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5) FDSC 300 > Lecture 11 - Mineral Content > Flashcards

Lecture 11 - Mineral Content Flashcards

1
Q

What are minerals?

A

inorganic species of substances that re neither animal or plant origin ( no CHON skeleton)

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2
Q

What is the relevance of the minerals?

A
  • nutrition
  • food safety
  • foo fraud
  • government regulation
  • food processing
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3
Q

What does a lack fo iron, calcium and Na/K lead to?

A

Anemia, osteoperosis and heart failure

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4
Q

What is the importance of minerals in food safety

A

products could be adulterated or comtaminated

ex. mercury

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5
Q

What is the importance of food fraud

A

manufacturers can lie about what is in a food
ex vegetable vs. animal protein
soy–> silica present can be adulterated with sand

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6
Q

What is the importance of minerals and government regulation?

A

Nutrition labelling form the FDR, needed for Na, Fe, Ca because of their importance with hypertension, anemia, impeding development

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7
Q

What is the importance of food processing?

A

Food can be fortified to allow for the addition of nutrients that would be lacking naturally

ex. iodized salt
ex. breakfast cereals

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8
Q

What are the 4 classifications?

A

Macrominerals
Trace minerals
Ultra trace minerals
Heavy metals

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9
Q

What are some examples of Macro mienrals, trace minerals, ultrea trace minerals and heavy metals?

A

Macro >100mg/day –> Ca, P, Na, K, Mg, Cl, S
Trace mg-ug/day –> Fe, I, Z, Cu, Cr, Mn, Mb, F, Se, Si
Ultra trace minerals: do not have clear defined biochemical role
Heavy metals: toxic–> Pb, Hg, Cd, As

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10
Q

What is Potentiometry using ion-selective electrodes (ISEs)?

A

Based on a sensor (transducer) that specifically bind to the dissolved ions to produce electrical potential

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11
Q

What is Anodic stripping voltammetry?

A

involves (i) pre-concentration of a metal phase onto a solid electrode surface or into Hg (liquid) at negative potentials and (ii) selective oxidation of each metal phase species during an anodic potential sweep. Depending on the type of metal ions present, the current will change when increasing potential is applied to the electrode.

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12
Q

What are the two methods of Titrimetry

A

EDTA complexometric titration

Precipitation titration

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13
Q

What is the principle of the complexometric titration

A

Usually used for the hardness of water
The hexadentate ligand ethylenediaminetetraacetate(EDTA) forms stable 1:1 complexes with numerous 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 (i.e., less affinity for mineral ions) and that produce different colors in each of their complexed and free states

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14
Q

What indicators are used in the titrimetry test?

A

Calmagite and Eriochrome Black T (EBT) are such indicators that change from blue to pink when they complex with calcium or magnesium.
- The endpoint of a complexometric EDTA titration using either Calmagite or EBT as the indicator is detected as the color changes from pink to blue.
○ Sample with Ca or Mg + Calmagite (pH 10)—> Pink complex
○ Pink Complex +EDTA –> Blue complex

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15
Q

What is the steps of the EDTA complexomteric titration?

A

Calmagite Indicator: ( Analysis of calcium and Magnesium in milk)
1-Prepare 0.036M EDTA solution.
2-Prepare ammonia buffer. Mix of ammonium hydroxide and ammonium chloride (pH 10-11).– Stability
3-In a 250ml Erlenmeyer flask add 50ml of milk, 3ml ammonia buffer (to make alkaline solution )and few drops of calmagiteindicator.
4-Titrated with EDTA solution.

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16
Q

What causes stability in the calmagite indicator?

A

the ammonium chloride buffer

17
Q

What is the relevance of the ammonia buffer?

A

• To maintain pH of solution at pH10 ± 0.1.
Calcium and Mg will precipitate if the pH goes too high or too low
• Improve the stability of EDTA-Metal ion complex
• Improves the sharpness of endpoint
If the solution is not stable, you will not be able to find the endpoint
• Make sure pH does not exceed 11 as Ca and Mg will precipitate as hydroxides

18
Q

What are the two types of preciptation reactions

A

Mohr Method

Volard Method

19
Q

What is the principle of the precipitation titration?

A

When the least one product of a titration reaction is an isoluble precipitate, it is referred to as the precipitate

20
Q

What is the mohr method?

