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Food Chemistry - FDSC251 > U3 > Flashcards

U3 Flashcards

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1
Q

majority oil source consumed

A

oil seeds

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2
Q

first steps in oilseed treatment

A
  1. crushing

2. heating - destroy enzymes

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3
Q

adverse effect of tissue disruption

A

exposing the lipid to enzymes, oxygen and other reactive agents. now many deteriorate reactions can occur

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4
Q

function of lipase

A

catalyze lipolysis

hydrolyzes the ester linkage between glycerol and fatty acids

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5
Q

function of lipoxygenases

A

catalyze direct oxidation of polyunsaturated fatty acids with methylene group between 2 cis double bonds (cis,cis-1,4-pentadiene group)

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6
Q

how to reduce effects of lipoxygenase and lipase?

A

heat denaturation

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7
Q

what steps follow crushing and heating

A
  1. hydraulic pressing
  2. expelling
  3. solvent extraction
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8
Q

hydraulic pressing

A

use of a screw press to apply pressure and crush the oilseed to force oil out

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9
Q

negatives of hydraulic pressing

A

slow and ineffiecient. due to time factor, the oil is subject to degenerative reactions

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10
Q

what oil uses hydraulic pressing

A

virgin olive oil - no chemical treatment

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11
Q

expelling

A

expeller is used - archimedes screw in a barrel increases pressure and squeezes the oil out. it is a mechanical, continuous version of hydraulic pressing

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12
Q

solvent extraction

A

follows expelling since there is still some oil in the cake. organic solvent (hexane) extracts the residual oil from the oilseed cake

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13
Q

negatives of solvent extraction

A

advanced, expensive technology required. scale of production must be worth it to purchase the equipment

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14
Q

what sources is rendering used for>

A

animal and fish sources. usually waste by-products from meat and fish processing

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15
Q

why is rendering used rather than solvent extraction for these sources?

A

animal and fish fats have high levels of moisture so a hydrophobic solvent is inefficient

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16
Q

process of rendering

A

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

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17
Q

true or false: the processing procedure is the same for every fat/oil source

A

false - due to each source’s unique properties, a unique process is needed for each

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18
Q

what is animal feed

A

residual press cake after being desolventized

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19
Q

what is the oil extract like?

A

dark brown, smelly, contains a lot of particles, liquid

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20
Q

what particles exist in the oil extract

A
  1. free fatty aicds
  2. oxidative breakdown products
  3. phospholipids
  4. metal ions
  5. flavor components
    work in conjunction to decrease quality and value of oils, so further processing must be done
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21
Q

steps in subsequent processing

A
  1. settling and degumming
  2. refining
  3. bleaching
  4. deodorization
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22
Q

process of settling and degumming

A

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

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23
Q

what oil contains 5% lecithin and what is this used for?

A

soybean oil

used as a commercial emulsifier

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24
Q

purpose of refining

A

remove free fatty acids

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25
Q

purpose of settling/degumming

A

remove hydrophobic particles

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26
Q

process of refining

A

treatment of the oil with dilute alkali to convert the fatty acids into a soap

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27
Q

equation for refining

A

RCOOH + NaOH -> RCOONa + H2O.

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28
Q

what is soap and does it remain in the oil solution?

A

salt of a fatty acid

no, it is removed with the aqueous phase

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29
Q

what can occur during refining that processors must be careful of? how to avoid this process?

A

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

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30
Q

what percent of particulates are removed from centrifuging and filtration

A

99.99% - thus the product of these processes is essentially dry

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31
Q

how do settling, degumming, and refining occur in modern processing?

A

they are combined into one operation. there is steam injection of dilute base and constant centrifuging

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32
Q

purpose of bleaching

A

remove colored materials from the oil

33
Q

process of bleaching

A

pass the centrifuged oil through a bed of dry bentonite or activated charcoal, which absorbs the color compounds

34
Q

what is dry bentonite

A

bleaching clay or aluminum phyllosilicate clay

35
Q

what additional effect does bleaching have

A

it is a secondary filtration process, removing colloidal material or hydrogenation catalyst from oils

36
Q

what is the product of bleaching like

A

clear pale yellow oil

37
Q

what are the colored materials removed by bleaching. properties?

