Spoilage of perishable foods

1. SPOILAGE OF
PERISHABLES
MUNNA IYPE JOY
BTF 11 222
2-7-2013

2. CLASSES OF FOODS ACCORDING TO
EASE OF SPOILAGE
i. Non-perishable/stable: Poor handling only causes
spoilage(Sugar,Flour etc.)
i. Semi-perishable:If properly handled,remains
unspoiled for a fairly long period(Potato)
i. Perishable:Spoiled readily unless special preservation
methods emplyed(Fruits and Vegetables)

3. SPOILAGE(DEF)
Any undesirabe change in normal state of food
which makes it unfit for human consumption
i.Biological factors
●
Microbiological(bacteria, yeasts, moulds (most
common))
●
Macrobiological(rodents, insects, birds, parasites)
ii.Biochemical factors
●
Action of Enzymes
FACTORS OF SPOILAGE

4. iii.Characteristics and storage condition of food
iv.Mechanical damage

5. 1.BIOLOGICAL FACTORS
(i)MICROBIAL SPOILAGE
●
Microbes present everywhere
●
They may or may not cause spoilage
(A)BACTERIA
●
unicellular microbes
●
Length is about 1μm and somewhat smaller dia
●
Spores more resistant to processing conditions
●
Cannot grow in acidic media(few exceptions)

6. (A)BACTERIAcontd..
●
Multiply by fission
●
Temperature plays imp role in growth
(optimum- 37ºc)
●
Bacteria sensitive to acid- destroyed by boiling
(for acidic fruits)
●
Vegetables -non-acidic-121ºc
●
Spores destroyed by heating 120ºc for 30-40
mins

7. GROUPS OF BACTERIA
SHAPE
●
Cocci-shperical
●
Bacilli- rod shaped
●
Vibrio- spiral
OXYGEN REQUIREMENT
●
Aerobes
●
Facultative anaerobes
●
Anaerobes

8. TEMPERATURE
●
Mesophiles(below 38ºc)
●
Thermophiles(45-60ºc)
●
Psychrotrophes(refrigerated conditions)
SOME SPOILAGE BACTERIA
●
Acetobactor,Glucanobactor,Clostrisium,Propio
nibacterium,Bacillus,Pseudomonas,Proteus.

9. (B)YEASTS
●
Unicellular fungi
●
Cell length 10μm and dia one third of length
●
Multiplies by budding
●
Yeast converts sugars to alcohol and CO2
●
Prefer low conc of sugar- grow best in 66%
sugar & 0.5% acetic acid.
●
Boiling destrys yeasts comletely
●
Eg:Saccharomyces , Candida

10. (C)MOULDS
●
Multicellular, filamentous fungi.
●
Main parts are network of hyphae(mycelium)&
spore.
●
Thrive best in closed,moist,damp & dark
situations
●
Prefer sugar containing products(jams, jellies
etc.)
●
Acid medium favours growth and hence spoils
pickles,juices
●
Eg: Penicillium sp.,Aspergillus sp.,Mucor sp.

11. YEAST CELLS
MOULD

12. (i)MACROBIOLOGICAL SPOILAGE
●
Caused by insects,parasites,rodents etc.
●
Losses due to insects varies from 5-50%
depending upon the care taken in field and during
storage.
●
Insects prevented or destryed by fumigating with:
●
Ethylene oxide
●
Methyl bromide
●
Propylene oxide
●
Indirect spoilage includes secretions,dead
bodies,cuts they make in food etc.

13. ●
Parasites like Entamoeba histolytica(amoebic
dysentry)
●
When raw human excrement is used as
fertilizer for crops infestation happens.
●
Infected water and poor hygeine also spreads
parasite.
●
Cooking kills these parasites.
--
●
Rats also destroys food by consuming and
contaminate it with urine,droppings which
having disease causing bacteria (typhoid
,plague etc.)

14. 2.BIOCHEMICAL FACTORS
ENZYME ACTION
●
Changes in food during storage caused by
(i)enzymes present in them
enzymes present in banana cause ripening and if ripening
is uncontroled it becomes too soft and unfit for
consumption
(ii)enzymes from microbes that contaminate
food
spoils the fruit.
●
Enzymatic browning(phenolase oxidase)

15. Brownig of skin of banana
Browning of cut apple
●
Can be controlled by regulating temp,excluding moisture and air
●
All enzymes inactivated at temp above 80ºc

16. 3.CHARACTERISTICS AND STORAGE CONDITION
OF FOOD
CHARACTERISTICS
Char. Of a fruit tells which microbe will grow in it.
(a)Composition
●
Proteins degraded by proteolytic microbes like
Pseudomonas,Proteus,Moulds
●
Fats degraded by molds and some G-ve bacteria
●
CHO degraded by Streptococcus, Leuconostac,
Micrococcus
(b)Acidity
●
Acid(pH<4.5)-Molds,yeasts
●
Non-acid (pH>4.5)-Bacteria

17. (C) Moisture
●
Fruits deteriorate fast since it contains more
moisture.
●
Microbes require 13% free water in food
●
Foods having more salt or sugar content do
not support microbes.
●
Bacteria inhibited-salt conc-5-15%
●
Yeast tolerate >15% salt
●
Sugar- 65-70%- Moulds
- 50%- bacteria,yeasts

18. STORAGE CONDITIONS
(a) Temperature
●
The rate of a reaction doubles at 10ºc increase
●
Several fruits and vegetables deteriorate even at
refr. Temperature(4ºc)
●
Food stored at -18ºc remains free from microbial
growth.
●
Foods stored at room temperature undergo
mesophilic spoilage

19. (b) Oxygen
●
Continuous contact with air causes destruction
of colour,flavour, vit-A,vit-C.
●
Moulds will not grow in anaerobic conditions.
●
Hence vacuum packaging,deaeration,nitrogen
flushing, oxygen absobing chemicals prevent
mould.
(C)Light
●
Light destroys vit-B2,A and C
●
Protecting food by impervious packaging
●
Containers that screen spcific wavelength.

20. (d)Duration
●
All deteriorating factors are time dependent.
●
Time deteriorates foods except cheese,wine and
fermented foods.
4. MECHANICAL DAMAGE
●
During picking, cleaning , grading etc. damage occurs.
●
Injured spots becomes the entrance point of microbes
causing spoilage.
●
Eg: crown rot in banana,pedicel rot in pine apple, blue
mould in apple
●
Removal of scratched or damaged fruits,fungicide
treatment (thiabendazole,benomyl,sodium
orthophenylphenate) reduce after effects of mech.
damages.

22. REFERENCE
●
R.P. Srivastava,Sanjeev Kumar,2006(3),Fruit and
Vegetable preservation priciples and practices,
International Book Distributing Co.,Lucknow,p61-72

23. Thank
You