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Food Analysis > Lecture 13 - Minerals > Flashcards

Lecture 13 - Minerals Flashcards

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1
Q

what are examples of minor food components?

A

minerals, vitamins, organic acids, enzymes, alcohols, neutraceuticals

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2
Q

what are examples of nutraceuticals

A

phenolic compounds, pigments, FAs, peptides

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3
Q

what is the classification of minor components based on?

A

distribution and amount of components

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4
Q

what is the definition of minerals

A

minerals are inorganic species or substances that are of neither animal nor plant origin

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5
Q

what constitutes the major part of dry ash after ignition of organic matter?

A

inorganic elements

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6
Q

which dietary macrominerals are needed at more than 100mg/day by adults?

A 
Ca
Mg
Na
K
P
Cl
S
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7
Q

what is teh relevance of minerals in food

A

nutrition

food safety (contamination or adulteration)

food fraud (veg vs animal protein)

government regulations (nutrition labels)

food processing (fortification)

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8
Q

example of food safety issue with minerals?

A

contamination or adulteration

eg. siliceous matter in grans

seafood contamination w/ metal

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9
Q

what are examples of fortification? why is it important?

A

fortification of foods has allowed adding minerals above natural levels found in food

cereals w/ Ca, Fe, Zn

salt w/ iodine

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10
Q

what are 4 classifications of minerals in food

A
  1. macrominerals: need m
    re than 100mg per day (adult)
  2. trace minerals: required in milli or micrograms each day
  3. ultra trace minerals: being investigated for possible biological function, but don’t have a clearly defined biochemical role
  4. heavy metals: toxic to body
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11
Q

what are the macrominerals

A

Ca, P, Na, K, Mg, Cl, S

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12
Q

what are the trace minerals in food?

A

Fe, I, Zn, Cu, Chromium, Manganese, molybdenum, fluoride, selenium, silica

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13
Q

what are the ultra trace minerals in food?

A 
vanadium
tin
nickel
arsenic
boron
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14
Q

what are the heavy metals in food?

A

lead
mercury
cadmium
arsenic

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15
Q

5 methods of food mineral analysis?

A
  1. potentiometry using ion-selective electrodes (ISEs)
  2. anodic stripping voltammetry (ASV)
  3. titrimetry (EDTA complexometric titration and precipitation titration)
  4. colorimetric methods or spectrophotometry methods
  5. instrumental methods (atomic absorption spectroscopy and atomic emission spectroscophy)
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16
Q

what are the forms of atomic absorption spectroscopy (an instrumental methods)?

A

forms of AAS:

  1. flame atomic absorption spectroscophy (FAAS)
  2. graphite furnace atomic absorption spectroscopy (GFAAS)
  3. cold vapour atomic absorption spectroscopy (CVAAS)
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17
Q

what are the forms of atomic emission spectroscopy (an instrumental methods)?

A

forms of AES:

  1. flame atomic emission spectroscophy (FAAS)
  2. inductively coupled plasma atomic emission spectroscopy (ICP-AES)
  3. inductively coupled plasma optical emission spectroscophy (ICP-OES)
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18
Q

what are 2 forms of titrations used for mineral analysis?

A
  1. EDTA complexometric titration

2. precipitation titration

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19
Q

what is the principle behind EDTA complexometric titration? what is it used for?

A
  • used for testing hardness of water

principle:
- EDTA forms stable 1:1 complexes with mineral ions.
- This gives complexometric titration using EDTA broad application in mineral analysis
- endpoints are detected using mineral chelators that have coordination constants lower than EDTA (less affinity for mineral ions) and produces different colors in each of their complexed and free states

20
Q

what are the indicators used in EDTA complexometric titration? what colors do they change to?

A

calmagite and erinochrome black T (EBT)

changes from blue to pink when they complex with Ca or Mg

21
Q

in EDTA complexometric titration, when a sample with Ca or Mg is mixed with calmagite, what color forms? what pH is needed?

A

forms pink complex

at pH 10

22
Q

in EDTA complexometric titration, how does the blue complex form

A

pink complex (product of first reaction) mixes with EDTA to form a blue complex

23
Q

procedure of the analysis of calcium in milk?

A

calmigite indicator

  1. weigh EDTA. dissolve in 1000mL. Results in 0.036M EDTA solution
  2. prepare ammonia buffer. Mix of ammonium hydroxide and ammonium chloride (pH 10-11)
  3. add milk + ammonia buffer and a few drops of calmagite indicator
  4. titrate with EDTA
24
Q

what is the principle behind precipitation titration

A

when at least one product of a titration reaction is an insoluble precipitate

25
Q

what are the 2 methods for precipitation titration

A
  1. mohr method

2. volhard method

26
Q

what is the mohr method?

what reaction occurs?

