerosis, and has been associated with a myriad of health problems. For this reason, cholesterol is considered "bad" by the masses. Functions of cholesterol however include modulation of membrane fluidity and permeability, maintenance of the structural integrity of membranes, development and functioning of central nervous system, sperm development, and embryonic development. Additionally, it is a precursor in the biosynthesis of vitamin D, steroid hormones, and bile acids. The latter facilitate the digestion and absorption of lipids and the prevention of cholesterol buildup in the bile. This is owing to their strong emulsifying properties.

21.2.3 Vitamin D

The fat-soluble vitamin D (cholecalciferol) is known mostly for its role in calcium and phosphorus metabolism, and, by extension, bone development and the prevention of rickets. Humans and other animals naturally produce this vitamin (from cholesterol) in their skin upon exposure to sunlight. It may also be obtained from the diet (only small amounts are naturally present in most foods) or dietary supplements. Good food sources of vitamin D include fatty fish, such as salmon, sardines, and herring, beef, eggs, and fortified foods, such as cereal and milk.

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Microalgal Application in Cosmetics

Céline Couteau , Laurence Coiffard , in Microalgae in Health and Disease Prevention, 2018

4 Microalgae as a Source of Active Ingredients

In spite of the very diverse metabolic contents among microalgae, most of them possess many proteins (Klamczynstea and Mooney, 2017). Their lipid content is also of great interest for the cosmetic industry. Lipid content in microalgae varies between 1% and 70%, but some species accumulate lipids up to 90% of dry weight (Li et al., 2008a, 2008b). We can also find vitamins (A, B1, B2, B6, B12, C) (Carballo-Cárdenas et al., 2003; Grossman, 2016); pigments, especially carotenoids (β-carotene, lycopene, cryptoxanthine, canthaxantine, astaxantine, lutein) (Gong and Bassi, 2016; Rajesh et al., 2017); and phycobiliproteins (phycocyanins, phycoerythrins) (Lorenz and Cysewski, 2000; Li and Chen, 2001; Cuellar-Bermudez et al., 2015).

4.1 Microalgae Extracts as Active Ingredients for Moisturizing Products

4.1.1 Reminders About Skin Moisturizing

The skin water content, especially in the epidermal layer, Stratum corneum, is a fundamental factor for skin moisture. A rate of 10% reveals an uncomfortably dry skin, sometimes associated with a feeling of pruritus, mainly among old people (Dupuis et al., 1997; Verdier-Sévrain and Bonté, 2007). Different mechanisms help to keep the skin moisturized. Among these, aquaporins (AQP), proteins able to facilitate the transport of water across cell membranes, play an important role. AQP3 expression is related to the expressions of other epidermal proteins involved in water maintenance (i.e., CD44, claudin-1, and filaggrin) (Dumas et al., 2007).

To overcome the drawbacks of a dry skin, the cosmetic product formulator can use two different, but additional, methods. He can either use occlusive and film-forming ingredients or moisturizing active substances (Couteau and Coiffard, 2014). The first method creates a hydrophobic barrier that prevents water evaporation: these are hydrocarbons (vaseline, paraffinium, liquid paraffinium), plant oils and fats (sweet almond oil, wheat germ oil, jojoba oil, argan oil, shea butter), fatty alcohols (cetylic alcohol, for example), but also hydrophilic film-forming substances (hyaluronic acid and its salts, collagen, elastin), gelling substances (carbomer) (Wehr et al., 1986; Masson, 2010; Salwowska et al., 2016). The second ones belong to the Natural Moisturizing Factor (NMF). This can be urea, for example, or lactic acid and its salts (Middleton, 1978; Wehr et al., 1986; Fluhr et al., 2008). We will also point out the interest of amino acids such as serin or pyrrolidone-carboxylic acid and its sodium salt (3%–5%) (McCallion and Li Wan Po, 1995).

