Unit 4: Food Chemistry

Describe the physical and chemical properties of water such as polarity, solubility, boiling point, freezing point, water activity, specific heat (water)

PSBFWS

Polarity: water has an ability to form hydrogen bonds with other molecules due to the polarity of the electronegative oxygen in the O-H bond

Solubility: water has an ability to dissolve polar molecules and an inability to dissolve large non-polar molecules.

• dissolves molecules by ionization and hydrogen bonding

Boiling point: is the temperature at which VP = AP.

• Above sea level (at higher altitudes- a mountain top) the atmospheric pressure is lower, Thus at higher altitudes, the VP has to overcome less AP and thus water boils at lower than 100C at higher altitude

Freezing point: frozen state, each water molecule forms stable hydrogen bonds with four other water molecules, producing open cage like hexagonal structure, this structure is less dense than water and floats to the top

Water activity: is the partial vapor pressure of water in a substance divided by the partial vapor pressure of water at the same temperature.

• Essentially it is an expression of relative humidity surrounding the food system

Specific heat of water: Highest specific heat means it can absorb and lose the most heat when temperature increases or decreases by 1C

• high specific heat of water contributes to faster cookin

Explain how these properties impact food quality (water)

Polarity: relates to solubility

Solubility: cannot dissolve large non polar molecules (like in fats and oils). Ionization occurs to form a true solution

Boiling point: Thus the water will boil at temp higher than 100C. This is the principle of pressure cooking. Another way to increase the boiling point of water is by dissolving solutes in water. For example when sugar is dissolved in water, sugar forms hydrogen bonding with water

• Thus extra heat would be needed to break the hydrogen bonds between sugar and water, to achieve VP = AP, thus the boiling point would increase.

Freezing point: How quickly the water freezes also has an impact on food quality. When water starts to freeze it forms nuclei or ice (starting ice crystal. The smaller the ice crystals the less is the damage to the tissue.

Water activity (aw): Low water activity inhibits microbial growth, provides textural characteristics such as crispness and crunchiness in products like snack foods and ready to eat breakfast cereals.

Specific heat: high specific heat of water contributes to faster cooking. Food cooks much faster in boiling water (100C) than in oven at 100C. In oven, it is the dry heat that is cooking the food. Dry heat has much lower specific heat than water

Polarity

Water is able to form hydrogen bonds with other molecules due to the polarity of the OH bond.

Solubility

Water cannot dissolve large non-polar molecules such as the molecules present in fats and oils (fats and oil chemistry is discussed later).

Water dissolves molecules by two phenomenon, ionization and hydrogen bonding

Ionization: Common salt, NaCl ionizes in water with Na taking partial positive charge and Cl taking partial negative charge, and thus dissolves in water and forms a true solution.

Hydrogen bonding:

Sugar: much larger organic molecule (macromolecule) which forms hydrogen bonds with water and thus dissolves in water to form a true solution

Starch: made up of thousands of sugar molecules however doesn’t dissolve in water at room temperature (covalent bonds between the sugar molecules in starch are much stronger)

• starch settles at the bottom forming a suspension

Sugar

is a much larger organic molecule (macromolecule) which forms hydrogen bonds with water and thus dissolves in water to form a true solution.

Starch

made up of thousands of sugar molecules, doesn’t dissolve in water at room temperature.

• The covalent bonds between the sugar molecules in starch are much stronger than the hydrogen bonds these molecules can form with water, and thus starch settles at the bottom (forming a suspension).

hydrophilic

substances that readily dissolve in water

hydrophobic

Substances that do not dissolve in water

Suspension

A substance settles at the bottom of water.

• observed when starch in water (does not dissolve due to covalent bonds between sugar and starch being larger than the H bonds starch could form w water )

Oil in water emulsion

small droplets of fats and oils can remain dispersed in water

• Milk is an example of oil-in-water emulsion

• In milk, water is the continuous phase in which fat is disperse

Water in oil emulsion

water can remain dispersed in fat/oil to form a water-in-oil emulsion.

