Food Technology: Basic Processes and Operations

Food Technology - Old Exam Collection

Basic Processes Definition

• Technical measures are primarily for chemical or biochemical or enzymatic conversion of food or food components
• Based on the theoretical foundations and laws of reaction kinetics
• Mainly components of processing stage II

Basic Operations Definition

• Indivisible technical measures are mainly for physical changes of food or food components
• Based on the theoretical principles and laws of heat, mass and momentum exchange and transport
• Mainly components of process stages I and III

Goals of Cooking

• Improved digestibility (protein denaturation, breakdown of the plant cell wall, starch gelatinization) is the primary function
• Better taste and texture (increase of sensory value) is the secondary function
• Removal or destruction of antinutritive substances (increase of health value) is the tertiary function

Malnutrition

• Describes either too high or too low intake of food energy (calories)
• Leads to over- or undernutrition

Undernutrition

• Inadequate food intake or poor health and hygiene conditions prevent the body from properly utilizing the food consumed
• Inadequate supply of energy in the form of proteins, carbohydrates, and fats represents a deficiency of macronutrients
• Malnutrition is an insufficient or incorrectly composed diet
• Must be seen in relation to the resulting health problems

Overnutrition

• Occurs when food intake continuously exceeds requirements

Definition of Nutritional Security

• Ensuring a quantitatively and qualitatively adequate diet for the world's population

Causes of Food Spoilage

• Endogenous factors include raw material-specific enzymes, reactions between or from food components
• Exogenous factors include prions, viruses, microorganisms (bacteria, yeast, mold), protozoa, macroparasites (insects, rodents), environmental influences (light, atmospheric oxygen, humidity, temperature)

Sedimentation

• Deposition of particles from liquids or gases under the influence of gravity or centrifugal force
• The resulting layer of suspended matter is sediment, bottom sediment, or loose sediment
• Deposition of solids suspended in liquids or gases by the action of gravity

Starch Gelatinization and Retrogradation

• The ratio of amylose to amylopectin influences the gelatinization temperature, viscosity, retrogradation, and gel formation

Starch Gelatinization

• Starch granules can swell in warm water but are water-insoluble

• Starch gelatinizes when starch is heated in an aqueous suspension, and the crystalline order is lost

• Starch properties change, including starch granule swelling capacity, loss of birefringence, crystalline melting capacity, viscosity, and solubility

• The onset of gelatinization (temperature), gelatinization range, and behavior depend on starch concentration, starch granule type, structure, and method

• Starch gelatinization during processing (through heat) significantly affects product quality

• Starch gelatinizes differently depending on water content

• Water influences the swelling of starch granules, disorder, glassy state, melting behavior of amylose and amylopectin, depending on the degree of hydration of the starch granules

• At high water content, water acts as a solvent, and the starch granules are fully hydrated

• Both amorphous and crystalline regions swell and gelatinize

• Inter- and intramolecular hydrogen bonds and hydrophobic bonds are broken, which leads to the formation of intermolecular bonds between starch and water

• "Al dente" refers to a partially gelatinized starch

• During starch gelatinization, as an aqueous starch suspension is heated above the gelatinization temperature, energy input successively splits the hydrogen bonds between the starch molecules

• The ordered structures in the starch granule dissolve with water incorporation

Starch Retrogradation

• Concerns the process of starch after gelatinization
• Amylose retrogrades first, then amylopectin
• Describes the process of reassociation of the starch molecules
• Two chains associate, and under favorable conditions, a crystalline structure reforms
• Structurally modified to influence retrogradation behavior
• Retrograded starch shows type B pattern
• Native starch granules -> Gelatinization -> Retrogradation Stage 1 -> Retrogradation Stage 2

Definition of Heat Conduction/Heat Transfer

• Heat conduction is the transport of thermal energy, where heat always flows only in the direction of lower temperature, without loss of heat energy
• Energy moves from a place of higher temperature through macroscopically resting material to a place of lower temperature
• Conduction happens in solid bodies and immobile liquids, within a substance due to molecular collisions
• Heat transfer (convection) involves heating, warming, and cooling, with or without phase change (heating, cooling, evaporation, condensation, melting, solidification, sublimation, desublimation)

How and By What is Food Preserved Longer by Deep Freezing?

