Major non-starch components of grains Flashcards
FODMAP
Fermentable oligo-, di-, mono- saccharides and polyols.
NSPS
Hemicellulose/ non-starch polysaccharides
Major hemicellulose
- Arabinoxylan
- Beta-glucan
minor hemicellulose
- Galactomannan
- Glucomannan
- Pectin
- Inulin (Fructans)
Why is cellulose water insoluble?
Intramolecular hydrogen bonding
* CHO are polymers of sugar and cellulose in polymer of glucose with lots of function hydroxyls so as individual molecules the glucose can hydrate with water but in the polymer there is the potential to pack very tightly and align forming hydrogen bonding and water cannot penetrate.
* Can be further strengthed by lignan
What is MCC?
micro-crystalline cellulose - celluose derivative
* used in food applications as texturizer, anti-caking agent, fat substitute, emulsifier, extender, bulking agent, etc. Also, highly used in the formulation of vitamin supplements or tablets.
* Use HCl to penetrate amorphous regions of cellulose to separate crystals and makes a powder
What is in the cellulose biomass structure?
lignin and hemicellulose can be present with the cellulose from pulping residue so first have to purify the cellulose
About hemicellulose
- Polysaccharide components of plant cell walls other than cellulose
- Water soluble and insoluble fractions exist; but all hydrate well
- Extractable by dilute alkaline solutions
- Exist in abundance in wood tissues (1/3), grain husk (1/4) and bran (1/12)
major hemicellulose consumed in Canada
- arabinoxylan
- fructans
What grain is rich in arabinoxlyan?
Wheat: cell wall >90% Arabinoxylan
About AX
arabinoxylan
* pentosan (polymer of pentose sugars)
* Cell wall polysaccharide
* Beta (1-4) linked xylan backbone
* Arabinofuranose side chains through alpha 1-2 or 1-3 glycosidic linkage
* Important in baking (functions in sync with gluten protein to hold gas)
* Improves water binding and loaf volume in baked goods.
* Retards staling.
* Usually exist in complex with phytochemicals, which influence their solubility
Solubility of AX
AX in wheat bran is mainly water insoluble. However, AX in wheat endosperm & white wheat flour show better solubility
* Water insoluble AX pentosans are higher in molecular weight and highly branched than water soluble AX pentosans
ferulic acid with AX
- Esterified with ferulic acid (phenolic acid)
- Less soluble
- Impede xylanase action
- hydrophilic and hydrophobic sections
treatment for ferulic acid-AX
Ferulic acid esterase or alkaline treatment can enhance xylanase hydrolysis
diferulate with AX
Peroxidase can catalyse the “diferulate” formation creating a cross-link further compacting the structure
* Cross-linked by diferulate
* Less soluble
* Impede xylanase action
AX is naturally a soluble fibre but in wheat bran it is insoluble why is this?
AX interacts with other things in the bran, complexing them and making it less hydrophillic, thus less water soluble
treatment for diferulate-AX
Ferulic acid esterase or alkaline treatment can enhance xylanase hydrolysis
phytic acid with AX
- Cross-linked by phytic acid
- Less soluble
- Impede xylanase action
Role of methylation in pectin
Some are methylated and can form hydrogen bonding (hydroxyls too) allowing pectin to connect to form the network of the pectin units (intermolecular associations) and network formation produces the gel.
* Depending on the degree of methylation can produce soft gels or hard gels. If lots of methyl and hydroxyl groups present than can for the hard methylation pectin (HMP) or if there is less then LMP
About Inulin (fructan)
- Soluble Dietary Fiber – low caloric
- Primary use in food (Prebiotic, increase Ca2+ absorption)
- Bland flavor; Sweetness – 1/10 of sucrose
- Very low aqueous viscosity
- Helpful in blood sugar management (i.e. Type 2 diabetes)
- Lead to gas and bloating
- Inulin is a fructose polymer by β(2→1) glycosidic links with terminal glucose
molecular structure of cereal beta-glucan
Linear polymer of beta-glucose units
* mixed linkages: Linear cellulosic units connected through beta (1→4) or (1→3) linkages creating a kink.
* The more kinks the more soluble, the more linear units the less soluble
Network formation by β-Glucan
occurs possibly through micelle formation
* zones of longer chains interact when hydrated forming junction zones or Cellulosic Microcrystalline Region
junction zones of beta glucan
tend to for hydrogen bonding when highly packed sections overlap
What factors influence beta-glucan aqueous solubility and viscosity?
Major Health Benefits of Barley/Oat Beta-glucan
- Cholesterol reduction and cardiovascular health
- Helps in the management of diabetes
- Improves gut health and immune function
- Body weight management
3 major mechanisms by which beta-glucan lowers cholesterol
- The bile acids aid in fat digestion and are pushed into GIT. The b-glucan has ability to trap the bile acids so does not complete the fat absorption and is excreted.
- Without beta-glucan the bile acids are reabsorbed and go back to liver and recirculated but instead liver takes up circulating cholesterol to make more bile acids.
- Liver also synthesizes cholesterol so the beta-glucan when fermented generates the SCFAs. The propionic acid can be absorbed and can block some enzymes that are for bile acid synthesis.
key attribute of beta-glucans for health benefits
viscosity via micelle formation