• butter is an example of water-in-oil emulsion

• In butter, fat is the continuous phase in which water droplets are dispersed

Emulsifier

a variety of molecules that stabilize an emulsion. An emulsifier is a substance that keeps two immiscible phases mixed together.

• Some proteins and fats can act as emulsifiers

Boiling point

boiling point is the temperature at which VP = AP. Normal boiling point is 100C at sea level

• vapours move upward and exert an upward pressure. The amount of this upward pressure is called vapor pressure (VP). Atmospheric pressure (AP) puts downward pressure on the water surface.

• Above sea level (higher altitudes- mountain top), the atmospheric pressure is lower. Thus at higher altitudes, the VP has to overcome less AP and thus water boils at lower than 100C at higher altitude

• On the other hand, if the atmospheric pressure can be raised above 1013.25 mbar, the water will need to produce higher VP to overcome this AP, this is applied in pressure cooking

At higher altitudes what happens to the boiling point?

at higher altitudes, the VP has to overcome less AP and thus water boils at lower than 100C at higher altitudes

• when we cook in water on the mountains, it takes longer to cook because the water is less hot than 100

What happens if the atmospheric pressure can be raised above 1013.25 mbar?

the water will need to produce higher VP to overcome this AP. Thus the water will boil at temp higher than 100C.

(Used in pressure cooking)

Increasing boiling point

Typical home pressure cookers and pressure canners raise the boiling point of pure water to 116C. Thus, the food cooks much faster in a pressure cooker; the higher the temperature the faster is the cooking.

Another way to increase the boiling point of water is by dissolving solutes in water

When sugar is dissolved in water, sugar forms hydrogen bonding with water

Addition of table salt (and other salts) also increases the boiling point of water because NaCl forms ionic bonds with water.

Boiling point and jams

If you are cooking jams which typically contain 65% sugar, the boiling jam is hotter than boiling water. Thus boiling jam (105C) will cause more severe burn than normal boiling water (100C).

Due to hydrogen bonding the water is tightly bound to sugar and cant escape that easily.

sugar solution will have lower VP than pure water. Heating breaks the hydrogen bonds. Thus extra heat would be needed to break the hydrogen bonds between sugar and water, to achieve VP = AP, thus the boiling point would increase.

Boiling point and salt

Addition of table salt (and other salts) also increases the boiling point of water because NaCl forms ionic bonds with water.

Freezing point

Pure water at sea level freezes at 0C.

• As the water is cooled to or below 0C, the movement of water molecules slows down such that the hydrogen bonds between water molecules stabilize.

• In the frozen state, each water molecule forms stable hydrogen bonds with four other water molecules, producing open cage like hexagonal structure.

• Since the structure is more open than it was in liquid state, the density of ice is lower than water in liquid state

Lowering the freezing point

• Freezing point is lowered because of dissolved solids. For example, adding sugar or salt to water would lower waters freezing pointy to below 0C.

• freezing is detrimental to frozen food quality.

• If the ice cream is frozen at much lower temperatures (<40), then most of the fluid with dissolved solids freezes and thus ice cream ends up being smooth and creamy (smaller ice crystals uniformly spread in the ice cream).

Freezing and food quality

• How quickly the water freezes also has an impact on food quality. When water starts to freeze it forms nuclei or ice (starting ice crystal)

• The larger the ice crystals (nuclei) the more tissue damage they cause. If the strawberries were instead frozen at -80C, most water in the berries would freeze immediately and will not be able to migrate to form larger nuclei. Thus, at such low temperature more but much smaller ice crystals would be formed. The smaller the ice crystals the less is the damage to the tissue.

Water activity

Water activity (aw) is the partial vapor pressure of water in a substance divided by the partial vapor pressure of water at the same temperature. Essentially it is an expression of relative humidity surrounding the food system

• Water activity does not correlate with the amount of water, rather with the amount of solute in the mixture.

