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NUTR*3210 Midterm > Unit 2 > Flashcards

Unit 2 Flashcards

1
Q

What is proximate analysis?

A

basic determination of 6 components by subtraction, don’t get specific AA, minerals, lipids or CHO, just get totals

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2
Q

What do the southgate/van soest methods replace?

A

NFE and crude fibre for modern CHO labelling

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3
Q

What are the 6 steps to proximate anaylsis?

A
  1. moisture content - water in food (determined by drying)
  2. crude fat (total fat) - via ether extract
  3. ash (minerals/inorganic portion of sample)
  4. crude protein (N content is quantified via Kjeldahl method)
  5. crude fibre (type of CHO) - extracted via hot acid & basic salts ** NEW METHODS **
  6. available CHO (nitrogen free extract NFE) - all the above values are subtracted from initial sample weight to estimate available CHO ** NEW METHODS **
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4
Q

Describe the process, errors, and importance of Moisture content

A

process: food sample is dried (oven/freeze), loss in weight = moisture content
errors: loss of other volatile compounds (VFAs & alcohols) = overestimation of moisture (modern improvements: freeze>oven)
importance: most further analysis (#2-6) require a dry sample, agriculture systems work with food data on DM basis (human: weight weight/”as is” basis)
* water content has an affect on palatability & shelf life in human foods

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5
Q

How is moisture content calculated?

A

%DM = (dry weight of sample / wet weight of sample) * 100

% moisture = 100% - %DM

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6
Q

Describe the process, errors and the goal of crude fat (step 2)

A

process: dried food sample is extracted with non-polar solvent ether to get liquids out (or ether is dried down (evaporates) and lipids/fats remaining are weighed)
errors: ether is poor @ extracting phospholipids & method does not identify specific types of FA
goal: to quantify important dietary lipids (incl. triglycerides (TG), phospholipids (PL), cholesterol & specific FAs)

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7
Q

How is crude fat calculated?

A

% crude fat = (weight of crude fat / dry weight of sample) * 100

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8
Q

Describe the process, errors and importance of ash (step 3)

A

process: dried sample is burned in a high temp oven & remaining ash is weight - represents the minerals/inorganic portion of the sample
errors: method doesn’t quantify individual minerals - need separate analysis to determine individual mineral content of food

importance:

  • nutritional labeling
  • quality & taste of food
  • microbiological stability
  • nutritional requirements
  • processing
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9
Q

How is ash calculated?

A

% ash = (weigh of ash / dry weight of sample) * 100

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10
Q

Describe the process, errors, modern improvements, and importance of crude protein/nitrogen (Kjeldahl method) (step 4)

A

process: digestion with sulfuric acid, converting all N in sample to ammonia, which is then quantified, multiple grams of N by 6.25 to get grams of protein
errors: nitrogen is also liberated from other components like DNA, RNA; specific AAs are not determined via this methodology

modern improvements: if you know the exact %N in your food protein, you can fine-tune 6.25 correction factor; specific AA profiles need to be quantified via chromatography

importance: protein = expensive macronutrient in human & animal foods + accurate analysis is important for human food labeling & agricultural diet calcualtions

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11
Q

how is crude protein calculated?

A

% crude protein = (N in sample*6.25 / dry weight of sample) * 100

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12
Q

where does 6.25 come from?

A

kjeldahl analysis assumption: all protein has 16% N

100% (protein) / 16% (N) = 6.25
therefore N x 6.25 = CP

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13
Q

what are potential errors of assuming a factor of 6.25?

A
  • assumes all proteins have 16% N
  • actual range is 13% - 19 %
    (other sources of N: nitrates & nitrites, urea, nucleic acids)
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14
Q

What is fibre?

A
  • non-digestible complex carbohydrate (CHO)
  • structural part of plants
  • fibre is NOT digested in SI (remains intact until reaches colon)
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15
Q

Describe insoluble fibre

A

ex. lignin, cellulose, hemicellulose
- speeds up rate of movement of gut contents (decreased transit time - digested food spends less time in GIT)
- helps control intestinal pH, which can benefit microbiota
- increased laxation (passage of feces)
- reduces risk of diverticulitis, colon cancer
- provides some energy thru SCFA production - energy for microbiota & colon epithelial cell

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16
Q

describe soluble fibre

A

ex. hemicellulose, pectins, gums, mucilages
- can bind with cholesterol & bile acids to decrease absorption
- can slow stomach emptying, which may slow digestion of simple starches and sugars (decreased glycemic index)
- provides significant energy & maintains colon & microbiota health thru fermentation & release of SCFAs - several beneficial effects on human health (e.g. anti-inflammatory)

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17
Q

What is step 5 - crude fibre/NFE replaced by? why?

