Food And Fermentation Part 2

Food And Fermentation Part 2

• Course: SC/NATS1560 3.0 Understanding Food
• Instructor: Dr. Angela Cope
• Year: 2024

Learning Objectives

• Describe alcoholic fermentation, defining "wild yeasts" and identifying the most common microorganism used (Saccharomyces cerevisiae).
• Detail common drinks and foods made via alcoholic fermentation, their raw materials, and processing methods. Examples include wine, beer, and bread.

Alcoholic Fermentation

• Yeasts convert sugars into ethyl alcohol and carbon dioxide.
• Ethyl alcohol (ethanol) is a psychoactive substance and narcotic.
• Moderate amounts cause mild inebriation; larger amounts lead to intoxication and addiction.
• It's an antiseptic, killing harmful microbes.
• "Wild yeasts" or natural starters are also used.

Wine I

• Primarily from Vitis vinifera grapes (over 1300 varieties).
• Examples: Cabernet Sauvignon, Merlot, Pinot Noir, Syrah, Grenache, etc.
• "Terroir" (place of origin) influences distinctive character.
• Alcohol content: 8%-14% ABV.
• Also made from other fruits (e.g., cherries, dates, apples, pears).

Wine II (Vinification)

• Grapes are crushed into must.
• Wild yeasts or Saccharomyces cerevisiae convert sugars into CO₂, ethanol, and aromatic molecules.
• Skins are steeped to give wine colour and stronger flavours.
• Wine is racked to remove dregs (dead yeasts and skins).
• Filtered and fined.
• Aging in oak casks imparts complexity to flavour.
• Finest wines can age up to 30-40 years.

Test Review - Microorganism

• Most used microorganism for alcoholic fermentation: Saccharomyces cerevisiae.

Test Review - Wine Character

• Contributing factors to wine's distinctive character: Terroir, steeping of grape skins, and aging in casks.

Beer

• Made from grains (barley, wheat, oats, rice, corn).
• Grains become malt through sprouting and kilning.
• Amylase enzymes convert starch into sugars.
• Hops are added to the wort for flavour.
• Yeast converts sugars into CO₂ and alcohol.
• Alcohol content: 4-5% (up to 10%).
• Ale: warm brewing (21-25°C), top fermentation with Saccharomyces cerevisiae.
• Lager: bottom fermentation (6-8°C), Saccharomyces uvarum.

Brewing Beer (Process)

• Malting the grains
• Kilning and grounding the malt
• Mashing the malt
• Adding hops and boiling the wort
• Adding yeast and fermenting
• Conditioning (re-fermenting, fining, centrifuging).

Test Review - Lager vs. Ale

• Key differences between lager and ale include bottom vs. top fermentation, cold vs. warm brewing, and differing yeast species (Saccharomyces uvarum vs. Saccharomyces cerevisiae).

Bread

• Made from milled grains (flour).
• Hard wheat has high gluten content (glutenin and gliadin).
• Amylase breaks down some starch into sugars.
• Flour + water = dough.
• Glutenin + gliadin form gluten, making dough elastic.
• Kneading develops gluten structure.
• Leavening using yeast (wild or Saccharomyces cerevisiae).
• Yeast converts sugars into CO₂ and alcohol, causing dough to rise.

(Butt) Bread

• Heat solidifies stretched dough.
• Sourdough uses a starter containing wild yeasts and lactic acid bacteria.
• Baking completes and stops fermentation.
• Surface water evaporation and Maillard reactions form crust and crumb.

Unfermented Breads

• Unleavened flatbreads include matzo, lavash, rotis, etc.
• Made from corn flour, and others.
• Quick breads are leavened by CO₂ producing chemical reactions without fermentation.
• Examples: cakes, scones, cookies, pastries, biscuits.
• Chemical leavening agents include baking powder, baking soda, and ammonia salts.

Test Review - Sourdough vs. Non-Sourdough Bread

• Sourdough bread uses a starter (wild yeasts and lactic acid bacteria) to leaven.
• Non-sourdough bread doesn't use a starter as it is typically leavened with other techniques like chemical leavening.

Home Review

• Milk curdling and its relation to cheese production.
• Mold's effect on cheese.
• Three examples of each main type of fermentation.
• Malt and its use in beer brewing.
• Key differences between wine and beer brewing.