• Water will migrate from areas of high a w to areas of low aw

A consequence of this is that the surface could ultimately gain enough moisture for mold growth on the surface. Another example is that crackers which have an aw of 0.3 are exposed to air with 80% relative humidity, the crackers will lose crisp-ness and snap when eaten. If salami (a w 0.87) is exposed to dry air (a

w 0.5), the salami will lose moisture

Specific heat of water

water has higher specific heat than all known liquids because of its hydrogen bonding. Highest specific heat means it can absorb and lose the most heat when temperature increases or decreases by 1C.

• In foods, the high specific heat of water contributes to faster cooking. Food cooks much faster in boiling water (100C) than in oven at 100C. In oven, it is the dry heat that is cooking the food. Dry heat has much lower specific heat than water

• In foods, the high specific heat of water contributes to faster cooking. Food cooks much faster in boiling water (100C) than in oven at 100C. In oven, it is the dry heat that is cooking the food. Dry heat has much lower specific heat than water. The higher the moisture in the air the hotter it feels. Steam (air+water) from food causes more sever burns than dry heat coming out of the oven.

Identify the role of water in food spoilage (water)

The crispiness of vegetables and fruits is dependent on the osmotic pressure of their cells. As the fruits and vegetables stale, they lose moisture from their extra-cellular spaces due to evaporation (diffusion), but this leads to high concentration of solutes in the extra cellular spaces, leading to water loss from inside the cells due to osmosis.

• The water loss from both extra and intracellular spaces lead to loss or crispiness of the vegetables and fruits.

• To minimize this water loss, many fruits are coated with paraffin wax which seals the pores on the fruit skin preventing evaporation. Osmosis has an application in food dehydration discussed later in the course.

Water containing foods

• Raw ripe tomatoes may have as must as 94% water

• milk approximately 88% water

• cooked chicken about 65% water

• cooked salami 45% water

• butter approximately 15%

• Typically vegetables and fruits contain more water than meats, and grain

Carbohydrate

hydrates of carbon and are thus made up of carbon, hydrogen and oxygen. Formed in green plants through photosynthesis whereby the sun’s energy converts carbon dioxide from the atmosphere and water from the soil into glucose.

Classify carbohydrates based on the number of saccharide molecules

The carbohydrates are classified as..

Sugars: Monosaccharides, Disaccharides

Oligosaccharides: Oligosaccharides contain 3-10 sugar molecules connected together. Humans lack enzymes to digest oligosaccharides, they pass unchanged to the colon, where the normal intestinal bacteria ferment them to gases (methane, carbon dioxide and hydrogen) Present in beans

• raffinose, stachyose, and verbascose (made up of three, four, and five sugar molecules)

Polysaccharides: are complex carbohydrates that contain more than 10 but typically hundreds of sugar molecules connected

Classes: starches, fibres and glycogen.

Classes of polysaccharides

Starch: is a storage form of carbohydrates in plant cells. starch polymers are packed in granules called starch granules.

Human digestive system produces the enzymes required for the digestion of starch but the starch must be gelatinized/cooked (gelatinization is discussed below) for its effective digestion.

When completely digested starch is broken down into monomers of glucose.

• Plant foods such as potatoes, yam, cassava, cereal grains, beans and lentils are good sources of starch

• Starch is sometimes extracted form foods because it can increase the viscosity of liquid foods

• Glycogen: more branched than starch. human body produces enzymes to break down glycogen as well. This is the storage form of carbohydrate in human beings and other animals, mainly stored in their liver and muscles.

Fibres: resistant to enzymatic digestion in human digestive system.

• cellulose, noncellulosic polysaccharides such as hemicellulose, pectic substances, gums, mucilages and a non-carbohydrate component lignin.

