Chapter 7: Food Deterioration and Its Control

major causes of food deterioration

- Growth and activities of microorganisms - Activities of food enzymes and other chemical reactions within food itself - Infestation by insects, parasites, and other rodents - Inappropriate temperatures for a given food - Either the gain or loss of moisture - Reaction with oxygen - Physical stress or abuse Time

how can water activity be decreased?

- adding solutes (salt and sugar), which bind water and make it unavailable to bacteria - drying or freezing

factors adversely affecting foods

- changes in temperature (heat and cold) - light and other radiation - oxygen - changes in moisture content (water loss or uptake) - detrimental enzymes of the food - microorganisms and macro organisms - industrial contaminants (packaging material) - close proximity of other foods - time

Molds as compared to bacteria can generally grow at:

- lower pH (more acid conditions) - lower moisture contents (dryer conditions) - higher salt concentrations, and lower temperatures (in refrigerated foods). (Pseudomonas spp.)

optimum conditions for bacteria

- moist environment - warmth (between 5˚C and 60˚C) - time to grow - food supply - low-acid environment

Food deterioration includes declines in...

- organoleptic desirability - nutritional value - safety (i.e., product quality) - aesthetic appeal - the highly sensitive organic and inorganic compounds which make up food and the balance between these compounds - the uniquely organized structures and dispersion contributing to texture - The consistency of unprocessed and manufactured products

what are the uses of code dates?

- to predict and monitor shelf-life - models for predicting shelf-life are particularly useful for new products without a distribution history

under ideal conditions, bacteria double in number every ____ minutes

20

what percentage of grain crops do insects destroy annually in the US? In other parts of the world?

5 to 10% can reach 50%

One kind of parasitic nematode that invades saltwater types such as herring, cod, mackerel, and salmon belongs to the genus ____________.

Anisakis

name the major parasite(s) causing foodborne diseases that are helmints

Anisakis, Trichinella

what are the two exceptions of molds that do not only cause spoilage but are also unsafe? and why?

Aspergillus flavus and Aspergillus parasiticus. they produce aflatoxins which are potent hepatocarcinogens

Microscopic organisms that cause food poisoning as a result of being consumed live in food or consuming the toxins that the bacteria produce once in your stomach

Bacteria

Beneficial Bacteria

Bifidobacteria, Streptococcus lactis and other lactic acid bacteria, Streptococcus thermophilus

difference between Clostridium and Bacillus

Clostridium is anaerobic and Bacillus is aerobic

name the major parasite(s) causing foodborne diseases that are Protozoal

Entamoeba histolytica

this parasite is responsible for amoebic dysentery

Entamoeba histolytica

food enzymes

Enzymes inherent in food continue to function after death of animal or plant; some enzymatic activities can be accelerated following death

T/F: Milk held at room temperature don't have a different shelf life than milk held under proper/good refrigeration

F

______ and _______ will increase growth and activities of microorganisms.

Heat and moisture

If foods are to be kept only for short period of time, then there are two very simple rules:

Keep food alive as long as possible; kill the animal or plant just before it is to be used. Example: Lobsters alive in a tank in a supermarket or restaurant - while alive and healthy, they do not seriously deteriorate. This is also practiced with fish, poultry, fruits and vegetables where possible. However,, the possibilities are limited. If food must be killed (e.g., for meat). If the food must be killed, clean it, cover it, and cool it as quickly as possible. However, cleaning, covering, and cooling will only delay deterioration for a short time, for hours or perhaps at most for a few days. Microorganisms and natural food enzymes will not be destroyed or totally inactivated and so will take over very quickly

Food Pathogens

Salmonella, Campylobacter jejuni, Listeria monocytogenes

T/F: Canned and processed milk stored at room temperature will outlast pasteurized milk held at refrigeration temperature

T

T/F: One cannot accurately say what the shelf life of fresh milk is without indicating the conditions

T

T/F: Some commodities have allowable levels for insect parts as it is recognized that these foods cannot be produced without some contaminiation

T

What progresses with time.

The growth of microorganisms, destruction by insects, action of food enzymes, non-enzymatic interaction of food constituents, loss of flavor volatiles, and the effects of heat, cold, light, moisture, and oxygen

define shelf-life

The time it takes for a product to deteriorate to an unacceptable level (what is unacceptable is sometimes a matter of opinion).

An important food-borne parasite is the trichinosis nematode, __________ __________, which can enter hogs eating uncooked food wastes

Trichinella spiralis

Listeria monocytogenes

a food pathogen which can grow even in refrigerated foods

Entamoeba histolytica

a parasitic contaminant of foods that causes much distress

visible light

a source of energy

oxygen

a very highly reactive element of the atmosphere

Bifidobacteria

are beneficial to the gastro-intestinal tract. They are also called probiotic bacteria

microorganisms can be...

bacteria, yeasts, and molds

which fruits are subject to "chill injury" at <10 C

bananas, lemons, squash and tomatoes

how does non-respiring foods in a moisture-barrier package give up moisture?

changing the relative humidity of the package headspace and with a drop of temperature, condensation in the package occurs

oxygen causes substantial deteriorative effects in many foods due to what?

chemical oxidation of nutrients (especially vitamins A and C), food colors, flavors, and other food constituents

when a solution becomes more ____________, the vapor pressure falls and aw falls from a maximum of 1.0 for pure water

concentrated

rodents both ________ and __________ food

consume and contaminate

Healthy living tissue (internally) is usually sterile; hence the presence of spoilage organisms is mostly the result of _______________.

