Food Analysis Exam 1

Specificity / selectivity

ability to detect the component of interest specifically in the presence of other components

• affected by presence of interfering substances

broad spectrum s very specific

• crude fat analysis: compounds soluble in an organic solvent, including triglycerides, phospholipids , cholesterol, fat soluble vitamins ( A, D , E and K )

• GC-TEA (gas chromatograph thermal energy analyzer) : analysis of N -nitrosamines : selectively analyze the compounds with no structure

accuracy

describes nearness of an experimental value to the true value

• methodology : calibration , standard reference material , % rrecovery , omparison to a well characterized method

precision

describes the reproducibility of replicate measurements. Precision refers to the agreement between values in a set of data.

accuracy vs precision

• all replicate measreuments agreeing welel doesn’t mean they are close to true valueall replicate measreuments agreeing welel doesn’t mean they are close to true value

evaluating precision

1) mean

2) SD

3) Coefficient of variation ( SD / mean ) x 100%

• a CV below 5% = acceptable

sensitivity

ratio between the magnitude of the intrumental response and the amount of the compound analyzed

detection limit

the lowest concentration of an analyte that can be detected with a statistical significance

• in instrumental analysis , the limit of detection can be researched when the signal to nose ratio is 2:1

signal to nose ratio

the response to the analyte divided by the electronic noise of the detection system

Linear range

interval between upper and lower levels of analyte in a linear doese-response

• directly proportional to analyte concentration within a given range

standard curves

used to determine unknown concentrations

• concentration of substance must be prortional to measurement

• linear regression most often used to construct curve

systematic errors

errors that can be determined and eliminated are called systematic errors or determinate errors

sources :

• methods, equipment / materials , personal judgements, mistakes

random errors

random errors that cant be determined and controlled , also called indeterminate errors

• effects can be effect of many small uncontrollable variables and personal judgements that lead to uncertainty in a measured value

Daily Value terms ( RDI and DRV )

RDI (Reference daily intake) : used for essential vitamins and minerals

Daily Reference value (DRV) : used for food components : total fat , saturated fat , cholersterol, total carbohydrate, dietary fat , sodium, potassium , protein

• based on 2000 or 2500 calorie intake

adding significant figures

he sum or difference of two measurements

can be no more accurate than the least accurate

of any individual measurement

moisture vs total solids

moisture = measure of the water content of a material

total solids: dry matter after moisture removal

water + solids = 100%

structure of water

dipolar nature . “ H slgightly positive and O slightly negative . one molecular can bind 4 molecular throuhgh hydrogen bonds

types of water

free water, bound water, water of crystallization

free water

• immobolized water : blocked by cell membrane or subcellular structures, not flow freely

• capillary water : hold by capillary force or intercellular water

• fluid water: freely move ex: blood

free water retains physcial properties and acts as solvent and is easy to form ice which causes damage of tissue strucutre