Term
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Definition
| the development, application & study of analytical methods for characterizing foods & their constituents |
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Term
| What is nutrient density? |
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Definition
| the amount of nutrients in a food in comparison to caloric content |
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Term
| What are the components of proximate analysis? |
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Definition
Moisture
Ether extract
Ash
Nitrogen
Crude |
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Term
| Why is determining water content in particular important? |
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Definition
-high water content = food spoils faster
-how water content = less palatable
-food water is an important means of hydration esp. in tropical regions |
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Term
| When analyzing moisture content in agriculture we look at _______ while for human consumption we are concerned about _________ |
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Definition
| dry matter....wet weight basis |
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Term
| What are the steps for analyzing moisture content? |
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Definition
1. Weigh food samples
2. Dry at 105C or freeze dry |
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Term
| What is the calculation for moisture content? |
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Definition
| weight loss / wet weight X 100 |
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Term
| What is the calculation for dry matter content? |
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Definition
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Term
| What are some sources of error in analyzing moisture content? |
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Definition
| -other volatiles can be removed e.g. short chain fatty acids, alcohols |
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Term
| What is obtained from the extraction of ether? |
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Definition
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Term
| What is the goal of ether extraction? |
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Definition
to quantify important dietary lipids
e.g. TGs, PLs, C, FA |
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Term
| How do you calculate % crude fat? |
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Definition
| weight of crude fat / wet weight of sample X 100 |
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Term
| What are some potential errors in determining crude fat content? |
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Definition
-plant products remain e.g. chlorophyl, carotenoids
-PL extraction is often incomplete
-poor definition of subclasses (PUFA, MUFA, saturates) |
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Term
True or False
Phospholipids are polar |
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Definition
False
they are often slightly nonpolar |
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Term
| What does the calculation of ash give you? |
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Definition
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Term
| How do you calculate mineral content? |
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Definition
| weight of ash / wet weight x 100 |
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Term
| What are some potential errors in calculating mineral content? |
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Definition
| -volatile minerals lost (Fe, Cu, Zn) which are critical in animal diets |
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Term
| How do you determine the Na, Ca and Fe content of food? |
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Definition
| take the %ash, dissolve in acid and perform Atomic Acid Spectroscopy |
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Term
| What does Kjeldahl Analysis determine? |
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Definition
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Term
| What assumptions are made for Kjeldahl Analysis? |
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Definition
-all protein is 16% N
-all food N is in the form of AA's (protein) |
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Term
| What are the 3 main steps of the Kjeldahl Analysis? |
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Definition
1. Digestion - mix homogoneous sample with sulfuric acid (ammonia)
2. Distillation - separating ammonia
3. Titration - quantify the amount of ammonia |
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Term
| How do you calculate % crude protein? |
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Definition
| Nitrogen in sample X 6.25 / wet weight of sample X 100 |
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Term
| What are some potential errors with the Kjeldahl analysis? |
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Definition
-assume all proteins have 16% N
-actual range of N is 13-19%
-other forms of N exist such as nitrates, urea, nucleic acids |
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Term
| What step involves calculation by subtraction? |
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Definition
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Term
| How do you calculate % crude fibre? |
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Definition
| (wet weight of ash + crude fibre) - wet weight of ash / wet weight of sample X 100 |
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Term
| What are some potential errors in calculating crude fibre? |
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Definition
-underestimates fibre (loss of pectin, hemicellulose, hydrocolloids)
-most soluble fibre is missed
-crude fibre doesnt equal dietary fibre |
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Term
| What substances make up crude fibre? |
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Definition
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Term
| What substances make up dietary fibre? |
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Definition
| cellulose, hemicellulose, pectin, hydrocolloids, lignin |
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Term
| What is NFE mainly made of? |
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Definition
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Term
| How do you calculate % NFE? |
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Definition
| 100 - (%moisture + %crude fat + %ash + %crude protein + %crude fibre) |
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Term
| What are the potential errors in calculating NFE? |
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Definition
-errors from each method accumulate
-doesn't differentiate sugars |
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Term
True or False
Proximal Analysis gives an excellent idea of digestibilty |
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Definition
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Term
| Is proximal analysis sufficient for gaining information for modern food labels? |
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Definition
| No. No information on specific AAs, minerals, lipids, carbohydrates |
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Term
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Definition
non-digestible CHO
-structural part of plants |
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Term
| Which portions of dietary fibre remain intact through the GI tract? |
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Definition
insoluble fibres
(cellulose, lignin, hemicellulose) |
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Term
| What fibre ferments in the colon to produce VFAs? |
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Definition
soluble fibres
(pectins, gums & mucilages) |
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Term
True or False
Dietary fibre is digested in the stomach |
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Definition
False
It is fermented & digested in the colon |
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Term
| What method is used today for labelling animal feeds? |
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Definition
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Term
| What method is used today for labelling human food products? |
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Definition
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Term
| The Van Soest method is also known as... |
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Definition
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Term
| What does the Van Soest method do? |
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Definition
-differentiates between insoluble fibre components
Digestible cellulose & hemicellulose
Indigestible lignin |
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Term
| Why is the Van Soest method not suitable for labelling human food? |
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Definition
| -doesn't differentiate sugars, starches or cell solubles well |
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Term
| What does the Southgate method do? |
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Definition
| -quantifies sugars, starch & fibre |
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Term
| Why is the Southgate method not suitable for labelling agricultural foods? |
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Definition
| -does not differentiate fibre components well (not enough information on fermentability) |
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