Water soluble fibres (aka viscous fibres): These fibres when consumed increase the viscosity of the chyme in our digestive system. This leads to slow movement of the chyme through our digestive system making you feel fuller for longer

Water-insoluble (non- viscous fibers): Celluloses, some hemicelluloses and lignin are insoluble fibres. These fibres are present in the outer layers of all plant foods such as fruit peels, vegetables, whole grains, beans etc.

Glycogen: made up of hundreds and thousands of glucose molecules but is more branched than starch. human body produces enzymes to break down glycogen as well. This is the storage form of carbohydrate in human beings and other animals, mainly stored in their liver and muscl

Applications of starch

starch gelatinization: starch granules swell up by absorbing water which leads to the thickening of the solution. Upon cooling this thick mixture, it starts to form a three-dimensional gel (starch gelation).

• starch used as a food thickener, binder to meat plant proteins and for a soft gel texture in baked goods

Dextrinization: When starch is heated in the absence of water, it turns brown and starts to breakdown. The dextrinized starch tastes sweet, has flavor, color and aroma.

• Dextrinization also reduces the starch’s ability to form a gel

Starch as a sweetener: if the starch is hydrolyzed (hydrolysis is the breakdown of chemical bond by addition of a water molecule), the glucose molecules start to become free which can bind to our taste receptors, and thus taste sweet

• Corn starch and water mixture is treated with alpha and beta-amylases which are the enzymes that help hydrolyze starch. As these enzymes breakdown the starch, the mixture starts becoming sweeter

Fiber applications

improving texture: Soluble fibres increase the viscosity and bind water. Thus soluble fibres are often added to baked goods to retain water in the baked goods

manage moisture in the replacement of fat: They can give creamy smooth texture to low fat frozen desserts.

add colour: Fibres, especially insoluble fibres are bound to many color compounds especially In vegetables and fruits. color compounds and other phytochemicals may act as natural antioxidants.

Pectic substances (soluble fiber) form a transparent gel under special circumstances and have a wide application in fruit jam and jelly industry.

Sugars

Monosaccharides: are simple sugars and are sweet in taste that contain one sugar molecule

Ex: are glucose, fructose, and galactose. (GFG)

• monosaccharides are the simplest forms of carbohydrates they do not require Digestion.

Disaccharides: are also called simple sugars but contain two sugar molecules connected together. They require digestion, the two sugar molecules must be separated into monosaccharides before they are absorbed.

• digestion is done via enzymes

Some examples of disaccharides are sucrose, maltose and lactose (SML)

sucrose → enzyme sucrase

Lactose → enzyme lactase

Maltose→ enzyme maltase

• most healthy individuals have adequate production of these enzymes and therefore they can digest these disaccharides. In the absence of the appropriate enzyme the disaccharides cannot be digested.

Sources of sugars

Sources: Sugars are naturally present in plant tissues and milk.

• In free form sugars are mainly present in fruits and honey. Sugar cane and sugar beets contain sucrose and are used for making the table sugar.

• milk is the only non-plant source of sugar.

Sweetness

Sweetener: The table sugar is considered a reference for sweetness; so if it has sweetness of 1, then lactose has a much lower sweetness level of 0.16. Maltose- 0.33-0.45, Glucose- 0.74-0.8, and Fructose is much sweeter at sweetness level between 1.17-1.75.

Sweetness (least-most): LMGTF (let me gtf out)

Lactose, maltose, Glucose, table sugar (reference), fructose

• How sweet a sugar tastes to us is also dependent upon our genetics.

• sugars taste sweeter at high temperatures

Hygroscopicity

hygroscopic: attract water and adsorb or absorb water (in other words they bind water). Due to this property, the sugars can be used as humectants.

Humectant: is a substance that holds moisture in food, absorbs water from the surrounding, used to retain moisture in baked goods.

Sugar applications

Preservative: Sugar in high concentration makes the water unavailable to the microbes and thus prevents their multiplication. This preservative effect of sugars is seen in jams and jellies.

