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FDSC 300 > Lecture 14 - Vitamins > Flashcards

Lecture 14 - Vitamins Flashcards

1
Q

define a vitamin

A

relatively low-molecular weight compounds which are required in small quantities for normal metabolism

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2
Q

why do we analyze for vitamins?

A
  • nutritional value
  • health benefits
  • regulatory requirements
  • shelf life
  • affects packaging
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3
Q

how are vitamins classified?

A

based on their solubility
fat soluble: ADEK
water soluble: B and C

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4
Q

what’s an IU?

A

unit of measurement based on BIOLOGICAL ACTIVITY or effect

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5
Q

what units can vitamins be expressed in?

A
  • mg
  • ug
  • IU
  • US Pharmacopeia (USP)
  • % DV
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6
Q

how do vitamin extractions usually go?

A

remove from its biological matrix prior to analysis

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7
Q

what methods of extraction are there for vitamins?

A
  • heat
  • acid
  • alkali
  • solvents
  • enzymes
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8
Q

how to extract ascorbic acid?

A

cold extraction with metaphosphoric acid/acetic acid

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9
Q

how to extract vitamin B1 and B2?

A

boiling or autoclaving, plus enzyme treatment

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10
Q

how to extract niacin?

A

autoclaving acid (everything else) or alkali (cereal) products

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11
Q

how to extract folate?

A

enzyme extraction with a-amylase, protease and y-glutamyl hydrolase

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12
Q

how to extract vitamins A, E, or D?

A

organic solvent extraction, saponification, and re-extracctino with organic solvents

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13
Q

what challenges does milk present for vitamin D analysis?

A
  • relatively low concentration
  • poor stability in response to heat, light, oxidation
  • possible interference from milk components

so we use solvent extraction; saponification; re-extraction

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14
Q

what are the classifications of vitamin assays?

A
  • bioassays
  • microbiological assays
  • physiochemical assays
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15
Q

what’s a bioassay method?

A
  • rats

- used to analyze vit B12 and D (line test)

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16
Q

principle of microbiological assays?

A
  • growth of microorganisms is proportional to their requirement for a specific vitamin
  • vitamin being tested acts as a growth limiting nutrient
17
Q

how is microbial growth measured?

A
  • turbidity
  • acid production
  • gravimetrically
  • respiration
18
Q

microbiological assay for niacin?

A

niacin:
- weight sample
- H2SO4
- autoclave
- filter mixture
- add Difco Niacin Assay Medium to filtrate
- autoclave again
- add lactobacillus plantarum
- incubate
- measure optical density

19
Q

microbiological assay for folate?

A
  • weigh sample
  • add buffer
  • add a-amylase, protease, and conjugate and allow for the digestion of the matrix components
  • deactivate enzymes by boiling the mixture for 5 mins
  • filter
  • add bacterial growth medium to filtrate
  • autoclave
  • add lactobacillus case
  • incubate
  • measure optical density and compare with bacterial growth of medium containing known amount of vitamin
20
Q

what method do you use to analyze vitamin A?

A
  • vit A is sensitive to UV light, high temps, and moisture so need to avoid this
  • HPLC is the only acceptable method to provide accurate method
21
Q

steps for analyzing vitamin A:

A
  • test sample saponified (with KOH)
  • vit A extracted into organic solvent (diethyl ether) and concentrated
  • vit A isomers are determined by HPLC on a silica column
22
Q

what method do you use to analyze for vitamin C?

A
  • vit C is oxidized to L-dehydro-ascorbic acid by redox indicator dye 2,6-dichloroindophenol (DCP)
  • DCP is reduced to colorless form
  • end point indicated by appearance of rose-pink color
23
Q

true or false: vitamin C is not susceptible to oxidative deterioration

A

false, it is

24
Q

what accelerates oxidative deterioration of vitamin C?

A
  • high pH

- presence o f ferric and cupric ions

25
Q

what do you do if your complex has a lot of Fe or Cu ions?

A

include a chelating agent (EDTA)

26
Q

expand EDTA

A

ethylenediaminetetraacetic acid

27
Q

what method is used to analyze for thiamine?

A

thiochrom fluorometric procedure

28
Q

describe the steps of the thiochrom fluorometric procedure

A
  • extraction of thiamine in H2SO4 with dilute acid
  • enzymatic hydrolysis (takadiastase) of thiamine’s phosphate-esters at pH 4.0-4.5 in presence of sodium acetate
  • chromatographic cleanup
  • oxidation to thiochrome with alkaline potassium ferricyanide
  • measurement using fluorescence intensity using a fluorometer
  • compare value against a known concentration
29
Q

what factors are considered in the selection of methods?

A
  • method accuracy/precision
  • need for bioavailability info
  • time & instrumental requirements
  • personnel
  • matrix nature
  • number of samples
  • regulatory requirements
  • suitability of method
30
Q

microbiological assays are suitable for both fat and water soluble vitamins

A

false. mostly used for water-soluble vitamins (niacin, B12, and pantothenic acid)

FDSC 300 (9 decks)

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