A
  • type of precipitation titration (direct or forward)
  • used for chloride determination

reaction:

  1. AgNO3 + Cl- –> AgCl + NaNO3 (until all Cl- is complexed)
  2. 2Ag + K2CrO4 –> Ag2CrO4 (orange only after Cl- is all complexed)

Ag2CrO4 = silver chromate (orange colored). This is formed after silver from silver nitrate has complexed with all available chloride)

27
Q

the mohr method is for ___ determination

it is a ____ or ___ titration method

A

chloride

direct or forward

28
Q

what color is silver chromate formed in the mohr method

A

orange

Ag2CrO4 = silver chromate (orange colored). This is formed after silver from silver nitrate has complexed with all available chloride)

29
Q

procedure of the mohr method to determine Cl in butter?

A
  1. weight butter and add boiling H2O
  2. let stand for 5-10 min
  3. add 2mL of 5% solution of K2CrO4 with H2O
  4. titrate with 0.1N AgNO3 until orange-brown color forms
30
Q

what is the procedure of the volhard method?

A
  1. treat sample with excess AgNO3
  2. wet ash with HNO3
  3. add FeHN4 (SO4)2.12H2O (indicator)
  4. excess AgNO3 is back titrated with potassium thiocyanate (KSCN)
  5. formation of ferric thiocyanate FeSCN2+ complex
31
Q

why is it important to add AgNO3 before HNO3 in the volhard method?

A
  • to ensure complete precipitation of the chlorides
  • if HNO3 is added first, there will be loss of Cl- by volatilization as HCl (b/c HCl has a higher vapor pressure than HNO3
32
Q

in the volhard method, why does AgNO3 need to be added in excess to the solution?

A

so that there is enough AgNO3 to react with ALL the chlorides in the sample

33
Q

in the volhard method, what is added as an indicator?

what does it react with? what does this form?

A

FeNH4(SO4)2

reacts with excess thiocyanate

forms ferric thiocyantate (FESCH2+), which is salmon colored. This indicates the endpoint of the reaction

34
Q

what indicates the endpoint in the volhard method?

A

the formation of ferric thiocyanate (FeSCN2+)

salmon coloured complex

35
Q

what are chromogens

A

chemicals that form a colored product upon reaction with the compound of interest

they selectively react with a wider variety of minerals

eg. alizarin 3 sulphonate for calcium determination

ferrozine and ferene-5 for iron determination

36
Q

what is alizarin-3-sulphonate?

A

it is a chromagen used for calcium determination

37
Q

what is ferrozine and ferene-5?

A

they are chromagens used for Fe determination

38
Q

describe the determination of Fe in meat

what reaction occurs?

A

react ferrous (Fe2+) with o-phenanthroline to form an orange-red complex ion (phenanthroline2+)

reaction:
ortho-phenanthroline + Fe2+ –> ferrous tris-o-phenanthroline 2+

39
Q

what are 2 types of instrumental spectroscopy methods?

A
  1. atomic absorption spectroscopy (AAS)

2. atomic emission spectroscopy (AES)

40
Q

what are 3 types of atomic absorption spectrscopy (AAS)?

A
  1. flam AAS (FAAS)
  2. graphite furnace AAS (GFAAS)
  3. cold vapour AAS (CVAAS)
41
Q

what are 3 types of atomic emission spectroscophy (AES)?

A
  1. flame AES (FAES)
  2. inductively coupled plasma AES (ICP-AES)
  3. inductively coupled plasma optical emission spectroscopy (ICP-OES)
42
Q

when are absorption spectra produced?

A

when ground state atoms (or ions) absorb energy from a radiation source

43
Q

when are atomic emission spectra produced?

A

when excited neutral atoms emit energy on returning to the ground state or a lower energy state

44
Q

what does atomization involve?

A

separating particles into individual molecules (vaporization) and breaking molecules into atoms

usually accomplished by exposing the analyte (substance being measured) to high temperatures in a flame or plamsa

45
Q

what are sources of energy for atomization?

A

flame elctrothermal

inductively coupled argon plasma

46
Q

stages of atomization?

A
  1. solution to solid (desolvation)
  2. solid to gas (vaporization)
  3. gas to atom (atomization)
  4. atom to ion (ionization)

atoms and ions can both be excited

Food Analysis (17 decks)

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