January 28, 2023


The Food Universe

Hazard Analysis of Vegetable-Based Food Products

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.
Vegetables 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.

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.

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.

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.