Food technology Flashcards
What is food quality?
A product’s ability to satisfy a person’s expectations of the product at a given time to a reasonable price.
How is food quality evaluated?
- By sensory testing
- By objective testing
How is sensory testing performed?
- Consumer panel: gives information on consumers perception of a food product (preferences, liking, willingness to pay)
- Trained panel: people trained to be able to detect, describe and quantify subtle changes in specific flavor notes. Provides data on the sensory attributes of a product.
Does objective data alone provide enough information about the sensory aspects of a food product?
No! It needs to be compared with sensory perception or a reference product.
How is objective testing performed?
- Uses equipment
- Measures one particular attribute like: texture, colour, composition, viscosity, pH, moisture content, size, particle size etc.
What is the general indication of the “keyhole” label?
- Less and/or healthier fats
- Less sugar
- Less salt
- More dietary fiber and whole grain
What should be included in information on food packaging?
Name, list of ingredients, allergener, quantity of certain ingredients or categories of ingredients, net quantity, “use by”-date, storage conditions, conditions of use, name/business name and address of food business operator, country of origin or provenance(in some cases), instructions if needed, alcoholic strength if above 1,2 %, nutrition declaration
What is water activity Aw?
Aw = Ps/Pw
The ratio of the vapor pressure of water in a solution to the vapor pressure of pure water.
Why does water activity need to be controlled?
Microorganisms such as bacteria, mold and yeast multiply at high Aw. Preservation techniques against spoilage due to these m.o. take into account the water activity of the food. Sugar and salt are both effective preservatives, as they decrease Aw. Salt decreases Aw even more effectively than sugar due to its chemical structure that ionizes and attracts water.
What is invert sugar?
An equimolar mixture of glucose and fructose, formed by hydrolysis of sucrose by acid and heat or by enzymes such as invertase or sucrase.
Where is invert sugar important and why
In production of candies and jellies, as invert sugar prevents unwanted or excessive crystallization of sucrose.
What is starch?
A glucose polymer that contains two types of molecules, amylose and amylopectin. Both are long chains of glucose molecules joined by alfa-1-4 glycosidic bonds. Amylose is a linear chain. Amylopectin has branching every 15-30 glucose. Amylopectin is less soluble in water than amylose.
What is a cereal?
A cultivated grass which produces an edible seed
What 8 types of cereal are discussed in the lecture?
Barley, wheat, rye, oats, rice, sorghum (durra), millets, corn
What are 3 examples of pseudo-cereals?
Amaranth, buckwheat and quinoa
What are the 3 parts of a cereal kernel?
Endosperm, germ and bran
What is a whole grain cereal/product?
Contains all 3 parts of the kernel, in proportions equal to those naturally occuring in the kernel.
What is the chemical composition of cereals?
- Water (13-14 % in storage) - Starch (40-80 %) - Non-starch polysaccharides (10-40 %) - Protein (10-15%) - Fat (3-8 %) - Low molecular sugars (1-50 %) - Minerals (1-3 %) - Vitamins - Phytochemicals
Why should the water content in stored cereals not exceed 12-14 %?
The grain might sprout if water content is higher than that, which decreases yield and falling number
What is one way of classifying proteins in plants?
- Albumins (soluble in water)
- Globulins (soluble in salt solutions)
- Prolamins (soluble in 70 % alcohol)
- Glutelins (soluble in weak acid or alkaline solution)
What is celiaki?
The body produces antibodies against prolamines found in wheat, rye, barley; which causes inflammation; which damages villi/microvilli;which decreases the surface area of the intestine, leading to malabsorption, nutrient deficiency and weight loss
What vitamins are present in whole grain cereals?
B-vitamins and vitamin E. Carotenoids in durum wheat.
What minerals are present in whole grain cereals?
K, P, Mg, Ca
What phytochemicals are present in whole grain cereals?
Phenolic acid and its derivatives, phytosterols
What is the bran?
A technological term for the outer part of a kernel, including fruit wall, seed coat and the aleurone layer, which is really a part of the endosperm but that ends up with the bran in cereal processing
The bran is rich in…
Cellulose, beta-glucan and arabinoxylan which are dietary fibers from the cell walls. Lipids, pigments, metabolic proteins, sugars, minerals, vitamins B & E, phytochemicals (polyphenols)
The endosperm is rich in…
Starch granules encapsulated in a storage protein matrix
Whole grain consumption is associated with decreased risk of:
Cardiovascular disease - Diabetes - Weight gain - Colon cancer - Inflammatory related diseases
A large consumption of plant foods decreases the risk of
Metabolic syndrome
What is the metabolic syndrome?