A

Chloride determination
Direct titration method
Based on the formation of orange- coloured solid silver chromate after silver from silver nitrate has complexed with all the available chloride

21
Q

What is the importance of water in the mohr method?

A

water is important to determine because it can interfere with:K2CrO4 reacts with water and might have some chloride that is present in solution

22
Q

What are the steps in the Mohr method? (chloride in butter)

A

1-Weigh about 5 g of butter into 250-ml Erlenmeyer flask and add 100 ml
of boiling H2O.
2-Let it stand for 5–10 min with occasional swirling.
3-Add 2 ml of a 5% solution of K2CrO4in H2O.
4 Titrate with 0.1 N AgNO3until having an orange-brown color.

23
Q

What is the principle of the Volhard method? (Cl determination)

A

volume of AgNO3 solution added must be in excess of that required to react with the chlorides in the sample

24
Q

What indicator is used in the Volhard method?

A

Ferric ammonium sulfate (FeNH4(SO4)2)is added as an indicator

25
Q

What are the steps of the Volhard method?

A
  • back-titrate the excess AgNO3 with potassium thiocyante(KSCN) solution.
    • The FeNH4(SO4)2 reacts with an excess of thiocyanate (when all the Ag ions from AgNO3are used up), forming the salmon colored complex, ferric thiocyanate FeSCN++, indicating the end point.
26
Q

What are the reactions with the Volhard

A 
Ag+ + Cl- -> AgCl (until all Cl- is
	complexed and is precipitated)
	Ag+ + SCN- -> AgSCN
	(to quantitate silver not complexed
	with chloride)
	SCN- + Fe3 -> [FeSCN]2+
	(red when there is any SCN that is
	not complexed to Ag+ after all the
	Ag+ ions are depleted)
	--> back titration
27
Q

What is the principle of the Volhard reaction?

A

1.
The sample is added with AgNO3 where AgCl is precipitated out and excess of AgNO3 remains. We are measuring moles of AgNO3 left behind in the subsequent steps
2.
The sample is wet-ashed with HNO3 (to digest organic matter),
3.
The excess AgNO3 is back titrated with Potassium thiocyanate (KSCN), using ferric ammonium sulfate as indicator

28
Q

What is the Volhard reaction used for?

A

determination of high salt content

29
Q

What is the flow chart of the Volhard reaction?

A

Sample + AgNO3–> AgCl + Excess AgNO3 + Organic compounds –> (wet ashing with hNO3)–> AgCl +Excess AgNO3–> FeNH4(SO4)2 *12H2O (indicator) –> Back titratio with KSCN–> Ferric thiocyanate (endpoint)

30
Q

What is the colorimetric method?

A
  • Chromgens are chemical that upon reaction with the compounds of interest, form colored products
    • Chromogens are available that selctively react with a wide variety of minerals
    • Each chromogen reacts with its corrsponding mineral to produce a soluble colored product that can be quantified by absorption of light at specified wavelength
31
Q

How do you determine the iron content in meat?

A
  • By reacting ferrous iron (Fe2+) with o-phenanthroline to form an orange-red complex ion according to the followring equation
32
Q

What are the instrumental methods for mineral determination?

A

Atomic absorption spectroscopy (AAS)

Atomic Emission

33
Q

What is atmic absorption spectroscopy?

A
  • Can determine a lot of minerals form one test

- Atomic absorption spectra produced whe the ground state atoms or ions absorb energy froma radiation source

34
Q

What is Atomic Emission

A
  • Atomic absorption spectra ar produced when ground state atoms absorb energy form a radiation source
    • Atomic emission spectra are produced when excited neutral atoms emit energy on returning to the ground state or a lower energy state
35
Q

What is atomization?

A

Atomization involves separating particles into individual molecules
(vaporization) and breaking molecules into atoms.
It is usually accomplished by exposing the analyte (the substance being measured) to high temperatures in a flame or plasma
although other methods may be used.

36
Q

Absorption spectroscopy

A

atoms absorb light

37
Q

Emission spectroscopy

A

ions emit light (at very high temperature)

38
Q

What does Atomic spectroscopy require?

A

that atomsof the element of interest be in
the atomic state (not combined with other elements in a compound)
and that they be well separated in space.
-In foods, virtually all elements are present as compounds or complexes
and, therefore, must be converted to neutral atoms (atomized)
before atomic absorption or emission measurements can be made.

5) FDSC 300 (14 decks)

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