• Microorganisms can no longer grow or growth is slowed due to the cold temperatures (-15°C)
• Raw material-specific enzymes delay enzymatic reactions

When is Food Considered Unsafe?

• If it is harmful to health or unsuitable for human consumption

Operations for Reducing the Size of Food

• Van der Waals forces, apolar, hydrophobic forces, heteropolar, electrostatic forces, and hydrogen bonds
• Pressure like breaking, grinding, cutting
• Impact (Prall)
• Shearing

What Happens During Sterilization?

• The temperature range for sterilization begins at 100°C

• At this temperature, the glass transition temperature of the spores of Clostridium botulinum is reached, resulting in an inactivation effect

• The temperature is limited only by technical possibilities, with high temperatures reached and cooled down again very quickly

• The upper limit is 150°C and heating times are as short as 1 second

• The temperature range for pasteurization begins at the protein coagulation temperature

• The temperature is limited only by technical possibilities, with high temperatures reached and cooled down again very quickly

• The usual temperature range is between 60-100°C

• The "F-value" (F from Fahrenheit) is a measure of the achieved or desired heat treatment during sterilization

• The F-value indicates the sum of all killing effects of the spores obtained during a heating process

• The "p-value" (P from pasteurization) is a measure of the achieved or desired heat treatment during pasteurization

• The P-value indicates the sum of all killing effects for vegetative bacteria obtained during a heating process

• In contrast to sterilization, there is no uniform reference temperature and several reference germs in pasteurization

• In pasteurization, the most dangerous type of microorganism for a product group is used as a reference germ, with each type of microorganism having a different z-value

Pasta - Form of Starch in It

• Resistant starch is partially gelatinized starch, is not completely digested

Malnutrition Which Vitamins?

• Micronutrient deficiency, iodine, Vitamin A and iron deficiency

Cooking - What are the Primary Goals?

• Protein denaturation (collagen breakdown), breakdown of plant cell walls (pectin breakdown), starch gelatinization, and Maillard reaction

Water Activity (Aw)

• Pure water has an Aw value of 1

• Any addition of water-binding substances such as salt, sugar, and proteins or water removal by drying or deep-freezing lowers the value

• Water activity (Aw) indicates the amount of water available for biological activity of microorganisms

• Every type of microorganism has a minimum value for water activity below which no growth is possible

What Trends in Nutrition are There?

• Social development, ecological development, economic development, technological development, and product trends

Difference Between Amylose and Amylopectin

Amylose

• Linear macromolecule of alpha-D-glucopyranose linked by (1→4) bonds
• Degree of polymerization (DP): 100-10,000
• Each molecule has one reducing and non-reducing end
• It can contain 2-8 branches per molecule that are 4-100 DP in length
• Sometimes amylose contains phosphate groups, probably at the C6 atom
• Hydrophilic properties depend on the frequency of OH-groups
• Amylose chains often arrange themselves parallel to each other due to their linear character
• H-bonds reduce water affinity, and the solution becomes more opaque
• Amylose chains form helices that can enclose substances such as lipids, iodine, and monoglycerides
• The physico-chemical properties of starch are determined by the content, the molecular weight, and the molecular weight distribution of amylose
• It affects the glycemic index

Amylopectin

• Alpha-D-glucopyranose is linked by (1→4) bonds with additional alpha bonds
• It has a higher degree of branching than amylose
• MW from 10^6 to 10^9 makes it one of the largest biological molecules
• Its high molecular weight and branching limits solubility and H-bonding
• There are three types depending on the length and type of branching: A-chains include short chains with no branching points; B-chains which are branched by A-chains or other B-chains; C-chains which contain B-chains, and are the only chain with the reducing chain end
• It contains covalently bound phosphate monoesters
• Amylopectin's linear chains are arranged in double helices
• Amylopectin is organized in clusters

Ways to Vacuum Freeze Products

• Vacuum-steam-vacuum-surface pasteurization and hot water treatment; vacuum packaging

Methods for Preserving Starch

• Spray drying, roll drying, and hot extrusion

Protein Denaturation

• Proteins have water-free cavities (void volumes) inside them.