Central obesity (bukfetma), high blood pressure, glucose/insulin imbalance (insulin resistance), Dyslipidemia (lågt HDL, höga TG, hög LDL). Associated with increased risk of CVD, diabetes type II, inflammation and some types of cancer.
What are dietary fibers?
Carbohydrates that humans can’t digest in the small intestine (tunntarmen), that are fermented by bacteria in the large intestine.
What are examples of non-starch polysaccharides?
Cellulose, betaglucan, arabinoxylan, fructan, pectin
What is gelatinization?
Raw starch is crystalline and not soluble in water. When starch granules are cooked in water, granules swell. Hydrogen bonds within the starch molecules are broken, molecular order is disrupted. Starch forms hydrogen bonds with water. As hydrogen bonds are formed, water is able to penetrate further into the starch granule, which swell more. Amylose leaches out. Swollen granules take up more space and the mixture thickens as the enlarged granules leach amylose (and possibly amylopectin)
What is retrogradation?
Starch reassociates to a more ordered, crystalline structure upon cooling. More likely to occur in a high amylose starch. Water is lost.
What is RS1, resistant starch type 1?
Starch granules that are physically inaccessible to enzymes ex. enclosed in cell walls.
What is RS2, resistant starch type 2?
Starch granules in natural, granular form
What is RS3, resistant starch type 3?
Gelatinized starch granules, cooked and cooled. Starch becomes retrograded & less accessible to enzymes
What is RS4, resistant starch type 4?
Starches that have been chemically modified to resist digestion and does not retrograde. Not found in nature.
Stearic acid
C18:0
Linoleic acid
C18:2, omega-6
Oleic acid
C18:1, omega-9
Alpha-linoleic acid
C18:3, omega-3
EPA (eicosapentaenoic acid)
C20:5, omega-3
DHA (docosahexaenoic acid)
C22:6, omega-3
What are phytochemicals?
Low molecular weight organic compounds from food plants other than the common nutrients & which have health effects
How is acrylamide formed?
Asparagine + reducing sugars (high temp)-> acrylamide (CH2=CH-CONH2)
What is maltodextrin?
Intermediate length polymers of D-glucose formed from the hydrolysis of starches such as tapioca, potato and wheat. Maltodextrins simulate the viscosity and mouthfeel of fats/oils and are used to reduce the fat content of some foods.
What is a gel?
Elastic solid formed upon cooling of a gelatinized starch paste; a two-phase system that contains a solid continuous phase and a liquid dispersed phase.
What is viscosity?
Resistance to flow of a liquid when force is applied. A measure of how easily a liquid will flow. Thin liquids have a low viscosity. Thick liquids or gels have a high viscosity and flow slowly.
What are pectic substances?
Linear polymers of D-galacturonic acid joined by alfa-1-4 glycosidic linkages. Some COOH are esterified with methanol. Important constituents of plant tissue found mainly in the cell wall.
What are the three categories of pectic substances?
- Protopectin, found in immature fruits. Insoluble in water. Cannot form gels. High molecular weight.
- Pectinic acid, formed by enzymatic hydrolysis of protopectin as a fruit ripens. High-molecular weight pectinic acids are known as pectins.
- Pectic acid, shorter-chain derivative of pectinic acid that is formed as a fruit overripens. Incapable of gel formation.
What are gums?
Complex hydrophilic carbohydrates containing 1000’s of monosaccharide units, of which Galactose is the most common. Most gums are unable to form gels due to a highly branched structure. However, they are able to trap or bind large amounts of water within their branches. Aqueous dispersions therefore tend to be very viscous, because the molecules become entangled.
What is malt?
The barley grain is soaked and sprouted. When it sprouts it produces an enzyme that hydrolyzes starch to a shorter carbon chain, maltose. Maltose is a fermentable carbohydrate that is used to feed yeast and produce Co2 and alcohol in bread and liquor making.
What is gluten?
Protein substances left in the flour after the starch has been removed, which when hydrated and kneaded produce the elastic, cohesive structure of dough.
What are the four pigment classes found in plants?
