Introduction to Food Science and Technology ( Dr. Çiğdem SOYSAL )

•Dr. Çiğdem Soysal
•Reference Books
•1. P. Fellows, Food Processing Technology
•2. R. Paul Sing, Introduction to Food Engineering
•3. Romeo T. Toledo, Fundamentals of Food Process Engineering
•Course Content
•Historical development of food science and technology
• Principles of biological and physical sciences related to the human food system.
• Structure and properties of food materials
• Unit operations in food processing
• Food legislation
• Environmental considerations
•Introducing historical development of food engineering
•Learn about various unit operations used in the food processing industry to process raw materials into finished product
•Develop knowledge on the food legislation and environmental consideration
•Exams – There will be two mid-terms (in class closed book), and a final exam.
Evaluation % of grade
1. Midterm 30
2. Midterm 30
Final exam 40
Application of the basic sciences and engineering to study the fundamental physical, chemical and biochemical nature of foods and the principles of food processing.
•Food Chemistry
•Food Microbiology
•Food Quality Control
Food technology is the use of the information generated by food science in the selection, preservation, processing, packaging and distribution, as it affects the the consumption of safe, nutritious and wholesome food.
•Process Control
•Fluid Mechanics
•Food Processing Operations
Scope of Food Science and Technology includes:
•Efforts to make it possible to supply great quantities of food to crowded populations (result of urbanization)
•Efforts to develop new (novel) foods agreeable to consumers (increase type, availability at all times)
•To maintain (if possible to improve) nutritional value and quality of foods.
The core of food science and technology courses includes both lecture and laboratory components
The present day food industry has its origins in pre-history when the first food processing took place;
•To preserve foods against famine (for ex; sun drying of grain to extend storage life)
•Or to improve their eating quality (for ex; roasting of meat to improve flavor)
Mechanical processing equipment was developed to reduce the time labour involved in manual methods. For example, water, wind and animal power were used to mill grains.
The first biochemical processing began in Egypt with the development of fermented products, including cheeses and wines.
For a long period such preservation and preparation methods were only used on a domestic scale to serve the needs of the family.
As societies developed, specialization took place and trades developed (bakers and brewers)
These were the forerunners of current food industries.
Food processing techniques were developed;
•To allow food to be stored through the winter months
•To increase the availability of foods out of season and
•To allow foods to be transported from rural areas to urban areas
During the 19th century, larger scales of production were achieved in factories to produce basic commodities, including starch, sugar, butter and baked goods. These processes were based on tradition and experience, and no detailed knowledge of the composition of foods or changes during processing was available.
Towards the end of that century; an increase in scientific understanding started the change from craft-based industry to science-based industry that is continuing today.
The aims of the food industry today;
1.To extent the period during which a food remains the shelf life by preservation techniques which increase the stability during production, distribution and home storage
2.To increase variety in the diet by providing a range of attractive flavors,colors, aromas and textures in food wheat flour, bread, macaroni, biscuits, cake, etc milk cheese, yoghurt, butter,etc meat sausage, kebab, köfte, etc
3.To provide the nutrients required for health (nutritional quality of food; vitamin, protein, fat, carbohydrate, mineral)
4.To generate income for the manufacturing factory
The aims of the food industry today:
1.To extent the period during which a food remains the shelf life by preservation techniques which increase the stability during production, distribution and home storage
2.To increase variety in the diet by providing a range of attractive flavors, colors, aromas and textures in food
wheat → flour, bread, macaroni, biscuits, cake, etc
milk → cheese, yoghurt, butter,etc
meat → sausage, kebab, köfte, etc
3.To provide the nutrients required for health (nutritional quality of food; vitamin, protein, fat, carbohydrate, mineral)
4.To generate income for the manufacturing factory
•All food processing involves a combination of procedures to achieve the intended changes to the raw materials. These are categorized as unit operations.
•Unit operations are grouped together to form a process. The combination and sequence of operations determines the nature of the final product.
Cleaning Cleaning
Sorting Sorting
Peeling Peeling
Size reduction (to slice) Size reduction (to pulp)
Mixing(sugar+water) Mixing (sugar)
Filling Heat treatment
Sealing Filling
Heat sterilization(canning) Sealing
Canned fruit slices UHT Fruit Juice
Foods undergo changes as a result of processing, such changes may be;
So, there is a need of food engineer for all steps of food production from harvesting to consuming.
