Marine By-Products as Functional Food Ingredients

Colin J. Barrow Ocean Nutrition Canada Halifax, Canada

INTRODUCTION

Some common bioactive materials, used as supplements or functional food ingredients, have been developed from by-products of the food and agriculture industries. Two examples from marine by-products are glucosamine, which is derived mainly from shrimp and crab shells, and long-chain (LC) omega-3 oil, a by-product from fishmeal processing. The North American functional food market is currently valued at more than US$30 billion, although marine-derived ingredients account for only a small portion of this total. Glucosamine and LC omega-3 oils are in the top 20 selling North American supplements, and both are poised for rapid growth as functional food ingredients. Other marine by-products that have potential as functional food ingredients include protein hydrolysates from fish processing waste and under-utilised fish species, chitosan from crustacean shell, macro-algae (seaweed) and micro algae-derived bioactives. This brief review will discuss the potential and challenges involved in developing functional food ingredients from these marine sources.

MARINE-DERIVED LONG-CHAIN OMEGA 3 OIL: THE NEXT SOY?

The science behind LC omega-3 and its ability to impact health is extremely strong. Multiple double-blind placebo-controlled clinical trials confirm that adequate intake of LC omega-3 oil lowers triglycerides, reduces overall mortality, mortality due to myocardial infarction, and sudden death in patients with coronary heart disease¹. The strength of scientific data is such that the FDA has issued a conditional health claim for LC omega-3 oil and decreased risk of cardiovascular disease. This claim applies specifically to docosahexaenoic acid (DHA) and eicosapentaenoic acid (EPA), the major LC omega-3 compounds derived from fish oil, and not to the short-chain omega-3 such as alpha-linolenic acid found in flax seed oil. Significant clinical data also exist indicating that LC omega-3 oils improve retinal and brain development in infants, and improve patient prognosis in a variety of inflammatory and mental disorders including arthritis, Crohn disease, lupus, Huntington's disease, Parkinson's disease, Alzheimer's disease, depression and schizophrenia².

The use of LC omega-3 oil as a functional food ingredient is currently more common in Japan than in North America. In Japan LC omega-3 oil is used in several baked goods, margarines and infant formulas³. In North America LC omega-3 oil is beginning to be incorporated into food products. For example, Martek has obtained generally recognized as safe (GRAS) approval for the use of marine-algal derived DHA in infant formula. Also, Ocean Nutrition Canada has obtained self-affirmed GRAS for a variety of LC omega-3 concentrates for use in functional foods. However, a major hurdle to the incorporation of LC omega-3 oils into a broad variety of food products is the instability of EPA and DHA. These molecules are susceptible to oxidation because of the high number of unsaturated double bonds in the fatty acyl chains. Even trace amounts of some of the aldehydic degradation products leads to an unpleasant smell and taste associated with the oil and any food product that incorporates it. To be successful as a broad based functional food ingredient technologies need to be developed that enable the incorporation of LC omega-3 oils into foods while protecting the oil from oxidation. The major strategies being developed to do this include using fortified feed to increase natural omega-3 levels in eggs and certain meats⁴, adding deodorized, partially stabilized oils to single serving short-lifetime products, and microencapsulating oil to form a stable powdered ingredient. Of these three strategies only microencapsulation has the ability to enable access to a broad variety of processed food products.

Omega-3 levels have been enriched in animals such as chicken, pigs and cattle by feeding these animals both omega-3 rich fishmeal and marine microorganisms rich in omega-3. For example, spray dried Schizochrytrium species microorganisms containing about 20% DHA by weight were fed to dairy cattle, leading to a 100% increase in the level of DHA in their milk⁵. Similar feeding of chickens has enabled the production of high DHA eggs that are marketed in several European countries⁶. This type of approach to introducing LC omega-3 oil into food is limited and does not enable additional processing which exposes the oil to oxidative conditions. For broader access to processed foods such as battered products, baked goods, and drinks, microencapsulation is a more successful and cost effective strategy. Microencapsulation by emulsion spray drying has been used to enable the enrichment of infant formulas and breads⁷. Companies including Roche, Basel, Switzerland (ROPUFA), BASF, Ludwigshafen, Germany (DryN3), and Loders Croklaan, Wormerveer, Netherlands (Marinol) are marketing microencapsulated LC omega-3 ingredients. However, emulsion technology often leads to products with undesirable sensory properties, low percentage weight of oil at 20-40%, large particle size that impacts mouth feel (>100μM), and relatively high cost per dose. A related technology, used by Wacker Biochem Corp, is to complex LC omega-3 oils with γ-cyclodextrin, which reduces unpleasant taste and odour, and produces a product whose particle size can be modified by grinding. However, γ-cyclodextrin complexed oil is expensive and has a low percentage oil by weight. Several other companies, including Ocean Nutrition Canada, Halifax, Canada and Clover Corporation Melbourne, Australia are working on novel technologies to deliver LC omega-3 cost effectively to a broad range of food products. Although several technical hurdles remain, it is likely that within the next few years a broad range of LC omega-3 containing foods, with efficacious dosages of DHA and EPA, will be available in the North American market.

