Week11C2 : cold processing Flashcards
How does the cold processing work to increase the shelf life
doesn’t kill microbes or denature enzymes but it slows the rate of deterioration of food.
What is the temperature of common refrigerators
below 4˚C or 40˚F.
What are the variable that needs to be controlled in refrigeration
- high RH
- Good air circulation
- Temperature
- Gas atmopsheres
T or F : freezing results in change in the sensory qualities
False not if it is done properly
What other kitchen appliance has improved the convenience of frozen foods
microwave
T or F : the freezing point of food products is 0˚C
false
Complete : dissolved solutes results in freezing point ____
depression
What is the temperature of the eutectic point for most foods?
-50˚C
What is the common commercial temperature of freezing
-18˚C
What is the eutectic point
the temperature at which the residual and the solutes water co-crystallize.
At commercial temperature _____ of the water in a food products is in the crystalline state
99%
Why does frozen product can continue to deteriorate?
because some water is still available for chemical reactions
What are the changes that can occur in frozen foods ?
- reduction in solubility
- Denaturation of proteins
- change in pH
- Destruction of sensitive emulsion
What is the reason of the formation of crystals in ice cream?
reduction in the solubility of lactose with water
Why is there denaturation of protein in frozen foods
because the remaining salt or acids are concentrated in frozen food and that can have an impact on the peptide bonds.
Why can’t you put mayo in the freezer?
because it will loose the emulsion
Why can’t you put coke in the freezer
because of the loss of gas solubility.
Why does the water expands in the freezer?
because of its hydrogen bonding.
Slow freezing produces ____ crystals while fast freezing produces _____ ice crystals
larger
smaller
Complete : as _____ increases, the rate of freezing increases
airflow
____ the temperature differential and faster is the rate of freezing
Higher
What is the freezing point of liquid nitrogen?
-198˚C
what percentage of the food product cost is due to freezing?
10%
what are the fluctuating temperature of freezers?
-22˚C to -12˚C
Subjecting milk to temperatures >100°C for ~1 second using direct steam injection is ……
UHT
A container that is made of cardboard, aluminum foil and plastic and that is formed on-site is ……
tetra brick
The decrease of the freezing point of a solvent on addition of a non-volatile solute is ……
freezing point depression
Fast freezing produces …… ice crystals
large
Production (freezing) represents …… of the total cost of frozen products.
10%
According to the U.S. National Institute of Standards and Technology, liquids of gases that have boiling points below -180 °C are referred to as ……
cryogenic liquids
…… °C is the accepted temperature financially and commercially to store frozen products.
-18
What the boiling point of cryogenic liquids?
Below -180˚C