• Their three-dimensional structure is fixed via various bonds, like ionic bonds, salt bridges, hydrogen bonds

• High pressure treatment causes protein unfolding, which is denaturation (=achieving a disordered, amorphous protein structure, where no more "void volumes" are present)

• This in turn can inactivate microorganisms and enzymes, and lead to structural, textural, and viscosity changes in food

• The forces that stabilize the secondary, tertiary, and quaternary structure can be broken though various chemical and physical treatments (=protein denaturation), without affecting peptide bonds

• Protein unfolding is the dissolution of the ordered protein structure into a randomly ordered peptide chain

• Globular proteins aggregate due to denaturation, because the previously hidden hydrophobic residues are exposed to the surrounding solution

• Protein denaturation can be achieved through acids, salts, bases, detergents, extreme temperatures and UV radiation

Starch Modification

• The general goal is to change the starch properties, increase cold water solubility, change the viscosity properties and stability, change the thickening properties, change the retrogradation behavior and improve the shelf life of the end product
• Methods include physical, chemical, and biotechnological modification

Agglomerated Products (Processes)

• Enlargment (Kornvergösserung) involves building up granulation, sintering, compression molding, and flocculation
• Mechanical procedures that describe particle size enlargement into a coarser size range

Nutritional Deficiencies

Iodine Deficiency

• Caused by food production on iodine-poor soils and with low iodine levels in groundwater
• Symptoms include enlargement of the thyroid gland, neurological disorders, speech disorders, impaired coordination, numbness, and brain damage
• Can be combatted with iodized oil, potassium iodide tablets, and food fortification

Vitamin A deficiency

• Due to too little intake, often associated with protein and energy deficiency
• Symptoms include night blindness, infections, respiratory diseases, diarrhea
• Prevention with fortification of foods, distribution of Vitamin A capsules, and education about nutritional issues

Iron Deficiency

• Due to too little intake or availability, often with pregnancy or infectious diseases
• Symptoms include anemia, pale skin, fatigue, exhaustion, loss of appetite, headaches, irritability, digestive disorders
• Treatment includes iron supplements, nutritional education, and increased consumption of iron-containing foods

General Options for Preservation

• Maintaining the biological functions, inhibiting of enzymes, microorganisms, and pests
• Lowering water activity by evaporation, freezing, drying, substance addition, cooling
• Inactivation or killing of enzymes, microorganisms, and pests: adding substances that kill, adding thermal energy, electromagnetic energy, mechanical energy
• Mechanical removal and remote maintenance of microorganisms: sterilization filtration, centrifugal sterilization, cleanroom technology, aseptic filling
• Eliminating environmental influences with antioxidant additives, shielding with gas and packaging

Factors Determining the Sedimentation Rate

• Particle size, density and viscosity

Methods for Meat Protein Denaturation

• Thermal, mechanical, and enzymatic

Why Does Deep Freezing Preserve Food Longer?

• Aw value decreases, microorganisms can no longer grow, and enzymatic reactions are delayed

Which Processes are Used to Reduce the Size of Food?

• Pressure, cutting, impact (Prall) and shear

What is Meant by Sous Vide Cooking?

• Vacuum cooking. In the packaging, there is no oxygen, low temperatures, and usually a high pH value
• Food is cooked after O2 removal at a constant temperature
• This can exacerbate the microbial risk in chilled foods

Advantages

• Prevents extraction losses and oxidation-sensitive vitamins are more likely to be preserved because oxygen is removed during vacuuming
• Genusswert is preserved because there is no cooking taste and aroma is generated
• Extends the storage time

Disadvantages

• Vegetative microorganisms are usually killed during cooking in the packaging
• Spores can be inactivated and can germinate, posing health risks
• Often results in psychotropic, anaerobic spore formers spreading in the niche

What is Sterilization of Food and What is the Goal?

• Microorganisms, enzymes, and pests are killed or inactivated, making the food last longer. Other methods include pasteurization or blanching, adding alcohol, pickling, smoking, high and low-pressure fumigation, electromagnetic radiation, microwaves, UV, ultrasound waves, and preservatives

Why Does Cooking Fish Require a Lower Core Temperature than Meat?

• Fish have a lower collagen content than beef, so they require a lower core temperature
• Cooking is energy gaining. Classical cooking methods are thermal energy such as electromagnetic energy; or mechanical energy such as hot extrusion or raw material-specific enzymes; or microorganisms-fermentation; and chemicals-pickling
• A beta-elimination, a thermal splitting of the pectin main chain, is a mechanism that occurs during cooking. It breaks down the cell walls and leads to plant tissue becoming soft and cell walls permeable promoting bioavailability of the cell contents
• This reaction can also be accelerated by high methyl ester content, high temperatures, pH value and monovalent salts
• The goal of cooking is to change the chemical, mechanical-structural, or chemical-physical properties of the food ingredients, improving sensory and nutritional properties which improves digestibility, better taste, better texture and better health

What Trends Can Be Recognized Today?

