NBA7 Food matrix and digestion: lipids
29 important questions on NBA7 Food matrix and digestion: lipids
What are dietary lipids?
- Triglycerides (TAG): 90-95% dietary intake (30-150 g/day)
- Phospholipids
- Sphingolipids
- Glycolipids
- wax and wax esters
- Cholesterol and cholesterol esters
- Lipophilic vitamins: A, E, D, K
- Carotenoids
Fatty acids (FA)
What is the relevance of lipid digestion to human health?
- Amount of lipids absorbed
- caloric content of food
- bioavailability of essential nutrients: omega-3 fatty acids; lipophilic vitamins
- amount of fat and bile salts delivered to gut
- Kinetics of lipid digestion (appearance of lipid products in the gastrointestinal lumen and blood)
- inflammation and development of cardiovascular events, etc.
- regulation of satiety and caloric intake
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In what forms are lipids in the food matrixes?
- Continuous phase (e.g. Olive oil)
- Oil in water emulsions (e.g. Mayonnaise)
- Water in oil emulsions (e.g. Butter, margarine)
- Continuous solid matrix embedding other solids (e.g. Chocolate)
- Lipids inclusions in a continuous matrix (e.g. Cheese, cookies)
- Lipids encapsulated within cell walls (e.g. Intact nuts, soybean, etc.
- Continuous phase in porous matrix (e.g. Fried products)
- In the core of natural emulsions (oil bodies in plants; milk fat globules; lipoproteins in eggs; organelles in adipocytes
What are the molecular aspects of lipid digestion
- gastric lipase: digests short and medium-chain fatty acids
- pancreatic lipase with colipase: digests triacylglycerols
- phospholipase: digests phospholipids
- cholesterol esterase: digests cholesterol esters
Kinetics of FA release form TAG of different composition
- Steric hindrance on ester bonds
- FA transfer into mixed micelles [the speed depends on the length of the FA]
- Precipitation with Ca2+
Kinetics of FA release form TAG of different composition
- Steric hindrance on ester bonds
- FA transfer into mixed micelles [the speed depends on the length of the FA]
- Precipitation with Ca2+
Stereo-specificity of FA distribution in TAGds to be known ?
CM with PUFA preferentially on sn-2 higher PUFA levels at early stage
CM with PUFA preferentially on sn-1 and 3
Affects the stereo-specificity of TG re-assembled in enterocytes
- Peripheral hydrolysis of TGs (chylomicron clearance and postprandial lipoemia)?
- lipid metabolism?
Stereo-specificity of FA distribution in TAGds to be known ?
CM with PUFA preferentially on sn-2 higher PUFA levels at early stage
CM with PUFA preferentially on sn-1 and 3
Affects the stereo-specificity of TG re-assembled in enterocytes
- Peripheral hydrolysis of TGs (chylomicron clearance and postprandial lipoemia)?
- lipid metabolism?
What are the colloidal aspects of lipid digestion: droplet interface
- Lipase activity occurs at the droplet interface
- Multiple surface active compo
unds compete for the interface
- lipase activity can be hindered by surface active molecules at the surface
What are the colloidal aspects of lipid digestion: effect of emulsions properties on lipid digestion [human studies]
- Pre-emulsification of dairy fat (milk vs spread) increases the rate of appearance of chylomicron-rich fraction TAGs in blood
- Reduction of droplet size increases the rate of lipid digestion in stomach and small intestine
- No effect on total lipid bioavailability!
What are the colloidal aspects of lipid digestion: effect of emulsions properties on lipid digestion [human studies]
- Pre-emulsification of dairy fat (milk vs spread) increases the rate of appearance of chylomicron-rich fraction TAGs in blood
- Reduction of droplet size increases the rate of lipid digestion in stomach and small intestine
- No effect on total lipid bioavailability!