• Contributes colors and flavors through browning phenomena:

Caramelization: When dry heated at high temperatures, sugars melt and turn brown

Maillard reaction: production of a complex mixture of brown compounds called melanoidins, which also impart distinct aroma. via a non-enzymatic reaction between a reducing sugar (all monosaccharides and most disaccharides except sucrose are reducing sugars), and an amino acid. When heated, these sugars and amino acids undergo a series of reactions which lead to the

Examples include the brown crust of breads, cakes and cookies, or the grill marks on the steak

Reducing the freezing point: The higher the concentration of sugar, the lower the freezing point. A low freezing point reduces the risk of large crystals of ice forming which are undesirable in frozen desserts

Crystallization: revolves around how saturated a sugar solution is, a supersaturated sugar solution (water is holding more sugar than it is capable of) is cooled, and the sugar separates from water and recrystallizes

let this solution cool slowly without disturbing it. This would result in large sugar crystals desirable in such candies

Defend the recommendation of Canada Food Guide to eat more whole fruits and vegetables than drinking their juices.

Whole fruits and vegetables contain dietary fibre, which is largely removed during the juicing process

Whole fruits and vegetables contain important vitamins, minerals, and phytochemicals. While juice still contains some nutrients, processing and exposure to oxygen can reduce certain vitamins (such as vitamin C) and remove beneficial plant compounds found in the skins and pulp

Differentiate between lactose intolerance and milk allergy

Lactose intolerance is lacking the enzyme (lactase) to breakdown lactose whereas a milk allergy involves the immune system and IgE causing a histamine release

Lipids

organic macromolecules that are generally insoluble in water but are soluble in non- polar solvents such as alcohol and ether. Are broadly classified as fats and oils and also as triglycerides, phospholipids, and sterols

• The more solid a lipid at room temperature the more saturated fatty acids it contains

Differentiate between fats and oils, and identify their sources in human diet.

Fats: are solid at room-temperature (22 degree Celsius

Sources of fats: most animal foods such as beef, chicken, turkey, pork, and mutton, palm and coconut oils (wrongly called oils).

Oils: are liquid at room-temperature.

Sources of oils: plant lipids such as canola, rapeseed, grapeseed, olives, sunflower seed, fish oil.

Identify the general structures of triglycerides, phospholipids, sterols, saturated, unsaturated (mono and poly) fatty acids, trans fats.

Triglycerides (triacylglycerol): is the major form of dietary lipid in fats and oils, whether derived from plants or animal, composed of three fatty acids esterified to a glycerol molecule.

Phospholipids: phospholipids act as emulsifiers. An emulsifier is a substance that can keep two immiscible states mixed.

Sterols: class of lipids containing a common steroid core of a fused four-ring structure with a hydrocarbon side chain and an alcohol group. The most common form of a steroid in animal cells is cholesterol

Saturated: only single bonds, solid at room temp usually

Unsaturated: Unsaturated fatty acids provide some protection against heart diseases if not consumed in excess, contains a double bond

(Mono= one double bond poly= multiple double bonds)

Explain the chemical changes taking place during hydrogenation.

In food science, hydrogenation converts unsaturated vegetable oils into more solid fats, This increases: Melting point, stability and shelf life.

• can also produce trans fats, which are associated with negative health effects.

Defend the recommendation of Canada Food Guide to replace some of the animal source protein with plant source protein, and to include fish in our diet.

Unsaturated fatty acids provide some protection against heart diseases if not consumed in excess. This is one of the reasons the Canada Food guide recommends replacing some of the animal-based protein foods with plant-based proteins in our diet and include fish in our diet. Since 2018, Health Canada has banned artificially produced trans-fat in foods sold in Canada.

