FDSN 311 midterm

Is nutritional labeling required for all food?

No, not for all food.  Infant formula, vitamins, raw vegetables, fruit, and fish

What agencies regulate nutrition labeling?

USDA- meat, poultry, egg products

FDA- everything else

What type of analytical methods are required to obtain the values listed on the Nutrition label? 

For USDA, USDA Analytical Chemistry Guidebook or AOAC method if method is not in the Guidebook.  

For FDA, AOAC International methods, unless a specific method is specified.

Is the label in compliance when an added nutrient level is 80% of what is listed on the label? 

No, it is not.  Added nutrients need to be at 100% level of compliance while naturally occurring ingredients need to be at least 80%.

What are some of the risks associated with sampling?

Consumer’s risk- probability of accepting poor quality population (

 Define composite sampling and where it is used?

Some aliquoots are taken from different bags or containers and are combined together to form a composite sample that is used for analysis.  It is used to obtain samples from bagged products such as flours, seeds, or larger items in bulk.

List some problems with sampling

Sampling bias, inappropriate sampling plan, sample degradation due to poor sample storage, mistaken sample identification due to mislabeling, susceptibility to tampering- need to seal and label appropriately

Define precision and accuracy by giving an example in each case. 

Accuracy is how close a measurement is to the true value.  An example of accuracy is if the true value is 94, the measurements are 94.3, 94.0, 93.7.  These are accurate because they are close to the true value. 

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Precision is how close the replicate measurements are to each other.  For example, if the true value is 94, and the measurements are 89.0, 89.1, and 89.1.  The measurements are precise but not very accurate. 

What does absolute or relative error tell us? 

The absolute error is the difference between experimental value and true value.  Eabs= x-T

The relative error is the comparison difference between experimental value and true value, against the true value.  %Erel= (x-T)/T  x100%

You ran an experiment with triplicate samples and found out one of the values is way off compared to other two. What kind of statistical test you can use to omit that value? 

Q-test

What are different ways to report concentration? 

Percent, ppm (parts per million), molarity, normality

Why there is need to determine moisture content? 

Quality factors affecting stability, reduced moisture used for convenience in packaging or shipping as it lowers cost, specified in compositional standards and standards of identity, required for nutrition label calculations, moisture data are used to express results of other analytical determinations on a uniform basis.

List at least 4 direct methods of moisture analysis?

Forced draft oven, vacuum oven, microwave analyzer, rapid moisture analyzer, karl fisher titration

What could be potential sources of error in oven drying methods? 

Particle size, high temperature, volatile compounds present (overestimation), splattering (overestimation)

What are some advantages and disadvantages of vacuum oven? 

Advantage is that one can obtain a more complete removal of water without decomposition of the sample. Disadvantages are uneven distribution of heat, volatile compounds may evaporate, a water trap is required so that moisture does not go to the vacuum pump

 Why is microwave drying better than oven drying? 

It provides a fast, accurate method to analyze many foods for moisture content

What are some advantages of chemical reaction methods? 

They are rapid, accurate, and use no heat.

Define Ash?

Ash is an inorganic residue remaining after either ignition or complete oxidation of organic matter

Solvent Extraction methods

Fat is extracted with solvent.  Fat content is measured by weight loss of sample or by weight of fat removed.  

Goldfisch Fat extractor and soxhlet extraction apparatus

Non-solvent wet extraction methods 

Sulfuric acid and/or amyl alcohol digests protein, generates heat, and releases fat. Sample is centrifuged and fat content is measured volumetrically. No need to dry sample.

Babcock Method and Gerber Method

Instrumental methods 

Use of instruments to analyze fat.

Infrared Spectroscopy and NMR

What kind of sample preparation is needed for fat analysis? 

Pre-drying sample= makes sample easier to grind, breaks fat-water emulstions to more easily dissolve fats in organic solvents, and helps free fat from food tissue.

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Particle size reduciton= increases extraction efficiency \n

Acid hydrolysis= breaks both covoalently and ionically bound lipids into easily extractable lipid forms

Differentiate between ethylether and petroleum ether as solvents for fat extraction?

Ethylether is the generally better solvent for lipids because it can solubilize both polar and non-polar lipids, but are more expensive and hygroscopic.  Petroleum ether is selective for more hydrophobic lipids but is cheaper and less flammable.

What is supercritical fluid extraction? 

When pressurized CO2 is heated above a certain critical temperature, it becomes supercritical fluid which has some properties of gas and some of liquid.  Fat is precipitated from solvent by decreasing the pressure, which turns CO2 to gas again.  

official method of analysis for Moisture

oven drying methods

official method of analysis for fat

soxhlet and mojonner

official method of analysis for ash

dry ashing

List steps involved in GC analysis of fat. Why is this method important? 

* Sample is subjected to acid and/or alkaline hydrolysis
* Pyrogallic acid added to minimize oxidative degradation of fatty acids
* Triglyceride added as an internal standard
* Extract fat with ether
* Methylate fatty acids to fatty acid methyl esters
* Separate and quantify FAMEs by capillary gas chromatography against internal standard

What is proximate composition analysis? 

Moisture + ash + fat + protein + total carb = 100%

In which method you can measure the water directly after analysis?

Distillation

Identify some potential sources of error in the preparation of samples for ash analysis? 

The sample may not be representative, microelement contamination, loss of sample in drying before ashing, volatilization of elements, incomplete combustion

What is the difference between molarity and normality?

Molarity is the number of moles per liter of a solution. Normality is the number of equivalents per liter of a solution. Normality is useful for acid-base titrations.

What is difference between dry and wet ashing? 

Dry ashing is when the sample is heated to temperatures, all organic matter is incinerated and the inorganic material can be quantified gravimetrically.  It is used to determine total ash content and sometimes as preparation for specific mineral analysis.

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Wet ashing is when organic matter is oxidized using acids and oxidizing agents, leaving inorganic matter.  It is used for preparation for specific mineral analysis not for total ash.