What are the aspects of lipid digestion: effect of type of emulsifier and emulsion stability
- change of charge
- digestion of interfacial proteins by pepsin and pancreatin
- displacement by hydrolysis products
- viscoalasticity of interface as barrier to coalescence
Colloidal aspects of lipid digestion: in e.g. Milk
lipolysis faster on smaller compared to larger NATIVE globules
No difference in lipolysis in HOMOGENIZED compared to NATIVE globules!
Colloidal aspects of lipid digestion: in e.g. Hazelnuts
raw --> the co-lipase lipase and bile salts can not enter
roasted --> the co-lipase lipase and bile salts can enter
Colloidal aspects of lipid digestion: emulsion stability in the stomach
Fast delivery of fat-depleted fluids to small intestine. Less activation of the inhibitory feedback including CCK
Food structure and lipid digestion, liquid, gel ish, fast
the digestion is different with the different food structures
area under the curve
How goes the lipid digestion in cheese?
- Rate of proteolysis
- Gastric emptying half time
- Size of the fat globules
- Calcium levels
Physical state (solid/liquid) of dietary fat
- Solid fat digested more slowly than liquid fat
- lipase absorbs more easily to liquid then solid droplets
- lipids tightly packed into crystals less accessible to lipase
level of starvation decreases and rate of lipolysis decreases [from oil to butter]
Plant tissues, cell wall integrity and lipid digestibility; why are almonds in real time 480kcal in stead of 630kcal?
What is the effect size across different nuts? [plant tissues, cell wall integrity and lipid digestibility]
particle size distribution after mastication?
almond 26% less
walnut 20% less
pistache 5% less
What is the effect of mastication (chewing)
- 43.7% after 10 chews
- 32.7% after 25 chews
- 30.8% after 40 chews
Where else you expect to find lipids within cell walls?
- (table) Olives
- sunflower seeds
- chia seeds
- storage seeds:
- cereals
- legumes
- tree nuts
- seeds
- fruits: avocado
- algae and microalgae
- fungi/mushrooms
Ca2+ ions , what is important [dietary modulators of lipid digestion]
- Solubility of calcium soaps decreases with the FA chain length
- Solubility of calcium soaps decrease with saturation level
What needs to be know about Ca2+ ions and lipid digestibility of infant formulas?
- Palmitic acid (C16:0) mostly esterified in sn-2 in breast milk compared to infant formulas
- better absorption of palmitic acid and fat (less fat lost in stool)
- higher fraction of post-p
randial TG with palmitic acid at sn-2
What are the roles/impacts of dietary fibre [dietary modulators of lipid digestion]
- Slow down rate of gastric emptying (soluble DF)
- Slow down propulsion and mixing (soluble DF)
- Reduce diffusion coefficients for lipid droplets, lipase and mixed micelles (soluble DF)
- Reduces emulsification efficiency: bigger droplets, less surface area available to lipases (soluble DF)
- May induce coalescence or flocculation of lipid droplet (depletion flocculation): bigger droplets, less surface area for lipases
- May interact and sequester bile acids: reduces emulsification
- May sequester Ca2+ ions
reduces lipid digestion (rate and/or extent)!
What are lipase inhibitors?
- Polyphenols
- Flacan-3-ol monogallate esters
- procyanidins (tannins)
- theaflavins
- Alkaloids (caffeine, theobromine, theophylline)
- Saponins (in species, legumes)
- Fucoxanthin and fucoxanthinol (in brown algae)
- Alginates (in algae or as an additive)
Which of this statements on pancreatic lipase is wrong?
- it acts at the interface between fat globules and water
- it can be inhibited by polyphenols
- surfactant may hinder its binding to the surface of the globule
- its action on TAGs produces 3 free fatty acids glycerol
Which of the following statements is wrong
- emulsification improves rate of lipid digestion in SI
- grinding increases caloric content of nuts
- interesterification can change the kinetics of TG hydrolysis
- Rate of lipid digestion is inversely proportional to emulsion surface area
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