lecture 3/4 Flashcards
What is food analysis?
Anylizaing by using qualitative determination, quantitation and structure eludication to target chemical species in sample.
Define analyte.
-the traget to be anylzed
Define matrix.
-entire sample material including anyalyte
Why is analyzing food samples important? (6)
Nutrition labeling
Nutrient and health claims
Quality control and assurance
Toxin identifaction
Research
Regulatory
What are the procedures and considerations that need to be taken into acount?
-define problem
-choose appropriate instrument
-sampling
-sample pre treatments
-accurte analysis and reporting
-realiabilty of data
Define analytical techniques and some analyte properties that measurement may include.
-physiochemical process that provides basis for analytical measuremnts like mass or molecular size, emission/absorption of electromagnetic radiation, electrical/thermal properties
What are examples of sampling methods?
-random selcetion
-cone and quarter
-riffle box splitting
-repeated sampling
Define error, accuracy and precision.
Error: differnce between true answer and observation
Accuracy: closeness of values to true or accepted value
Precision: closeness of values from replicated experiments, variability, dispersion
What are the AOAC methods used in food analysis?
calories-equation
total carb-equation
protien-dumas
total fat-gas chromatography
cholesterol-capillary gas chromatography
moisture-draft oven
sodium, calcium, iron, potasium-inductively coupled plasma, optical emision spectroscopy
What is the atwater method for measuring energy value?
Calories =( g of carb x 4cal/g)+(g of protien x4 cal/g)+ (G of fat x 9 cal/g)
For analyzing protien content in food, nitrogen content can be analyzed what are the 2 methods used and briefly describe them
Kjedahl: digestion, neutralzation, distilation and titration (N x6.25), inexpesnive, but only measures total N not just protien N and is very time consuming, lower precision
Duma: combustion done at high temp to release N and then uses gas chromatography and then (N x6.25), rapid, no hazardous chemicals, automated, expensive equipment, doesn’t just measure protien N
What is the colormetric method for measuring protien?
Biuret and lowry methods: based one peptide bond, complexed with cupric ions to be treated with spectroscopy, less expensive, faster and more simple but cannot detect insoluble protien
Describe Moisture content method : oven drying.
Mass loss of product after heating =(wet weight-dry weight)/wet weight x100
-doesn’t for sure reflect true water content as tightly bound water escapes detection and volatile substances may interfere
describe the 3 Mineral anaylsis content methods:
Dry ashing
-some minerals lost, 500-600 degrees, gravimetric analysis
Wet ashing
-boiling in mixture of acids/oxidizing agents, no lose
Atomic absorption/ emission spectroscopy
-solubized in acid and can absorb or emit light of specific wavelengths
ICP-MS
-recomoneded by CFIA for labelling
describe the anylitcal methods for Lipids:
Soxhlet method
-content measured by weight loss of sample or weight of fat removed, using a distilation flask and allow to evaporate then measure
-time consuming but complete extraction, manual process, lipids may escape, no worry about temp
GC (gas chromatography)
-seperation done by difference in volatility of compounds and their affinitys to phase column
-convert to TAg equivalents
-can be used to determine cholesterol content using saponifcation and toluene, then using cholestane as a refernce
-measures only true fats, and can separate fats, time consuming and expensive