4.1.2 The Interest of Microalgae in the Field of Skin Moisturizing

Microalgae rich in amino acids, especially serin, belonging to the genus Thalassiosira, present here a great interest for moisturizing products, but also those rich in polyunsaturated fatty acids, such as Monodus subterraneus (Derrien et al., 1998; Khozin-Goldberg and Cohen, 2006; Cardozo et al., 2007). In general, the ability to restore transepidermal water loss to a regular state resides within the n-6 family of essential fatty acids (EFAs) and specifically in the 18-carbon atom fatty acids, linoleic acid and y-linolenic acid (Hartop and Prottey, 1974; Ziboh and Chapkin, 1987). Microalgae belonging to the genus Nannochloropsis present a specific interest because of their high linolenic acid content (Guedes et al., 2011).

4.2 Microalgae Extracts as Active Ingredients for Skin Aging

4.2.1 Reminders About Skin Aging and Wrinkles

Aging is an inevitable phenomenon, the causes of which are intrinsic (firstly linked to genetics), but also extrinsic or environmental. Among these, we will point out sun exposure, natural or artificial; smoking; severe weather (wind exposure, for example). Wrinkles are visible signs of aging and are considered as age indicators. They have been classified by Kligman in 1985. He distinguishes 3 types of wrinkles. First are the crinkles, nonpermanent wrinkles that disappear when stretching the skin, caused by the deterioration of elastic fibers in the dermis as one reaches 30   years of age. Second are the glyphic wrinkles, which are the permanent accentuation of skin micro relief called dermatoglyph. These wrinkles are worsened by sun exposure. They can be observed mostly in the nape area (cutis rhomboidalis ruchae) and on the cheeks. Thirdly, he defined facial linear wrinkles caused due to face expressions. They appear early in age and get erased for young people when face tensions relax, but they last for old people (Hatzis, 2004). Stimulating collagen synthesis and using antioxidants remain the 2 major methods for fighting wrinkles (Coiffard and Couteau, 2012). Formulators mainly use vitamins C and E, as well as carotenoids as antioxidants.

4.2.2 Microalgae Extracts as Active Ingredients for Antiaging Products

As mentioned above, carotenoids represent major active substances in antiaging products. First of all, carotenoids are yellow/orange liposoluble pigments. These linear polyenes, derived from isoprene, are composed of eight units of five carbon atoms in which single and double bounds alternate. Their role is to inhibit the formation of reactive oxygen species. β-carotene tops this family of pigments. It is the main carotenoid produced by the halotolerant microalgae Dunaliella salina, up to 10% of its dry weight (De Jesus Raposo et al., 2013). β-carotene is known for its provitamin A activity; hence it finds use in antiaging products. Astaxanthin has applications in antiaging products because of its remarkable antioxidant properties, which are much greater than that of tocopherol (Terao, 1989). Haematococcus pluvialis is the richest source of natural astaxanthin (it can accumulate more than 3   g of astaxanthin by kg of dry biomass) and is now grown at an industrial scale (Tripathi et al., 1999; Olaizola and Huntley, 2003; Wan et al., 2014).

One of the most recent innovations in the antiaging field concerns Algenist products of the firm Solazyme, formulated using alguronic acid. In fact, this is a mixture of polysaccharides produced by a microalgae and patented under this generic name by the brand. It is supposed to be capable of stimulating cell renewal and of furthering elastin synthesis (Bloch and Tardieu-Guigues, 2014). There is also a polysaccharide extracted from Porphyridium sp. (Alguard PF—Frutarom) proposed for the treatment of small wrinkles. It is also known to enhance skin moisturizing by increasing its barrier function.

Daniel Jouvance Laboratories made an original choice by using the bioluminescent microalgae Pyrocystis noctulica to formulate the product Eclaceane. Bioluminescence is a long-time known phenomenon which results due to the presence of luciferin and luciferase (Schmitter et al., 1976; Nicolas et al., 1987). The effect on skin is due to glittering properties of this species (Cussatlegras and Le Gal, 2004; Valiadi and Iglesias-Rodriguez, 2013). We must remain careful because of missing studies about its components. An extract of Chlorella vulgaris appears to be promising in the field of antiaging as it seems to enhance synthesis of collagen (Wang et al., 2015), a macromolecule of the extracellular matrix of the dermis the rate of which decreases with age, causing the formation of wrinkles.