Chlorophyll (green), carotenoids (yellow, red, orange), anthocyanin (red, blue, purple), anthoxanthin (white)
Properties of chlorophyll
Fat-soluble, porphyrin ring with Mg at the center, found in chloroplasts. If Mg is removed by prolonged storage, cooking etc, chlorophyll loses colour.
What are the two types of carotenoids?
Carotenes and xanthophylls
Properties of carotenoids
Fat-soluble, found in chloroplasts and chromoplasts, found mostly in flowers, fruits and roots, conjugated double bonds are responsible for the colour, more conjugated double bonds = deeper colour.
Properties of anthocyanin
Differs from anthoxanthin in its positively charged oxygen, water-soluble, found in cell sap, colour affected by pH (turns turquoise in alkaline conditions)
Properties of anthoxanthin
White or pale yellowish, water-soluble, found in cell sap, turns brownish grey from prolonged heat.
What are tannins?
Polyphenolic compounds that add both colour and astringent flavour. Range in colour from pale yellow to light brown. Tannins in wine & teas contain antioxidant properties correlated with good health.
What is the difference between climacteric and non-climacteric fruits?
Climacteric ripens AFTER harvesting (avocado, banana, tomato)
Non-climacteric ripens BEFORE harvesting (cherry, citrus, strawberry)
What happens in ripening?
- Chlorophyll degradation reveals carotenoid pigments
- Sugar increases
- Acid decreases
- Ethylene gas produced stimulates further ripening, ex softening of plant cell wall.
What is enzymatic oxidative browning?
Discoloration of some fruits or vegetables when bruised or cut due to reaction between phenolic compounds and enzymes when exposed to oxygen
How can unwanted enzymatic oxidative browning be prevented?
- Avoiding contact between substrate and oxygen
- Covering with film wrap or sugar syrup
- Application of citric acid powder to the cut surface means the citric acid is oxidized instead of the pigment. Acidic pH also inhibits enzymatic action.
- Blanching destroys polyphenol oxidase enzyme, enabling long freezer storage
What happens to water retention in a plant cell when it is cooked?
Cell membranes lose selective permeability, allowing movement of sugars, some nutrients and water.
Diffusion and osmosis occurs as substances move, and the plant cell loses form, water and turgor.
What affects the nutritive value of cooked fruits and vegetables?
Nutrients naturally present, type of cooking medium, duration of cooking, added substances.
How are juices treated to control microbial growth?
- Pasteurized
- UV irradiation treatment
What is the USDA:s definition of “organic foods”?
- Grown without use of chemical pesticides, herbicides or fertilizers
- Have verifiable records of their systems of production
- Products must be 95 % organically produced
What are neutraceuticals?
A suggested term for isolated compounds of fruits, vegetables and other foods that are thought to provide health and medicinal benefits to the diet.
What is allium?
Flavour compounds in the genus allium that contain sulfur compounds and offer phytochemical value
What is brassica?
Flavour compound of Brassica genus including cruciferous vegetables with sulfur compounds
In a solution at pH 7, all amino acids are…
Zwitterions - amino group and carboxylic group are both ionized and exist as COO- and NH3+. Therefore, amino acids are amphoteric
What does it mean that a compound is amphoteric?
That it can behave as an acid or as a base in water depending on the pH
How do proteins behave at pI (isoelectric point)?
They usually precipitate, like in cottage cheese where acid is added to bring the pH to pI for the major milk proteins (casein)
What is denaturation?
The protein unfolds, but there is no change in amino acid sequence (primary structure)
What can cause denaturation?
Heat - pH change - ionic strength (salt conc.) - freezing - surface change
what are examples of desirable denaturation?
- heating of beaten egg whites to produce meringues - cottage cheese - inactivating enzymes by blanching before freezing
what are examples of undesirable denaturation?
frozen eggyolks are lumpy when thawed because lipoproteins denature and aggregate - overheating can cause denaturation
what happens when a protein is hydrolyzed?
peptide bonds are broken to form smaller peptide chains
caused by acid or proteolytic enzymes
how can proteolytic enzymes be used in food production?
