There are many “microbial contamination sources” in the food processing process. Preventing food from being contaminated is definitely the primary task. Microbial contamination sources include bacteria, molds, yeasts, viruses, and other spoilage bacteria, and mold is only one of them. If it is not controlled, it will inevitably affect the shelf life of the food. So how to control mold contamination in the product?
Here we will introduce the main mold prevention and control methods in detail!
01
What are the common molds?
To control mold contamination, we must first understand the types and characteristics of molds. On this basis, we can propose reasonable and practical prevention and control methods to improve the quality and safety of products.
(1)-Aspergillus
- It is widely distributed in nature. It uses soil or air as a medium to cause mold and deterioration of food, grains fruits, and vegetables. Some can produce carcinogenic aflatoxin. Because of its strong resistance to drying, this mold is often separated from some dry foods, and sugar and shell processing factories are also often contaminated by this type of mold. Baked products are also often contaminated by Aspergillus due to raw materials such as sugar, peanuts, oil, rice, and other raw materials. Color is an important basis for the classification of Aspergillus.
(2)-Penicillium
- Like Aspergillus, it is widely distributed in nature and has the same ecology. However, Aspergillus grows at medium to high temperatures, while Penicillium is mainly mesophilic. Its representative species is glaucous-green Penicillium, which is easy to separate from soil or air. Penicillium spores are highly heat-resistant and their bacterial growth temperature is relatively low. Tartaric acid, malic acid, citric acid, and other acidulants commonly used in baked products are its favorite carbon sources, which often cause these products to mold. It is the main mold in dry shell product processing factories.
(3)-Alternaria
- Alternaria is a mesophilic and hydrophilic mold that is prone to decay, corruption, and allergies. In high-humidity factory environments (such as cakes, fish, aquatic product processing, and meat processing environments), the black mold on the ceilings, walls, floors, and water pipes is almost always this fungus or Cladosporium. The colonies are fluffy and mostly gray-black to black.
(4) – Fusarium
- Fusarium is a fungus distributed worldwide. It can not only survive the winter and summer in the soil but also infect a variety of plants (food crops, cash crops, medicinal plants, and ornamental plants), causing a variety of plant diseases such as root rot, stem rot, stems base rot, flower rot, and ear rot. There are more than 100 host plants. The colors are generally yellow, white, purple, red, green, etc. The shape of the sclerotium is mostly spherical, solitary, or clustered.
02
What kind of reproduction conditions do molds generally require?
The growth and reproduction of molds are closely related to moisture, temperature, substrate, ventilation, and other conditions. Therefore, only by fully understanding the growth habits of molds can we provide a theoretical basis for controlling molds.
(1) – Moisture
- The primary condition for the growth and reproduction of molds is to maintain a certain amount of moisture. Most molds grow easily in a high-humidity environment with a relative humidity of more than 90% and a water content of 18%. When the water activity in food is 0.98, mold is most likely to grow and reproduce. When the water activity is below 0.7, mold reproduction is truly inhibited and toxin production is prevented. Therefore, the higher the water content of the product, the better the taste, but the higher the risk of mold growth.
(2)-Temperature
- Temperature has an important impact on mold reproduction and toxin production. Different types of molds have different optimum temperatures. The most suitable temperature for most molds is 25-30℃. Below 0℃ or above 30℃, toxin production cannot be achieved or toxin production is weakened. For example, the lowest reproduction temperature range of Aspergillus flavus is 6-8℃, the highest reproduction temperature is 44-46℃, and the optimum growth temperature is about 37℃, but the toxin production temperature is different, slightly lower than the optimum growth temperature. Its optimum toxin production temperature is 28-32℃.
(3)-Nutrient matrix
- Like the conditions for the growth and reproduction of other microorganisms, the growth of mold in different food matrices is different. Generally speaking, nutrient-rich foods (such as plant-based food raw materials with carbohydrates as the main component) are more likely to grow mold, and natural matrices are better at producing toxins than artificial culture media.
(4)-Oxygen
- Mold is an absolutely aerobic microorganism and grows better in a well-ventilated environment, so its growth can be inhibited under anaerobic conditions.
03
Sources of mold contamination in food processing plants
The sources of mold contamination in food processing plants generally come from water, ventilation, operators, machinery and equipment, food raw materials, and packaging materials.
(1)-A large amount of water vapor is often produced during food processing, which can easily cause damp walls and condensation water to form, which is easy to breed mold.
(2)-Some water environments such as sinks, buckets, water pipes, taps, water pipes, floors, and baseboards are often contaminated due to long-term water storage. For example, the workshop floor, open drains, and gas caps are damp with accumulated water; the condensation water pipes, walls, ceilings, air conditioning outlets, etc.; the liquid waste generated during the production process is not cleaned out of the workshop in time; the equipment surface close to the wall and the ground, the damp wall surface, and the air cooler are prone to condensation water and mold.
