Food AnalysisFood Analysis

Advanced course for graduate students Advanced course for graduate students majoring Food Process and Safetymajoring Food Process and Safety

Feb. 2006Feb. 2006

Chapter One

General

Necessity of food analysis 1) Quality controlling in the raw material, food processing, and products. Delicious, Nutritional (protein, lipids,carbohydrates, fibre, water,vitamin, etc.) 2) Quality monitoring for food safety Healthy

Careful of your food

Sudan Red I is an industrial dye. It can beautify the color of food, and it can lead to cancer.

Inject unknown liquid , perhaps to keep it fresh.

Harmful food package

Hazardous materials exist. Usually it includes industrial CaCO3, cycled plastics, industrial wax, etc. when it contact hot water, or it was heated in the microwave oven, harmful substances was dissolved in the food.

Preservative film

DEHA is a kind of plasticizing agent. When it was heated or contact oil and fats, it can move into the food. It can interrupt endocrine system of people and lead to mammary cancer, infant deformity, and harm reproductive system of males.

Malachite green is a kind of dyes. It can kill fungi, and can length the life of fish in the transportation. The chemical is highly toxic, residual, and it can lead to carcinosis. Malachite green is banned in the aquiculture.

Food additives, such as saccharin sodium. They are chemically synthesized. Much more ingestion can induce carcinoma of urinary bladder, harm the liver and nerve system.

Harmful to your health

Acrylamide

Benzopyrene

Trans fatty acids

Benzopyrene

Cancer

Fats and Oils Cycled from restaurant. Much harmful materials exists in it, such as toxins, trans fatty acids, benzopyrene, etc.

Delicious ?

Food analysis concepts

Special research on establishing the method of analyzing the components of food or nutriments and its related principles, thereby evaluating the food quality.

Food analysis contents

1) Nutritional components of food Protein, lipids, carbohydrates, water, vitamin, miner

al, fibre, etc.

Functional components, such as PUFA(polyunsatuated fatty acids).

2) Analysis of food safety Food additives(e.g. pigment) Residual drug (e.g. pesticide) Food package (e.g. DEHA) Microbial contamination ( e.g. E.coli,toxins) Harmful ingredients (e.g. As) Harmful components produced in food process(e.

g. acrylamide)

3) Sensory evaluation of food

See if new food can be accepted by consumer (delicious or not) , it will be realized by sense organ ( nose, tongue).

Standard

1) Trade standard2) National standard3) International standard ISO: International Organization for Standardization WHO: World Health Organization CAC: Codex Alimentarius4) Advanced international standard regional standard national standard of developed country 5) AOAC Association of Official Agricultural Chemists

How to learn “food analysis”?

1) Knowledge on food processing2) Principles and practices of instrumentation3) Theory of methods (physical , chemical, bioche

mistry, enzymology, molecular biology, etc.)

Chapter two

Sampling and preparation of samples

SamplingSampling concept

Drawing representative sample from a bulk of

Materials. It should have the characteristics as

following:

An ideal sample should be identical in all of its intrinsic properties with the bulk of the material from which it is taken.

Importance of sampling

Sampling and any subsequent separations may be the greatest sources of error in food analyses.

1)Representative

2) No change or loss

3) No contaminant

Major steps in sampling1) Identification of the population from which the

sample is to be obtained.2) Selection and obtaining of gross samples of the

population.3) Reduction of each gross sample to be

laboratory-sized sample suitable for analysis. One is used for analysis.One should be packed and stored in such a way that no significant changes occur from the moment of sampling until the analysis is completed.

Types of sampling methods 1)Simple random sampling: for populations in which

all elements have an equal and independent chance of being included in a sample.

2) Stratified random sampling: by separating the population elements into overlapping groups (strata) and selecting a simple random sample from each strata.

3) Systematic sampling: drawing a 1 in K sample from a list of units. From the sampling frame, a starting point is chosen at random, and thereafter at regular intervals.

4) Judgment sampling: drawing samples based on the judgement and experience of the investigator.

Necessity of sample preparation1) Complexity of food compositions (components,

shape, etc.)2) Complex action of different components in the

food3) Quantity of components analyzed in the food

(toxin,microbe)4) Unstable components analyzed in the food (some

volatile components, compositional changes by action of microbe,enzyme and biochemistry, etc.)

Sample preparation

Purpose of sample preparation:Purification of

components analyzed, remove the interfering

materials.

Principles of sample preparation: object in the

food should be kept completely.

Methods in the sample preparation

1)Grinding dry and moist materials

2) Enzyme treatment or inactivation

3) Organic matter degradation

4) Distillation

5) Solvent extraction

6)Chromatography

7)Chemical purification

8)Concentration

Grinding dry and moist materials

1) Dry materials:

Hammer, ball mills etc

2) Moist material:

bowl cutter, meat mincers, colloid mills etc.

3) Extraction can be performed well.

2) Enzyme treatment or inactivation

1) To disintegrate the tissue mildly, avoid the destroy of objective components by acid or alkali.

2) To inactive the enzyme in the tissue, avoid the changes caused by the enzyme catalysis.

3) Organic matter degradation

Fundamentals: organic phase into inorganic phase

1) Ashing: samples—ashing(500~600℃） --analysis; for example, P analysis.

2) Digesting: samples– acid – analysis, for example, protein analysis

3) Microwave-digestion: samples-microwave -analysis, for example, Pb analysis.

4) UV photolysis: samples– UV(85 )—analysis, ℃for example, ion analysis.

4) Distillation

Fundamentals: distill the volatile components by water, or other solvents.

5) Solvent extraction

Fundamentals: solubility in different solvents.

Such as water, ethanol, or CO2.

6)ChromatographyAbsorption chromatography Absorb some components to purify the

object.Partition chromatography Different ability of distribution in two

mediator.one phase is mobile, the other is immobile. Such as HPLC.

Ion chromatography Ion exchange between ions.

7)Chemical purification

Saponification

Sulfonation

Separation by precipitation

Masking method

8) Concentration

Increase the concentration of components by distill, column chromatography etc.