So, there is a relationship of food engineering to; Chemistry, Microbiology, Nutrition, Mathematics, Food processing, etc.
It is the starting point for need of Food Engineer.
Food Engineer is a person who blends principles with applications to food processing.
For ex;
•If a food engineer is asked to design a food process that involves heating or cooling; she/he must be well aware of the physical principles that govern heat transfer.
•The engineer’s work is often expected to be quantitative, so, use of mathematic is essential
•Kinetic of chemical changes is a prerequisite to the design and analysis of food processes, so, he/she must be know these changes.
Variables and Functions
A variable is a quantity that can assume any value. A function represents the mathematical relationship between variables.
For ex; the temperature in a solid which is being heated in an oven may be expressed as a function of time and position using the mathematical expression; T = F(x,t)
– center cannot heat immediately
Oven – heat flows through distance x
– within a time t interval
solid food
For equation, y = ax + b a and b are constants
x and y are variables
Variables may be dependent or independent.
For y= F(x) y is the dependent variable, x is the independent variable
For x= F(y) x is the dependent variable, y is the independent variable
In physical or chemical systems;
•Independent variables are those fixed in the design of experiment
•Dependent variables are those which are measured.
For example; when determining the loss of ascorbic acid (vitamin C) in stored canned foods with time – ascorbic acid concentration is the dependent variable
– time is the independent variable
In an experiment where a sample of food is taken and both moisture content and water activity are measured, either of the two variables may be designated as dependent or independent variable.
Each data point obtained in an experiment is a set of numbers representing the values of the independent and dependent variables. Experimental data are often presented as a graph.
When plotting experimental data;
•The independent variable is plotted on the horizontal axis, or abscissa
•The dependent variable is plotted on the vertical axis, or ordinate y dependent x, independent Equations An equation is a statement of equality. Equations are useful for presenting experimental data.
Fitting is the application of an equation to experimental data.
Experimental data may be fitted to an equation using any of the following techniques;
1.Linear and polynomial regression: Statistical methods are used to determine the coefficients of a linear or polynomial expression involving the dependent and independent variables
2.Linearization: The equation to which the data is being fitted is linearized
3.Graphing: The data are plotted to form a straight line and from slope and intercept, the coefficients of variables in the equation are determined.
Linear Equations In linear equations there is a linear relationship between variables,x and y.
1.The slope-intercept form: y = ax + b
a is the slope and b is the intercept when x= 0.
y2 slope = a
α slope= tgα= dy/dx= (y2-y1)/(x2-x1)= a
x1 x2 x
2. The point-slope form: (y-b) = a(x-c)
a is the slope
b and c represents coordinates of a point (c,b) through which the line must pass.
slope = a
c x
1 -Materials Handling
Includes various operations:
..Hand and mechanical harvesting on the farm
..Refrigerated trucking of perishable produce
..Box car transportation of live cattle
..Pneumatic conveying of flour from railcar to bakery storage bins.
..Aim: The movement of produce from farm to processing plant and of raw materials through the plant.
It may take many forms:
Example: Oranges are moved by truck trailers to the washing and grading area. The length of time is important since fruits and vegetables are alive and respire causing a rise in temperature of a batch. Thus, spoilage may occur.
Types of equipments for moving materials:
Pneumatic lift systems, Pneumatic conveyors, Screw conveyors, Bucket conveyors, Belt conveyors, Vibratory conveyors
Aim: Foods by the nature of the way they are grown or produced on farms in open environments often require cleaning before use.
Cleaning ranges from:
•Simple removal of dirt from eggshells with an abrasive brush to
•Complex removal of bacteria from a liquid food by passing it through a microporous membrane
Cleaning can be accomplished with:
Brushes, High-velocity air, Steam, Water, Vacuum, Magnetic attraction of metal contaminants,
Mechanical separation (depending on the product and the nature of dirt)
Separating can involve:
•Separating a solid from a solid–peeling of potatoes, shelling of nuts
•Separating a solid from a liquid–filtration
•Separating a liquid from a solid–pressing juice from a fruit
•Separating a liquid from a liquid–centrifuging oil from water
•Removing a gas from a solid or a liquid–vacuum removal of air from canned food in vacuum canning.
Forms of separation in the food industry:
•Hand sorting and grading (vegetables and fruits)
•Mechanical and electronic sorting devices (difference in color)
•Automatic separation (according to size by passing over different size screens, holes or slits.)
Example; The skins of fruits and vegetables may be separated using a lye peeler.