- ficin, papain & bromelain are used as meat tenderers
- too much hydrolysis would make the meat “mushy”
- rennet hydrolyzes a specific peptide bond in milk, causing milk proteins to aggregate
Maillard browning is the reaction responsible for?
the browning of baked products. A free carbonyl group of a reducing sugar reacts with a free amino group on a protein when heated. Affects flavour and colour. Reaction causes loss of lysine, arginine, tryptophan and histidine, as they have free amino groups able to react with reducing sugars. All except arginine are essential.
what are high quality proteins?
those that are readily digestible and contain the dietary essential amino acids in quantities that respond to human requirements
what is an amphiphilic molecule?
one that contains both hydrophilic and hydrophobic sections
what is a functional property?
a characteristic of a molecule that enables it to perform a specific role in a food, ex. solubility, thickening, binding, gelation, foaming, emulsifying (for proteins)
what is salting-in?
addition of a dilute salt solution to improve the dispersibility of a protein
what is salting-out?
addition of a concentrated salt solution to precipitate a protein
the water-binding capacity of a protein depends on…
the number of charged an polar groups along the protein chain
meat is composed of what major 3 parts?
muscle, connective tissue and fat
what are the three primary types of proteins in meat?
- myofibril proteins make up the muscle bundles
- stromal proteins (connective tissue proteins): collagen, elastin, reticulin
- sarcoplasmic proteins: pigments & enzymes (hemoglobin, myoglobin)
muscle contraction starts when..
a nerve impulse causes release of calcium ions from the sarcoplasmic reticulum into the sarcoplasm, a jelly-like substance surrounding the myofibrils. Calcium ions bind to actin, enabling reaction with myosin. ATP is needed as energy source for both relaxation and contraction.
why does rigor mortis happen?
this stiffening is due to loss of extensibility by the myofibril proteins actin and myosin, once energy reserves are depleted. Meat cooked while in rigor mortis is extremely tough.
what happens in aging/conditioning of meat?
enzymatic breakdown of proteins that hold muscle fibers together. Allows muscles to relax and become soft.
what is the biological action behind rigor mortis?
animal is killed - aerobic respiration ceases, blood flow stops - no oxygen supplied to muscle - anaerobic glycolysis continues - lactic acid formed - pH decreases - at pH 5,5 glycolysis enzymes denature - ATP supply depleted quickly - lack of ATP means calcium is not pumped out - actin & myosin bind irreversibly forming actomyosin cross-links - muscle becomes rigid
what is the “ultimate pH”?
the pH that is reached when glycolysis ceases, ~5,5. Low ultimate pH inhibits microbial growth and is desired. High ultimate pH binds more water, but has poor m.o. resistance
how does the rate of change of pH affect the quality of meat?
rapid pH change while the temperature is still high causes considerable denaturation of contractile and/or sarcoplasmic proteins and loss of water-holding capacity. Lysozomal proteins are released at high temp, these cause hydrolysis of proteins. This might happen if the carcass is not cooled rapidly after slaughter.
meat aging occurs as…
muscles become tender due to protein & actomyosin breakdown. A protease which is active at around pH 5,5 breaks down the thin myofilaments at the Z-lines. Sarcoplasmic proteins denature and myofibrils denature somewhat, resulting in loss of water-holding capacity. Collagen and elastin do not denature significantly during aging.
aging of meat is achieved by
hanging the carcass in 2 degrees celsius for 1-4 weeks. Pork and lamb do not require aging since they are young at slaughter.
meat appears as red or white depending upon…
the predominant pigment and its concentration in the meat. The 2 major pigments in meat are myoglobin and hemoglobin
myoglobin is present in…
frequently exercised portions of the animal that expend great amounts of oxygen like chicken legs. more myoglobin in: cows than pigs, older sheep than lambs, bulls than cows.
what is the function of myoglobin?
stores oxygen in the muscles
what is the function of hemoglobin?
carries oxygen in the bloodstream
what causes undesirable brownish-red coloured meat?
when myoglobin is exposed to oxygen, bright red oxygenated oxymyoglobin is produced. Oxidation of oxymyoglobin or myoglobin results in metmyoglobin.
what are the effects of cooking on collagen?
hydrogen bonds and heat-sensitive crosslinks are broken. some of the tough-structured collagen is then solubilized and converted to gelatin. faster at higher temp.
why is nitrite added to processed meat?
to preserve colour and inhibit Clostridium botulinum
why is fish softer and flakier than mammals or poultry?
because muscle fibers exist as short bundles. Also contains less connective tissue, and more of it converts to gelatin during cooking.
what are legumes?
the seeds of a pod of the Leguminosae family.
how is legume protein affected by cooking?
the protein is coagulated and its availability is higher following cooking.
what is tofu?
soy milk that has been coagulated to make the gel
what is quorn?
a fungus “mycoprotein” produced by fusarium venenatum
at what temperature is salmonella killed?
