Lecture 11 - Analysis

Question 1

5 objectives of analysis

Answer 1

• Classify
• Estimate energy content
• Calculate protein value (e.g. biological)
• Labels
• To evaluate differences e.g. in geographical area, year, season

Question 2

5 steps

Answer 2

• sampling
• packaging and transport
• preparation for analysis
• analysis
• report

Question 3

Sampled Portion

Answer 3

a unit that has characteristics presumed to be uniform.

Question 4

Incremental Sample

Answer 4

quantity taken from one point of the sample portion

Question 5

Aggregate Sample

Answer 5

combination of multiple incremental samples from the same sampled portion.

Question 6

Reduced Sample

Answer 6

Representative part of the aggregate sample, by a process of reduction

Question 7

Final Sample

Answer 7

part of the reduced sample or of the homogenised aggregate sample

Question 8

PACKAGING AND TRANSPORT, things to consider

Answer 8

• light -> dark
• oxygen ->vacuum
• heat ->freeze or refrigerate

Question 9

Possible PREPARATIONS OF SAMPLES

Answer 9

• Lyophilization
• Preliminary drying
• Grinding

Question 10

What Is Done in Proximate Analysis

Answer 10

• 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

Question 11

Dry Matter (DM)

Answer 11

sample is heated in an oven at 103C until it has a constant weight
Dry Matter (%) = 100 - Moisture

Question 12

Ash

Answer 12

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 (%)

Question 13

Crude Protein (CP)

Answer 13

Crude Protein (%) = N x 6,25
determines Nitrogen content assuming that it's 16% in proteins

Question 14

Ether Extract (EE)

Answer 14

Extraction with some solvent (petroleum ether) that gives the fat of the sample

Question 15

Crude Fiber (CF)

Answer 15

Treatments of the sample with boiling acid followed by alkali in defined concentrations

Question 16

Nitrogen Free Extract (NFE)

Answer 16

heterogeneous mixture of all those components that were not determined in the other analyses
NFE (%) = 100 – Moisture (%) – Ash (%) – CP (%) – EE (%) – CF (%)

Question 17

VAN SOEST ANALYSIS

Answer 17

based on the solubility of the cell wall components (fibrous fractions), in different pH solutions
FOR RUMINANTS, GRAVIMETRIC METHOD

Question 18

NDF (Neutral-Detergent Fiber)

Answer 18

represents all the parts of the plant cell wall
Cell content (CC) = 100 – NDF (%)
The higher the NDF, the lower the DM intake.

Question 19

ADF (Acid-Detergent Fiber)

Answer 19

acidic solution removes the hemicellulose

Hemicellulose (%) =NDF (%) – ADF (%)

Question 20

Acid Detergent Lignin (ADL)

Answer 20

sulfuric acid solution removes cellulose. What remains at the end is: lignin and insoluble ash
Cellulose (%) = ADF (%) – ADL (%)

Question 21

Lignin

Answer 21

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

Question 22

Is the dietary fiber analysis used for ruminants?

Answer 22

NO, it’s a van soest for MONOGASTRIC ANIMALS

Question 23

Dietary Fiber

Answer 23

Lignin plus those polysaccharides that cannot be digested by monogastric endogenous enzymes
soluble + insoluble

Question 24

Dietary fiber analysis procedure (4 steps)

Answer 24

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

Question 25

Can you perform proximate analysis, van soest and dietary fiber analysis on the same sample?

Answer 25

Yes, this will give you the full chemical composition of feed/food

Question 26

NIR (NEAR INFRARED) SPECTROSCOPY

Answer 26

The machine irradiates a sample, and in the memory of the machine are some predetermined values that will be compared to the sample to give its nutrient composition.