Additives and oligosaccharides: 337 foods rated

Cassia gum is a galactomannan from a legume seed - the same plant family as the pulses that dominate this axis, and the same galactose-based chemistry. It is used in small quantities, which is what keeps a fermentable galactan from being worse.

Karaya gum is a branched polysaccharide, longer than an oligosaccharide by definition - but the criterion that decides this axis in practice is fermentability, not chain length, and the colonic bacteria break this one down readily. It is also used as a bulk laxative, which is the same property under another name.

Konjac is glucomannan, and it is used precisely because it is not digested: it swells in water and is sold for satiety. What human enzymes leave alone, colonic bacteria ferment - and it is that fermentation, not the chain length, that puts glucomannan with the oligosaccharides.

Tragacanth is a plant exudate used as a thickener, and a substantial fraction of it ferments. Chain length would put it outside the oligosaccharides; behaviour in the colon puts it inside, and behaviour is what the level reflects.

Acacia gum is a branched arabinogalactan, and it is sold as a prebiotic fibre for exactly the reason it counts as an oligosaccharide here: the colonic bacteria ferment it. It does so more slowly and more evenly than inulin, which is why it is often better tolerated than its level suggests.

Polydextrose is glucose polymerised at random into chains of every length, and the short end of that distribution falls squarely in the oligosaccharide range. The random branching is the point: no human enzyme recognises it, so it passes to the colon whole.

Dextrin is partially hydrolysed starch — glucose chains cut short, which puts some of them in the oligosaccharide range rather than the polysaccharide one, and that is why it reaches this axis at all where an intact starch does not. What holds it low is that the chains are glucose: Noack and Timm measured it fermenting more slowly and with less gas than inulin, which is a fructan. Both worked in vitro on a purified supplement, so they compare fibres and do not give a content per 100 g.

• Timm D.A. et al., J Med Food 13:4 (2010) 961-966
• Noack J. et al., Nutrients 5:5 (2013) 1500-1510, in vitro fermentation of wheat dextrin against inulin and psyllium

Lecithin is a phospholipid - a fat, a phosphate and a small polar head. There is no chain of sugar units in the molecule, so no oligosaccharide, and it is used in fractions of a percent.

Maltodextrin has "dextrin" in the name and short chains in the bottle, which is exactly why it gets avoided by mistake. The chains are alpha-1,4 glucose, the linkage our own enzymes are built for - so what makes an oligosaccharide here is the linkage and not the length.

Pea protein is isolated with water, and the pea's GOS are water-soluble - so they go into the fraction that is thrown away. A pea protein powder and a bowl of peas are opposite ends of this axis despite the same origin.

• Švejstil R. et al., Sci Agric Bohem 46:2 (2015) 73-77, raffinose-series oligosaccharides in soybean products

Pectin is a long chain - a polysaccharide of hundreds of units, not the three to ten of an oligosaccharide - and it is used at well under one percent. It ferments, which is why the level is low rather than none.

Ponceau 4R is an azo dye - a synthetic aromatic molecule with no sugar unit anywhere in it - used in milligrams. It sits at low rather than none because the additive category is reviewed as a block, not because an oligosaccharide was found in it.

Potassium nitrite is a mineral salt, and salts have no carbohydrate chemistry at all. What is worth checking is the curing mix it comes in, which often carries dextrose as a carrier - glucose, a single unit, and never an oligosaccharide.

Soy protein isolate is the protein separated from everything else in the bean, and the GOS are part of the everything else - they leave in the water. Protein extraction is one of the most effective ways to strip a legume of its chains.

• Švejstil R. et al., Sci Agric Bohem 46:2 (2015) 73-77, raffinose-series oligosaccharides in soybean products

Soybean hemicellulose is a cell-wall polysaccharide recovered from the okara left after soy milk is made. It is a long branched chain rather than a short one, and it is used in small quantities to stop drinks separating.

• Švejstil R. et al., Sci Agric Bohem 46:2 (2015) 73-77, raffinose-series oligosaccharides in soybean products

Tara gum is a galactomannan from a legume seed, so the chemistry is the same galactose-based one as the pulses - but it is used as a thickener at well under one percent. Chemistry puts it on this axis; dose keeps it low on it.

Xanthan is a bacterial polysaccharide, far longer than an oligosaccharide, and used at a fraction of a percent. It ferments in the colon, which is what keeps it at low rather than none - the criterion here is behaviour, not just length.