Peaches, apricots are passed through a heated lye solution.
The lye or caustic softens the skin,
So it can be slipped from the fruit by gentle action of mechanical fingers or by jets of water.
Differences in the density of the fruit and skin can then be used to float away the removed skin.
Aim: To subdivide large pieces of food into smaller units or particles.
• Cutting
• Grinding
• Pulping
• Homogenizing
..The dicing of vegetables is done on automatic machines
..The cutting of meat represents a time-consuming, hand-labor operation
..Laser beams also can replace knives in some cutting applications.
..Homogenizing produces disintegration of fat globules in milk or cream from large globules and clusters into minute globules.
..The smaller fat globules then remain evenly distributed throughout the milk or cream with less tendency to separate from the water phase of the milk.
Ways to homogenize:
1.Forcing the milk or cream under high pressure through a hole with very small openings
2. Use of ultrasonic energy to disintegrate fat globules or break up particles.
..Aim: Moving of liquids and solids from one location or processing step to another.
..There are many kinds of pumps and the choice depends on the character of the food to be moved.
•Gear pumps–effective for moving liquids and pastes, chew up chunk-like foods reducing them to purees.
•Screw pumps–best for moving food with large pieces without disintegration (cornkernels, grapes)
An essential feature for all food pumps is ease of disassembly for thorough cleaning.
..Kinds of mixers depend on the materials to be mixed
1. Solids with solids–Dry cake mix
2. Liquids with liquids–milk with coffee
3. Liquids with solids–sugar with water
4. Gases with liquids–coke
..Conical blender: for simple mixing of dry ingredients
..Ribbon blender: Cut the shortening into the flour, sugar and other ingredients (in cake mixes)
..A propeller type agitator-for mixing solids into liquids to dissolve them
..Increase in temperature is a problem during mixing.
7. Fluid Flow: It concerns the principle that determine the flow or transportation of any fluid from one point to another.
A Fluid is a substance that does not permanently resist distortion.
For ex; gases; air, nitrogen, etc.
liquids; water, milk, fruit juice,etc.
A typical liquid transport system consist of 4 basic component; tank, pipe, pump and valve.
8. Heat Transfer: It deals with the principles that govern accumulation and transfer of heat and energy from one place to another.
Heat is a thermal energy, heat= f(T)
Heat cannot be measured directly, temperature can be measured
Heat can be transferred from one material to another when there is a difference in their temperatures.
There are 3 types of heat tranfer;
a)Heat transfer by conduction: When heat is transferred between adjacent molecules, the process is called conduction. This is the mechanism of heat transfer in solids (no motion of molecules).
b) Heat transfer by convection: It is the mechanism of heat transfer by bulk transport and mixing of macroscopic elements of warmer portions with cooler portions of a gas or a liquid. In convection, there is a physical movement of the medium undergoing heating or cooling.
Qconvection= h.A.ΔT T∞
Ts convection
hot iron block
Q = hA(Ts-T∞)
h: convective heat transfer coeffiecient (W/m2K)
A: heat transfer area (m2)
Ts: surface temperature (K)
T∞: temp. of the fluid sufficiently far from the surface (K)
Heat transfer by convection
Natural (free) convection Forced convection
1.Natural convection: Heat transfer occurs when a solid surface is in contact with a gas or liquid which is at a different temperature from the surface. Density differences in the fluid arising from the heating process provide the buoyancy force required to move the fluid. In natural convection, warmer or cooler fluid next to the solid surface causes a circulation because of a density difference resulting from the temperature difference in the fluid (buoyancy force).
cold air warm air
hot egg
1.Forced convection: The fluid is forced to flow over a surface or in a pipe by external means such as pump or a fun.
air flow
hot plate, 110 C
fluid pumped
cold plate, 30 C
c) Heat transfer by radiation: Radiation is the transfer of energy through space by means of electromagnetic waves in much the same way as electromagnetic light waves transfer light. Radiation differs from conduction and convection in that no physical medium is needed for its propogation. The most important example is the transport of heat to the earth from the sun.
Stephen-Boltzman Law: Qradiation= A.σ.ε.T4
σ: stephen-boltzman constant ( 5,6732×10-8 W/m2K4)
ε: emmisivity, measure of the ability of a surface to absorb radiation
For black bodies: 1 and
gray bodies< 1
Example for radiation: sun radiation (drying)
infrared radiation (drying, baking)
microwave radiation (heating, cooking, drying)
9. EVAPORATION is a special case of heat transfer, which deals with the evaporation of a volatile solvent such as water from nonvolatile solute such as salt or any other material in solution.
