food spoilage

Question 1

what is food spoilage

Answer 1

process or change which renders a product undesirable or unacceptable for consumption- can cause water loss, increase in moisture of dry foods, freezer burn and recrystallisation of frozen foods

Question 2

what can microorganisms cause in food (agents of…)

Answer 2

agents of food production, agents of disease and agents of food spoilage

Question 3

what is microbial food spoilage

Answer 3

Microbial growth introducing unwanted alterations in food-appearance, smell and taste
o Changes not necessarily harmful!

Question 4

what is hakarl

Answer 4

fermented shark

Question 5

what are examples of highly perishable foods

Answer 5

meat, fruit, milk, vegetables
(wet foods)

Question 6

what are examples of semi- perishable foods

Answer 6

potatoes and nuts

Question 7

what are examples of stable foods

Answer 7

rice, flour and dry beans (dry foods)

Question 8

what defines each food group (the amounts of…)

Answer 8

the amounts of water

Question 9

explain spoilage in milk

Answer 9

o Bacterial growth on milk sugars
o (Lactobacillus spp., Lactococcus spp.)
o pH reduction due to lactic acid build-up
o Change in bacterial population
o further pH reductions and much more lactic acid, continues until all sugars depleted
o Yeasts and moulds dominate and use lactic acid for growth.
o pH rise allowing further bacterial growth
o Bacteria use proteins as major nutrient
o (Primary amines produced- Smelly!!!!!)

Question 10

look diagrams in booklet

Question 11

What factors influence spoilage

Answer 11

-Moisture content
-Environmental conditions- temp and atmosphere
-Nature of the food –Chemical composition, Ph, Indigenous microflora and Introduced microflora

Question 12

what occurs in the preservation of food

Answer 12

-Removal or killing of all microbes from a food will prevent spoilage!
-Removal or killing of all microbes from a food will drastically alter the food taste, texture and nutritional content
-Compromise needed: reduce overall numbers!

Question 13

why are a number of parameters manipulated

Answer 13

to slow down mirobial growth

Question 14

what is One of the most important parameters for controlling growth

Answer 14

Moisture content {water activity (Aw)} because bacteria favour wet conditions

Question 15

what is the Aw of pure water

Answer 15

1

Question 16

what foods have a high Aw and how are they perserved

Answer 16

perishable foods- preserved by lowering Aw

Question 17

how are foods preserved by reducing water activity

Answer 17

-Drying- sun, heat, freeze - dried (expensive!)
-addition of salt or sugar- water needed to keep salt and sugar in solution- salt is a dehydrating agent

Question 18

how are foods preserved by controlling pH

Answer 18

-pH- very few bacteria grow below pH 5.0
-How to make food acidic?- Add acid e.g. acetic acid, Allow bacteria to make acid from natural food components, lactic acid bacteria
-understanding lactic acids bacteria is a major aim of food production companies

Question 19

how are foods preserved by controlling temperature

Answer 19

-storage at 4oC degrees- rate of spoilage decreased
-storage at -20oC degrees- rate of spoilage extremely slow
-need -70oC to eliminate spoilage- to eliminates growth u need -70 degrees- very expensive

Question 20

how are foods preserved by canning

Answer 20

-Canning- sterilization by heat, 115oC for up to 100 minutes, Milder conditions also used, bacteria and endospores killed
-canning gets rid of everything- basically autoclaving- seal food in airtight container and apply conditions to get rid of endospores and organisms
-canning removes texture

Question 21

what is pasteurisation

Answer 21

-Pasteurization= a mild heat treatment, disinfection by heat, overall microbial population is reduced and pathogens are eliminated since these tend to be more heat sensitive than other organisms
-we don’t need to kill everything- reduce numbers is pasteurisation
-if you increase dose you reduce time you need to contact

Question 22

what temperature is pasteurisation

Answer 22

63 degrees for 30 min

Question 23

what temperature is flash pasturisation

Answer 23

72 degrees for 15 seconds- expensive

Question 24

what is flash past

Answer 24

-HTST- High temperature –Short Time
-Industry standard: milk and other beverages
-flash pasteurisation- continuous process- milk flows over heat

Question 25

how is food preserved by irradiation

Answer 25

-Radiation= Gamma rays from Co60, Electron beam irradiation. And microbes killed by free radicals
-Food can be packaged!
-No recontamination possible
-Pasteurization of meat, poultry, cheese
- No alteration of food- controversial claim
uses ionizing rays (gamma) and nonionizing (UV) radiation

Question 26

what is MAP

Answer 26

Modified atmosphere packaging- o bacteria requires oxygen- modified atmosphere packaging- when it contains a lot of oxygen to prevent organism growth controls gas mixture and slows down shelf life

Question 27

what is the high oxygen in MAP

Answer 27

70% O2 20-30 CO2 and 0-10% N2

Question 28

what is the low oxygen in MAP

Answer 28

10% O2 20-30 CO2 and 70 % N2

Question 29

what can foods naturally contain

Answer 29

Foods may naturally contain antimicrobial substances including, complex chemical inhibitors and enzymes

Question 30

what are examples of foods with antimicrobial substances

Answer 30

–coumarins – fruits and vegetables
–lysozyme – cow’s milk and eggs
–aldehydic and phenolic compounds – herbs and spices such as cinnamon
–allicin – garlic
–polyphenols – green and black teas

Question 31

what does carbon monoixde do to meat

Answer 31

interacts with myoglobin to forms a stable, bright red colour but this reaction prevents meat from browning naturally with age so it is difficult to tell how fresh the meat is (Brooks, 2008). For this reason, the use of CO for meats stored under MAP is banned in the European Union, but is still permitted in the United States and is used in small concentrations (<1%) for some New Zealand meats.

Question 32

are GRAs safe

Answer 32

they are generally considered safe

Question 33

what bacterium mainly spoils milk

Answer 33

bacterium Bacillus cereus is the main cause of spoilage of milk. The presence of psychotropic bacteria present in milk is exposed to heat and oxygen and reacts to become spoiled. The relation between temperature and growth of bacteria in dairy products are mainly responsible for defects of milk- this has been exploited commercially

Question 34

what foods have reduced Aw

Answer 34

salted fish, dry fermented sausage, dry fish, cheeses, flour and cereals

Question 35

what does teperature affect

Answer 35

affects storage time, and food deteriorates faster at higher temperatures

Question 36

what is the temp for a cupboard

Answer 36

50-70 F

Question 37

what is the temp for a fridge

Answer 37

34-40 F

Question 38

what is the temp for a freezer

Answer 38

0 F or below