Many plants use starch polysaccharides as a form of energy storage Two non starch polysaccharides used in much the same way are Inulin Konjac glucomannan
Inulin is composed of beta D fructofuranosyl units linked 2 1 Chains often (but not always) terminate at the reducing end with a sucrose unit DP 60 DP range generally 2 60 Most abundant fraction DP 15 22 Second most abundant fraction 27 34
Very susceptible to hydrolysis due to fructosyl moiety Inulin is a storage polysaccharide and thus is constantly being synthesized and broken down so usually it occurs as a mixture of fructose oligosaccharides (FOS)
Depends on a number of factors such as source, growing conditions, harvesting conditions, and storage time after harvesting Botanical sources Onion Asparagus Banana Chicory (main commercial source) Jerusalem artichoke root
Long history of use since humans have been eating the sources from antiquity Jerusalem artichoke was a major source of carbohydrate for Western Europeans before introduction of the potato
Treat with lime, then carbon dioxide, centrifuge or spray drying
Extract is largely a mixture of oligosaccharides (see Table 9.1) Monosaccharide: 2% Disaccharide: 5% Oligosaccharide: 93% DP range: 3 60 DP avg: 8 10 Max amount of inulin in chicory roots is about 18% (dry weight basis)
Water soluble especially when heated (40 80 o C) Should be neutral as inulin is very sensitive to acidcatalyzed hydrolysis Max concentration 50% When greater than 25% hot solutions are cooled, they form a thermoreversible gel Gel strength increases as concentration increases Synergism with alginate, some carrageenans, gellan, low methoxyl pectin, starch and gelatin
Gels may be described as particle gels Fat like, creamy texture Hence, its use as a fat mimetic and/or processing aid in Ice creams and sauces No fat icings, whipped toppings, potato products Nutrition, breakfast, meal replacement and sports/energy bars Soy beverages and vegetable patties
Nutritional/physiological effects Increased fecal weight Laxative effect ph reduction of contents of the large intestine Stimulation of Bifidobacterium growth (good bacteria) Reduction of total and LDL cholesterol Glycemic index of zero Modulation of blood glucose levels
Supplies about 1.6-2.0 kcal/gram O
Inulin is often deliberately depolymerized to produce inulodextrins (FOS) May be had as a syrup or powder FOS are non digestible in the small intestine and are thus a component of dietary fiber Excellent prebiotics
Also known as konjac, conjac and konnyaku A mixture of beta D mannopyranosyl and beta Dglucopyranosyl units linked 1 4 Man:Glu = 1.5 2.0:1 with random distribution along the chain Very slightly branched (1.2 1.6% branch points) Native gum is slightly acetylated at C 6 (DS 0.05 0.17); MW ~ 10 6 O
KG flour obtained from the tubers of Amorphophallus konjac K.Koch Known as elephant yam, devil s tongue and voodoo lily in SE Asia Widely consumed in Asia in soups and stews
Clean tubers are sliced Dried Dry milled Cyclone separation from starch Glucomannan content 60-70% Washed and dried Ground: glucomannan content 80-95%
KG hydrates rapidly, absorbing up to 200x it s weight in water Viscous, pseudoplastic dispersions Higher temp and shear decreases time for full hydration Fairly acid stable Viscosity at 1%: 18,000 MPas
Thermally reversible gels produced by cooling hot solutions of KG and kappa carrageenan or xanthan Gels are strong and elastic Texture can be controlled by varying ratio of polysaccharides and total polysaccharide concentration More stable than pure kappa carrageenan gels KG more effective synergizer with kappacarrageenan than locust bean gum Best ratio of KG:kappa carrageenan = 2:3 O
Combination with xanthan can produce viscosity 3 times that of either gum alone Neither gum gels by itself Mixture produces gels with good freeze thaw stability KG more effective synergizer with xanthan than locust bean gum Some interaction with starches and modified starches to increase viscosity Heat stable gels are produced by freezing such cooked mixtures
Acetyl groups prevent native KG from gelling however if Ac groups are removed by deesterfication, gels can be formed De esterification: Treatment with calcium hydroxide (lime) and slight heating Cooling this produces a gel that withstands boiling or even retorting without melting Gels are stable at low ph
Methods of gelation KG + kappa carrageenan KG + xanthan KG + alkali KG + alkali + pasted starch KG + pasted starch + freezing KG + xanthan + heating KG + kappa carrageenan + retorting Thermoreversible Heat-stable
KG is seldom used in the US Low ph stability makes it possible to make shelfstable desserts and gummy candies Can be used as a fat mimetic in meat products and vegetable burgers Binder in surimi, pasta, and noodles A source of dietary fiber Labelling: konjac, konjac flour, konjac gum, konjac glucomannan, or konnyaku