The convergence of consumer demands for better nutrition and lower-carb foods is turning product developers toward flax. Daniel Best separates the wheat from the chaff
Flaxseed once again finds itself the subject of an image makeover. Its medicinal and nutritional qualities were recognised in ancient times but fell by the wayside as other food grains gained prominence in the industrial age. Modern nutritional and medical science has restored an appreciation for flaxseed?s unique nutraceutical qualities. Flaxseed, also known as linseed, is broadly recognised by many consumers as a ?good for you? nutraceutical grain—primarily for its high concentration of omega-3s and, increasingly so, for its lignans, dietary fibre and antioxidants.
Flaxseed?s omega-3s and lignan phyto-oestrogens, in particular, are the focus of mounting evidence documenting their benefits for a wide range of health conditions, including cardiovascular disease, cancer, diabetes, autoimmune diseases, and, more recently, neurological and mental health disorders. Today, consumers buy flaxseed as whole seeds for grinding in coffee mills or for consumption as flaxseed oil in gel capsules. It?s now left to the food industry to make flaxseed available to consumers in new, convenient and innovative forms.
Composition and function
Flaxseed?s composition is unique among food grains. Nutritionally dense with a mild, toasty-cereal flavour, it should have everything going for it. First, it is an oil seed, containing 40 per cent oil by weight, 95 per cent of which is unsaturated and 55 per cent as highly desirable omega-3s. In addition, the whole seed consists of 20 per cent protein, 27 per cent dietary fibre and 2 per cent polyphenolic antioxidants, including lignan phyto-oestrogens.
All this, when corrected for ash and moisture, leaves little room for digestible carbohydrates—known to marketers as ?net? carbs—which weigh in at 0-3 per cent. Whole flaxseed typically contains 0-3 per cent net carbs. Flaxseed is available to food manufacturers in a variety of forms.
Whole flaxseeds are used primarily for decoration and texture in baked products, or purchased for home grinding. It is critical, however, that whole flaxseeds be of high quality—damaged seeds are prone to develop rancidity, a process detectable by a musty ?oil paint? smell in the seeds.
Rancidity is not just unappealing, it?s unhealthy because oxidation of fatty acids produces free radicals. Note also that seeds must be cracked or ground to access their full nutritional value—whole seeds were designed by nature to travel through gastrointestinal tracts intact.
Flaxseed oil is highly unsaturated and consumed for its omega-3s, which exist as alpha-linolenic acid. Lignans are not found in flaxseed oil except as suspended solids. The average American consumes too many omega-6s, not enough omega-3s. Flaxseed is the only major grain in which omega-3 content far exceeds its omega-6 content.
Omega-3s have two primary functions: as structural fats in membrane tissues, and as precursors for prostaglandins, which are mediators in controlling blood pressure, clotting, immunity and other physiological activities. Human metabolism converts 5-10 per cent of alpha-linolenic acid into the long-chain omega-3s, docosahexaenoic acid, DHA, and eicosapentaenoic acid, EPA, the omega-3s typically obtained from fish oil or algae. All three omega-3s are important to cell-membrane function and metabolic health.
Pure flaxseed oil, however, is highly susceptible to oxidation. Hence, it must be protected by gelatine layers, encapsulation or antioxidant admixtures. It is more practical for use as a nutritional supplement than as a food ingredient, although it could be added to certain products, such as salad dressings and margarines, with very low heat exposure or dissolved oxygen content.
Flaxseed meal is created by pressing flaxseed oil for food or industrial purposes (as linseed oil), typically using screw presses that leave a residual meal. The meal typically contains only about 10 per cent residual flaxseed oil (approximately 5-6 per cent omega-3s) and proportionally higher levels of protein and dietary fibre. The meal can be ground into fine flours that offer good water-binding properties in baked and other food products. Care should be taken, however, to ensure that residual oils in the flour have not been overly abused or exposed to oxygen during pressing. A simple peroxide valuation test should ascertain whether the meal is stable or not.
