Spoilage, Contamination, Sources, Prevention of Cereal and Cereal Products
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This presentation provides a concise overview of the spoilage of cereal and cereal products. It highlights the major causes such as microbial contamination, insect infestation, chemical and physical changes. The slides also explain common spoilage organisms, signs of spoilage in different products, and preventive measures. Ideal for students of food science, nutrition, microbiology, and related fields, this resource is useful for academic learning and teaching purposes.
Spoilage, Contamination, Sources, Prevention of Cereal and Cereal Products
- 1. FOOD MICROBIOLOGY CEREAL AND CEREAL PRODUCTS
- 2. CONTENT •Microorganisms and cereals •Contamination •Factors affecting microbial growth •Prevention •Spoilage
- 3. Microorganisms •Molds: Aspergillus, Penicillium, Fusarium (thrive in humid conditions) •Bacteria: Spore-forming types like Bacillus •Yeasts: Can sometimes be present in cereal-based products •Beneficial Microorganisms: Used in fermentation (e.g., for idli or dosa batter)
- 4. Contamination causes Low Moisture Content: Cereals are naturally low in moisture, reducing microbial growth. Mold Contamination: Molds are the primary concern due to their ability to grow in low moisture environments. Common molds: Aspergillus, Penicillium, Fusarium. Storage Conditions: High humidity and poor ventilation promote mold growth and spoilage. Mycotoxin Production: Molds can produce harmful mycotoxins (e.g., aflatoxins) that pose health risks. Insect Infestation: Insect activity can introduce microorganisms and contribute to spoilage. Heat-Resistant Bacteria: Spore-forming bacteria like Bacillus can survive in processed cereal products. Fermented Cereal Products: Beneficial microorganisms are used in products like idli and dosa batter. Preservation Methods: Proper drying and storage in airtight containers to reduce spoilage. Use of low- temperature storage to inhibit microbial growth. Processing and Pasteurization: Heat treatments during processing help eliminate harmful microorganisms. Packaging: Use of moisture-proof and oxygen barrier packaging to extend shelf life.
- 5. Sources of Contamination •Soil: Contains diverse microorganisms, including Bacillus, Clostridium, Pseudomonas, Micrococcus, molds, and yeasts. Soil dust during harvesting and storage can introduce microbial contaminants. •Water: Used for irrigation, washing, or processing cereals. Contamination may occur due to untreated or improperly treated water. Common microorganisms: Pseudomonas, Enterobacter, Escherichia coli. •Air: Airborne dust and spores contribute to contamination. Mold spores can land on cereal surfaces during storage and processing. •Plant Surface Flora: Natural flora includes Pseudomonas, Micrococcus, Bacillus, and lactic acid bacteria such as Lactobacillus plantarum and Leuconostoc mesenteroides. Unwashed grains often have higher microbial loads. •Animal Sources: Contact with animal feces, feathers, and hides during harvesting. Possible contamination with Salmonella, Staphylococcus, and enteric pathogens.
- 6. Microorganisms Associated with Cereal Contamination •Bacteria: Bacillus cereus: Spore-forming, heat-resistant, causes foodborne illness. Pseudomonas spp., Micrococcus spp., Enterobacter spp. •Yeasts and Molds: Aspergillus spp., Penicillium spp., Rhizopus spp. Associated with mycotoxin production and spoilage.
- 7. Factors Affecting Microbial Growth in Cereals Moisture Content: •Low moisture (<14%) inhibits microbial growth. •High moisture during storage promotes mold and bacterial growth. pH Levels: •Cereals generally have a near-neutral pH (6.0–7.0), conducive to microbial activity. Processing and Handling: •Milling removes protective layers, making cereals more susceptible to contamination. •Poor sanitation during processing and packaging increases contamination risks. Oxidation-Reduction (O-R) Potential: •Higher oxygen levels favor aerobic microorganisms like molds. •Airtight storage reduces oxygen exposure, limiting growth. Nutrient Availability: •Carbohydrate-rich cereals support microbial growth. •Processed cereals may be more susceptible due to added nutrients. Natural Barriers/Inhibitory Substances: •Whole grains have protective husks and bran layers. •Processing (like milling) removes these barriers, increasing susceptibility. •Some cereals naturally contain antimicrobial compounds.
- 8. Preventive Measures Asepsis (Keeping Out Microorganisms) •Store cereals in clean, dry, and sealed packaging to prevent microbial contamination. •Ensure storage areas are protected from pests like rodents and insects. •Maintain a hygienic environment during the processing and handling stages. Moisture Control (Drying) •Keep moisture content below 12% to prevent the growth of molds and bacteria. •Ensure proper drying after harvest to reduce moisture levels in grains. •Use desiccants or moisture absorbers in storage containers to maintain a dry environment. Low Temperature Storage •Store cereals in cool environments to slow down microbial activity and insect infestation. •Use refrigerated storage for high-moisture cereal products if required. Chemical Preservation •Apply approved chemical preservatives like propionic acid to prevent mold growth. •Use fumigants (e.g., phosphine) for insect control during storage, ensuring proper safety guidelines are followed.
- 9. Anaerobic Storage • Use vacuum packaging or modified atmosphere packaging (MAP) to limit oxygen availability and inhibit microbial growth. Mechanical Cleaning and Filtration • Clean cereals thoroughly to remove dust, chaff, and contaminants that may harbor microorganisms. • Sieve and filter cereal products to remove unwanted microbial or insect particles. Heat Treatment • Apply heat treatments like parboiling, roasting, or steam treatment to destroy microorganisms. • Process cereals at high temperatures during milling to reduce microbial load. Irradiation • Use food-grade gamma irradiation where permissible to sterilize cereals and eliminate microbial contamination. Pest Control and Monitoring • Regularly inspect storage areas for signs of pest infestation. • Use physical barriers and traps to control insects. Proper Packaging • Use moisture-proof and air-tight packaging materials. • Ensure packaging is resistant to punctures and tears to prevent contamination.
- 10. Spoilage • Cereal products include: Grains, Meals, Flours, Alimentary pastes, Bakery products (breads, cakes, etc.) • Freshly harvested grains contain thousands to millions of microorganisms. •Types of bacteria in wheat flour: Bacillus, coliform bacteria, Achromobacter, etc. •Mold spores: Aspergillus, Penicillium, Fusarium. •Microbial counts: White wheat flour: 100s-1000s of bacteria per gram. Whole wheat: 8,000 to 12,000 per gram. •Mold contamination in grains and products is a public health concern due to potential mycotoxins: Aflatoxins (e.g., Aspergillus flavus) •Other molds: Fusarium, Penicillium. •Factors favoring mold growth: High moisture content, Improper storage
- 11. Spoilage in Bakery Products • Molds: Main cause of spoilage in baked goods. • Ropiness: Caused by Bacillus species. • Red bread: Caused by Serratia marcescens. • Chalky bread: Caused by yeast-like fungi. Endomycopsis fibuligera &Trichosporon
- 12. Prevention of Microbial Spoilage Methods: • Clean and sanitize equipment. • Prevent contamination during cooling, slicing, and wrapping. • Use preservatives like calcium propionate, sorbates. • Proper storage conditions: cool and dry.