Understanding Acids and Bases in Food Science

1. Chp. 10 Acids & Bases FOOD SCIENCE

2. What do you think of when you hear the term “acid?” • Acids are used in the Chemistry lab. • Lime juice & vinegar contain acids; • acids are also found in chlorine bleach & car batteries. • Antacids, blood, household cleaners and baking soda are all ex. of bases. • So what makes a substance an acid or a base?

3. Ionization of Water • Ionization- is the process of forming ions in water solution. • When water ionizes, both hydrogen (H+) and hydroxide (OH-)ions are produced. • Hydrogen ions are hydrogen atoms that have lost their electron and become positively charged. Hydrogen ion carries a plus sign (H+). Hydroxide ions are composed of 1 oxygen atom bonded to 1 hydrogen atom. They have a negative charge (OH-).

4. All water contains some hydrogen ions and some hydroxide ions. • Pure water has an equal number of hydrogen & hydroxide ions, so it is said to be neutral. • So then, hydrogen ions & hydroxide ions are products of ionization, can combine to form H2O, & carry opposite charges.

5. Defining Acids & Bases • When some substances dissolve in H2O, they release hydrogen ions, while others release hydroxide ions. • Acids contain H+. When acids dissolve in water, their molecules break apart and release hydrogen ions into the solution. • Bases are the chemical opposite, they release hydroxide ions into the solution. • Some compounds that dissolve in H2O are neither acids nor bases.

6. Strength of Acids & Bases • Strong acids and bases are said to ionize completely when they dissolve in water. • When acid molecules are added to a solution, nearly all of the acid molecules break apart and release hydrogen ions into the solution. • When basic molecules are added to a solution, nearly all of the basic molecules break apart and release hydroxide ions into the solution. • Ex. HCL separates into H+ & Cl- in water solution. Hydrochloric acid is a strong acid.

7. In weaker acids, like acetic acid (vinegar), only a small fraction of molecules ionize in water. • Ex. Hydrochloric acid- it ionized completely in H2O, so it’s a strong acid.

8. Neutralization of Acids & Bases • What happens when you mix an acid with a base? The solution either becomes less acidic or less basic. • If you add enough base to a solution, the solution eventually becomes neutral. • Neutralization- a chemical reaction in which hydrogen ions from an acid react with hydroxide ions from a base to produce water molecules. • H+ + OH- H2O

9. General Properties of Acids & Bases • Acids & bases have distinct properties. • The intensity of these properties varies according to the quantity of hydrogen ions or hydroxide ions released in solution. • Acids- Sour describes how acids taste. The citric acid in a lemon or grapefruit is an ex. of acidic tartness. Acids can change the color of some foods and some flowers. • Bases- Taste bitter. Milk of magnesia is an example. Bases can be slippery, ex. Bar soap. Glass cleaner make windows slick.

10. 1. What happens when water ionizes? When water ionizes, both hydrogen (H+) and hydroxide (OH-) ions are produced. H2O H+ + OH- • 2. What is the difference between strong & weak when referring to acids & bases? Strong acids & bases ionize completely when they dissolve in water. In weak acids or bases, only a small fraction of molecules ionize in water.

11. 3. Compare the general properties of acids & bases. Acids- taste sour, some ex. are the citric acid in lemon or grapefruit, can change the color of food and some flowers. Bases- taste bitter, ex. Magnesium hydroxide (Milk of Magnesia), bar soap that is slippery in the shower, glass cleaners that contain ammonia that make windows slick.

12. THE PH SCALE • A mathematical scale in which the concentration of hydrogen ions in solution is expressed as a number from 0-14. This scale indicates the relative number of hydrogen & hydroxide ions in a solution. • pH of 7 is neutral. When a solution is neutral, the number of H+ ions = number of OH-. Acidic & basic properties disappear. • Greater acidity results in values less than 7. Therefore a solution that has a pH less than 7 contains more free H+ ions than free OH- ions.

13. Values above 7 are basic and indicates a greater ratio of OH- ions than H+ ions in a solution. • Strong bases can be just as strong as strong acids. Ex. Sodium hydroxide (drain opener), bleach is a base.

14. Measuring ph • pH meter can be used by a scientist to measure the exact pH of a solution. • Another way to measure pH is with an indicator- a substance that changes color depending on the pH. The dry indicator paper is dipped in the solution and its color is compared with a scale that matches with pH values.

15. pH indicators give less exact results than pH meters. • Indicators used for labs are commercially prepared. • Anthocyanins- are pigments in food that give the color of blue or red. In acid solutions, anthocyanins turn red, but in basic solution solutions they stay blue. In neutral solutions, they turn light violet or colorless. • Litmus paper works the same way.

16. