Food Deterioration and Control
what are three things that enzyme activity in food causes?
-flavor deterioration -color deterioration -texture deterioration
what is mechanical damage? what class of deterioration is it?
-packaging, vibration, stacking, dropping, etc -physical
what are examples of macroorganisms involved in food deterioration and how do they participate?
-rodents and insects -may not consume food entirely, but cause damage and introduce pathogens
what is moisture migration? what class of deterioration is it?
-water vapor migrates from a region of high humidity to a region of lower humidity, water gain or loss in food is undesirable -physical
what are the 3 classifications of deterioration factors?
1) Physical 2) Chemical and enzymatical 3) biological (microorganisms and macroorganisms)
what 9 things may cause the food properties to change?
1) growth and activities of microorganisms, principally bacteria, yeasts, and molds 2) activities of food enzymes and other chemical reactions within food itself 3) infestation by insects, parasites, and rodents 4) inappropriate temperatures for a given food 5) either the gain or loss of moisture 6) reaction with oxygen 7) light 8) physical stress or abuse 9) time
what are 4 factors that affect microbial activity?
1) temperature 2) acid foods 3) water activity 4) oxygen
what is water activity?
a measure of the free moisture in a product
what are foods that have a natural pH of 4.6 or below?
acid foods
what 2 categories can microbes be classified as according to oxygen preference?
aerobic (need oxygen) and anaerobic (don't need oxygen)
apple juice that is sold as both cloudy and clear is an example of which food property?
appearance
what property of food includes the factors size, shape, wholeness, different forms of damage, gloss, transparency, color, and consistency?
appearance
what are the three main properties of food?
appearance, texture, flavor
what are two ways enzymes are found in food?
are either naturally occurring or microbially produced
what class of deterioration are macroorganisms and microorganisms?
biological
what class of deterioration occurs when food components react among themselves, with the environment, or with the packaging material?
chemical
what class of deterioration occurs where oxygen in the environment interacts with unsaturated lipids (rancidity caused by oxidation)?
chemical
what does the enzyme polyphenoloxidase deteriorate in certain foods?
color
what characteristics of foods may change when they deteriorate?
color, texture, flavor, or another quality attribute
when do all foods undergo varying degrees of deterioration?
during storage
since some foods were once living, what do they depend on for metabolism and subsequent growth?
enzymes
what are large protein molecules that act as catalysts and only small amounts are needed to be effective?
enzymes
what are examples of by products microorganisms synthesize that change the characteristics of food?
ferment sugar; decompose starches, fats proteins to form acid; produce gas and toxins
what does the enzyme lipase deteriorate in certain foods?
flavor
what property of food includes the factors sweet, salty, sour and bitter, and aromas perceived by the nose?
flavor
what includes losses in desirability, nutritional value, safety, and aesthetic appeal?
food deterioration
e.coli, listeria, and salmonella are examples of microorganisms that cause...?
food infection
what occurs when a microorganism is present in the food at the time of consumption and grows in the host, causing disease?
food infection
what are the 2 types of food-borne illnesses?
food infection and intoxication
what occurs when a microorganisms produces toxin in the food prior to consumption and causes disease upon ingestion?
food intoxication
staphylococcus aureus and clostridium botulinum are examples of microorganisms that cause...?
food intoxications
what is defined as the degree of excellence and includes taste, appearance, and nutritional content?
food quality
what cycle can damage frozen foods like vegetables and ice cream?
freeze-thaw
what are foods with a finished equilibrium pH greater than 4.6 and a water activity of greater the 0.85?
low acid foods
what are 3 applications of protease?
meat tenderizing, cheese manufacturing, and textural modification
why are flavor and aroma difficult to measure accurately and agree upon?
often subjective
which enzyme reacts with molecules associated with color, is found in plant tissue, and causes browning?
polyphenoloxidase
what does the enzyme protease decompose and what can this cause?
proteins: hydrolyzes peptide bonds and causes off odors and flavors (ex. bitter cheese products)
what are the 3 categories microbes be classified into according to temperature preference?
psychrophiles, mesophiles, and thermophiles
under optimal conditions, what do microorganisms do that can cause food deterioration?
reproduce and in the process synthesize by products
what does the enzyme pectinase deteriorate in certain foods?
texture
what property of food includes the factors hand feel and mouthfeel of firmness, softness, juiciness, chewiness, and grittiness?
texture
which property of food is often a major determinant of how little or well we like a food?
texture
why do bruises, cuts and other mechanical damage cause browning is foods like peaches, apples, grapes, bananas, etc?
the damage allows oxygen and causes rapid browning
what are the 3 classes of microorganisms?
yeast, bacteria, mold