A
  1. carotenoids
  2. chlorophyll
  3. pheophytin
    they are double bonded and thus have an extent of oxidation - slightly more polar
38
Q

purpose of deodorization

A

remove volatile compounds that give off flavors

39
Q

process of deodorization

A

steam stripping. spraying the oil into an evacuated chamber containing superheated steam flowing counter-current to the oil droplets, carrying the volatiles away

40
Q

product of deodorization

A

bland clear oil. ready to be bottled and sold

41
Q

what is virgin olive oil

A

only physical processing, no chemical processing (no refining, just hydraulic pressing so flavor and color compounds are not removed)

42
Q

definition of refined oil

A

an oil that has been chemically treated to neutralize strong tastes and neurtalize the acid content (FFA)

43
Q

what is olive pomace oil

A

oil extracted from the pomace using solvents and heat

44
Q

true or false: all of the subsequent steps are integrated into a continuous operation

A

true - exception is olive oil

45
Q

3 additional supplementary processes

A

winterization
hydrogenation
interesterification

46
Q

process of winterization

A

use heat exchanger for fractional crystallization of oils to remove more saturated triglycerides

47
Q

what is produced by winterization

A

salad oils from oils not usually suitable for this

48
Q

what oil was winterization first used for

A

cottonseed oil

49
Q

why is clouding bad

A
  1. looks

2. crystallization breaks emulsion

50
Q

what is the underlying purpose of hydrogenation?

A

change the physical and chemical properties of fats and oils by overall degree of saturation

51
Q

2 uses of hydrogenation. which is the main?

A
    • convert an oil to a fat. produces margarine and shortenings
  2. reduce the susceptibility of an oil to oxidative rancidity
52
Q

process of hydrogenation

A

addition of a hydrogen across the double bond of an unsaturated fatty acid in the presence of high temperatures, high pressures, and a catalyst

53
Q

what selectivity occurs during hydrogenation?

A

preferentially hydrogenating more highly unsaturated fatty acids

54
Q

from what source is stearic acid produced more quickly, linoleic or oleic acid?

A

linolenic - favors more highly unsaturated

55
Q

why does selectivity occur?

A

catalysts have a higher affinity to more highly unsaturated fatty acids

56
Q

why is hydrogenation capable of substituting oil sources?

A

since it produces a fat with consistent specific physical properties, it can use different sources depending on the price and availability

57
Q

2 catalysts used in hydrogenation

A

nickel and copper (copper chromium has a high selectivity for linolenic acid)

58
Q

5 steps in hydrogenation

A
  1. transfer/diffusion
  2. absorption
  3. hydrogenation/isomerization
  4. desporption
  5. transfer
59
Q

transfer

A

transfer of reactants and products to and from the bulk of the liquid oil phase and outside surface of the catalyst

60
Q

diffusion

A

diffusion of reactant into the pores of the catalyst and diffusion of products out of the pores of the catalyst

61
Q

what 4 independent variables affect rate of hydrogenation?

A
  1. form/conc. of catalyst
  2. temp
  3. pressure of H2 gas
  4. amount of agitation
62
Q

what are the 3 dependent variables in hydrogenation

A
  1. selectivity
  2. trans fatty acid content
  3. reaction rate
63
Q

if you increase temperature, what happens to selectivity, trans fatty acids, and rate?

A

all increase

64
Q

if you increase pressure, what happens to selectivity, trans fatty acids, and rate?

A

selectivity and trans - decrease

rate - increase

65
Q

if you increase agitation, what happens to selectivity, trans fatty acids, and rate?

A

selectivity and trans - decrease

rate - increase

66
Q

if you increase agitation, what happens to selectivity, trans fatty acids, and rate?

A

all increase

67
Q

what side reaction occurs during hydrogenation?

A

isomerization from cis to trans

68
Q

why do fats solidify when they undergo catalytic hydrogenation?

A

combination of decreasing degree of unsaturation and formation of trans isomers

69
Q

true or false: hydrogenation of fatty acids in triglycerides depends on their location

A

false

70
Q

true or false: increasing the pressure during hydrogenation will increase the trans fatty acid content of the product

A

false

71
Q

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

A

b

72
Q

True or false

The extracted oil is mixed with water to eliminate unacceptable flavors

A

false

73
Q

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..

A

refining

74
Q

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

A

b

75
Q

The ratio that refers to preferential hydrogenation of the more highly unsaturated fatty acids is…

A

selectivity ratio

76
Q

The process that removes volatile compounds that give the oil off-flavors not acceptable to most consumers is called…

A

deodorization

77
Q

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

A

b

78
Q

Hydraulic pressing is used for extracting oil because

a. Efficient
b. Fast
c. Good quality
d. All
e. none

A

e

Food Chemistry - FDSC251 (10 decks)

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