Food/Feed Composition

Question 1

What is the role of government regulations in correlation with food composition?

Answer 1

ensures the food industry makes safe foods with high quality

• fair competition between companies
• eliminate economic fraud

Question 2

what are the five different categories that wet weight feed samples end up as?

Answer 2

1. moisture
2. ether extract
3. ash
4. nitrogen
5. crude fibre

Question 3

how does a feed sample turn into dry matter?

Answer 3

by air drying the feed sample, it will release moisture, turning it to dry matter

Question 4

why is determining water content in feed important

Answer 4

• price of feed (weight)
• moisture content plays a role in storage conditions
• moisture dilutes energy and nutrients
• impt for optimum intake and performance of animals

Question 5

what is the equation used when calculating %moisture?

Answer 5

[(wet weight - dry weight)/ (wet weight)] [100]

Question 6

what is the equation use when calculating % dry matter?

Answer 6

100- (%moisture)

Question 7

what are the potential sources of error when calculating % moisture

Answer 7

drying can remove other volatile compounds (fatty acids, minerals)
- results in under-estimation of dry weight

Question 8

how does a feed sample get turned into ether extract?

Answer 8

1. the wet feed sample is dried into dry matter.
2. an ether extraction is then done on the dry matter (solution is transferred to a new tube and then dried down- the resulting precipitate is the fat)

Question 9

what is the equation used when calculating % crude fat

Answer 9

% crude fat= [(weight of ether extract) / (wet weight of sample)] [100]

Question 10

what are the potential sources of error when calculating % crude fat

Answer 10

other things are soluble in ether extract (chlorophyl, resins)
- will over estimate crude fat determination

Question 11

how do you get ASH(mineral) from feed sample?

Answer 11

1. dry the feed sample
2. sample is now dry matter
3. after the ether extraction, ignite the residue (precipitation)

Question 12

why is it important to measure ash content

Answer 12

• nutritional labelling
• quality and taste of food
• stability

Question 13

what is the equation used when calculating ash content

Answer 13

% ash= (weight of ash) /wet weight

Question 14

what are the potential sources of error when calculating % ash

Answer 14

• volatile minerals may be lost when burning residue

- gives no info on individual minerals

Question 15

how do you get nitrogen from a feed sample

Answer 15

after dried, a kjeldahl analysis is done on the dry matter

Question 16

what are the assumptions made for the kjeldahl analysis

Answer 16

1. all nitrogen is protein

2. all protein contains 16% nitrogen

Question 17

what are the three main steps to the kjeldahl analysis?

Answer 17

1. digestion- a food sample is mixed with surlfuric acid, which converts nitrogen into ammonia
2. distillation- separates the ammonia
3. titration- to quantify the amount of ammonia a\

Question 18

what is the equation used when calculating % crude protein

Answer 18

% crude protein= [(N in sample * 6.25)/(wet weight)] * 100

Question 19

what are the errors within the kjeldahl analysis

Answer 19

1. assumes all proteins have 16% nitrogen (when the actual range is 13-19%)
2. there are other sources of nitrogen
   (so the crude protein content would be slightly over-estimated)

Question 20

from a feed sample, how do you get crude fibre?

Answer 20

• feed sample gets dried into dry matter
• ether extraction is done on the dry matter
• either extract is then boiled in acid
• the residue is then boiled in base
• the crude fibre and ASH is ignited

Question 21

what is the equation used when calculating % crude fibre

Answer 21

[(weight of ASH + Crude fibre)-(weight of ash)]/ (wet weight of sample

Question 22

what is crude fibre

Answer 22

• mainly cellulose and lignin

Question 23

what are the potential sources of error for calculating crude fibre

Answer 23

-unable to distinguish different fibre components
- measuring crude fibre under-estimates the actual dietary fibre content of feed up to 50%
(soluble fibres are lost during proximate analysis)

Question 24

what does nitrogen free extract =

Answer 24

digestible carbohydrate

- estimates starch and sugar content

Question 25

where are the potential sources of error when calculating NFE

Answer 25

NFE accumulates all of the errors that exist for the other components

Question 26

what is used as the basis for human food labelling and animal feed analyses?

Answer 26

the proximate analysis

Question 27

what is dietary fibre

Answer 27

- non-digestible complex CHO | - structural part of plants

Question 28

what are the insoluble dietary fibres

Answer 28

- cellulose - lignin - hemicellulose

Question 29

what are the soluble dietary fibres

Answer 29

- pectin - gums - mucilages

Question 30

what do the insoluble dietary fibres do through the intestinal tracT?

Answer 30

insoluble dietary fibre remains intact through intestinal tract - reduces inflammation

Question 31

what do the soluble dietary fibres do through the intestinal tract

Answer 31

soluble dietary fibres form gel (they dissolve in water)

Question 32

what is the Soest method for Fibre Analysis in Feeds?

Answer 32

an detergent fibre analysis

Question 33

what does the Soest method determine?

Answer 33

- differentiated between insoluble fibres (cellulose & hemicellulose, lignin) - determines fermentable and non-fermentable CHO - poorly differentiates sugars, starches, and soluble fibres

Question 34

what is the Southgate method

Answer 34

- provides information about sugars, starch, and various fibres - useful for human nutrition and food labelling - does not differentiate between various fibre components adequately