Chapter 28 Applied and Industrial Microbiology Food Microbiology

Chapter 28 Applied and Industrial Microbiology

Food Microbiology • Food preservation essential for modern civilization – Many methods discovered by accident • Foods prepared centrally and widely distributed • FDA and USDA – Hazard Analysis & Critical Control Point • “Farm to the Fork”

• Home canning • Commercial sterilization – Uses retort – Thermophilic bacteria may be resistant

• Thermophilic anaerobic spoilage – low-acid foods – Can swells, lowered p. H and sour smell • Flat sour spoilage – Can not swollen as no gas is produced • Mesophilic spoilage – under processed or contaminated foods

• Lower temps used with acidic foods • Some microbes both heat and acid resistant

• Aseptic packaging – Plastics or paper – Hydrogen peroxide, UV light, electron beams • High pressure

• Radiation – completely sterilizes food – Doesn’t change taste or appearance – gamma rays or electron accelerators – Electronic pasteurization

Microbes in Food Production • Cheese – Curd (casein protein) separated from liquid whey – Aided by action of Lactococcus and rennin enzyme – Ripened or un-ripened – Physical and microbial ripening

– Classified by degree of hardness – Hard cheeses • Ripened by lactic acid bacteria in interior • The longer the incubation the higher the acidity and sharper the flavor • Propionibacterium – swiss cheese – Softer cheeses are ripened by aerobic bacterium and molds on surface • Penicillium – blue cheese

• Other fermented dairy products: – Buttermilk, sour cream, yogurt and fermented milk beverages – Lactococcus lactis, Streptococcus thermophilus and Lactobacillus bulgaricus

• Non-Dairy fermentations – Sauerkraut, coffee, pickles, soy sauce, chocolate, coffee, olives, meats and fish – Lactococcus, Streptococcus, Lactobacillus and Aspergillus

• Bread fermentations: – Saccharomyces cervisiae – Aerobic conditions favor CO 2 production • Kneading – Lactic acid bacteria produce tart flavor • sourdough and rye breads

• Alcoholic fermentations – Yeasts, molds and bacteria ferment grains, rice or fruits – Saccharomyces cervisiae, Aspergillus, Leuconostoc – Beer and ale require malting • Starch converted to glucose – Aspergillus molds used in Sake (rice wine)

– Wines made from fruits do not require malting – Malolactic fermentation with grapes • Leuconostoc convert malic acid into lactic acid – Distilled spirits involve fermentation of fruits, grains, or vegetables

• Vinegar production – Aerobic bacteria oxidize ethanol to acetic acid – Different flavors due to different starting materials – Acetobacter and Gluconobacter

Industrial Microbiology • Biotechnology – r. DNA technology • Industrial fermentation

Bioreactors

Primary Metabolites Formed with new cells, during the log phase or trophophase

Secondary Metabolites Produced during the stationary phase or idiophase May be due to conversion of primary metabolites

Industrial Products • Food additives and supplements – Amino acids – Organic acids • Citric acid – Aspergillus • Acetic acid - Acetobacter – Vitamins • Pseudomonas, Ashbya fungi, Acetobacter

• Microbial enzymes – Amylases – Aspergillus • 1 st biological patent – Pectinase – Clostridium – Proteases – Restriction enzymes and polymerases

• Pharmaceuticals – Antibiotics • Streptomyces – Steroids • Cortisone; estrogen; progesterone – Hormones • Insulin; human growth hormone – Vaccines

• Dyes – Green jeans • Alternative fuels – Renewable resources – Bioconversion Biomass Methane, ethanol, hydrogen

• Microorganisms themselves as products – Baker’s yeast – Saccharomyces cerevisiae – Insecticide - Bacillus thurengenisis • Bt toxin – Frost inhibitor – Pseudomonas syringae ice-