Preservation Power of Honey

Discuss with a partner Why does food spoil? What conditions make this more likely? Why does food spoil or go bad? (Microbial growth, usually from bacteria) What conditions make this more likely to happen? (Unsanitary conditions, when food is kept in conditions favorable for bacterial growth (temperature, moisture, etc.) when food is not cooked thoroughly enough)

How do we prevent the following foods from spoiling? Beef jerky Bread Milk Pickles Raw steak Cucumber Cupcakes Croutons Twinkies Discuss removing water (dehydration), keeping out air (sealing), refrigeration, increasing acidity (adding vinegar), and adding preservatives.

What does bacterial growth look like? Petri dishes with growth medium Bacteria growing in a petri dish Bacteria is all around us, but bacteria is so tiny it’s hard to see. However, if we provide a food source, proper growing conditions, and enough time, we can grow large colonies of bacteria in the laboratory allowing us to observe bacteria in a controlled setting.

What is a zone of inhibition? Bacteria is evenly applied to growth medium in a petri dish Antibiotic discs are added Petri dish is incubated to promote bacterial growth Zone of inhibition: the area around the disc that contains no bacterial growth Antibiotic disc Bacteria growing No bacteria growing

Measuring effectiveness of antibiotics Antibiotics are not equally effective against all types of bacteria. Some work better than others. How might we judge if antibiotics are effective or not? How might we judge if antibiotics are effective or not? Measuring and comparing the zones of inhibition for different antibiotics is one way

Measuring a zone of inhibition Use a metric ruler to measure the diameter of the empty area surrounding the disc in millimeters If no bacterial growth was inhibited, report the size of the disc What are the sizes of zones of inhibition pictured here? What are the sizes of zones of inhibition pictured here? Zone of inhibition on the left is 6mm Zone of inhibition on the right is 17 mm

Honey What have we learned about honey? How can we apply what we learned to benefit society? What we have learned? Honey has antibacterial properties demonstrated in the lab, these properties are greater with higher concentrations of honey. How can we apply what we learned to benefit society? Honey could be used as a wound dressing to help prevent bacteria from growing during the healing process. Honey might also be added to foods to assist in preserving them when other preservation practices are not available (such as refrigeration)

Turbidity What is turbidity? How does measuring turbidity help us to determine bacterial growth in milk? What is turbity? (a measure of how clear a liquid is) How does measuring turbidity help us to determine bacteria growth in milk? (turbidity is an indicator of bacterial presence; the cloudier a liquid is, the higher the turbidity, the more bacterial is assumed to be present)

Image credits Milk: https://pixabay.com/en/milk-glass-drink-fresh-beverage-435295/ "Good Food Display - NCI Visuals Online" by Unknown - This image was released by the National Cancer Institute, an agency part of the National Institutes of Health, with the ID 2397. Licensed under Public Domain via Commons - https://commons.wikimedia.org/wiki/File:Good_Food_Display_- _NCI_Visuals_Online.jpg#/media/File:Good_Food_Display_-_NCI_Visuals_Online.jpg "Agar Plate" by Y tambe - Y tambe's file. Licensed under CC BY-SA 3.0 via Commons - https://commons.wikimedia.org/wiki/File:Agar_Plate.jpg#/media/File:Agar_Plate.jpg "Agar plate with colonies". Licensed under Public Domain via Commons - https://commons.wikimedia.org/wiki/File:Agar_plate_with_colonies.jpg#/media/File:Agar_plate_with_colonies.jp g "Bacterial lawn 01". Licensed under Public Domain via Commons - https://commons.wikimedia.org/wiki/File:Bacterial_lawn_01.jpg#/media/File:Bacterial_lawn_01.jpg Ruler: http://biologyasifitmattered.blogspot.com/2011/09/how-to-use-microscope-at-our-school-we.html Measuring zones of inhibition: http://www.cdc.gov/std/gonorrhea/lab/diskdiff.htm "Runny hunny" by Scott Bauer, USDA ARS. Licensed under Public Domain via Commons - https://commons.wikimedia.org/wiki/File:Runny_hunny.jpg#/media/File:Runny_hunny.jpg Turbidity vials: http://water.usgs.gov/edu/turbidity.html