CAN GLUCOSAMINE TRANSITION FROM A SUPPLEMENT TO A FUNCTIONAL FOOD INGREDIENT?

Glucosamine is currently ranked third behind multivitamins and calcium in the North American supplement category by dollar sales, with retail sales estimated at over $700 million per annum. The evidence for biological efficacy of glucosamine is strong, but this compound does not yet have GRAS approval in the United States. The safety and efficacy of glucosamine in normal adults for the treatment of osteoarthritis has been established by several clinical studies^8,9. However, safety in children, pregnant women and diabetics remains to be established. GRAS approval requires additional safety data on these populations. Safety hurdles are higher for functional food ingredients than for supplements because once an ingredient is in a food intake is less controlled and the product may be consumed unwittingly by people of all ages and condition.

Mechanistically, glucosamine serves as a substrate in the biosynthesis of component building blocks of cartilage and may also play a signalling role in cartilage turnover. Unlike non-steroidal anti-inflammatory drugs normally used in the treatment of osteroarthritis, which simply provide relief of symptoms, glucosamine can delay the progression of osteoarthritis by decreasing progressive joint space narrowing¹⁰. If GRAS approval can be obtained for glucosamine, its use in functional foods will grow exponentially, because it is a stable, water-soluble ingredient that has little impact on taste and is ideally suited for formulation into a variety of foods, including sports drinks. Several glucosamine drinks are in fact on the market in North America, but are currently being sold as supplements.

CHITOSAN: SAFE BUT IS IT EFFECTIVE?

Chitosan is derived from de-N-acetylation of chitin. Chitin is the second most abundant natural biopolymer and is composed from N-acetyl-D-glucosamine units. Chitin can be derived from the exoskeletons of crustaceans, from insects, and from the cell walls of certain fungi and yeasts. Chitosan is actually a family of polymers with varying deacetylation levels, size and charge distribution¹¹. The variation in chitosan composition based on its method of derivation from chitin makes interpretation of bioactivity difficult, and partially explains the conflicting results obtained in clinical studies. Both chitin and chitosan find extensive applications in medicine, agriculture, food and supplement industries. Chitosan has excellent biocompatibility, is biodegradable and has low toxicity. It is used surgically in wound healing including burns as well as in drug delivery¹².

As a supplement chitosan is used to lower cholesterol and to decrease fat absorption, and therefore decrease obesity. The US retail market for chitosan is small at only about US$20 million per annum, partially because of inconsistent clinical data. Several studies have established the ability of correctly prepared chitosan to decrease both cholesterol and fat absorption levels in both animals and humans delivered at dosages as low as 1.2g per day in supplement or food form^13,14.

Chitosan has been approved by the FDA for use in certain food applications, such as an edible film to protect foods. Although not widely used as a functional food ingredient in North America, chitosan produced by Primex of Norway has GRAS approval. In Japan several foods including soybean paste, potato chips and noodles are available with added chitosan, as cholesterol-lowering functional foods¹⁵. Chitosan is well positioned as a functional food ingredient but has not made major inroads into the North American market. Challenges for chitosan as a functional food ingredient include inconsistent clinical data, difficulties in producing a structurally consistent product, the requirement of relatively high dosages for efficacy, and competition from fibre products with FDA health claims such as oats, bran, psyllium fibre, soy protein and phytosterol esters.