A

Southgate & Van Soest methods

NFE measured all carbohydrates AND all accumulated errors of previous steps (not good); does not differentiate b/w simple sugars & starches –> unknown CHO composition

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18
Q

What is the southgate method?

A

quantifies sugars & starches & TOTAL fibre

but no breakdown of soluble vs. insoluble fibre types - only tells total fibre

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19
Q

what is the van soest method?

A

differentiates & quantifies b/w soluble vs insoluble types of fibre (cellulose + hemicellulose, lignin)

provides a poor differentiation of sugars & starches important for ruminants that consume high fibre diets

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20
Q

what method is recommended for human food labeling? for agriculture systems?

A

southgate = human

van soest = agricultural

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21
Q

what is NFE?

A
  • nitrogen free extract
    = digestible CHO
  • measured by subtractions of all other components (steps 1-5)
  • potential errors: NFE accumulates ALL errors that exist for the other components of PA
22
Q

What are the 4 types of digestion systems?

A
  1. simple system (non-functional caecum)
  2. simple system (functional caecum)
  3. ruminant system
  4. avian system
23
Q

what are the components in the GIT?

A

mouth, esophagus, stomach, SI, caecum, LI, rectum

24
Q

what is a digestive system?

A

GIT + all associated organs (liver, pancreas, gallbladder) which provide & store various secretions (typically enzymes) required for digestion

25
Q

Describe the simple system with “non-functional caecum”

A

e. g. human, pig, cat, dog
- monogastric
- non-functional caecum = appendix
- suited for a nutrient dense, low fibre diet
- human digestive tract = ~16 ft
- lipid digestion: liver & gall bladder

26
Q

Describe digestion for a monogastric (non-functional caecum) in the oral cavity

A
  • food is chewed
  • 2 enzymes secreted in saliva:
    - alpha-amylase (breaks down starches into glucose)
    - lingual lipase (starts breakdown of lipids)
27
Q

Describe digestion for a monogastric (non-functional caecum) in the stomach

A
  • via pepsin & HCL
  • acidic compartment (pH ~2) kills bacteria, denatures proteins
  • 2 sphincters:
    - entrance: lower esphageal sphincter
    - exit: pyloric sphincter
  • elastic (empty = 50mL, filled = 1-1.5L)
  • gastric glands secrete: H2O, mucus (protect stomach & coat food), electrolytes, HCL, enzymes –> all referred to as gastric juice
  • digesting/denatured food = chyme
  • gastric emptying = 2-6hrs
28
Q

Describe digestion for a monogastric (non-functional caecum) in the SI

A
  • duodenum, jejunum, ileum
  • main site for nutrient digestion & absorption (if miss this point, no opportunity for absorption)
  • intestinal motility (longitudinal & circular - impeding waves) of 2 different types of muscles
    - circular muscles squeeze inwards towards lumen
    - longitudinal muscles squeeze inwards from either end
  • chyme acidity neutralized by pancreatic juice (pH 2 —-> pH 7 (basic secretions))
  • pancreas: provides secretions that neutralize stomach acid
  • digestion of food via pancreatic juice (basic, lots of enzymes) and bile acids (lipid digestion)
29
Q

Describe absorption in the SI for simple systems with non-functional caecums

A
  • gross folds (kerckring folds) - increase SA 3 fold
  • villi - increase SA 10 fold
  • microvilli - on each cell (enterocyte) - increase SA by another 20 fold
  • total: ~1000 fold increase in SA
  • lacteal: lymph vessel (important for lipid absorption)
30
Q

How are nutrients transported across an enterocyte?

A
  1. diffusion: no energy required, needs a concentration gradient
  2. facilitated diffusion: requires a transporter (passive transport), needs a concentration gradient
  3. active transport - ATP is needed to maintain a [ ] gradient across membrane
31
Q

Describe digestion for a monogastric (non-functional caecum) in the LI (colon)

A
  • fermentation of fibre occurs to produce SCFAs (energy source for colonocytes)
  • fermentation of fibre by colon bacteria
  • water & electrolyte absorption/reabsorption
  • low O2 levels in colon
32
Q

What is the microbiota?