Discuss the health impact of different types of lipids in our food

High intake of saturated and trans fat intake are linked with increased risk of heart diseases. The more animal source foods, and process foods we consume the higher is our intake of saturated and/trans fats. Unsaturated fatty acids provide some protection against heart diseases if not consumed in exces

Properties and Applications of lipids in foods

Frying: food cooks much faster when fried in hot oil or fat since oils/fats can be heated to temperatures higher than 160 degree Celsius.

• smoke point: the temperature at which an oil or a fat starts producing a steady stream of smoke and cant be heated beyond that temperature

Plasticity: the ability of a solid material to undergo permanent deformation, a non-reversible change of shape in response to applied forces.

• Solid fats exhibit this property thus such fats spread easily and are used in a variety of spreads and in baking

Flavouring property: Fats mask undesirable flavours such as bitterness. Have different flavour profiles (oils used in salad dressings, baked goods, cheese etc), can retain flavour in dried herbs.

Tenderness: Plastic fat provides tenderness to the food product. This why the baked goods like cakes, muffins, croissants, biscuits are tender

• meat has 2 different types of fat (location based)

• Cover fat: the fat layer that surrounds meat, no impact on tenderness

• Marbled fat: the fat that is intramuscular that means it is marbled across the flesh. The higher the marbled fat, the more tender the meat is upon cookin

Identify the basic structure of an amino acid

Amino acids are linked by peptide (amide) bonds formed between amino and carboxylic acid groups of neighbouring amino acids in the polypeptide sequence

Explain the primary secondary, tertiary and quaternary structure of proteins

Primary: linear structure and indicates the sequence of amino acids in the chain(s).

Secondary structure: The backbones of amino acids in a polypeptide chain form hydrogen bonding's with one another, leading to the folding of the chain. This leads to a two-dimensional structure of the protein.

folding patterns: alpha helix and beta sheets.

Tertiary: The side chains of the amino acids in a polypeptide chain interact with one another and lead to the folding of the beta sheets or alpha helices (secondary two-dimensional structure).

• The specific sequence of amino acids determines the type of interactions and thus the three-dimensional shape. This shape is critical to the protein functionality

Quaternary: Many proteins are formed from multiple (2 or more) polypeptide chains. These are called subunits of the protein. The interactions between the subunits results in a unique shape of the protein. This is called quaternary structure of proteins that are made from multiple polypeptide chains.

Define denaturation and identify the role of a variety of denaturation agents in food quality

Denaturing agents: change the structure and therefore function of the protein

pH change (Acid):

• Hydrochloric acid is produced in our stomach primarily to denature the food proteins

• proteins in the mucous membrane lining the stomach wall which damages the mucous membrane.

Heat:

• Heating an egg denatures its proteins, leading to solidification of the egg. This is desirable when you wish to eat an omelet, or in baking a cake or macaroons or meringue.

• we cook meat to a certain minimum internal temperature, not just to denature meat proteins but also to kill bacterial cells by denaturing their proteins by heat. This makes the meat safe for consumption.

Alcohol:

• A use of alcohol is as a disinfectant which denature the proteins of the microbes (bacteria, viruses etc), thus killing them.

• When we consume alcohol (ethanol), it penetrates our cells and denatures cell protein (Therefore considered a toxin)

UV radiations: Exposure to strong UV radiations causes denaturation of some of the proteins in our skin cells (Sun burn)

Heavy metals (ex. Mercury): Mercury can denature our muscle cell proteins, leading to muscle weakening and other toxic effects.

Water holding capacity and solubility

• Protein solubility and water-holding capacity affect how tender and juicy meat is.

• After slaughter, lactic acid forms, causing the pH of meat to drop to about 5.5.

• At pH ≈ 5.5, meat proteins (especially collagen) are more soluble and the meat holds more water, making it tender and juicy.

• If the pH is too high or too low, the meat holds less water and becomes tougher.

Marinating Tough Meat:

• Tough meat (often with pH above 5.5) is sometimes marinated before cooking.

• Marinades often contain acids like yogurt, vinegar, or lemon juice.

