Food/Feed Composition Flashcards
What is the role of government regulations in correlation with food composition?
ensures the food industry makes safe foods with high quality
- fair competition between companies
- eliminate economic fraud
what are the five different categories that wet weight feed samples end up as?
- moisture
- ether extract
- ash
- nitrogen
- crude fibre
how does a feed sample turn into dry matter?
by air drying the feed sample, it will release moisture, turning it to dry matter
why is determining water content in feed important
- 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
what is the equation used when calculating %moisture?
[(wet weight - dry weight)/ (wet weight)] [100]
what is the equation use when calculating % dry matter?
100- (%moisture)
what are the potential sources of error when calculating % moisture
drying can remove other volatile compounds (fatty acids, minerals)
- results in under-estimation of dry weight
how does a feed sample get turned into ether extract?
- the wet feed sample is dried into dry matter.
- 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)
what is the equation used when calculating % crude fat
% crude fat= [(weight of ether extract) / (wet weight of sample)] [100]
what are the potential sources of error when calculating % crude fat
other things are soluble in ether extract (chlorophyl, resins)
- will over estimate crude fat determination
how do you get ASH(mineral) from feed sample?
- dry the feed sample
- sample is now dry matter
- after the ether extraction, ignite the residue (precipitation)
why is it important to measure ash content
- nutritional labelling
- quality and taste of food
- stability
what is the equation used when calculating ash content
% ash= (weight of ash) /wet weight
what are the potential sources of error when calculating % ash
- volatile minerals may be lost when burning residue
- gives no info on individual minerals
how do you get nitrogen from a feed sample
after dried, a kjeldahl analysis is done on the dry matter
what are the assumptions made for the kjeldahl analysis
- all nitrogen is protein
2. all protein contains 16% nitrogen
what are the three main steps to the kjeldahl analysis?
- digestion- a food sample is mixed with surlfuric acid, which converts nitrogen into ammonia
- distillation- separates the ammonia
- titration- to quantify the amount of ammonia a\
what is the equation used when calculating % crude protein
% crude protein= [(N in sample * 6.25)/(wet weight)] * 100
what are the errors within the kjeldahl analysis
- assumes all proteins have 16% nitrogen (when the actual range is 13-19%)
- there are other sources of nitrogen
(so the crude protein content would be slightly over-estimated)
from a feed sample, how do you get crude fibre?
- 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
what is the equation used when calculating % crude fibre
[(weight of ASH + Crude fibre)-(weight of ash)]/ (wet weight of sample
what is crude fibre
- mainly cellulose and lignin
what are the potential sources of error for calculating crude fibre
-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)
what does nitrogen free extract =
digestible carbohydrate
- estimates starch and sugar content
where are the potential sources of error when calculating NFE
NFE accumulates all of the errors that exist for the other components
what is used as the basis for human food labelling and animal feed analyses?
the proximate analysis
what is dietary fibre
- non-digestible complex CHO
- structural part of plants
what are the insoluble dietary fibres
- cellulose
- lignin
- hemicellulose
what are the soluble dietary fibres
- pectin
- gums
- mucilages
what do the insoluble dietary fibres do through the intestinal tracT?
insoluble dietary fibre remains intact through intestinal tract
- reduces inflammation
what do the soluble dietary fibres do through the intestinal tract
soluble dietary fibres form gel (they dissolve in water)
what is the Soest method for Fibre Analysis in Feeds?
an detergent fibre analysis
what does the Soest method determine?
- differentiated between insoluble fibres (cellulose & hemicellulose, lignin)
- determines fermentable and non-fermentable CHO
- poorly differentiates sugars, starches, and soluble fibres
what is the Southgate method
- provides information about sugars, starch, and various fibres
- useful for human nutrition and food labelling
- does not differentiate between various fibre components adequately
