MICROBIOLOGY OF FRUITS AND VEGETABLES

Question 1

SOURCE OF CONTAMINATION
DURING PRE -HARVEST

Answer 1

-Fecal contamination from manure
-Untreated sewage can contaminate water source for irrigation
* Soils – Bacillus cereus, Listeria
monocytogenes, and Clostridium
botulinum occur naturally in soil

Question 2

Source of microbial contamination during processing

Answer 2

➢Poorly sanitized equipment
➢Contaminated wash water / ice
➢Unhygienic food handler
➢Improper storage
➢Fluid flow from fruits & vegetable tissue can serve as
substrate for microbial growth
➢Pest / insect in the processing plan

Question 3

MECHANISM OF MICROBIAL SPOILAGE

Answer 3

1. Microbes need to overcome the protective barrier (skin or peel)
2. Microbe penetrate the external barrier and invade the internal tissue
3. Release microbial enzyme responsible for the degradation of plant tissue (pectinase celllulase protease phosphatase and dehydrogenase

Question 4

TYPES OF SPOILAGE IN FRUITS (fungal)

Answer 4

➢Yeast spoilage - Saccharomyces, Candida
➢Blue rot– Penicillium italicum, P. expansum, P. verrucosum
(Berries, grapes, lemon, apples)
➢Green rot - P. digitatum
➢Black rot – Alternaria alternata
➢Antrachnose – Colletotrichum
➢Gray rot – Botrytis cinerea (berries, grapes, apples)

Question 5

TYPES OF SPOILAGE IN FRUITS (pathogen)

Answer 5

➢L. monocytogenes in melon
➢E. Coli O157:H7 in fruit cut
➢Salmonella in apple

Question 6

TYPES OF SPOILAGE IN FRUITS (mycotoxin)

Answer 6

➢Patulin – Penicillium expansum
➢Ochratoxin A – Aspergillus carbonarius
➢Aflatoxin – Aspergillus flavus

Question 7

TYPES OF SPOILAGE IN VEGETABLE (bacterial)

Answer 7

➢Soft rot - Erwinia carotovara (potato, cassava, carrot, tomato,
onion, cabbage)
➢Blackleg - Erwinia carotovara

Question 8

TYPES OF SPOILAGE IN VEGETABLE (fungal)

Answer 8

➢Gray mold – Botrytis cinerea (Asparagus, onions, tomatoes, carrot)
➢Black rot – Aspergillus niger and Alternaria
➢Rhizopus rot – Rhizopus tolonifera (berries)
➢Sour rot – Geotrichum candidum (Asparagus, onions, tomatoes,
cabbage)
➢Anthracnose – Colletotricum coccodes

Question 9

TYPES OF SPOILAGE IN VEGETABLE (pathogen)

Answer 9

➢Spore forming bacteria – Bacillus cereus, Clostridium botulinum (can grow in canned vegetables and MAP packaged product)

Question 10

PRESERVATION OF VEGETABLES

Answer 10

• Washing with water containing chlorine
• Use of heat (Canning, blanching)
• Use of low temperature (Chilling, Freezing)
• Use of preservatives
• Vacum packaging
• Modified atmosphere packaging
• Drying