PROTEIN HYDROLYZATES: FROM FISH WASTE TO HEALTH FOOD

Protein, including fish protein from processing waste, can be broken down into smaller fragments using enzymes called proteases. Protein hydrolysates are currently used in a range of food products including infant formula, formulas for the elderly, protein supplements, beverages as stabilizers, and confectionery as flavour enhancers^16,17. Some fish protein and protein hydrolysates have specific health benefits, including the ability to lower blood pressure through ACE inhibition, the ability to decrease the risk of type-II diabetes through increasing the availability of bradykinin¹⁸, and the ability to improve glucose tolerance and insulin sensitivity¹⁹.

Protein hydrolysates from the bonito and sardine are widely available as supplements in Japan. Sardine protein hydrolysis incorporated at a dosage of 0.5g into a vegetable drink was shown in a randomised double-blind placebo-controlled study on 63 subjects over 13 weeks to lower systolic blood pressure by 11mmHg, while the control group showed no decrease²⁰. Bonito hydrolysate is being sold in North America as a supplement to lower blood pressure. Similar products have been derived from other proteins, including soy and whey. However, active dosages in these non-marine products are 1020g per day, whereas bonito protein hydrolysis for example has a recommended daily dosage of only 1.5g per day. A low daily dose is important for both ingredient cost and ease of formulation. Many protein hydrolysates have a bitter flavour. Further work is needed to simultaneously optimise the bioactivity and flavour of protein hydrolysates before they will be widely used as functional food ingredients.

ALGAL PRODUCTS: WEEDS OR GEMS OF THE SEA?

Worldwide, close to 150 species of macro algae (seaweed) are used as foods and over 100 species for phycocolloid production, including the production of agar, alginate and carrageenan²¹. These phycocolloid products represent a US$200 million dollar industry and are recognized as GRAS. A variety of brown and red algae species are themselves recognized as GRAS in the US, FOSHU in Japan and authorised for consumption as foods in many European countries. Porphyra species, or "nori" is the most widely eaten seaweed and is used in sushi. Nori is a US$2 billion food product worldwide and over 18,000 metric tones are harvested each year²².

Seaweed extracts, similar to terrestrial plant extracts, have been shown to have a wide range of biological activities^23,24,25. The two major classes of molecules in seaweeds that are of the most potential as functional food ingredients are polysaccharides and polyphenolics. Polyphenolics are abundant in seaweeds, have potent antioxidant activity, and have been successfully incorporated into drinks such as teas²⁶. Seaweed polysaccharides are unique, abundant, and cost effectively isolated. Larger polysaccharides need to be partially hydrolysed for inclusion in drinks due to their gelling properties. Seaweed polysaccharides have been shown to have heparin-like anticoagulation activity, antiviral, immune-enhancing and anticancer activities, cholesterol lowering activity, lipid lowering effects, and blood pressure-lowering benefits. A particularly interesting product is hydrolysed alginic acid potassium salt that reduced blood pressure in hypertensive individuals by up to 20mmHg over a 3 week period at a dosage of 5 grams per day²⁷. This safe and efficacious product is readily soluble in water and has great potential as a functional food ingredient, especially in drinks.

WHERE FROM HERE?

The North American functional food market is projected to grow by more than 20% per year for the next several years. Marine-derived ingredients are popular in Japan and many other Asian countries but are a small part of the North American market. LC omega-3 oil is poised to grow rapidly as a functional food ingredient, and is estimated to have the potential to be a $100 to $500 million dollars ingredient within the next five years. Glucosamine is the third largest selling supplement by dollar sales and is well supported clinically, but requires additional safety studies before GRAS approval is given. Glucosamine will not penetrate the functional food market in any significant way unless GRAS status is achieved. Chitosan, protein hydrolysates, and marine algae polysaccharides and polyphenolics are well positioned to make rapid inroads to the North American functional food market over the next few years. However, these materials require additional clinical support, formulation studies and consumer awareness before they can become well-established ingredients in the functional food market.

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BIOGRAPHY

Dr. Colin Barrow is Executive Director of Research and Development for Ocean Nutrition Canada (ONC). He is responsible for a research team of more than 35 scientists working on the discovery and development of new nutraceutical and functional food products and technologies. Before joining ONC Dr. Barrow was Professor of Chemistry at the University of Melbourne, Australia and spent a decade in the Japanese and American Biotech and Pharmaceuticals industries in the area of Natural Products Drug Discovery. Dr. Barrow has over 60 peer-reviewed publications and has presented at numerous conferences and workshops.