A
  • collection of ALL the bacteria that reside in an established environment
33
Q

what is the microbiome?

A

ALL the genetic material found within the microbiota (bacteria genome)

34
Q

Describe the simple system with a functional caecum

A

e. g. horse, rabbit, hamster
- functional caecum
- suited for diet with large amounts of forage
- digestion takes place in hindgut (large functional caecum & LI (colon)) - produce SCFAs

35
Q

How does digestion work in the simple system with a functional caecum?

A
  • enormous hindgut with bacteria for breakdown of most fibres to sugars & SCFAs
  • also produces various vitamins thru action of bacteria in caecum
  • LI is 45% of horses digestive tract so LONG transit times
  • slow transit times = max breakdown of nutrients and absorption
  • up to 70% energy for horse comes from SCFAs
36
Q

Describe the ruminant/multiple system

A

e. g. cattle, sheep, goat
- foregut fermentation
- presence of large stomach divided into 4 sections: rumen, reticulum, omasum, abomasum
- system suited to very high roughage diets

37
Q

Describe digestion in the reticulum

A
  • honeycomb appearance
  • traps foreign materials (wire, nails, etc.)
  • rich in bacteria
38
Q

Describe digestion in the rumen

A
  • largest section of the stomach
  • rumen papillae - increased SA for absorption
  • rich in bacteria - 60-80% of energy from SCFA are produced & absorbed here
39
Q

Describe digestion in the omasum

A
  • reabsorption of water & some electrolytes

- filters large particles

40
Q

Describe digestion in the abomasum

A
  • “true stomach”

- digestive enzymes secreted from gastric glands

41
Q

What are the advantages and disadvantages of the ruminant system?

A

advantages:
- vitamin synthesis
- bacterial synthesis of essential AA
- mineral availability
- NPN utilization

disadvantages:

  • “destruction” of available CHO, protein
  • heat and gas production
42
Q

Describe the avian system

A

e. g. chicken, turkey
- beaks & claws are important for breaking up foods into smaller pieces that birds can swallow
- light in order to fly
- rapid digestion - short transit time
- birds are “sight” feeders - poor sense of taste & smell

43
Q

How does digestion work in the avian system?

A

crop
- enlarged area of esophagus, serves as temp storage location for food
two chambered stomach
- glandular portion = proventriculus, gastric enzymes + HCL secreted (&mucus)
- muscular portion = gizzard, muscular contractions to help breakdown food, grind + digest, pick up small rocks
small intestine
- site of nutrient absorption
ceca (2 large cecums)
- minor site of bacterial fermentation
large intestine
- very short, serves mainly to connect SI to cloaca
- storage of undigested material
- water & electrolyte absorption
cloaca
- where digestive, urinary & reproductive systems meet
- uric acid mixes with feces

44
Q

what is digestibility?

A

measure of the fraction of a specific nutrient or of energy that is extracted by the GI tract

45
Q

how is digestibility calculated?

A

calculate coefficient (b/w 0 & 1), multiply this # by 100 = % digestibility

calculated from amount of nutrient in diet & amount appearing in feces

46
Q

Describe the total collection method

A
  • allow animal to adapt to diet (7-21 days)
  • isolate animal for qualitative analysis
  • measure intake over 3-10 day period
  • collect & weigh all feces
  • analyze feces for amount of nutrient of interest that is still in feces
47
Q

How is the apparent digestibility coefficient calculated?

A

ADC = (total intake - total feces) / total intake

48
Q

what is apparent digestibility

A

assumes that all of the contents of the feces are non-digested material originating from the diet

49
Q

Describe the indicator method

A
  • “marker technique”
  • requires that a specific component in the food can be identified as a marker
  • marker can be internal (natural component of feed) or external (component added to feed)
  • characteristics of a good marker:
    - should be non-absorbable & move through GIT uniformly
    - must not alter GIT function
    - must mix well with the other food/feed components
    - must be easily & accurately measured in feed & fecal samples
50
Q

what is true digestibility

A
  1. perform digestibility study using TEST DIET (collect feces) containing nutrient X
  2. switch to diet free of nutrient X, collect feces
  3. subtract level of nutrient X in feces of animals fed zero nutrient diet from test diet
51
Q

How is true digestibility calculated?

A

true/accurate digestibility of nutrient X = test diet fecal content of nutrient X - zero nutrient diet content of X

NUTR*3210 Midterm (5 decks)

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