Technical Challenges (2) Flashcards
what are examples of other functions of sugars, besides nutritional value?
- sweeteners
- humectants
- plasticizers
- color and flavor producers through browning rxns
- texturizing agents (crystallization)
- flavor binding
- food preservatives
what are 2 types of alternative sweeteners to reduce need for sucrose in food pdts?
describe each. examples?
- bulk sweeteners:
- caloric alternatives; more intense sweeteners than sucrose
- eg. crstalline fructose, high fructose corn syrup, mannitol - intense sweeteners:
- contributes no/few calories to food
- not approved in any country
describe mannitol
- high laxation potential
- low solubility
- high melting point
describe maltitol
- disaccharide with half the calories
- 90% sucrose sweetness
describe xylitol
- non-cariogenic properties
- cooling effect (hence it’s popularity in oral care, chewing gum and mint pdts)
describe tagatose
- monosaccharide made from whey
- 92% sweetness of sucrose
what are 4 major determinants for choosing a sweetener
- quality of flavor (bitter or undesirable aftertastes)
- cost
- consumer perception of safety
- stability in food system
describe aspartame
- 180x sweeter than sucrose
- limited heat stability
- hydrolyzes at acidic pH to yield methanol and dipeptide
- participates in non-enzymatic browning
describe neotame
- 30-60x swweter than aspartame
- 6,000-10,000 sweeter than sugar
- doesn’t participate in maillard browning rxns
- approved for use as a sweetener and flavor enhancer in foods (except meat and poultry)
describe sucralose
- 600x sweeter than sucrose
- heat stable
describe saccharin
- 300x sweeter than sucrose
- bitter after taste
- heat stable
- not legal in canada
describe acesulfame K
- used in Aspartame blends
- heat stable
- bitter aftertaste
describe stevioside
- 300x sweeter than sucrose
- extract of stevia leaves
- not permitted everywhere
how do sugars function as humectants?
- through hydrophilic nature of CHOs
- promotes moisture retention
- increases water mobility
define plasticizer or softeners
additives that increase the softness or fluidity of the foods to which they are added
why are hygroscopic sugars used in baked goods, plastic candies and chewy foods?
they help to retain moisture and inhibit crystallization
why are sugars added in intermediate moisture foods (Aw of 0.5-0.9)?
to prevent their toughening and hardening
what happens when enough h2o is removed from a sugar solution?
crystallization occurs as in a fondant or fudge
crystallization can’t occur until what?
the phase is supersaturated or undercooled = nucleation and growth
as sugar crystallizes, amount of plasticizer ___ (incr/decr)
decreases
what is the function of osmotically active materials in ice cream?
they act as cyroprotectants to control ice crystals in frozen food systems
what does the boiling point elevation curve describe?
how the boiling point temp increases as the amount of dissolved solids increases
sweetener solubility is governed by what?
molecular interaction b/w sweetener and h2o
what does the equation by Pancoast and Junk describe?
relationship between sucrose, temp and sucrose solubility
what needs to be considered in sweetener mixtures?
each sweetener influences the solubility concentration of the others
when does glass transition occur?
(Tg)
when the glassy state converts to the rubbery state
what equation can be used to predict Tg?
Gordon-Taylor equation
Tg = (w1Tg1 + kw2Tg2)/ (w1+kw2)
describe the state diagrams of fondant vs hard candy
fondant: increase temp until sucrose is soluble, then cool quickly to crystallization temp (approx 40C)
hard candy: reach peak temp and then cool quickly to glass transition temp (approx20C)
what are the effects of staying in the glassy state?
minimized crystallization and damage due to crystal growth
example, drying of pasta is improved by controlling glass transition
higher sucrose in synergy with other polysaccharides reduces what? why?
growth of ice crystals
b/c sugar renders the cryoprotectant more effective
describe how sugars act as color and flavor producers
through non-enzymatic browning (maillard reaction)
describe how sugars act as flavor binding agents
sugars can bind to water, alcohols, esters and ketones
with starches, what are the 2 levels that needs to be considered
- molecular level: amylose and amylopectin ratio
2. morphology of the granule (mechanical properties of starch)
what are main functional properties of starch?
- thickening agent
- gelling agent
- edible films
- textural modifier
what two features are responsible for the behaviour of starch in foods?
- ease with which the polymer forms inclusion complexes
2. ability of the molecules to form crystalline bodies with strong molecular interactions
describe the process of starch gelatinization
- H bond rupture within the starch granule
- H2O penetration into the loosened disorganized structure
- heat addition enables H2O to enter and enlarge granules (swelling) which increases viscosity of solution
- cooling: gel forms (uless only amylopectin molecules are present)
compare starches with high amylose vs high amylopectin
starches w/ high amylose content makes a stronger and firmer gel b/c more amylose can move out of the granule and into the water
a starch with only amylopectin molecules cannot form a gel
what is retrogression?
- problem that starch is prone to
- causes starch to form granular and compact textures in the final pdt
compare retrogradation to crystallization
retrogradation occurs more often that crystallization
what is crystallization?
when starch molecules become irreversibly insoluble in water due to the formation of very powerful intermolecular bonds
can the retrogradatioon of amylopectin and amylose be reversed? if yes, how?
amylopectin retrogradation can be reversed by heating
strong retrogradation of amylose can’t be reversed
The cross-bonding of starches effects what physical properties?
- swelling of the granules
- increases stability against breakdown in viscosity in acid foods and at high temp
how does substitution of ester or ether groups for OH groups affect retrogradation?
it decreases retrogradation by decreasing association of the OH groups
acid modified starches allow for what?
preparation of hot starch solutions of low viscosity which gel upon cooling
tapioca starches create what kind of products?
creamy products
describe resistant starches
- undigested
- serves as dietary fiber
- has health promoting effects
what are the 4 types of resistant starches?
type 1 RS: physically unavailable starch. Amylolytic enzymes have no access to starch accumulated in plant cells since the GI tract lacks enzymes capable of degrading plant cell walls
type 2RS: raw starch of some plant species
type 3 RS: retrograded starch occurring in the form of H2O insoluble semi-crystalline structures
type 4 RS: chemically or physically modified
how does the presence of sugars affect the properties of starches?
- sugars compete with starch for water, retarding the swelling of the granule which reduces viscosity and gel strength
- sugars minimizes retrogradation of starch
how do fats affect the properties of starches?
they have little effect on viscosity of starch suspension but an increase in fat content causes temp of max viscosity to decrease
when fat content increases, how does this affect the temp of max viscosity of starches?
incr fat content = decr max viscosity
how do monoglycerides with emulsifiers affect the properties of starches?
- increase the temp which granules swell
2. prevents gel formation