(3) – Secondary pollution of floating mold in the air, such as mold growing in the air, bacteria contained in the dust on the ground when people walk, and mold blown out of the air conditioner or fresh air duct.
(4) – Secondary pollution of the operator himself, such as incomplete hand disinfection, contact with food with unclean clothes and gloves, violation of the hygiene management system, and bad hygiene habits, such as not wearing a mask to cover the nose as required, not wearing a jumpsuit as required in the packaging room, etc.
(5) – Cross-infection of equipment and containers, such as equipment and containers not being cleaned regularly according to the prescribed process, improper selection of disinfectants or insufficient dosage, etc.
(6) – Secondary pollution brought in by raw materials, which may be contaminated by mold due to poor quality or improper storage conditions.
(7)-Contamination through packaging materials, such as poor sealing of packaging materials, unclean outer packaging or packaging bag surface, and microorganisms attached. If sterilization is not thorough, the residual mycotoxins will directly contaminate food.
04
Prevention and control measures for mold contamination
(1)-Controlling workshop temperature and humidity
- To effectively control mold in the production workshop, the temperature and humidity of the workshop must be controlled first. Dehumidifiers and air conditioners should be turned on frequently, especially in humid weather. It is recommended that the workshop temperature be below 24 degrees and the humidity be controlled below 55% to ensure that the workshop is dry because excessive temperature and humidity will promote the growth of mold. At the same time, effective ventilation facilities should be set up to ensure the normal operation of the workshop dehumidifier and that the air inside the workshop can meet the required indicators. The degree of ventilation of the air conditioner directly affects the production of mold. If the workshop can ensure that the air containing a large amount of water is discharged from the workshop in time to prevent the indoor temperature from being too high, steam condensation or odor, the possibility of mold being present is greatly reduced.
(2)- Air disinfection in the workshop
- The packaging room can be equipped with ozone disinfection machines, ultraviolet lamps (installed above the packaging machine), etc. After the workers get off work in the evening, the air in the workshop can be sterilized by ozone disinfection machines and ultraviolet rays at the same time to prevent the accumulation of microorganisms in the air during the day and cause harm to the products. Of course, remember to open it after getting off work and close it before work the next day. During the disinfection period, personnel must evacuate. In humid weather, it is recommended that the packaging room be thoroughly fumigated with formaldehyde every 2 weeks.
(3)- Pay attention to the disinfection of tools before and after work
- Alcohol spray disinfection is a common method to prevent mold and bacterial contamination when manufacturing food. Before and after work every day, use 75% alcohol to spray and disinfect the walls, fans, sewers, counters, hands, apron sleeves, pre-cooling warehouses, and warehouse doors, quick-freezing warehouse doors, packaging rooms, and tool disinfection rooms. During the shift, 75% alcohol is used to spray the fans, walls, and sewers every 2 hours.
(4)-Control the hygiene in the workshop and avoid dead corners
- First of all, we must keep the internal tools of the production workshop clean and hygienic, and pay attention to strict sanitation and maintenance of some hygienic dead corners. Clean tools and equipment after getting off work every day, and perform deep cleaning every half month. That is, managers and operators should have a hygienic concept, pay attention to the hygiene of operations reduce the possibility of pollution at any time, and must start with strengthening employee hygiene education. For example, the back of the operating table, ceiling, walls, air conditioners, refrigeration fans, dehumidifiers, dryers, etc. should be cleaned. After cleaning, all walls, ceilings, equipment, utensils, and table surfaces should be wiped with alcohol more than twice.
(5)-Ensure the cleanliness of operators
- The work clothes and locker rooms of the operators must be kept clean and hygienic, cleaned regularly, and sterilized with ultraviolet or ozone to prevent cross-contamination of mold caused by humans (sterilization is not allowed when there are people).
- Before entering the workshop (especially the cooling and packaging room), workers should wash their hands with hand sanitizer, change into work clothes, wear sleeves, aprons, hats, and masks, and then soak their hands in disinfectant (chlorine dioxide solution or diluted disinfectant purchased from supermarkets for home use) for 5 seconds, and then spin dry directly or use a dryer to dry.
(6)- Eliminate pollution sources in the workshop and set up a clean room
- In the food factory, after heating and cooling to the packaging stage, it is most necessary to prevent the invasion of external floating bacteria and contamination by falling bacteria. If conditions permit, a clean room can be set up and air introduction facilities can be used to achieve air purification and reduce pollution.
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