UNIT 2: FOOD/FEED COMPOSITION ANALYSIS (& DIGESTIVE SYSTEMS) Flashcards
What are 3 chemical analysis methods of foods and feeds compositions?
- proximate analysis
- newer methods
- southgate analysis
Calories are a reflection of _____
metabolizable energy or gross energy
Metaboliszable energy
When do you not require nutrition fact labels?
- raw foods
- prepped foods
- alcoholic beverages
What expresses the total amount of essential nutrients in one serving of a food, relative to the energy content
Nutrient density.
i.e. cupcake provides lots of calories, but few other nutrients.
What are the 5 components obtained via Proximate Analysis?
- moisture
- ether extract (crude fat)
- ash (minerals)
- kiedal analysis of nitrogen (crude protein)
- crude fibre
What is the importance of moisture in proximate analysis?
- proximate analysis cannot be obtained with moisture, sample must be dried
What is the point of ether extract in proximate analysis?
- 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
What is used to further quantify fatty acids after ether extraction?
Gas Chromatography is used to measure relative amounts of fatty acids
What is left after combusting the organic molecules at very high heat (500-600C)?
Ash (inorganic)
= minerals
- i.e. Zn, Na, Ca
What is used to further identify and quantify the minerals after combustion?
Atomic absorption spectroscopy.
High moisture content can spoil food while ____ mineral content can preserve food.
mineral
What is the importance of ash/mineral analysis?
- nutritional labelling
- determine quality
- indicate high mineral content (retard growth of micororganisms)
- achieve optimal food processing (physiochemical properties)
What is the point in measuring nitrogen?
- to determine crude protein
- protein is primary nitrogen component in food
How is nitrogen measured in the proximate analysis method?
- Kjeldahl method
Does proximate analysis differentiate types of fibres?
No. Proximate analysis determines amount of fibre but not between fibre types.
it also underestimates fibre content because soluble fibre lost
What does the Van Soest Method do?
- differentiate fibre types
What is added to bulk feed?
- fibre
- however, this is controlled to prevent adding waste products to bulk feed
What is an alternative to proximate analysis to quantify sugars, fibres, starch?
Southgate method.
- required for human food labelling
What is a limit to the southgate methods?
- does not subdivid fibre from soluble and insoluble fractions
- limit: agricultural setting, fermentability critical to meet energy requirements
What type of fibres ferments in the colon to produce VFAs?
- soluble fibres
- pectins, gums, mucilages
- these form a gel
- dissolve in water
Which type of fibre remains largely intact in intestinal tract?
- insoluble fibres
- cellulose, lignin, hemicellulose
- does not dissolve in water
Does proximate analysis provide info on digestibility?
No.
It provides info on the basic composition of foods and are not specific (further assays are required for food labelling).
