Lecture 11 - Analysis Flashcards
5 objectives of analysis
- Classify
- Estimate energy content
- Calculate protein value (e.g. biological)
- Labels
- To evaluate differences e.g. in geographical area, year, season
5 steps
- sampling
- packaging and transport
- preparation for analysis
- analysis
- report
Sampled Portion
a unit that has characteristics presumed to be uniform.
Incremental Sample
quantity taken from one point of the sample portion
Aggregate Sample
combination of multiple incremental samples from the same sampled portion.
Reduced Sample
Representative part of the aggregate sample, by a process of reduction
Final Sample
part of the reduced sample or of the homogenised aggregate sample
PACKAGING AND TRANSPORT, things to consider
- light -> dark
- oxygen ->vacuum
- heat ->freeze or refrigerate
Possible PREPARATIONS OF SAMPLES
- Lyophilization
- Preliminary drying
- Grinding
What Is Done in Proximate Analysis
- food/feed gets separated into dry matter and moisture
- dry matter gets separated into organic matter and ash
- organic matter can be separated into crude protein and ternary compounds
Dry Matter (DM)
sample is heated in an oven at 103C until it has a constant weight Dry Matter (%) = 100 - Moisture
Ash
dry matter is burnt in a muffle oven at 550C until all the carbon has been removed and only minerals remain
Organic Matter “OM ” (%) = 100 - Moisture (%) - Ash (%)
Crude Protein (CP)
Crude Protein (%) = N x 6,25 determines Nitrogen content assuming that it's 16% in proteins
Ether Extract (EE)
Extraction with some solvent (petroleum ether) that gives the fat of the sample
Crude Fiber (CF)
Treatments of the sample with boiling acid followed by alkali in defined concentrations
Nitrogen Free Extract (NFE)
heterogeneous mixture of all those components that were not determined in the other analyses
NFE (%) = 100 – Moisture (%) – Ash (%) – CP (%) – EE (%) – CF (%)
VAN SOEST ANALYSIS
based on the solubility of the cell wall components (fibrous fractions), in different pH solutions
FOR RUMINANTS, GRAVIMETRIC METHOD
NDF (Neutral-Detergent Fiber)
represents all the parts of the plant cell wall Cell content (CC) = 100 – NDF (%) The higher the NDF, the lower the DM intake.
ADF (Acid-Detergent Fiber)
acidic solution removes the hemicellulose
Hemicellulose (%) =NDF (%) – ADF (%)
Acid Detergent Lignin (ADL)
sulfuric acid solution removes cellulose. What remains at the end is: lignin and insoluble ash
Cellulose (%) = ADF (%) – ADL (%)
Lignin
to determine the lignin content, ashing of the ADL residue is done at 550C in a muffle oven
Lignin (%) = ADL (%) – AIA (%)
important as ruminants cannot digest lignin
Is the dietary fiber analysis used for ruminants?
NO, it’s a van soest for MONOGASTRIC ANIMALS
Dietary Fiber
Lignin plus those polysaccharides that cannot be digested by monogastric endogenous enzymes
soluble + insoluble
Dietary fiber analysis procedure (4 steps)
Enzymatic method
- samples are gelatinised by heating
- treated with enzymes to remove starch and proteins
- total dietary fibre is precipitated with ethanol
- the residue is dried and weighed at the end