72 degrees celsius for 16 s or 62 degrees celsius for 30 min. Cook poultry to 74 degrees celsius.
at what temperature is the parasite trichinella spiralis killed?
68 degrees celsius. Cook pork to 68 degrees.
what is endomysium?
connective tissue layer that surrounds individual muscle fibers.
what is epimysium?
connective tissue layer that surrounds an entire muscle
what is perimysium?
connective tissue layer that surrounds muscle bundles
what are the contents of egg yolk?
all of the egg’s cholesterol - almost all of the egg’s fat - contains all known vitamins except vitamin C - triglycerides, phospholipids (primarily phosphatidyl choline/lecithine), sterols (ex. cholesterol) - 40 % of the egg’s protein - pigments (mainly xanthophylls, carotene, lycopene) from the hen’s feed
what are the contents of egg white?
60 % of the egg’s protein - riboflavin, niacin, biotin - magnesium, potassium
what are the contents of the egg shell?
94 % CaCO3 - 1 % MgCO3 - 1 % CaPO4 - 4 % organic matrix
egg shell colour depends on…
the breed of hen - has no known effect on flavour/quality
the yolk colour depends on…
the feed given to the hen
what happens with an egg as it ages?
contents inside the shell shrink and the air cell enlarges due to water loss - the yolk flattens as the vitelline membrane thins - pH rises from 7,6 to 9,6 allowing bacterial growth
what is candling?
a technique that allows a view of the shell and inside of eggs without breaking the shell - scanning with bright light
how can eggs act as binders?
eggs are viscous and coagulate, therefore they bind ingredients like in meatloaf, and they bind breading
how can eggs act as clarifying agent?
raw egg whites coagulate around foreign particles in a hot liquid. ex. clarifying soups, bringing stray material to the surface for removal
how can eggs act as emulsifiers?
egg yolks contain phospholipid emulsifiers, including lecithin. Emulsifiers allow two ordinarily immiscible liquids, such as oil and water to mix
how can eggs act as foaming, leavening agent
egg whites increase 6-8 times in volume when beaten to a foam. as the egg white foam is heated, the protein coagulates around air cells, maintaining a stable foam structure.
how can eggs act as gel?
a two-phase system of liquids in solids forms as eggs coagulate, forming a gel in custards.
how can eggs act as thickening agent?
eggs coagulate and thicken mixtures such as custards and hollandaise sauce
what is the air cell?
the empty space formed at the large end of the egg. holds oxygen. doesn’t exist initially. becomes large by age, cooling, moisture loss. can result in microbial spoilage due to oxygen supply.
why should eggs be packed with the large end up?
air movement from ar cell to yolk is minimized
what happens when an egg denatures?
proteins unfold and align in parallell fashion, forming intermolecular bonds, protein chains shrink. the egg becomes opaque when light cannot pass through the protein mass.
what happens when an egg coagulates?
the liquid/fluid egg is converted into a solid state (gel). water escapes from the structure as unfolded helices attach to each other. affected by heat, beating, pH, sugar, salt
why can yolk sometimes turn green?
occurs with long, high heat exposure. formation of ferrous sulfide from sulfur in egg protein and iron from the yolk.
what are the three components giving egg whites natural protection from bacteria?
avidin: binds biotin required for some m.o. growth
lysozyme: hydrolyzes cell walls of some bacteria
conalbumin: binds with the iron of the yolk, preventing growth of m.o. that require iron
what is curdling?
protein precipitates, releases water and becomes tough
how much of milk is water?
87-88 %
what is the primary carbohydrate of milk?
the disaccharide lactose. carbohydrates constitute about 5 % or less of milk.
what happens with lactose as cheese ages?
it is converted to lactic acid. aged cheese may be digestible by lactose intolerant persons.
what is the fat content of whole milk?
3.5 %
what pigments are found in milk fat?
carotene and xanthophyll
what is the protein content of milk?
