Unit 5.2 (Difficulty: Hard) Food Spoilage and Food Pathogens

• Undesirable microorganisms cause food spoilage

Food Spoilage

• Spoilage leads to food waste
• Spoilage is a change in the organoleptic properties of food
• Microbes cause spoilage by growing on food and producing organic acids, esters, carbonyls, diamines, sulfur compounds, hydrocarbons, and pigments
• Microbial growth can also cause changes in the appearance of colonies and texture

Food Pathogens

• Food pathogens are pathogenic spoilage organisms that cause illness in humans
• Salmonella spp. in vegetables, eggs, chicken, and pork cause diarrhea, fever, stomach cramps, and vomiting
• Listeria monocytogenes in unpasteurized milk and dairy, deli meat, raw fruits, and vegetables causes stiff neck, confusion, fever, and muscle aches, and can cause stillbirths in pregnant women, if it spreads beyond the gut
• Cyclospora in raspberries, basil, cilantro, snow peas, and mesclun lettuce causes diarrhea, loss of appetite, weight loss, stomach cramps/pain, bloating, increased gas, nausea, and fatigue with a one week incubation period
• Campylobacter in unpasteurized milk, chicken, shellfish, turkey, and water causes diarrhea, cramps, fever, and vomiting
• E. coli in contaminated, undercooked beef, milk, raw fruits, and vegetables causes severe diarrhea and stomach pain
• C. botulinum in improperly canned foods and honey in infants causes muscle weakness, blurred vision, and can result in death

Useful Microorganisms in Food

• Some fermented foods rely on microorganisms for preservation
• Examples of fermented foods are beer, wine, yogurt, kefir, vinegar, sauerkraut, and kimchi

Beer

• Beer is brewed from grains like barley and hops
• Beer flavors range from light and crisp to dark and malty
• Beer's brewing process is similar to cooking, allowing for ingredient and spice additions
• Beer contains protein, fiber, B vitamins, folate, and niacin, offering a food-like nutritional value
• Beer generally has lower alcohol content compared to wine
• A standard serving of beer has about the same amount of alcohol as a standard glass of wine and is generally cheaper than wine

Wine

• Wine is made from fermented grapes
• Wine has a more acidic and fruity taste profile
• Flavor varies depending on the grape variety, aging, and winemaking techniques
• Red wine contains antioxidants, particularly flavonoids and tannins, that contribute to heart health
• Wine typically has a higher alcohol and energy content than beer

Yogurt

• Yogurt cultures primarily contain Lactobacillus bulgaricus and Streptococcus thermophilus
• Yogurt is fermented using yogurt starter cultures, which are typically bacteria
• Yogurt is milder and sweeter, with a thicker, spoonable consistency; it is thicker and more solid than kefir

Kefir

• Kefir contains a wider variety of bacteria and yeasts, including Lactobacillus kefiri, Saccharomyces cerevisiae, and Saccharomyces unisporus
• Kefir is fermented using kefir grains, forming a symbiotic culture of bacteria and yeast
• Kefir is tangier and slightly sourer, with a thinner, more drinkable consistency; it is thinner and more liquid-like than yogurt

Sauerkraut

• Sauerkraut is made primarily from cabbage, salt, and sometimes caraway seeds
• Sauerkraut tastes tangy and sour
• Sauerkraut ferments for a longer time than kimchi, and is typically shredded

Kimchi

• Kimchi uses a wide variety of vegetables and spices
• Ingredients include napa cabbage, radishes, cucumbers, gochugaru chili powder, garlic, and ginger
• Kimchi can be spicy, salty, and tangy, depending on the ingredients and fermentation time
• Kimchi is served in larger chunks compared to sauerkraut