The rest of the course Flashcards
Which are the 5 most common food colour additives in Sweden?
Caramel, beta-carotene, Annato extract (carotenoid), anthocyanins and vitamin B2 (riboflavin)
Name some natural colors
Tetrapyrroles (heme, chlorophylls), Terpenoids (carotenoides), Flavanoids and betalanines
What give the red color in meat
The conjugated double-bond, also the oxidation state of iron
What happens to myoglobin when reacting with oxygen and nitrite and when it is oxidized and heated
Oxygen + myoglobin becomes oxymyoglobin which is Bright red. When this one is heated it becomes methmyoglobin which is Brown. When myoglobin is oxidized it also creates this Product. If both methmyoglobin and myoglobin is treated with NO it turns into a nitrosomyoglobin which is Bright red.
Which two compounds can make meat red
CO and NO
In which way do the partial pressure of oxygen affect myoglobin
The larger the oxygen partial pressure, the more oxymyoglobin. Where the oxygen is low (where plastic touch meat) there is high levels of methmyoglobin. Where it is none oxygen the deoxymyoglobin is present which give a Purple red color (vacuum pack).
How is the chlorophyll affected as a color?
It has a Mg in the middle (as heme has iron). If this is lost it becomes Brown; often in pH <6. If the pythol Group is removed (enzymatic) it becomes more hydrophilic and stable.
What can be done to preserve the green chlorophyll color
Higher pH, High temp/short time processing, transform to chlorophyllide (E140) or substitute the Mg to Cu (Boston gurka, Wakame)
Name some commonly used terenoids
- carotenes (lycopene- red in tomatoes, beta-carotene- orange n carrots)
- Xanthophylls (Lutein- yellow in egg yolk, astaxanthin- yellow egg yolk and salmon, bixin)
Describe the properties of terpenoids
Yellow to orange/red, soluble in lipids, sensitive to oxygen, radicals and light (oxidation)
Name a common flavanoid, the a
Anthocyanidins: give a red/blue/lilac color in blueberry and a lot of other berries and fruits. Affected by pH. At low it is red (and if oxidized it becomes colorless). When the pH increases it goes to violet (neutral) and lastly blue when basic.
What effect do sulfite have on anthocyanins
When sulfite binds it creates a colorless compound. The red color can be preserved by adding other polyphenols that bind to same Place as in red wine/cocktail cherry. White wine have sulfites (can be used to bleach red wine stains)
Name Another flavonoid, the p
Proanthocyanidins: colorless but easily oxidized to red-brownish color
Whats the properties of condensed tannins
Give a brownish color and in nature they occur in polymers, first detected in cocoa beans, ability to precipitate proteins: give that dry taste, inhibit metals (coffee inhibit iron uptake), antioxidant. Often present in tea.
Describe the properties of betalaines
red, heat sensitive, sensitive to oxygen and light - becomes brownish, not so affected by pH
Name a common synthetic colour
Azo-colours: used with restrictions, some are banned in the EU because of the effect in Children
Whats the defintion of vitamins
a Group of organic compounds, 13 recognized in human nutrition, essential in small amounts
Which vitamins are fat-soluble
Vitamin A, D, E, K and caretenoids
Which vitamins are water soluble
VItamin C and B
Whats a vitamer
a compound with similar biological properties to Another but some diff. exists in the chemical structure, ex. retinol (Vit. A), ergo- and colecalciferol (vit. D)
Whats a provitamin
a naturally occuring compound which can be converted into a vitamin by normal body metabolism, ex caretenoids
Whats a problem when analyzing folic acid
Only the reduced form can be detected
Name some precautions taken when sample prep. before analysis
Yellow light, homogenize the sample, do not use Stainless steel, nitrogen gas to prevent oxidation
Which analyze method is used for B6
There exists man diff. variants so you need to homogenize all so not all 3 needs to be detected. Detect by HPLC (fluorescence detection)
Whats the basic concept of Confocal microscopy?
gives 40% better Pictures than light microscopy, Project laser light and through flourescence the sample can be seen
Whats be basic concept of Transmisson electron microscopy?
Have an extensive sample prep since water and fat needs to be removed Works in a high vacuum system were electrons is focused on the sample
Whats the typical structure of ice cream
It has air bubbles inside that are stabilized with polysaccharides to prevent collaps. The fat+casein stabilizes as well.
Name a few roles polysaccharides can have in food
Thickener, gelation, fibre, water management, stabilizer, energy, aroma+taste, appearence, controlled release (drugs) etc.
Describe the typical structure of a gel
It consists mainly of water, have a 3 dimensional network of gel strands that are connected in junction zones (can be ionic and hydrogen bonds). Ions, pH, temperature etc. affect the gel.
Whats the basic structure of starch
It’s a mixture of linear and branched chains of glucose, amylose and amylopectin.
Whats the properties of starch granules
between 20-25% amylose and rest is amylopectin. See Picture… Amylase is in the amorphous region and amylopectin in the crystalling where a lot of branching. With alpha, beta chains. The granules can look different in maize, wheat etc.
What happens in gelation
The hydrogen bonds are broken during heating and the crystalline structure of amylose and amylopectin is lost. If this viscous solution is cooled the linear part of amylose retrograde and rearrange themselves again to a crystall structure. has become a starch gel.
What is retrogradation
It can expel water from the polymer network, this process is known as syneresis.
What happens when the bread is staling
Happens especially to refrigirated bread. Moisture and amylose migrate out of the starch granules, degelatinizing the starch. Amylose and amylopection realign themselves causing recrystalisation, resulting in harder texture.
What is resistant starch?
Starch that is resistant to digestion, found in raw potato and unripe bananas
What happens when repeated heat/cool cycles and stirring
water comes out and the stability is decreased. increased stirring lower the viscosity
What is pectin
a polymer tha appear in most plants. the polymer have smooth hairy regions. The smooth can create junctions but not the hairy. The degree of methylation is important. It is strongly hydrating and at neutral pH it is partly ionised which means the pectin repell each other
Describe the gealtion of highly methylated pectin
Sugar is needed as dehydrating agent. The pH needs to be lowered to remove the ionized pection regions COO- -> COOH, so that they do not longer repell each other. The smooth regions crystallize and form junctions.
What is needed for low methylated pectin gelation
Ions such as Ca2+ and low pH. Once again the positive ion help the ionized pectin to come together. Also called the egg box model where the Ca2+ is surrounded by the polymer with negative charges
