Unit 5.2 (Difficulty: Easy) Food Spoilage and Pathogens

• Undesirable microorganisms cause food spoilage, while desirable ones are useful in food production.

The Bad Guys: Food Spoilage

• Food spoilage contributes significantly to food waste.
• Spoilage is characterized by changes in a food's organoleptic properties.
• Microbes are the primary cause of food spoilage.

Microbial Products in Food

• Organic acids
• Esters
• Carbonyls
• Diamines
• Sulfur compounds
• Hydrocarbons
• Pigments
• Appearance of colonies
• Change in texture

The Bad Guys: Food Pathogens

• Food pathogens are a subgroup of food spoilage organisms that can cause illness in humans.

Specific Food Pathogens

• Salmonella spp: Found in vegetables, eggs, chicken, and pork, it causes diarrhea, fever, stomach cramps, and vomiting.
• Listeria monocytogenes: Present in unpasteurized milk and dairy products as well as ready-to-eat deli meats, raw fruits, and vegetables; it can cause stiff neck, confusion, fever, and muscle aches, and may lead to stillbirths in pregnant women.
• Cyclospora: Linked to raspberries, basil, cilantro, snow peas, and mesclun lettuce (including Arugula, Spinach, Swiss Chard, Endive, Kale, Mustards, and Lettuces), it causes diarrhea, loss of appetite and weight, stomach cramps/pain, bloating, increased gas, nausea, and fatigue, with symptoms appearing about one week after infection.
• Campylobacter: Found in unpasteurized milk, chicken, shellfish, turkey, and water; its symptoms include diarrhea, cramps, fever, and vomiting.
• E. coli: Associated with contaminated food (undercooked beef, milk, raw fruits, and vegetables) and causes severe diarrhea and stomach pain.
• C. botulinum: Results from improperly canned foods and honey in infants, leading to muscle weakness, blurred vision, and potentially death.

The Good Guys: Useful Microorganisms in Food

• The growth of useful microorganisms is crucial for the preservation of certain fermented foods.
• Examples of foods made with useful microorganisms include:

Examples of microorganisms in food

• Beer
• Wine
• Yogurt
• Kefir
• Vinegar (Acetic acid bacteria; Acetobacter)
• Sauerkraut
• Kimchi

Beer

• Produced from grains (such as barley) and hops; beer provides a range of flavors from light and crisp to dark and malty.
• Brewing is similar to cooking which allows for the addition of various ingredients and spices.
• It can contain protein, fiber, B vitamins, folate, and niacin.
• It typically has a lower alcohol content than wine, with a standard serving containing about the same amount of alcohol as a standard glass of wine.
• It is is generally more affordable than wine, especially when comparing higher-quality wines.

Wine

• Wines are made from fermented grapes.
• Wines typically have a more acidic and fruity taste profile.
• Flavor varies based on the grape variety, aging, and winemaking techniques used.
• Because of its antioxidants, particularly flavonoids and tannins, red wine is believed to contribute to heart health.
• Alcohol content is typically higher than that of beer and a pint of beer has 50% more energy.

Yogurt

• Primarily contains Lactobacillus bulgaricus and Streptococcus thermophilus.
• Result of fermentation of yogurt starter cultures which are bacteria.
• Yogurt has Milder and sweeter taste characteristics.
• A thicker, spoonable consistency is typical.

Kefir

• Contains a wider variety of bacteria and yeasts, including Lactobacillus kefiri, Saccharomyces cerevisiae, and Saccharomyces unisporus.
• Result of fermentation of keffir grains which are a symbiotic culture of bacteria and yeast.
• Tangier and slightly sourer taste.
• Thinner, more drinkable consistency.

Sauerkraut

• Primarily uses cabbage, salt, and sometimes caraway seeds.
• Has a more tangy and sour taste.
• Typically ferments for longer than kimchi.
• It is typically shredded.

Kimchi

• Uses a wide variety of vegetables (like napa cabbage, radishes, cucumbers, etc.) and spices (like gochugaru chili powder, garlic, ginger, etc.).
• Can be spicy, salty, and tangy depending on the ingredients and fermentation time.
• It can be served in larger chunks.