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Jennifer Grebow is editor-in-chief of Nutritional Outlook.
Why is fiber testing so challenging? One reason is the sheer gamut of dietary fiber types on the market.
Fiber health claims are prized by food and drink makers. In order to make a fiber claim, total fiber content must meet the legal threshold, and in order to calculate a product’s total fiber content, manufacturers must use accurate analytical methods. The reality today is that fiber content is often extremely difficult to quantify for various reasons. At the Institute of Food Technologists’ Annual Meeting and Food Expo in Chicago in July, Nutritional Outlook interviewed fiber suppliers Beneo (Manheim, Germany) and Tate & Lyle (Hoffman Estates, IL) about how fiber-testing methodologies are advancing.
Why is fiber testing so challenging? One reason is the sheer gamut of dietary fiber types on the market. There are insoluble and soluble high-molar-weight fibers (cellulose, pectins, lignans, beta-glucans, etc.). Then there are resistant starches. And, finally, there are low-molar-weight fibers, including prebiotics such as inulin, fructooligosaccharides, galactooligosaccharides, polydextrose, etc. The list goes on. Analytical laboratory Eurofins (Heerenveen, the Netherlands) provides a good breakdown of fiber ingredients on its website.
Fiber molecules themselves are also complicated, Mervyn L. de Souza, PhD, vice president, health and wellness, global R&D, innovation and commercial development, for Tate & Lyle, told Nutritional Outlook at IFT.
“Fiber tends to be a more complicated ingredient because it’s not like sodium,” de Souza said. “Other ingredients, like salt (sodium chloride), are a lot simpler. Fibers tend to be larger molecules, and they have different kinds of linkages. They’re just inherently more complex.”
Analyzing fiber content in a finished product containing other ingredients is even more difficult “because you have more confounding issues due to interactions with the food” and with other ingredients. “You can either sometimes get a higher reading or a lower reading depending on what else is in there and how it’s interacting with the ingredient,” he said.
To illustrate the challenges analyzing fiber, de Souza used beta-glucan as an example: “Beta-glucan is a beta-linked fiber, if you will. So, it’s glucose units linked by beta linkages. When you do a standard fiber analysis, you also have starch present. Starch is alpha linkages (glucose linked together with alpha bonds), but very often, in the standard analysis, the starch can contribute to the carbohydrate analysis, so you get an artificially high reading when you measure beta-glucan.”
One way Tate & Lyle has been able to overcome some of these challenges is to use an enzyme like alpha-amylase to “break down all the starch and then analyze for beta-glucan,” de Souza said. “So, you’ve taken out any confounding information. You break down the contaminants that might influence the ingredient you’re trying to analyze for.”
Scientists’ ability to analyze different fibers and to devise fit-for-purpose test methods are improving. Part of this is due to technology advances resulting in more accurate and reliable methods. “There have been a lot of advances in analytical technology just in terms of sensitivity,” de Souza said.
Andrew Estal, director, customer technical service, Americas region, Beneo, added, “We used to be able to detect parts per millions of things, and now we can detect parts per trillions of things, so test methods are always being refined.”
De Souza did caution that increased sensitivity can also lead to more “noise” in the results. “As detection methods get more and more, lower and lower, there’s a tendency to want to get more analytical in terms of the details that you can subject a product to,” he said. “The issue is, a lot of these analytical methods are also very sensitive. So, when you apply a sensitive method into a complex matrix, you can sometimes really skew the results. There’s a lot of noise.”
Getting on the Same Page
Fiber suppliers continue to work very closely with testing labs to refine test methods. Some of those labs include Eurofins, Medallion Laboratories (Minneapolis), Covance Laboratories (Madison, WI), and analytical test supplier Megazyme, among others. Fiber suppliers, who are experts on their individual ingredients, remain intricately involved in the process.
Many testing labs and fiber companies abide by AOAC methods, which are constantly being refined according to fiber type as well as form (liquid, powder, etc.). In fact, now that FDA has finally accepted more fiber ingredients in its new, legal fiber definition, Estal posits that AOAC could take “renewed interest” in working on improving methods.
Fiber suppliers can help laboratories pinpoint the target. “It’s using the right method and performing the method correctly,” said Estal. “if you send something for fiber analysis, you actually have to tell the lab that you’re looking for fiber from oligofructose or inulin, or else they will completely digest it, hydrolyze it, and they won’t find the fiber.”
“Testing problems only happen if you don’t know what you’re doing or if you use the wrong method,” he continued. “The methodology takes some practice to get down, so we actually have a list of laboratories in the U.S. and globally that we’ve done round robin testing with, and we’ve come back with results that agree.”
Ideally, everyone-from companies to testing labs to ingredient suppliers and, finally, regulators-will get on the same page regarding the most accurate test methods to use and when. Companies will want to make sure that they can accurately calculate the total fiber content in their products to meet requirements and ensure that results are not artificially lower or higher, lest regulators come knocking for substantiation.
Fiber suppliers also continue to help their customers understand how best to test and who to get assistance from. “It’s not something that a lot of our customers are actually able to do themselves because it does take practice,” Estal said. Also, he said, “it requires some equipment that is not really totally practical for every company to have, and so really the best bet is using a certified outside lab that’s used to doing it on a regular basis.”
De Souza said Tate & Lyle will “analyze samples for our customers, too. Very often, our customers will send us samples with our fibers, or with competitive fibers, and we’ll help them and assist with the analysis.” And, he added, “we’re educating our customers as well on the analytical methods that are being used, for complete transparency, so they know what’s going on.”
“The devil is always in the details,” he concluded. “As we understand and unravel more about the details that become important, then it’s educating our customers on the details that really becomes the big difference.”