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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
Describe the simple system with "non-functional caecum"
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
Describe digestion for a monogastric (non-functional caecum) in the oral cavity
- food is chewed - 2 enzymes secreted in saliva: - alpha-amylase (breaks down starches into glucose) - lingual lipase (starts breakdown of lipids)
27
Describe digestion for a monogastric (non-functional caecum) in the stomach
- 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
Describe digestion for a monogastric (non-functional caecum) in the SI
- 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
Describe absorption in the SI for simple systems with non-functional caecums
- 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
How are nutrients transported across an enterocyte?
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
Describe digestion for a monogastric (non-functional caecum) in the LI (colon)
- 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
What is the microbiota?
- collection of ALL the bacteria that reside in an established environment
33
what is the microbiome?
ALL the genetic material found within the microbiota (bacteria genome)
34
Describe the simple system with a functional caecum
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
How does digestion work in the simple system with a functional caecum?
- 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
Describe the ruminant/multiple system
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
Describe digestion in the reticulum
- honeycomb appearance - traps foreign materials (wire, nails, etc.) - rich in bacteria
38
Describe digestion in the rumen
- 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
Describe digestion in the omasum
- reabsorption of water & some electrolytes | - filters large particles
40
Describe digestion in the abomasum
- "true stomach" | - digestive enzymes secreted from gastric glands
41
What are the advantages and disadvantages of the ruminant system?
advantages: - vitamin synthesis - bacterial synthesis of essential AA - mineral availability - NPN utilization disadvantages: - "destruction" of available CHO, protein - heat and gas production
42
Describe the avian system
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
How does digestion work in the avian system?
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
what is digestibility?
measure of the fraction of a specific nutrient or of energy that is extracted by the GI tract
45
how is digestibility calculated?
calculate coefficient (b/w 0 & 1), multiply this # by 100 = % digestibility calculated from amount of nutrient in diet & amount appearing in feces
46
Describe the total collection method
- 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
How is the apparent digestibility coefficient calculated?
ADC = (total intake - total feces) / total intake
48
what is apparent digestibility
assumes that all of the contents of the feces are non-digested material originating from the diet
49
Describe the indicator method
- "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
what is true digestibility
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
How is true digestibility calculated?
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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