Mastering fibre in GI foods

Working with dietary fibre can be tricky. DANIEL BEST explains how to successfully formulate foods rich in whole grains and brans for the coming revolution in gastrointestinal health

The low-carb quake of 2004 delivered an unpleasant but necessary jolt to a complacent carbohydrate foods industry. The good news is that this opens a unique window of opportunity for carbohydrate foods manufacturers to help consumers regain a renewed appreciation for the essential importance of grain-based foods to health — and thereby buffer the industry against future jolts.

Dietary fibre is the defining component in whole-grain and bran ingredients. It is also one of the major reasons why these ingredients can be tricky to work with. As we work through the following examples, keep one concept firmly in mind: water management.

How to make the switch
Switching to whole grains from refined flour is hardly a seamless transition. For one, don?t make the mistake of thinking that all whole grains are necessarily ?high fibre.? Whole-oat flour typically has only 14 per cent total dietary fibre, whole wheat flour 12 per cent and whole brown rice five per cent. Even at these low levels, the fibre contents of whole-grain flours will significantly impact performance.

Flours high in soluble fibre content may be very gummy — flaxseed, oat, and barley flour come to mind — which limits their application levels in products. Whole wheat and corn flour, however, contain mostly insoluble fibre. Product gumminess can be partially mitigated through combinations of flours to balance soluble fibre content.

The good news about soluble fibres is that they bind moisture, inhibit staling and thereby extend shelf lives of bakery products. Insoluble fibres, however, absorb moisture slowly and, if not properly hydrated in process, can cause products to dry and stale prematurely. Dietary fibres can draw water away from other ingredients (eg, gums, wheat gluten) interfering with their functionality. So, the first lesson when working with whole grains is to try to predict how they will interact with water.

Consider the impact of constituent fibres on dough or batter viscosity, processing and handling, finished product quality and shelf life. It may be necessary to adjust water contents accordingly. Recognise that not all flours are equal — any flour will vary in composition by cultivar, growing region, season and year-to-year harvests (see sidebar) — so the quality of incoming whole-grain flours needs to be continuously monitored and formulas adjusted accordingly. And always shelf-life test high-fibre formulations before releasing them into the marketplace.

A second consideration, especially in baked goods, is proteins, particularly for flour systems where gluten activity is key to dough strength and structure. A switch from refined wheat flour to whole-grain wheat flour entails a reduction in gluten content, which will affect the mix tolerance and loaf volume in breads and the textural integrity, process-tolerance and spreadability of tortillas.

In some cases, you may need to compensate by adding back wheat gluten or wheat protein isolate, if making a leavened product, or a soy or milk protein to strengthen a cookie, cracker or extruded chip against breakage. In some cases, film-forming gums (xanthan) and proteins (milk whey or egg albumen) can be used to mimic the structure and gas-entrapping properties of a protein matrix (such approaches are used by companies marketing ?gluten-free? products).

However, if you need to add back commercial wheat glutens or isolates, compare and contrast them carefully as they vary considerably in their textural and handling properties. The ultimate test is when a dough formula is subjected to industrial processing conditions. High fibre, gluten-strengthened formulas may cause doughs to become overly tight or ?bucky? when submitted to high-speed production conditions. Third, many of the otherwise desirable phenolic antioxidants and other tannins in whole-grain flours are bitter tasting. Strong antioxidant activity can affect gluten formation in doughs, so consider using pro-oxidative dough conditioners to encourage gluten development. Traditionally, one can add salt to a formula to help mitigate bitterness, but a number of flavour companies have recently developed flavour systems designed to take the edge off whole-grain bitterness.

Finally, there is the issue of enzyme activity: the outer layers of grains can retain considerable enzyme activity harmful to product integrity. Probably the best recognised example of this are the lipase and lipoxygenase enzymes associated in oat flour, which can hydrolyse unsaturated fats to cause soapy flavours and odours to in products over time. Similar enzyme activities are found in other whole grains, such as wheat or barley.

Therefore, it may be important that whole-grain flours and brans be heat-inactivated prior to use. To this question, consult carefully with your suppliers as the degree of enzymatic deactivation to which their whole-grain flour, bran or dietary fibre has been subjected.

Bran identity
Brans offer all the nutritional, nutraceutical and ingredient-label benefits of whole grains, writ large. Ditto for their effects on product formulas — take each of the points made in the preceding two paragraphs and magnify them several-fold. The dietary fibre component of brans is much higher — corn bran contains approximately 85 per cent insoluble dietary fibre, while oat bran, of beta-glucan fame, typically contains 24 per cent total dietary fibre as a blend of both soluble and insoluble fibre fractions. Soy offers two types of fibre ingredients — soy bran or hull fibre is rich in insoluble cellulose fibre (75-78 per cent) — while soy cotyledon fibre is rich in soluble fibre.

Let it be said: Brans are water hogs. Pectin-rich sugar-beet fibre binds approximately three times its weight in water. Soy bran, corn bran, wheat bran and apple pulp fall only slightly behind, whereas rice and oat brans bind approximately their own weight in water. When formulating, both the degree and rate of water absorption need to be taken into account.

The textural and nutritional appeal of brans has much to do with their large particle size. Unfortunately, increased particle size reduces particle surface area and slows water uptake, which can complicate processing.

Ever wonder why good bran muffins cost so much? It could be because a bran muffin formula is used that requires the batter to be hydrated for 24 hours. A challenge is where to store a full production run of batter for 24 hours under refrigeration, so as to keep the wrong kind of microflora from prospering. This problem could be rectified by using a smaller particle size, but that would negate the bran?s textural contribution.

Not only are whole grains and brans good for you, they also convey a positive consumer-friendly image to an ingredient label. This has not gone unnoticed, as everyone is falling in line, from the largest food players — General Mills, The Quaker Oats Company and Kraft Foods — to smaller high-end ones such as Monterey Gourmet Foods. This is an industry-transforming race by companies big and small to reconfigure their product lines into next-generation carbohydrate foods.

There have been scattered industry reports of shortages for some bran ingredients, such as corn, as millers switch their production capacity from refined- to whole-grain flours to satisfy demand. Even with these challenges, one thing?s for sure — demand is only going up.

Daniel Best is president of BEST VANTAGE Inc, a food and nutritional ingredients market development firm based in Illinois. Respond: All correspondence will be forwarded to the author.

Reasons to use whole grains, brans and dietary fibres
  • They displace calories: insoluble fibres typically contribute less than 1.0Kcal/g and soluble fibres about 2.0-3.0Kcal/g, in contrast to proteins (4.0Kcal/g), digestible carbohydrates (4.0Kcal/g) and most oils (9.0Kcal/g).
  • They can bind and flush cholesterol, carcinogens and undesirable chemicals from the body.
  • They provide bulk, regulate intestinal motility and thereby help prevent the development of diverticulosis and other disorders of the gastrointestinal lining.
  • In the case of whole grains and brans, they contribute essential nutrients (antioxidants, minerals, lignans and omega-3s).
  • They can reduce a product?s glycaemic load — the rate at which a food releases sugar into the bloodstream — by displacing high-glycaemic carbohydrates (starches, sugars) interfering with enzymes that hydrolyze starches into sugars and impeding the diffusion of sugars from the intestine into the blood stream.
  • Whole grains, brans and dietary fibres are full of prebiotics, the Miracle-Gro for intestinal micro flora.

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