U3 Flashcards
majority oil source consumed
oil seeds
first steps in oilseed treatment
- crushing
2. heating - destroy enzymes
adverse effect of tissue disruption
exposing the lipid to enzymes, oxygen and other reactive agents. now many deteriorate reactions can occur
function of lipase
catalyze lipolysis
hydrolyzes the ester linkage between glycerol and fatty acids
function of lipoxygenases
catalyze direct oxidation of polyunsaturated fatty acids with methylene group between 2 cis double bonds (cis,cis-1,4-pentadiene group)
how to reduce effects of lipoxygenase and lipase?
heat denaturation
what steps follow crushing and heating
- hydraulic pressing
- expelling
- solvent extraction
hydraulic pressing
use of a screw press to apply pressure and crush the oilseed to force oil out
negatives of hydraulic pressing
slow and ineffiecient. due to time factor, the oil is subject to degenerative reactions
what oil uses hydraulic pressing
virgin olive oil - no chemical treatment
expelling
expeller is used - archimedes screw in a barrel increases pressure and squeezes the oil out. it is a mechanical, continuous version of hydraulic pressing
solvent extraction
follows expelling since there is still some oil in the cake. organic solvent (hexane) extracts the residual oil from the oilseed cake
negatives of solvent extraction
advanced, expensive technology required. scale of production must be worth it to purchase the equipment
what sources is rendering used for>
animal and fish sources. usually waste by-products from meat and fish processing
why is rendering used rather than solvent extraction for these sources?
animal and fish fats have high levels of moisture so a hydrophobic solvent is inefficient
process of rendering
ground fish/meat is heated with steam in a large, high pressure vessel. lipids melt and are released from tissue, allowing fat to be further processed
true or false: the processing procedure is the same for every fat/oil source
false - due to each source’s unique properties, a unique process is needed for each
what is animal feed
residual press cake after being desolventized
what is the oil extract like?
dark brown, smelly, contains a lot of particles, liquid
what particles exist in the oil extract
- free fatty aicds
- oxidative breakdown products
- phospholipids
- metal ions
- flavor components
work in conjunction to decrease quality and value of oils, so further processing must be done
steps in subsequent processing
- settling and degumming
- refining
- bleaching
- deodorization
process of settling and degumming
adding water to the oil. constant centrifuging and steam injection to the tank (increase hydration rate). hydophobic substances - proteins, phospholipids, carbs - hydrate and associate and eventually separate from the oil
what oil contains 5% lecithin and what is this used for?
soybean oil
used as a commercial emulsifier
purpose of refining
remove free fatty acids
purpose of settling/degumming
remove hydrophobic particles
process of refining
treatment of the oil with dilute alkali to convert the fatty acids into a soap
equation for refining
RCOOH + NaOH -> RCOONa + H2O.
what is soap and does it remain in the oil solution?
salt of a fatty acid
no, it is removed with the aqueous phase
what can occur during refining that processors must be careful of? how to avoid this process?
saponification in the presence of excess alkali.
knowing the exact amount of FFA content allows an accurate measurement of alkali needed to neutralize the solution, so that excess isn’t added
what percent of particulates are removed from centrifuging and filtration
99.99% - thus the product of these processes is essentially dry
how do settling, degumming, and refining occur in modern processing?
they are combined into one operation. there is steam injection of dilute base and constant centrifuging
purpose of bleaching
remove colored materials from the oil
process of bleaching
pass the centrifuged oil through a bed of dry bentonite or activated charcoal, which absorbs the color compounds
what is dry bentonite
bleaching clay or aluminum phyllosilicate clay
what additional effect does bleaching have
it is a secondary filtration process, removing colloidal material or hydrogenation catalyst from oils
what is the product of bleaching like
clear pale yellow oil
what are the colored materials removed by bleaching. properties?