3-4 %
what are the primary proteins of milk?
caseins, about 80 % of milk protein. Alpha-s, beta and kappa caseins.
what separates the different casein types?
alpha-s and beta contain several phosphate groups esterified to serine. these are calcium-sensitive and may be coagulated by addition of calcium. kappa-casein has only 1 phosphate-group and is not calcium-sensitive. alpha-s and beta are very hydrophobic. kappa-casein is a glycoprotein containing an acidic carbohydrate section and so is much more hydrophilic.
what are casein micelles?
casein fractions associate with each other and with colloidal calcium phosphate to form casein micelles. alpha-s and beta casein are mostly in the micelle’s interior, kappa casein on the outside. Carbohydrate “hairs” protrude from the micelle, and give steric hindrance.
how are casein micelles coagulated?
by addition of acid at a pH 4,6-5,2. as micelles approach pI, charge and extent of hydration is reduced, micelles are no longer stable. K-casein carbohydrate “hairs” flatten, reducing steric hindrance. Acid also causes some calcium to be removed from the micelles. They then coagulate
what is the action of rennin?
the enzyme rennin cleaves a specific bond in K-casein, causing the charged, hydrophilic “hairs” to be removed from the micelle. The now uncharged, hydrophobic, unstable micelles aggregate to form curds. Curds may be separated from whey and made into cheese!. Does not cause removal of calcium from micelles.
how are casein micelles affected by heat?
relatively stable, are not denatured by heat at neutral pH unless temperatures are very high and heating is prolonged.
what is whey/serum?
the second protein fraction of milk, makes up about 20 % of milk protein. includes lactalbumins and lactoglobulins. whey proteins are more hydrated than casein and are denatured and precipitated by heat rather than by acid.
what vitamins are contained in the nonfat portion of milk?
B1(thiamin), B2(riboflavin), B3(niacin), B5 (panthothenic acid), B6 (pyridoxine), B12(cobalamine), vitamin C and folate
what vitamins are found in milk fat?
vitamin A, D (small amounts), E and K (minor amounts)
what minerals are found in milk?
calcium 1/3 in solution, 2/3 colloidaly dispersed. Phosphorus, Cl, Mg, K, Na, S
shelf life of properly refrigerated milk..
14 days
what can cause off-flavours in milk?
excessive pasteurization temp - certain animal feed ex wild onions, lipase activity causing rancidity of fat unless destroyed by pasteurization - oxidation of fat or phospholipids by enzymes - light-induced flavour changes in proteins and riboflavin because riboflavin acts as a photosynthesizer - stage of lactation of the cow
how is milk affected by pasteurization?
destruction of pathogenic bacteria, yeasts and molds as well as 95-99% of nonpathogenic bacteria - vitamin destruction and protein denaturation are minimal
how can adequate pasteurization of milk be confirmed?
absence of the enzyme alkaline phosphatase which is destroyed at temperatures and times required for adequate pasteurization. If substrate is added, milk turns blue if there is enzyme activity. otherwise, milk stays white.
what is UHT pasteurization?
the use of sterilization temperatures (138-150 C) in combination with the use of presterilized containers under sterile conditions
what is the primary function of homogenization?
to prevent creaming (rising of fat to surface) - mechinally increases the number and reduces the size of the fat globules - permanently emulsifies
why is homogenization permanent?
as the surfaces of many new fat globules are formed, each fat globule becomes coated with a part of the lipoprotein membrane and additional proteins from casein and whey
what are probiotics?
live m.o. administered in adequate amounts which confer a beneficial health effect on the host
what are prebiotics?
nondigestible carbohydrates that act as food for probiotics. whole grain, banana, onions, garlic, honey
how is butter made from milk?
milk is churned (agitated, emulsion breaks, fat coalesces and water escapes) to form water and buttermilk
what is cream?
the high-fat component separated from whole milk as a result of the creaming process
what is ice cream?
a food produced by freezing while stirring a pasteurized mix containing dairy products
what happens as cheese ripens?
lactose is fermented by lactase to lactic acid. fat is hydrolyzed by lipase. protein undergoes mild hydrolysis to a.a. by rennin.
what cheeses are not ripened?
cottage cheese, cream cheese, feta, ricotta
what cheeses are ripened with bacteria?
cheddar, parmesan, swiss cheese (holes from gas-producing bacteria!)
what cheeses are ripened by mold?
camembert, brie (mold sprayed onto surface)
roquefort (inoculated internally with penicillium roqueforti)
what are some of the functions of fat?
add or modify flavour, texture, areate batters and doughs, contribute flakiness, contribute tenderness, emulsify, transfer heat, such as in frying, prevent sticking, provide satiety
glycerides include
monoglycerides and diglycerides (emulsifiers), triglycerides(most fat)
phospholipids..
