Potential Hazards associated with handling and processing vegetables
Fresh Vegetables
Vegetables and herbs are grown close to the soil. Food spoilage is often caused by micro-organisms native to that environment, i.e. moulds and yeasts, but bacteria such as the lactic acid types are also often involved. They can also be contaminated by human handlers (most common type of organism is staphylococcus aureus).
Vegetables have a very large number of bacteria (500,000/g) naturally present on their skins. If the protective skin is damaged during harvesting or subsequent handling then the passage of micro-organisms from the skin into tissues is facilitated. Breakdown of the inner tissues is due to enzymes secreted by the micro-organisms which affects structure and flavour of vegetables.
Organisms which possess pectinase can soften plant tissue and cause them to rot. Many moulds can cause rotting/softening of vegetables. The main causative species of these rots are Penicillium Rhizopus and Mucor.
It must be remembered that any organic object left in the atmosphere will be covered in fungal spores, therefore vegetables and herbs will inevitably be contaminated at the time of harvest. If the skin is intact through this will prevent germination but even the smallest abrasion will allow the spores to enter the moist inner tissues and find ideal conditions for germination and cause spoilage.
Bacterial spoilage can also occur in vegetables and herbs though it is less common but the main organisms involved are of the psychrophilic type as they would be naturally present in soil. Lactobacillus, leuconostoc and Pseudomonas are the bacteria most often implicated in vegetable and fruit spoilage.
Vegetables often contain contaminants such as stones, stalks, flower heads and caterpillars or other insects. Before using raw materials, cleaning or washing and inspection may need to be carried out.
Vegetables and herbs can be easily contaminated by e.g. poisonous chemicals, pests, etc. so they must be stored under condition which do not expose them to risk of contamination (animals and birds must be kept away from storage areas).
Determination of the critical control points (CCPs)
Good personal hygiene is essential. Hand washing must be carried out regularly e.g. after breaks, after using the toilet, after handling raw foods, after handling refuse, after cleaning to prevent contamination of foods by pathogens.
Protective clothing must be worn properly to cover all outdoor wear and also hair. All cuts must be completely covered by a suitable waterproof dressing.
Reporting of sickness and diarrhoea, coughs, colds, eye and ear infections is necessary. Smoking and eating must be prohibited in food handling areas. Tasting of foods should be carried out using a clean spoon which should then be washed.
Fresh vegetables and herbs must be stored separated from other kind of raw materials such meat, poultry, fish, eggs. They should be thoroughly washed (preferably with chlorinated water) before using, to minimise microbial load.
Freshly harvested vegetables and herbs are alive when harvested. They continue to ripen or deteriorate very quickly due to their active enzyme systems. As they respire they take in oxygen and give off carbon dioxide.
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The rate of this respiration is temperature dependent so in theory the shelf life such products can be extended by lowering the temperature as this would slow down respiration.
They can be stored in refrigerator between 1°C and 4°C (short term storage) to inhibit the growth of mesophilic pathogenic organisms and many spoilage organisms. However this is not always preferrable as cold temperature itself can have undesirable effect on the stored foods.
Colour coding of equipment is a method which is commonly adapted by food handlers to ensure separation of utensils like chopping boards (white chopping board is used for vegetables).
foods should be handled as little as possible e.g. disposable gloves can be used to help reducing contamination.
Care should be taken with cloths as they commonly spread bacteria from one place to another. Although colour coding and use of disinfectant solutions are hyginiecally acceptable (providing they are used correctly), but cloths should ideally be disposable.
Storage conditions are very important. Usually a cool, dry, well-ventilated store is recommended. If the store becomes too dry however, some plants e.g. celery may dry out and if ventilation is stagnant, spoilage may occur.
Verification procedures
Periodic sampling or appropriate tests are conducted to ensure all CCPs are under control:
- Food Sampling (before & after preservation and packaging)
Sampling can be aseptic pipetting of a known volume from the thoroughly mixed sample. < 500ml sample can be collected aseptically and transferred to the lab in a sterile container. Sterile pipettes or sampling tubes are used as sampling devices.
Dilutions can be prepared in either of two ways:
- 10 ml liquid and 90ml diluent give a 1:10 v/v dilution.
- 10 g liquid and 90ml diluent give 1:10 w/v dilution.
Counts are expressed as c.f.u / ml of food or c.f.u / g of food as appropriate.
- Cleaning procedures (monitoring and verification programms)
To endorse the sanitation procedures of the premises and equipment, an assessment procedure of plant hygiene should be established. The most immediate method to monitor hygiene is to inspect the cleaned equipment and environment to check that it looks, feels and smells clean. i.e. free from visible residues and taints, equipment corrosion.
Verification of the cleaning procedures can also be based on the enumeration of bacteria on the surfaces of the equipment used for the product such as chopping board, blender, exhaust box, steam jacket pan.
General shelf life testing of finished product
Shelf life test should be implemented using organoleptic evaluation (taste, odour, appearance, colour and texture). Organoleptic quality undesirably changes after a certain time since the existing micro-organisms grow and metabolise available nutrients in the food.
Primarily the sensory changes are due to the microbiological, physical (e.g. freezer burn) or chemical (e.g. rancidity) reactions.
Furthermore the finished product should be sampled and periodically examined for potentially chemical changes that may occur in flavour, appearance, smell, texture and colour. [1089]
