Technical Challenges (6) Flashcards
what are some main functionalities of lipids?
- lubricant and tenderizer
- heat exchange medium
- carriers of fat soluble vitamins
- contributors to mouthfeel and flavor
- textural ingredients of emulsions
- emulsifiers and surfactants
define a surfactant
lowers the surface tension between two compounds (between liquids, gases or solids)
what factors should be considered in selection of an appropriate lipid ingredient?
- nutritional profile
- flavor profile
- crystallization behaviour
- oxidative stability
- bulk physicochemical properties
- oil quality
what causes the distinctive flavour profiles of fats/oils?
their characteristic volatile breakdown products and impurities which can:
a) contribute directly
b) contribute indirectly
the partitioning of flavour molecules among oil, water and headspace regions during mastication depends on what?
the nature of the lipid phase (eg. polarity, viscosity, crystallinity)
what are important crystallization behaviours of lipids?
- melting and crystallization temp
- SFC (solid fat content) and temp profile
- crystal morphology
- polymorphic type
how can you limit crystallization? (3 methods)
- using oils with low melting points
- by removing high melting fractions
- adding components that retard crystal formation
how can you favour crystallization?
- use an oil with desired crystallization characteristics
2. modulating composition by blending, fractionation, inter-esterifcation or hydrogenation of oils
what word defines “solid-to-liquid” lipid transition
melting
what word defines “liquid-to-solid” lipid transition?
crystallization
what are internal and external factors of the morphology of crystals?
internal: molecular structure, composition, interactions
external: temp-time profile, agitation, impurities
nucleation rate increases more rapidly with ___ (incr/decr) temp than the crystallization rate
decreasing
what is nucleation?
the start of a new phase forming
compare the sensory properties of large and small crystals
large: grainy or sandy
small: causes cooling sensation
what is coalescence
when two or more particles merge during contact to form a single particle
describe partial and extensive partial coalescence
partial coalescence: increase in viscosity of an emulsion
extensive partial coalescence: conversion of an o/w emulsion to a w/o emulsion (eg. butters and margarines)
what should be considered when choosing an oil based on oxidative stability?
- ensure that lipid oxidation has not already occurred
2. has good oxidative stability throughout lifetime of the pdt
what affects the formation, stability and quality attributes of a food emulsion?
physico-chemical properties of the emulsion (such as viscosity, density, refractive index, etc…) which is affected by the type and conc of molecules within the oil phase
describe how oil quality have adversely affect suitability for a certain application
presence of off-flavours, pigments, phospholipids, FFAs
what 3 characteristics must a lipid ingredient have to be effective at enhancing formation and stability of emulsions?
- must rapidly absorb to the surface of the freshly formed emulsion droplets during homogenization
- must reduce interfacial tension by a significant amount
- must form an interfacial layer that prevents the droplets from aggregating under the conditions pertaining to the emulsion
what are functions of lipid ingredients as emulsifiers and surfactants?
- emulsifiers to improve emulsion formation and stability
- forming micelles
- solubilizers
- suspending agents
- crystallization modifiers
- wetting agents
- dispersibility
- complexing agents with biopolymers (starch and proteins)
what is HLB? define it.
hydrophile lipophile balance = ratio of hydrophilic to lipophilic groups
(aka the measure of the degree to which a surfactant is hydrophilic or lipophilic)
what is krafft point?
the minimum temperature to form micelles
what important functional properties should be considered for selection of a lipid emulsifier?
- surface activity and droplet stabilization (HLB: hydrophile-lipophile balance)
- molecular organization of surfactants (packing parameter and phase inversion temp)
- krafft point
- surfactant solubility (bancroft’s rule)
- cloud point
- solubilization ability of surfactants
what two factors should be considered when looking at the molecular organization of surfactants?
1) packing parameter
2) phase inversion temp
what is cloud point
temp in which a cloudy appearance begins
what is bancroft’s rule about surfactant solubility
The phase in which an emulsifier is more soluble constitutes the continuous phase
which phase is defined as the continuous phase? what rule is this based on?
the phase where the emulsifier is more soluble
based on bancroft’s rule
how can you increase stability of surface activity of a droplet (3)
- minimize contact area b/w hydrophilic and hydrophobic regions
- reduce interfacial tension
- enhance stability against aggregation by electrostatic and steric stabilization
what are 2 ways to determine HLB of a surfactant?
1) calculated from number and type of hydrophilic and lipophilic groups it contains
2) estimated from experimental measures
what is the equation used to calculate HLB?
HLB = 7 + sum of hydrophilic group numbers - sum of lipophilic group numbers
HLB provides useful indication of what? (2)
- solubility in either oil and/or water phases
2. type of emulsion that will be formed by a surfactant
describe a surfactant with HLB below 3
very hydrophobic
describe a surfactant with HLB of 3-6
hydrophobic
max emulsion w/o stability
describe a surfactant with HLB of 7-9
a good wetting agent
describe a surfactant with HLB of 10-18
hydrophilic
stabilizes o/w emulsions
forms micelles in water
describe a surfactant with HLB above 18
very hydrophillic
what are examples of products with high HLB numbers?
o/w emulsions: dressings, coffee whiteners, beverages
what are examples of pdts with low HLB
w/o emulsions: margarines and spreads
what are 3 drawbacks of HLB?