• Eating outside, meatless diets, various food trends based on health and ethical reasons
• Megatrend (convenience), Gegentrend (slow food, fresh, deindustrialization), nutritional supplement Ergänzungstrend, Cross over Trend (bio, ethical)

Which Options are There to Reduce the Required Knife Cutting Force for Cutting Food?

• Cutting force is only reduced if the cutting speed of the tool is less than the oscillation speed of the cutting edge
• The knife speed V depends on the knife normal speed VN and the knife tangential speed VT
• One possibility to reduce the cutting force is to use ultrasound-assisted cutting and the waterjet cutting system

Which Strategies Have People Developed to Prolong Food Over Time?

• Maintaining biological functions, inhibiting of enzymes, microorganisms, and pests
• Decrease water activity by evaporation, freezing and cooling
• Inactivation and killing of microorganisms.
• Add substances that kill using thermal energy, electromagnetic energy, or mechanical energy.
• Also through controlled atmospheres in packaging and sterilization.

Why are Emulsions Unstable and Tend to Separate Again?

• Emulsions are dispersed systems of two or more immiscible liquids
• One of the liquid phases forms the dispersion medium, known as the outer or continuous phase
• In the continuous phase, the other liquid is distributed in droplets (inner or dispersed phase)
• The size of the dispersed particles varies between 0.01-100 micrometers
• Besides the dispersed system of the emulsion, there are also other dispersed systems [e.g. suspension (solid-liquid), foam (gas-liquid)]in foodstuff
• When oil and water unite to form an emulsion, both the oil in the water and the water in the oil can be distributed
• Oil-in-water emulsions include milk, sauces, roasts, mayonnaise, mustard, orange juice, and sausage
• Water-in-oil emulsions include margarine, butter and other spreadable fat emulsions
• The dispersed phase strives to unite into larger areas through coalescence, reducing the interfacial energy between the two phases
• Emulsion decay begins when the droplets come into direct contact with each other, the interfacial film tears and larger droplets form

Stabilization of Emulsions

• The smaller the droplets and the more viscous the outer phase, the slower the creaming occurs according to Stokes' law
• Aggregation and agglomeration of the droplets is influenced by the surface properties of the droplets
• Surface-active substances or emulsifiers accumulate in the phase interfaces between the droplets and the surrounding outer phase
• This lowers the surface tension and reduces the emulsification work to be applied, stabilizing the finished emulsions
• Proteins have surface-active properties like the classic emulsifiers, and surfactants can counteract demixing and facilitate the formation of droplets

What Does the z-Value Mean?

• The amount (°C) (temperature difference) is the amount by which the killing temperature must be increased in order to reduce the required killing time to achieve a defined degree of sterilization by 90%
• The z-value is defined as the temperature difference [K] required to increase or decrease the D-value by a factor of 10, meaning that the reaction rate increases tenfold or is reduced to one tenth
• It is a measure of the temperature sensitivity of the microorganism
• The microorganism is more temperature-insensitive if “z” is high
• Changes in temperature have less influence on its inactivation.
• Small temperature changes show a large influence on the inactivation rate of the germ for low z-values
• Microorganisms usually have low z-values of around 10 K

Chemical reactions such as the degradation of vitamins have significantly higher z-values ​​of 20-30 K

• During thermal preservation when optimally selecting temperature-time regimes, all microorganisms can be killed, while the main part of the chemical components doesn’t change

LM Groups that Can Be Distorted in the Raw State

• Wild herbs, vegetables and fruits

LM Groups that Cannot Be Distorted in the Raw State

• Eggs, rhubarb, raw dough, chicken breast, and grains

Into Which Three Process Stages Can Most LM Manufacturing Processes be Classified

• Based on the manufacture of bread as an example, these include structural decomposition, fractionation, restructurings, and structural breakdown

Agglomeration Process

• Reversal of grinding, joining particles with the same composition and same phase state by creating binding sides or binding forces

Advantages

• better pourability, less dusty, fewer adhesions and unmixing, better transport and store, and better resolution properties