contain two fatty acids, in place of the third fatty acid is a polar group containing phosphoric acid and a nitrogen-containing group. the most common is lecithin(phosphatidylcholine)
tocopherols are…
antioxidants in fats (most vegetable oils) that help prevent oxidative rancidity. sources of vitamin E. partially removed by the heat of processing.
sterols are…
steroid with 8-10 carbon side chain and an alcohol group
fatty acids are…
long hydrocarbon chains with a methyl group at one end of the chain and a carboxylic acid group at the other. most contain an even number of carbons (4-24). trans double bonds have a higher melting point than cis. almost all naturally occuring fats and oils used in food exist in cis configuration
what happens when liquid fat is cooled?
molecular movement slows down - molecules are attracted to each other by van der Waals forces. fat molecules align and bond to form crystals.
how many forms can fat crystallize in?
alpha, beta-prim, intermediate, coarse beta
alpha fat crystals are…
smallest and least stable. formed if fats are chilled rapidly
beta prim fat crystals are…
small needlelike, 1 micrometer long. smooth texture
intermediate fat crystals are…
3-5 micrometer in size
coarse beta fat crystals are…
25-100 micrometers in length and have the highest melting point.
fats can exist in different crystalline forms, a phenomenon known as
polymorphism
formation of small fat crystals…
is favored by rapid cooling with agitation. desirable if a fat contributes aeration to a food. more likely with heterogenous fat.
growth of large fat crystals occur…
if cooling is slow. more likely with homogenous fats.
the melting points of individual fatty acids depends on…
chain length, degree of saturation, isomeric configuration
a plastic fat
contains both liquid oil and solid fat crystals. consistency depends on the ratio of solid to liquid triglycerides.
what are the two ways fat can deteriorate by rancidity?
hydrolytic rancidity (triglycerides react with water and free their farry acids from glycerol. catalyzed by heat and lipase ex. found in butter). oxidative rancidity (fat is oxidized and decomposes into volatile, stinky shorter carbon chains like fatty acids, aldehydes, ketones. catalyzed by heat, light, iron, copper, lipoxygenases)
what are hydrocolloids?
long-chain polymers, principally carbohydrate, that thicken or gel in aqueous systems, creating the creamy viscosity that mimicks fat. ex. hemicellulose, beta-glucans, microparticulates etc.
what is polydextrose?
a bulking agent created by the random polymerization of glucose, sorbitol and citric acid (89:10:1), substitute for either fat or sucrose.
What are examples of extruded foods?
Pasta, breakfast cereals, snacks like cheese doodles
What are the quality parameters of uncooked pasta?
Mechanically strong, yellow, translucent
What are the quality parameters of cooked pasta?
Remains in shape, elastic, give a firm bite, non-sticky, cooking water free of starch
What are some characteristics of good pasta flour?
Durum wheat or hard wheat which is high in protein content, intact starch granules give less sticky pasta, high carotenoid content for nice colour, low lipoxygenase activity
Why is low lipoxygenase activity desirable in pasta?
Lipoxygenase degrades carotenoids which leads to loss of colour and affected flavour
How is pasta dough made?
Flour is mixed with water (35-45 C) at a ratio of 3:1. The dough is extruded and the extruder die determines the shape of the pasta
Why is pasta dried?
To be stable in storage in room temperature
Water content in pasta is reduced from.. to ..
31% to under 12,5 %. Not too dry, pasta might crack. Too slow drying can lead to spoilage due to mold growth
How is extrusion cooking performed?
Dry and liquid ingredients are mixed and churned through a screw towards an extruder die. High pressure and heat are generated. As the dough flows out through the nozzle, pressure is released, temperature cools, and as moisture evaporates the dough expands and starch solidifies
What is needed for grains to puff?
The grain must be cooked to degrade starch granules. A large sudden drop in temperature and pressure gives puffing
What is the purpose and effects of fermentation?
Preservation of food through formation of inhibitory metabolites such as organic acid (lactic acid, acetic acid, formic acid, propionic acid), ethanol, bacteriocins, etc., often in combination with decrease of water activity (by
drying or use of salt) • Improving food safety through inhibition of pathogens or removal of toxic compounds
• Improving the nutritional value
• Organoleptic(sensory) quality of the food