1) doesn’t take into account that the functional properties of a surfactant molecule are altered by changes in temp or solution conditions
2) optimum HLB # required for a surfactant to create a stable emulsion depends on the oil type
3) doesn’t provide insight into size or amount of surfactant required to form a stable emulsion or the stability of the emulsion droplets once formed
what is CMC
critical micelle concentration
what factors are included in the molecular organization of surfactants?
- chemical structure of surfactant molecule
- interactions of the surfactant molecules
- nature of the continuous phase
- solution composition
- temp
what is packing parameter?
p = v/a0*l
where:
v is the surfactant tail volume
l is the tail length
a0 is the cross sectional area of the hydrophilic head group
describe the properties of a surfactant when packing parameter (p) < 1
optimum curvature is convex (H0 < 0)
o/w
describe the properties of a surfactant when packing parameter (p) = 1
zero curvature (straight) (H0 = 0)
unstable
describe the properties of a surfactant when packing parameter (p) > 1
optimum curvature is concave (H0 > 0)
w/o
forms reverse micelles
packing paramter is equal to what?
packing parameter (p) = phase inversion temp (PIT)
what is PIT
phase inversion temperature
describe
a) a micellar system
b) a reverse micellar system
micellar:
- p < 1
- o/w
reverse micellar
- p >1
- w/o
describe the PIT graph in terms of surface tension and coalescence instability
from low temp to PIT:
- decreasing surface tension
- increasing coalescence instability
from PIT to high temp
- increasing surface tension
- decreasing coalescence instability
what does bancroft’s rule state?
the phase in which the surfactant is most soluble will form the continuous phase of an emulsion
what type of surfactant should stabilize o/w emulsions?
water-soluble surfactant
what type of surfactant should stabilize w/o emulsions?
oil-soluble surfactant
what does Bancroft’s rule not provide?
insight into the relationship b/w the molecular structure of a surfactant and the long term stability of the emulsions formed
what happens when you heat above cloud point?
dehydration of the hydrophilic head groups
describe what happens when temp increases towards cloud point
- temp is increased towards cloud point
- interfacial tension decreases
- droplets are easier to disrupt but more prone to coalescence
what factors determine the functional properties of swollen micellar solutions?
- location of the solubilizate within the micelles
- max amount of material that can be solubilized per unit mass of surfactant
- solubilization rate
the solubilization ability of surfactants affects what?
- selective extraction of nonpolar molecules from oils
- controlled ingredient release
- incorporation of nonpolar substances into aqueous solutions
what are common food grade lipid emulsifiers and surfactants?
- monoglycerides
- organic acid esters of monoglycerides
- polyol esters of fatty acids
- stearoyl lactylate salts
- lecithin
define a monoglyceride
surfactants produced by interesterification of fats or oils with glycerol
nonionic oil-soluble surfactants with low HLB numbers (2-5)
monoglyceirdes can be esterified with organic acids to form what surfactants?
- ACETEM: acetylated monoglycerides
- LACTEM: lactylated monoglycerides
- DATEM: diacetyl tartaric acid monoglycerides
- CITREM: citric acid esters of monoglycerides
ACETEM and LACTEM are what kind of surfactants?
DATEM and CITREM are what?
ACETEM and LACTEM are:
- nonionic
- oil soluble
- low HLB
DATEM and CITREM are:
- anionic
- water dispersible surfactants
- intermediate or high HLB
what determines the functional characteristics of a surfactant?
type of polyol and fatty acids used
surfactants with large polyol head groups tend to be _____ with ____ (high/low) HLB)
surfactants with small polyol head groups tend to be ____ with ___ (high/low) HLB)
water dispersible; high HLB
oil soluble; low HLB
what is SSL
- sodium stearoyl lactyate
- anionic water dispersible surfactant
- intermediate HLB
what is CSL
- calcium stearoyl lactylate
- anionic oil soluble surfactant
- low HLB
what are lecithins? what can they be extracted from?
- naturally occurring surface active molecules with a mix of phospholipids and other lipids
- can be extracted from many sources (eg. soybeans, rapeseed, egg)
what are examples of phospholipids in lecithin?
- phosphatidylcholin (anionic)
- phosphotidyl-ethanolamine (zwitterionic)
- phosphatidyl-inositol (zwitterionic)
describe the properties of natural lecithin
- intermediate solubility
- HLB = 8
- not very suitable for stabilizing o/w or w/o emulsions when used by itself
how can lecithin be modified to be more capable of stabilizing o/w emulsions?
it can be chemically or enzymatically hydrolyzed to break off one of the hydrocarbon tails to produce more hydrophilic surfactants
