UNIT 2: FOOD/FEED COMPOSITION ANALYSIS (& DIGESTIVE SYSTEMS)

Question 1

What are 3 chemical analysis methods of foods and feeds compositions?

Answer 1

• proximate analysis
• newer methods
• southgate analysis

Question 2

Calories are a reflection of _____

metabolizable energy or gross energy

Answer 2

Metaboliszable energy

Question 3

When do you not require nutrition fact labels?

Answer 3

• raw foods
• prepped foods
• alcoholic beverages

Question 4

What expresses the total amount of essential nutrients in one serving of a food, relative to the energy content

Answer 4

Nutrient density.

i.e. cupcake provides lots of calories, but few other nutrients.

Question 5

What are the 5 components obtained via Proximate Analysis?

Answer 5

1. moisture
2. ether extract (crude fat)
3. ash (minerals)
4. kiedal analysis of nitrogen (crude protein)
5. crude fibre

Question 6

What is the importance of moisture in proximate analysis?

Answer 6

• proximate analysis cannot be obtained with moisture, sample must be dried

Question 7

What is the point of ether extract in proximate analysis?

Answer 7

• lipid-like substances; non-polar solvent that carries the lipids
• Goal: determine quantity of lipids in food sample with nutritional importance:
• triglycerides, phospholipids, cholesterol, fatty acids

Question 8

What is used to further quantify fatty acids after ether extraction?

Answer 8

Gas Chromatography is used to measure relative amounts of fatty acids

Question 9

What is left after combusting the organic molecules at very high heat (500-600C)?

Answer 9

Ash (inorganic)
= minerals
- i.e. Zn, Na, Ca

Question 10

What is used to further identify and quantify the minerals after combustion?

Answer 10

Atomic absorption spectroscopy.

Question 11

High moisture content can spoil food while ____ mineral content can preserve food.

Answer 11

mineral

Question 12

What is the importance of ash/mineral analysis?

Answer 12

• nutritional labelling
• determine quality
• indicate high mineral content (retard growth of micororganisms)
• achieve optimal food processing (physiochemical properties)

Question 13

What is the point in measuring nitrogen?

Answer 13

• to determine crude protein

- protein is primary nitrogen component in food

Question 14

How is nitrogen measured in the proximate analysis method?

Answer 14

• Kjeldahl method

Question 15

Does proximate analysis differentiate types of fibres?

Answer 15

No. Proximate analysis determines amount of fibre but not between fibre types.
it also underestimates fibre content because soluble fibre lost

Question 16

What does the Van Soest Method do?

Answer 16

• differentiate fibre types

Question 17

What is added to bulk feed?

Answer 17

• fibre

- however, this is controlled to prevent adding waste products to bulk feed

Question 18

What is an alternative to proximate analysis to quantify sugars, fibres, starch?

Answer 18

Southgate method.

- required for human food labelling

Question 19

What is a limit to the southgate methods?

Answer 19

• does not subdivid fibre from soluble and insoluble fractions
• limit: agricultural setting, fermentability critical to meet energy requirements

Question 20

What type of fibres ferments in the colon to produce VFAs?

Answer 20

• soluble fibres
• pectins, gums, mucilages
• these form a gel
• dissolve in water

Question 21

Which type of fibre remains largely intact in intestinal tract?

Answer 21

• insoluble fibres
• cellulose, lignin, hemicellulose
• does not dissolve in water

Question 22

Does proximate analysis provide info on digestibility?

Answer 22

No.
It provides info on the basic composition of foods and are not specific (further assays are required for food labelling).