biology lab 2

Brix Refractometer Food Lab-

List of lab equipment needed for the lab-

· portable refractometer

· Pipettes

· deionized water & kim wipes

· Kitchen knives

· Garlic Press to squeeze juice out of the food

· Mortar and Pestle to crush food into solution

Food Items Need

A variety of fruits and vegetables-

· ripe bananas, unripe bananas, oranges, tomatoes, tomato sauce, kiwi, apples

A variety of beverages-

· fruit juices, sodas diet vs regular, gatorade, milk, soymilk, almond milk

Background Science-

The maturation of fruits or Fruit Ripening-

· Is a sophisticated Epigenetic dance that has evolved over millions of years. Thousands of genes control the accumulation of sugars, acids, pigments, and other fruit volatiles.

· Fruits (seeds that are enclosed within an ovary)  are a distinctive characteristic of Angiosperms (the scientific name for flowering plants) the most diverse group of land plants on the planet with over 260,000 living species.   

· vs Gymnosperms that have “naked” seeds on the surface of scales or leaves (pine cones)

· In fleshy fruits, ripening results when genes are expressed that produce of a succulent sugar, flavorful compounds, colorful antioxidants, and a soft pericarp to attract animals for seed dispersal.  

http://www.education.com/science-fair/article/measure-sugar-ripe-fruit/

“The ripening of fruit is a complex procedure. Release of ethylene gas triggers whole families of enzymes, including amylases, kinases, hydrolases and pectinases to work their magic and neutralize acids, form anthocyanins that give colors to fruit, and soften hard, inedible fruits into toothsome, delicious ones. One critical element of the ripening involves the conversion of starches to sugars. Farmer use refractometers to use monitor this process and measure sugar content. This helps them know when to harvest crops.”

Flavor Science- thousands of volatile food compounds combine to give food its flavor.

· To survive our human & prehuman ancestors developed a highly sophisticated sense of taste.

· At the same time plants developed a wide variety of chemical compounds to prevent or encourage different animals to consume their fruit and distribute their seeds.   

· These compounds are characterized by their odor, volatility, and chemical properties.

· We naturally select for different combinations of these compounds when we choose what smells and tastes good to us, and decide what makes us healthy and feel good.

· For decades the food industry has added salt,  sugar, and artificial flavors to processed food to override our highly developed sense of taste and flavor.

· Due to push back from consumers the food industry is now trying to utilize natural flavor compounds found in food and reduce the amount of sugar, salt, and other additives in food.

Key Terms-

Use Google to explain how each of these terms are involved in the ripening of food.

Ethylene Gas-

Enzymes-

Pericarp-

Conversion of starches to sugars-

Volatile Compounds in Food (VCF)-

Abscission Zone-

Flavor Science-

Real World Things to Remember-

1. An infection of bacteria or fungi on the fruit can also accelerate fruit ripening and spoilage.

2. A wound, dent, or bruise will cause rapid ethylene production.

· This means that simply picking the fruit will often signal it to ripen

Five Important Enzymes Activated by Ethylene

http://plantphys.info/plants_human/fruitgrowripe.shtml  

Videos to watch to help you understand Brix Testing-

· Brix testing video- in brewing https://youtu.be/Qd9uJ9JitJw

· Food Quality Brix Testing- refractometer tutorial https://youtu.be/-GCpIp_xt_4

· How to calibrate an Brix optical refractometer-   https://youtu.be/hVceiuWZufI

Lab Procedure-

1. Practice using your pipette so you can accurately transfer liquids to the refractometer

a. First test your accuracy and the calibration of the pipette by transferring 1 ml of regular water to a weigh boat on a scale- (Each ml should weigh 1 gram)

i. To Do this- set a p1000 pipette to 1.00 and practice 5 times.

0. Calibrate your refractometer- make sure the refractometer reads 0 with deionized water.

a. Find a p200 pipette and transfer 200µl to the scale to be sure it is accurate. (should read .2 grams)

b. Transfer 200µl of deionized water to the refractometer’s plastic prism

c. Look into the eyepiece and make sure it reads zero with deionized water.  

0. Create a Google Sheet  to record your brix testing results.

a. The foods tested go down the rows in column 1. (Each person should test at least 20 foods total).

b. Create a column to describe each food or beverage before you perform your brix tests.

c. Create a column to describe the taste of each food if you can taste the food.

d. Create a column for each of the members of your group to record their brix value.

e. Create a column for your average brix value.

f. Create a column to explain your results and compare them to brix value charts .

g. Create a column for post lab analysis to discuss if any results surprised you and why.

After the Google Sheet has been created for the group all group members need to create their own copy of the document to record your own descriptions of the food and explanations of your brix results.

Before you begin testing

· Ensure that every person in the group will perform their own brix test on each of the food tested.

· Be sure to handle the refractometer with care and only use water and kimwipes to clean the plastic prism between tests. These are your professors personal brix testers and the plastic prism scratches easily.

0. Perform Brix tests on at least 10 different beverages-

a. It only takes 2 drops- Use a pipette to transfer 0.2 ml (200µl) to the refractometer’s plastic prism.

0. Using kitchen knives, the garlic press, and the mortar and pestle- prepare a variety of real food solutions and perform Brix tests on at least 10 Fruits and Vegetables

a. If possible- test the juices from the food first before you crush and blend the rest of the food into a whole food solution to test. (For Example- squeeze some orange or tomato juice out of the fruit to pipet onto the viewing slide of the refractometer before crushing the entire orange and pulp and seeds into the juice.) This way you can effectively test the brix value of both.

a. If you had to add deionized water to your food to bring your food to a liquid solution be sure to record both the weight of the food and how much water you added so you can determine the concentration of the food you tested.  For example- you might need to add water to bring kale & bananas into a testable solution.

6. Compare your brix value test to the expected brix value for the type of food you are testing http://www.healthy-vegetable-gardening.com/brix-scale.html

1. Note if the food you tested is Poor, Average, Good, or Excellent

1. What exactly does the brix value tell you about the food you tested.

Post Lab Analysis Questions-

Why would bruises or defects in the fruit or vegetable affect the brix readings of the food being tested?

Do your brix test results indicate any difference between fruit juice and the whole food solution?

How does this relate to the fact that whole foods are nutritionally better for you than the juices or extracts?

Some people actually take brix testers along with them to farmer’s markets to test the produce they purchase.

Would you want to be looking for when testing foods at the farmer’s market?

Target is going one step farther- Using handheld mass spec devices to test all types of food.

Target’s Future of Food Project-

http://www.cbsnews.com/news/target-teams-up-with-researchers-to-create-machine-that-scans-information-of-food/

After watching this video- what are your thoughts on food transparency?

Here are some notes to guide you-

What Target and The Future of Food wants to bring to the consumer-

1. The Nutritional Understanding of Food

2. Access to Quality Food and the Reduction of Waste.

3. Food Transparency and Trust

What a handheld food spectrometer can tell us-

· Nutrient content and nutritional value

· Pesticide and herbicide levels

· How long it has been stored and current shelf life

· How ripe it is and possibly how ripe it was when it was picked.

Dig Deeper into Flavor and Food Transparency-

1. Research the Science of Flavor-

· Use this link and other you find to in 2 complete paragraphs- describe how our sense of taste influences what we eat and how different flavors interact and combine. http://www.seriouseats.com/2016/07/how-do-we-taste-salt-sour-acid-sweet-bitter-flavor.html

· Be sure to cite your sources.

0. Research “food transparency” and put your thoughts together into 1-2 paragraphs that sums up- Why it is important, where food transparency is today, and where you think we will be in the future.