- carotenoids
- chlorophyll
- pheophytin
they are double bonded and thus have an extent of oxidation - slightly more polar
purpose of deodorization
remove volatile compounds that give off flavors
process of deodorization
steam stripping. spraying the oil into an evacuated chamber containing superheated steam flowing counter-current to the oil droplets, carrying the volatiles away
product of deodorization
bland clear oil. ready to be bottled and sold
what is virgin olive oil
only physical processing, no chemical processing (no refining, just hydraulic pressing so flavor and color compounds are not removed)
definition of refined oil
an oil that has been chemically treated to neutralize strong tastes and neurtalize the acid content (FFA)
what is olive pomace oil
oil extracted from the pomace using solvents and heat
true or false: all of the subsequent steps are integrated into a continuous operation
true - exception is olive oil
3 additional supplementary processes
winterization
hydrogenation
interesterification
process of winterization
use heat exchanger for fractional crystallization of oils to remove more saturated triglycerides
what is produced by winterization
salad oils from oils not usually suitable for this
what oil was winterization first used for
cottonseed oil
why is clouding bad
- looks
2. crystallization breaks emulsion
what is the underlying purpose of hydrogenation?
change the physical and chemical properties of fats and oils by overall degree of saturation
2 uses of hydrogenation. which is the main?
- convert an oil to a fat. produces margarine and shortenings
- reduce the susceptibility of an oil to oxidative rancidity
process of hydrogenation
addition of a hydrogen across the double bond of an unsaturated fatty acid in the presence of high temperatures, high pressures, and a catalyst
what selectivity occurs during hydrogenation?
preferentially hydrogenating more highly unsaturated fatty acids
from what source is stearic acid produced more quickly, linoleic or oleic acid?
linolenic - favors more highly unsaturated
why does selectivity occur?
catalysts have a higher affinity to more highly unsaturated fatty acids
why is hydrogenation capable of substituting oil sources?
since it produces a fat with consistent specific physical properties, it can use different sources depending on the price and availability
2 catalysts used in hydrogenation
nickel and copper (copper chromium has a high selectivity for linolenic acid)
5 steps in hydrogenation
- transfer/diffusion
- absorption
- hydrogenation/isomerization
- desporption
- transfer
transfer
transfer of reactants and products to and from the bulk of the liquid oil phase and outside surface of the catalyst
diffusion
diffusion of reactant into the pores of the catalyst and diffusion of products out of the pores of the catalyst
what 4 independent variables affect rate of hydrogenation?
- form/conc. of catalyst
- temp
- pressure of H2 gas
- amount of agitation
what are the 3 dependent variables in hydrogenation
- selectivity
- trans fatty acid content
- reaction rate
if you increase temperature, what happens to selectivity, trans fatty acids, and rate?
all increase
if you increase pressure, what happens to selectivity, trans fatty acids, and rate?
selectivity and trans - decrease
rate - increase
if you increase agitation, what happens to selectivity, trans fatty acids, and rate?
selectivity and trans - decrease
rate - increase
if you increase agitation, what happens to selectivity, trans fatty acids, and rate?
all increase
what side reaction occurs during hydrogenation?
isomerization from cis to trans
why do fats solidify when they undergo catalytic hydrogenation?
combination of decreasing degree of unsaturation and formation of trans isomers
true or false: hydrogenation of fatty acids in triglycerides depends on their location
false
true or false: increasing the pressure during hydrogenation will increase the trans fatty acid content of the product
false
crushed oilseeds must be subjected to heat treatment to…
a. Enhance the flavor compounds
b. Deactivate enzymes that might affect oil quality
c. Increase the amount of the extracted oil
b
True or false
The extracted oil is mixed with water to eliminate unacceptable flavors
false
The process that involves the treatment of the oil with dilute alkali to convert free FAs into soap to remove them from extracted oil is..
refining
Hydrogenated oil becomes solid due to…
a. Inc number of unsaturated bonds
b. Inc percent of trans FA
c. Decrease in length of fatty acids
d. None
e. all
b
The ratio that refers to preferential hydrogenation of the more highly unsaturated fatty acids is…
selectivity ratio
The process that removes volatile compounds that give the oil off-flavors not acceptable to most consumers is called…
deodorization
After extraction, the oil is
a. Light yellow liquid that can be consumed immediately
b. Dark smelly liquid that needs processing
c. Dark liquid that can be consumed but consumers prefer it to be light colored
b
Hydraulic pressing is used for extracting oil because
a. Efficient
b. Fast
c. Good quality
d. All
e. none
e