contamination

use by date or expiration date

date beyond which the product is no longer acceptable

sell by date

date by which the product should be sold

pack date

date of manufacture

display date

date the product was displayed

how does excessive heat deteriorate food?

denatures proteins, breaks emulsions, dries out foods, and destroys vitamins

Extreme heat and cold conditions cause ____________ of food if not controlled

deterioration

Nicolas Appert

developed the technology of canning (1809) as a result of prize money offered by Napoleon for preservation of food for the French army and navy

control is critical since mice and rats can reproduce very quickly; rodents can spread _________

disease

name the food product(s) that can last 360+ days in a generalized storage life of 21 degrees celcius

dried, salted, smoked meat and fish; dried fruit; dried seeds

why is Anisakis a problem in Japan and the Netherlands?

eating raw fish is common

Bacterial _____________ are most difficult to inactivate.

endospores

besides meat and pork, what else may also harbor parasitic worms?

fish

What foods do no get worse with time?

foods aged/fermented, such as cheeses and wines.

besides thoroughly cooking meat to destroy Trichinella spiralis, how else can it be destroyed?

frozen storage

name the food product(s) that can last 1-7 days in a generalized storage life of 21 degrees celcius

fruits

How can Anisakis be killed?

heating or freezing

what can trap moisture from respiration and transpiration in fruits & vegetable?

high moisture-barrier films

how does uncontrolled cold damage fruits and vegetables?

if allowed to freeze resulting in discoloration, and texture changes

besides being spread in the crops, where else can Entamoeba histolytica spread?

infected water and poor hygiene

Salmonella

infection of meat is one the major causes of food poisoning

foodborne illness

infections of poisoning due to microorganisms

________ damage crops so that spoilage microorganisms are more of a problem

insects

how does freezing milk deterioarate it?

it will break its emulsion and casein will curdle

use by date

last date of maximal quality

what is a better definition of shelf-life

length of time a product remains marketable

Milk in bottles exposed to the sun develops "sunlight" flavor due to what?

light-induced fat oxidation and changes in the protein

what can surface moisture from high relative humidity cause?

lumping, caking, browning, crystallization, and stickiness

what can Anisakis infect?

man

what does visible light cause deterioration of?

many food colors and flavors

name the food product(s) that can last 1-2 days in a generalized storage life of 21 degrees celcius

meat, fish, poultry, leafy vegetables

it is common for a food manufacturer to define a MAQ. What does MAQ stand for?

minimum acceptable quality

Excessive ____________ can lead to undesirable microbial growth

moisture

Containers are flushed with ___________ or ___________________ or in combination, and in some instances by adding to foods and containers oxygen scavengers, which promote removal of residual trace oxygen through chemical reaction

nitrogen or carbon dioxide

Campylobacter jejuni

one of the major causes of diarrhea in humans

Streptococcus thermophilus

one of the major yogurt-forming bacteria. The other is Lactobacillus bulgaricus

what can protect light-sensitive foods against light of specific wavelength?

opaque packaging and incorporating compounds into glass and transparent films

many bacteria require ____________

oxygen

molds require ___________ for growth

oxygen

food fermentation

process that changes the food's sensory characteristics and increases the shelf life of the original food

food spoilage

process that makes food inedible

what does the actual length of shelf-life depend on?

processing method, packaging, and storage conditions

does reducing water activity increase or reduce microbial growth?

reduce

what can food enzymes be controlled by?

refrigeration or blanching

what vitamins does visible light destroy?

riboflavin, vitamin A and Vitamin C

name the food product(s) that can last 7-20 days in a generalized storage life of 21 degrees celcius

root crops

microorganisms

small organisms invisible to the naked eye

what are the sources of these microorganisms

soil, water, air, food itself, humans, food equipment environment

more types of microorganisms can __________________than _________________________.

spoil food than cause food borne disease

what are molds usually only a problem with?

spoilage, not safety

if Trichinella spiralis is present in the mean and it is not cooked thoroughly what can happen?

the live worm can infect man

Although microorganism can spoil food, others are useful in food production. Give examples of those foods and name the bacteria

the manufacture of beer, cheese, yoghurt and wine (Saccharomyces cerevisiae)

define water activity (aw)

the ratio of the water vapor pressure of the food (p) to that of pure water (po) at the same temperature.

how is Entamoeba histolytica harmful when it is in its cyst form?

they are transmitted in feces and may contaminate foods where raw human excrement is used as fertilizer for crops

Trichinella spiralis

this parasite penetrates the hog's intestines and finds its way into the pork

what does excessive drying lead to?

undesirable texture changes and appearance

Streptococcus lactis and other lactic acid bacteria

used to make cheese. They ripen the cheese and provide characteristic flavour

When is peak time for quality of food

usually immediately or soon after harvest, slaughter or manufacture

Molds and aerobic bacteria require oxygen for growth so __________ or ___________ works well against these spoilage organisms

vacuum packaging or modified atmosphere packaging (MAP)

how is butter a means of preserving food?

while milk deteriorated in a day or two, clumps of butter fat that formed when milk was agitated could be removed from the milk and would store for weeks or months

does Anisakis survive normal refrigeration?

yes