• The acid lowers the pH, denatures proteins, and increases water-holding capacity, making the meat more tender and juicy.

• Protein solubility and water-holding capacity affect how tender and juicy meat is.

• After slaughter, lactic acid forms, causing the pH of meat to drop to about 5.5.

• At pH ≈ 5.5, meat proteins (especially collagen) are more soluble and the meat holds more water, making it tender and juicy.

• If the pH is too high or too low, the meat holds less water and becomes tougher.

Marinating Tough Meat

• Tough meat (often with pH above 5.5) is sometimes marinated before cooking.

• Marinades often contain acids like yogurt, vinegar, or lemon juice.

• The acid lowers the pH, denatures proteins, and increases water-holding capacity, making the meat more tender and juicy.

Collagen

a protein found in connective tissue in animals. In meat, it acts as a cementing material around muscle fibre

• is added to give a three-dimensional semi-solid structure to the dessert.

Cheese formation

Fresh milk pH about (6.5–6.7) acid can be added to hot milk. Which lowers the pH ≈ 4.6, casein proteins coagulate forming a curd.

• Curd is used to make cheeses like ricotta and paneer.

• Most cheeses are made using enzymes called rennet, which coagulate casein proteins instead of acid.

• the curd from which cheese is made has a gel like texture which is because of the gelling properties of the casein proteins in the milk.

How do emulsifiers work?

If on the surface of a protein there are both hydrophobic and hydrophilic side chains, such a protein acts as an emulsifier (ex: milk protein)

• will keep to immiscible states mixed together, such as oil and water

• Oil will bind to the hydrophobic chains while water will bind to the hydrophilic chains on the protein surface

Enzymes

Enzymes are specific in their action, i.e. a specific enzyme catalyzes a specific reaction.

breakdown starch→ amylase

breakdown proteins → proteases

breakdown lipids→ lipase i

meat products may contain papain. Papain is an enzyme that is extracted from raw unripe papaya. It is very effective in breaking meat proteins and thus is used as a meat tenderizer.

Colour

Myoglobin: main protein responsible for the red/pink color of meat (hemoglobin contributes slightly). stores oxygen in muscles

• Consumers associate the brightness of red color as a measure of freshness of the meat

• Myoglobin (pink) → when exposed to oxygen (bright red) → oxygen binds to myoglobin (fresh meat color)

• Metmyoglobin (brown) → prolonged oxygen exposure causes oxidation

• Brown meat (metmyoglobin) is not unsafe, but producers try to prevent browning to maintain appearance.

3D network

• Gluten is a viscoelastic network formed by wheat proteins gliadin and glutenin.

• Gluten gives bread its spongy, soft texture and helps determine loaf volume.

Least → Most Gluten

Corn (none), Barley (trace amounts) Rye (moderate amounts) Wheat (highest amount of gluten-forming proteins)

Pasta: Made mainly from durum wheat, which has very strong gluten.

• Strong gluten helps pasta withstand high pressure during extrusion without breaking

gluten intolerance/celiac disease

Autoimmune disease where the immune system attacks the intestinal lining when gluten is consumed.

• People with celiac disease must avoid all gluten-containing foods.

• Barley can still trigger reactions despite low gluten.

• Oats don’t contain gluten but are often contaminated with wheat, so only certified gluten-free oats are safe.

Texture

Proteins are important for the fibrous texture of the meat. Those who consume meat relish it partly because of the fibrous texture that is very hard to achieve from a plant protein

Foaming properties of proteins

ability form a foam and thus add volume and sponginess to the products.

Foam: mixture of air and a liquid. The air is trapped in the fluid to form a solid three-dimensional structure.

• common food used for foaming property is egg

• Eggs contain a variety of proteins. The the main protein in the albumen (egg white) is ovalbumin which has the highest foaming capacity amongst all food proteins.

• This is why eggs are added in cakes, meringue and several other baked goods when a spongy product is desirable.