4.3 Microalgae Extracts as Active Ingredients in the Field of Topical Photoprotection

4.3.1 Reminders About Skin and Ultraviolet Radiations

We usually classify sun radiation effects according to the time limit of their appearance after irradiation. Short-term effects are more or less positive, such as beneficial effects on mood, vitamin D production, immediate pigmentation, skin thickening, actinic erythema, and tanning (Webb and Engelsen, 2006; Cavalier et al., 2009). However, long-term effects are all negative. These include photo-induced skin aging and photocarcinogenesis related to immunosuppression induced by ultraviolet (UV) rays. Knowing the severity of these effects, it seems important to be protected during UV exposure. Clothing protection and topical protection are part of the overall protection strategy. Sunscreens are considered as cosmetics in Europe and as drugs in other parts of the world, like in the USA. Only around twenty molecules are available to formulate these products. Some of them, the benzophenones, for example, are known to be allergenic. So it urges to develop active research in this field to discover new interesting molecules. Marine world and specifically microalgae could offer interesting tracks.

4.3.2 Microalgae Extracts as Active Ingredients for Sunscreens

We noticed that researches to the use microalgae extracts in sunscreens are not very active. However, mycosporinelike amino acids (MAAs) have been detected in pure water microalgae, Aphanizomenon flos-aquae (Scoglio et al., 2014). It is known that aquatic organisms are able to accumulate UVB absorbing molecules when irradiated with UVB radiations (Carreto et al., 1990; Karentz et al., 1991; Garcia-Pichel et al., 1993; Hsiao-Wei et al., 2014). These compounds, called MAAs, such as palythine, have a maximum UV absorption between 310 and 360   nm of wavelength (Xiong et al., 1999). It would be interesting to study specifically some species of dinoflagellates that reveal a good potential in MAAs (Banaszak et al., 2000; Klisch et al., 2001; Montero and Lubián, 2003; Taira et al., 2004).

Besides, we must mention that an extract of Phaeodactylum tricornutum is proposed by the firm Soliance (Table 15.1) to prevent photo-induced aging. It would limit the accumulation of harmful proteins in the skin.

4.4 Microalgae Extracts as Active Ingredients in the Field of Skin Whitening

4.4.1 Reminders About Skin Pigmentation

A discoloration can be defined as a change of the tegument's usual color. In this chapter, we will only consider hyperchromia or hyperpigmentation. We will distinguish several different hyperchromias (Table 15.2).

Table 15.2. The Different Causes of Hyperpigmentation

Type of Hyperpigmentation Characteristics
Genetic hyperpigmentations Ephelides or freckles
Naevi or beauty spots
Sun lentigines or age spots
Metabolic hyperpigmentations Wilson disease (trouble in copper assimilation)
Endocrine hyperpigmentation Addison tanned disease
Chloasma, melasma, mask of pregnancy
Nutritional deficiency hyperpigmentations Avitaminose A
Pellagra
Scurvy
Photosensitivity result hyperpigmentation Dermatitis of the meadows or dermatitis of Oppenheim
Pigment dermatitis of perfumes or dermatitis in trinket
Toxic drug hyperpigmentations Chloroquine, phenytoin, amiodarone, minocyclin, bleomycine

Among these hyperpigmentations, we notice that sun lentigine, mask of pregnancy, or toxic drug hyperpigmentations lead to a request for lightening cosmetics (Couteau and Coiffard, 2014).

4.4.2 Microalgae Extracts as Active Ingredients for Skin Lightening Products

Since the use of hydroquinone in skin cosmetic products is forbidden from the first of March 2000, because of its numerous unwanted effects, hydroquinone remains the reference molecule. Active researches are trying to find substitutes for it. As tyrosinase is the key-enzyme for the synthesis of melanin, researchers are naturally looking for inhibitors of this enzyme. An extract of Nannochloropsis oculata seems to be interesting in this field. Presence of zeaxanthin would be responsible for its efficiency (Shen et al., 2011).

The firm Codif offers an extract of Chlorella (Table 15.1) that would cause a 10% decrease in skin pigmentation.

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