Flaxseed bran is a relatively recent addition to the flaxseed ingredient portfolio. Flaxseed bran contains 12 per cent fat, 55 per cent dietary fibre and 6 per cent lignan phyto-oestrogens in the form of secoisolariciresinol diglycoside (SDG). Recent groundbreaking studies at the universities of Saskatchewan and Toronto suggest that SDG lignans confer anticarcinogenic and cardio-protective properties. Several studies suggest that SDG lignans may alleviate menopausal discomfort and function as a natural hormone-replacement (HRT) alternative. Consequently, there has been interest in using flaxseed bran in both food and nutritional products that target women?s health (breast cancer and HRT) or men?s health (prostate and colon cancer).
The dietary fibre of flaxseed hull is about evenly split between an insoluble fibre fraction and a highly soluble, prebiotic mucilaginous fibre fraction. This gives the flaxseed hull a high-water absorption, moisture-binding capacity as well as lubricity. This helps dough through-put and puffing during extrusion processing (cereals, snacks or pet foods) or as a transfat-free shortening alternative in cookies, muffins, breads and other baked goods.
Whole-milled flaxseed is commercially available as either brown flaxseed or yellow flaxseed flour in a variety of mesh sizes. Its nutritional composition reflects that of the whole seed ? 20 per cent omega-3s, 27 per cent dietary fibre, 1 per cent lignans and very little net carbs.
Despite flaxseed?s high oil content, its mucilaginous fibre will hold considerable moisture in a formula, contributing softening while inhibiting drying or staling. Whole-milled flaxseed has traditionally been used in bread formulations, particularly in Canada, but driven in part by the low-net-carb revolution and its recent availability in new forms, it?s finding its way into a broader range of products. For example:
- Pizza crusts, flatbreads and tortillas: Replace 20-30 per cent of the flour in bread, pizza crust, flatbreads and tortilla formulations with whole-milled flaxseed. This will significantly reduce net carbs and contribute as much as 1,800mg omega-3 per 45g serving. Make sure to use a fast-acting yeast, minimise mixing times and pay particularly close attention to dough conditioners to improve machining quality. Use of a finer-grind flaxseed (20-mesh) also improves dough texture and machinability.
- Batters and breadings: Whole milled flaxseed holds up well under deep-frying, contributing colour and flavour, and can be used to replace up to 50 per cent of the bread crumb or flour portion of a batter, breading or crust.
- Beverages: A pasteurised, finely milled whole flaxseed suspended into soy milk, fruit beverages or meal-replacement beverages at 2-3 per cent will undergo pasteurisation and homogenisation and only minimally thicken the product. Adding 2.2 per cent flaxseed to a soy milk will contribute 1,200mg omega-3s, 1.4g dietary fibre and 85mg in total phyto-oestrogens, as lignans and isoflavones, to an 8oz (227g) serving.
As with other grain ingredients, attention needs to be paid to lipid stability. With proper seed selection and handling, the oil in flaxseed is encapsulated within a grain mix rich in protective antioxidant barriers.
As with many whole grains and brans, flaxseed exhibits a naturally high antioxidant content, about 2.5 times that of blueberries using the Trolox Equivalence assay. If these protective barriers are breached through insect damage, drought, weed stress or during processing and handling, oxidative rancidity could develop.
Some companies package flaxseed under vacuum, in nitrogen atmospheres, stabilised using heat or admixed with complex antioxidant packages. Pizzey?s Milling has patented a process that capitalises on the discovery that damaged or otherwise pro-oxidant seeds exhibited colour changes that allow them to be colour-sorted out of the incoming product stream prior to milling (US patent: 6,368,650).
Combined with proprietary milling and handling techniques, whole-milled flaxseeds thusly treated remain stable indefinitely under ordinary, ambient storage conditions. Stability should not be a concern if the flax is properly processed. If there is a concern, it is recommended to add a peroxide value specification to incoming ingredients.
Daniel Best is the Chicago-based marketing director for Pizzey?s Milling, North America?s largest supplier of speciality flaxseed ingredients.
All correspondence will be forwarded to the author.