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Food Chemistry > water > Flashcards

water Flashcards

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1
Q

roles for water in food system

A

A carrier of nutrients and waste

(2) A reactant and a reaction medium
(3) A stabilizer of biopolymer configuration

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2
Q

Texture is often associated with

A

moisture

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3
Q

The amount of water, its location and its interaction with the
chemical components in a food product is extremely important
from the standpoint of acceptability and

A

stability

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4
Q

Why is water so unusual?

A

two oxygen lone electron pairs left

in two of the sp3 orbitals. They produc electron rich regions

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5
Q

structure of water

A

In the liquid phase, water is considered to have “transitional”
structure, termed ”flickering clusters” - regions of threedimensionally hydrogen-bonded water molecules somewhat
similar in structure to ice

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6
Q

Number of clusters … with temperature but the number of

molecules per cluster …

A

increases and decreases

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7
Q

influence of ionic compounds in water

A

ionic compounds are dissolved in water. It forms a hydration shell which neutralize the charge of the respective ions

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8
Q

Essentially, a hydration shell forms around each ion to … the
charge of the respective ions

A

NEUTRALIZE

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9
Q

influence of H bonding compounds

A

H bonds compounds are also capable of disrupting the struture of water

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10
Q

inflence of nonpolar substances

A

form clathrate compounds - semicrystalline form

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11
Q

what is the eutectic point

A

solution can become concentrated to a point at which the remaining water will co crystallize with solute crystals to form and grow

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12
Q

type IV water

A

Aw= 1

pure water

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13
Q

type III water

A

Aw = 0.99-0.80
water entrapped in the tissue matrix
microorganism can grow

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14
Q

type II water

A

Aw= 0.80-0.25

microbial growth is halted

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15
Q

type I water

A

Aw= 0.25 - 0

Water that you cannot remove. strong H bonds

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16
Q

what is desorption

A

slow process, with moisture gradually

decreasing until the food is in equilibrium with its environment

17
Q

what is adsorption

A

dry food is placed in a wet environment

18
Q

what is moisture sorpton isotherm

A

process where a food is dried completely and placed into an enclosed chamber above a saturated salt solution

19
Q

what is hyteresis

A

is when the curve in agraph will depend if you loose water (desorption) or if you are gaining it (adsorption)

20
Q

what are the fcators of concern of water activity

A

(1) Enzymatic reactions
(2) Lipid oxidation
(3) Hydrolytic reactions
(4) Non-enzymatic browning
(5) Various forms of microbial growt

21
Q

control of water activity

A

remove water
convert free water to bound water
freeze the food

22
Q

what are the 3 classes of food dispersion

A

(1) True solutions (or molecular dispersions)
(2) Colloidal dispersions
(3) Suspensions

23
Q

what are the characteristics of true solution

A

(1) The molecules and ions are present in their lowest subdivision.
(2) The particles are <0.1 µm in diameter.
(3) The solution formed is transparent.
(4) The solution has high osmotic pressure
(5) The solution passes through parchment membranes

24
Q

characteristics of colloidal dispersions

A
  1. don’t pass a parchment membrane
  2. reduced osmotic pressure
  3. translucent
  4. may aggregate to form gels
25
Q

characteristics of suspensions

A
  • opaque
    less than 1ym
  • they can settle out
26
Q

why make emulsion?

A

(1)To incorporate oil into a food system without imparting an oily
sensation.
(2)To develop a unique texture, enhance the viscosity of the system
or obtain plastic properties.
(3) To change the optical characteristics of a product

27
Q

what are the 2 basic categories of emulsifiers?

A

(1) Non-ionic

(2) Ionic

28
Q

describe non ionic emulsifiers

A

most importantn and more used because they are insensitive to pH

29
Q

non ionic emulsifiers

A

1) Emulsifiers based on glycerol esters (mono- and
diglycerides) and their non-charged derivatives
2) sorbitan derivatives
3) esters of polyhydric compounds

30
Q

what are the 2 subcategories of ionic emulsifiers

A

Anionic (-)
Amphoteric (+/-)
Cationic (+) - used as cleaning compounds

31
Q

hydrocolloids

A

stabilizing agents

32
Q

what is HLB

A

hydrophilic-lipophilic balance. Is a system to select emulsifiers. It represents the weight percetage of hydrophilic group in a non ionic emulsifier divided by 5

33
Q 
HLB = 1-6 is
HLB = 12-20 is
HLB = 7-11 is
A

hydrophobic
hydrophilic
intermediate

Food Chemistry (11 decks)

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