Vapor, T1
Feed, Tf

Steam, Ts Condensate
Concentrated product, P
Q = U.A.∆T
Q = U.A. (Ts-T1)
Mass balance: F= V+ P
Main functions of evaporation are:
•to preconcentrate foods prior to drying or freezing by reducing weight and volume
•İt increases the solid content of foods and thus preserves it by reducing water activity
•İt changes the flavour and/or colour of food
10. DRYING OR DEHYDRATION is defined as the application of heat under controlled conditions to remove the majority of water normally present in a food by evaporation. The main purpose of drying is to extend the shelf life of foods by reduction in water activity. This inhibits microbial growth and enzyme activity but the product temperature is usually insufficient to cause inactivation.
Hot air Saturated air H2
Absolute humidity H1 H2 > H1

wet apricot
When hot air is blown over a wet food, heat is transferred to the surface and latent heat of vaporization causes water to evaporate. Water vapor diffuses through air.
When a liquid phase vaporizes to a vapor phase under its vapor pressure at constant temperature, the amount of heat needed is called the latent heat of vaporization.
Aim: Separation of components of liquid solution by boiling because of their differences in vapor pressure, which depends upon the distribution of these various components between a vapor and a liquid phase.
Example: distillation of alcohol-water solution in Rakı production.
Rakı is the distilled alcoholic beverage produced by fermentation of grape or raisin.
Grape Ethanol-water mixture + grape pomace
Distillation Ethanol+aniseed Rakı

Fermentation is a chemical change brought about enzymes or living organisms such as bacteria. During fermentation; large molecules are converted into small molecules:
a)Milk Yoghurt (acidulation of milk)
(lactose lactic acid)
b) Starch or sugar Ethanol+ CO2 (decomposition of sugar)
Distillate (alcohol)
(alcohol comes first, when finished water is distilled out)
Water (less volatile)
12. ABSORPTION When two contacting phases are a gas and a liquid, unit operation is called absorption.
Aim: absorption of solute from gas phase into liquid phase. For example; absorption of ammonia from air by liquid water. A common apparatus used for gas absorption is called packed tower.
Gas outlet (air)
Liquid inlet
Liquid outlet
(water+ammonia) Gas inlet (air+ammonia)
13. MEMBRANE SEPARATION The process involves the diffusion of a solute from a liquid or gas through a semipermeable membrane barrier to another fluid.
If the osmotic pressure of solution and that of solvent are different, the outward movement of solute will be accompanied by inward movement of pure solvent (osmosis).
Reverse osmosis: water movement from conc. Sol’n to dilute sol’n
14. LIQUID-LIQUID EXTRACTION In this case a solute in a liquid solution is removed by contacting with another liquid solvent which is relatively immiscible with the solution.
Example: extraction of nicotine (N) in water (W) with kerosene (K);
15. LIQUID-SOLID EXTRACTION (LEACHING): This involves treating a finely divided solid with a liquid (solvent) that dissolves out and removes a solute contained in the solid.
Example: extraction of oil from oil seeds by organic solvent, extraction of sugar from sugar beet.
16. CRYSTALLIZATION: This concerns the removal of a solute such as salt (or sugar) from a solution by precipitating the solute from the solution.
Example: crystallization of sucrose
Purposes of packaging:
•Protect the food from microbial contamination, physical
dirt, insect invasion, light, moisture pick up, flavor pick up,
•moisture loss, flavor loss, physical abuse
•Containment for shipping
•Unitizing into appropriate sizes
•Improve the usefulness of the product
Foods are packaged in: metal cans, glass and plastic bottles, paper and paperboard, a wide variety of plastic and metallic films, and combinations of these, by automatic machines.

Milk is packaged in paper cartoons. Containers are automatically formed from stacked paper flats, volumetrically filled, and sealed.
New processing technologies are constantly being developed :
Supercritical fluid extraction:
Uses gases such as carbon dioxide at high pressures to extract or separate food components. Example; extraction of caffeine from coffee to obtain decaffeinated product.
Ohmic heating:
The temperature of particulates in a conducting medium is raised quickly. Example; soups
High hydrostatic pressure:
Liquid foods such as fruit juices and beverages or particulate foods suspended in liquid are subjected to pressures as high as several thousand atmospheres Inactivate microorganisms and in some cases enzymic activity

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