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Lecture 2

NUTR 3210 Lecture Notes - Lecture 2: Passive Transport, Monogastric, Lingual Lipase

10 pages20 viewsFall 2017

Department
Nutrition
Course Code
NUTR 3210
Professor
Monk
Lecture
2

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NUTR*3210
Lecture 2- September 12, 2017
1
Food composition analysis
Methods that are used in the chemical analysis of foods (humans) and feeds (animals)
Proximate analysis
o Basic determination of 6 components by substraction:
1. moisture,
2. crude protein (Kjedahl analysis of nitrogen)
3. crude fat (ether extract)
4. crude fibre
5. ash (minerals)
6. available CHO (N Free Extract-NFE)
o only gives us totals (crude)
Newer method
o Replace or extend traditional components of proximate analysis (PA)
o i.e total fat, follow up w/ gas chromatography=>individual fatty acids
Southgate/Van Soest Methods
o Methods to replace nitrogen free extract (NFE) and Crude fibre for modern CHO
labelling
Why look at food composition?
Food analysis: the development, application and study of analytical methods for
characterizing foods and their constituents
o We want to know what is in our food
Why is this important?
o Information about foods allow the consumer to make informed decisions
o In this course, we start to understand the chemistry of nutrients
Government regulations
o “tipulate the utitio fats:, igediet list, ad health lais
o Try to eliminate economic fraud
Quality control in food and feeds industries
o Ensure consistent food composition for human/companion animal health
o Ag settings, encourage optimal animal growth/profitability
o Try to eliminate economic fraud by avoiding processors making false claims
o Important for quality control
Nutrition facts label
How do we get this info
Serving size: how much constitutes 1 serving, how much we are analyzing
Amount per serving: broken down in calories per servings
Total calories: served in every serving size
How much macros in each categories
o Broken down, get this info from proximate analysis
o Total fat, proteins, and total carbs from proximate analysis
Individual types of fats determined by additional analyses
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NUTR*3210
Lecture 2- September 12, 2017
2
Info about vit and mins:
o total minerals from proximate analysis
o individual tests for each vit and min
Poiate aalsis gets us stated o the ulk pat of ou utitio fats lael
Proximate analyses (PA)
Early methodology for quantification of nutrients in foods
Tells us what is in our food/crude estimates
1. Moisture content: WATER in the food (determined by drying food)
2. Crude Fat (Determined by ether extract)
3. Ash: minerals, or inorganic portion of the sample
4. Crude protein: Nitrogen content is quantified by the Kjeldahl method (nedd to know this
method)*
5. *Crude Fibre: extracted with hot acid and basic salts to mimics stomach and intestinal
digestion-> has been replaced w/ NEW METHODS
6. *Nitrogen Free Extract (NFE): all of the above values (#1-5) are subtracted from the
initial sample weight to estimate available carbohydrate (Starches and sugars)-> also
been replaces w/ NEW methods
General comments on proximate analysis
the composition of the food
no information on digestibility
no information on specific amino acids, minerals, lipids, or carbohydrates -> just get
TOTAL no information about the COMPOSITIONS
o need additional analyses for composition of each nutrient class (CHO, protein,
lipids, minerals, vitamins)
Still used in food labelling and animal feed analysis
Has provided the basis for developing more advanced analyses
1. Moisture content
Food sample is oven dried or freeze dried, loss in weight is equal to the moisture
content
Errors: the loss of other volatile compounds like volatile fatty acids and alcohols can
cause overestimation of moisture
Modern improvement: freeze drying is more accurate than oven drying
Importance
Most further analyses requires a dried sample (think of steps 2-6)
Ag, pets, and animal foods-dry matter basics
Human food labelling is on wet weight, o as is asis
Water content is important in human foods, having effects on:
Palatability (dry foods are sometimes less palatable)
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NUTR*3210
Lecture 2- September 12, 2017
3
Shelf life (high moisture content may cause foods to spoil, especially
in warm environments)
How do we calculate moisture content in foods?
Moisture=water
Food sample(weigh the food=wet weight) ->dry the sample -> dry matter
(=dry weight)=moisture content
Remember: Dry matter is the SUM of weights of all nutrients except
water
% dry matter=dry weight of sample/wet weight of sample x 100%
% moisture=100-%dry matter
2. Crude fat (or lipids)
Dried food sample is extracted with the non-polar solvent ether to get the lipids
out
When ether is dried down (evaporates away) and the lipids/fats remain, and are
weighed
Errors: Ether is poor at extracting phospholipids (lipoprotein:lipid + protein), and
the method does not identify specific types of fatty acids -> need to use other
methods (i.e. gas chromatography)
Goal: to quantify important dietary lipids, including triglycerides (TG),
phospholipids (PL), cholesterol and specific fatty acids
Graph: GC trace
What do I need to know about Step 2 of PA: crude fat?
Feed sample -> air dry -> dry matter (=moisture)->ether extraction=crude
fat/lipids
Ether extract=crude fat (lipid) content
% crude fat=weight of crude fat/dry weight of sample x 100%
Remember: denominator is written as dry weight, BUT exactly same formula
if we use wet weight of the food sample
3. Ash=mineral content
Dried sample (we use a subset/smaller amount of the total dry weight of the food
for the PA steps 2-6 b/c we calculate % content) is burned in a high T oven, and the
remaining ash is weighed, and it represents the minerals, or inorganic portion of the
sample
Eos: this ethod does’t uatif idiidual ieals
We need separate analysis to determine the individual mineral contnt of the
food
Ash otais ost of the ieals i the saple (i.e. Cl, Z, Na, “e, Fe, K, Ca, P,
Mg, Cr, Mn, Fl, Mb, etc.)
You would need to conduct individual tests to determine the content of each
mineral
Importance of knowing the Ash content of a food:
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