Food
Chemistry
Food Chemistry 2
Proteins etc
Misc 1
Misc 2
100

What is the chemical structure of: Lipids

Lipids are made up of – carbon, oxygen, and hydrogen

100

Hydrogenation is

Hydrogenation is a reaction between hydrogen gas and unsaturated fats +a catalyst that results in a more saturated fatty acid 

100

What is unique about the shape of enzymes

Each enzyme has a unique structure which enable it to attach to its specific substrate and catalyze the reaction. Look and key

100

What is the the lock and key model of enzyme activity ?

Enzymes are highly specific, only one substrate or a group of substrates will ‘fit’ into the enzyme. The substrate is the key of the enzyme lock. Only specific keys fit into a lock

100

What is Hurdle technology  ?

Hurdle technology is the use of more than one technology to limit food degradation.  Other names- combination preservation & barrier technology

200

What is the chemical structure of: Carbohydrates

  • Carbohydrates – carbon, hydrogen, and oxygen (CH20)
200

Proteins are generally divided into 2 classes ?

  • Proteins are generally divided into 2 classes: fibrous - common in structural protein s [such as meat]. & Globular proteins  such as enzymes, egg protein, myoglobin [ responsible for the red color in meat] and whey.
200

list a few desired effects of enzymes

  • What are examples of desired effects of enzymes-
  • Helps chemical reactions happen at lower temperatures – catalyze
  • Clotting of milk by rennet
  • Ripening of cheese during storage
  • Ripening of fruit
  • Tenderizing of meat (papain, bromelain, and ficin), hydrolysis of peptide bonds
200

Does Oxidative Rancidity require heat ?

Oxidative Rancidity (more common than hydrolytic)

-Can occur with or without the addition of heat

200

what is Gelatinization

Gelatinization – is the point where starch granules begin to hydrate and swell, and an increase in viscosity of the slurry is observed

300

What is the chemical structuer of Protein

Protein - carbon, hydrogen, oxygen and nitrogen (with 20 unique amino acids)

300

what is  the Isoelectric point

  • Isoelectric point (of protein) is the ph at which the protein is electrically neutral / the solubility of a protein is lowest at this point
300

list undesirable enzymatic reactions

  • Examples of undesirable enzymatic reactions 
  • Enzymatic browning of fruit, polyphenol oxidase

Hydrolytic Rancidity in lipids, lipase

300

Name any or all of the three steps of Oxidative Rancidity ?

Three steps

  • Initiation – free radical is crated (an atom or molecule with a single unpaired electron.) which is very unstable. One of the hydrogen atoms on the fatty acid chain breaks away from an unsaturated (double-bonded) carbon atom.
  • Propagation – With hydrogen removed, the carbon with only three bonds becomes an unstable, highly reactive free radical that readily binds with oxygen to become a peroxide free radical. The peroxide free radical “attacks” and removes another hydrogen from adjacent fatty acids, making a hydroperoxide. This is called auto-oxidation.
300

what is Retrogradation ?

Retrogradation or setback: the general increase of viscosity seen during the cooling phase, the higher the viscosity in the cooling phase, the more setback a starch will exhibit.

400

List some attributes of lipids  i.e. are the sold or liquid / when and why

  • Oils are liquid (typically from plant sources, fish oil is an exception) 
  • Fats are solid (typically from animals, coconut + palm are an exception)
  • Fats from crystal (physical) structure and their melting points contribute to stability and texture in food).
  • The fatty acids that make up lipids are classified by the number of carbons they have (chain length from4-24)
400

What is Denaturation

Denaturation involves the breaking of many of the weak linkages, or bonds

  • What can cause denaturation-
  • Heat
  • pH change
  • Ionic strength change (changes in the salt concentration)
  • Freezing
  • Surface changes (0ccuring while beating egg whites)
400

What is an example of:

-Enzymatic browning and how can it be controled

  • How to control Enzymatic Browning
  • pH – the optimal pH for the browning reaction is between 5.0 and 7.0. If the pH is below 3.0 the enzyme will be inactivated.
  • Citric acid and acetic acid lower the pH,
  • Decreases enzyme activity
  • Citric acid ties up copper ions and prevents them from participating in the reaction
  • Heat: Browning increases with increasing temperature until the polyphenol oxidase is inactivated
  • Low temperatures: Reduces the rate of reaction, does not inactivate the enzyme
  • Metal ions: Copper is necessary for the action of the polyphenol oxidase; other metal ions, such as iron, also increase the rate of the reaction.
400

What is Hydrolytic rancidly ?

Hydrolytic rancidly (water) requires an enzyme (lipase) water is added and glycerol and FFA are produced- ie where you have fat and water examples butter (short chain FFA)

400

What is water activity ?

Water activity is the ration of vapor pressure of water in a solution to vapor pressure of pure water at a given temperature

500

The fatty acids that make up lipids are classified by

  • The fatty acids that make up lipids are classified by the number of carbons they have (chain length from4-24)
500

What happens during Coagulation

Coagulation is the change in structure of a protein caused by heat, mechanical actions (sheer), acids or enzymes ie. cheese making

The amino acids lose the ability to repel each other, clump together and precipitate out.

500

Examples of desirable enzymatic reactions

Examples of desirable enzymatic reactions

  • Clotting of milk by rennet
  • Ripening of cheese during storage
  • Ripening of fruit
  • Tenderizing of meat (papain, bromelain, and ficin), hydrolysis of peptide bonds
500

How to antixidants help in food preservation

Antioxidants- help prevent oxidation (breakdown by exposure to oxygen) one example is enzymatic browning.  They aid in stopping the bonding of oxygen by scavenging oxygen free radicals and slowing the rate of their reaction.

500

Name one attribute of a:

-Plant cell

-Animal cell

Plant cells- have nucleus with chromosomes and DNA, cell walls composed of cellulose, pectin and sometimes lignin on the outside of the cell membrane. This give the cell the definite shape, have chloroplasts, which contain chlorophyll, the green-colored pigment that absorbs sunlight and allows the plant to make its own food by photosynthesis.

-Animal cells- have nucleus with chromosomes and DNA, and they mitochondria, environment outside the cell is separated from the cytoplasm (protoplasm inside the cell, outside the cell

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