Chapter 3: Food Preservation Flashcards
does not really preserve food, in a way, prolongs shelf life and destroys pathogenic and other organisms
cooking
name given to a group of compounds found in wood smoke that are expected to have some bacteriostatic and bactericidal effects
smoking
this temp can delay the spoilage of foods by retarding the metabolic activities of the microorganisms and prevent their growth, multiplication, pr production of toxin
low temperatures
temperature ranges from 1-10C
at 10C most pathogenic microorganism activities are slowed down
refrigeration
home refrigerators are maintained at this temp ranges
4-7C
process by which water changes from liquid to solid state under sub-zero celcius
can reduce Aw due to unavailability of liquid water
freezing
freezing in bulk and in air
formation of most ice crystals over 3-72 hours of freezing at temp relatice close to 0
forms larger sized crystals that may affect texture, palatability, unction, and nutritional quality of food
slow freezing
carried in a span of 30 mins or less using deep temps that range down to -40C
quick freezing
immersion of the food or the packaged food in a refrigerant
done in less than 30 mins
direct contact with
food is in contact with the passage container of refrigerant at -17.8 to -45.6C
indirect contact with the refrigerant
frigid air at -17.8 to -34.4C is blown across the material being frozen
air blast freezing
makes use of gases that liquefy at very low temp of -60C
rate of freezing is ultra fast
liquid nitrogen and carbon dioxide are the most commonly used
cryogenic freezing
hazard from putting food in the freezer: dehydration that results in a defect
freezer burn
hazard from putting food in the freezer: loss of ascorbic acid, onset of rancidity and discoloration
oxidative deterioration
too slow or too rapid melting of frozen foods, liquid may be leached out carrying with it some of soluble components of the food
thawing of frozen foods
the pink of reddish liquid that comes out from meat during thawing
drip or bleeding
liquid that comes out from fruits and vegetables are called
leakage
food is thawed slowly back to its normal fresh state by increasing storage temp
advantage: results in better food quality closer to its fresh state since most liquid are reabsorbed
disadvantage: enzymatic and microbial activities
slow thawing
food is thawed at a very rapid pace resulting in lesser danger of microbial growth
disadvantage: losing fresh quantities
rapid thawing
processing foods by using special microorganisms acting on food constituents with or without the addition of sugar, salt, or acid
fermentation
addition of vinegar to fruits and vegetables w/ or w/o spices that may be unfermented, partially, or fully fermented
pickling
reduction of water activity and the production of acid which is not conducive for growth of some microorganisms
osmotic dehydration
requires the action of yeast or a given substrate containing sugar or any fermentable carbohydrate to produce alcohol and carbon dioxide under aerobic or semi-aerobic conditions
ex: yeast breads, wines, beer, and distilled liquors
alcoholic
alcohol produced from alcoholic fermentation are further acted upon by Acetobacter bacteria to produce acid or vinegar
ex: vinegar
acetic acid fermentation
sugar in food is acted upon by lactic acid bacteria to produce lactic acid, alcohol, and carbon dioxide
ex: butter, yoghurt, cheese, pickles, fermented milk, burong mustasa, pickled vegetable product (atchara, cucumber pickles, singkamas)
lactic acid fermentation
factor affecting the the quality if fermented or pickled products
there must be the presence of sugar or any fermentable carbohydrates
right substrate
factor affecting the the quality if fermented or pickled products
presence of the enzymes to catalyze the chemical changes for the development of the desirable characteristics of the fermented products
right microorganism
factor affecting the the quality if fermented or pickled products
right temperature, humidity, pH, eater activity to allow maximum growth of the microorganisms
right environmental conditions
removal of available moisture in food to a level that will no longer be conducive for the growth and multiplication of spoilage microorganisms
drying and dehydration
applied to all methods of removing moisture in food, whether by heat of the sun or by artificially produced heat or by other means
ex: Sun drying, air drying, oven drying.
drying
drying by artificially-produced heat under controlled conditions of temperature, humidity, and air flow within a chamber
removes nearly all moisture in food
ex: freeze-drying, vacuum dehydration, hot-air dehydration
dehydration
food is exposed to solar energy, heat is not so intense, hence drying is slow
sun drying
food is exposed to hot air that move across the food
artificial heat
food is soaked in very high concentrated salt or sugar solutions or solvents to leach out the liquid within the cell of the food
process is repeated (step-up) until final moisture reduction level is attained
osmotic dehyration
process of dehydrating frozen foods under vacuum so the moisture content changes directly from a solid to gaseous state without undergoing through the liquid state (sublimation)
products can be rehydrated to its fresh form
expensive process
freeze drying
best temperature for drying
50-60C
sugar at high concentrations of 60% and above has a preserving effect because of the unfavorable osmotic pressure created by sugar in the food products
preservation in high sugar
preserves food by causing high osmotic pressure resulting in plasmolysis of the cells and in making water unavailable to microorganisms by binding or tying up moisture
preservation in high sugar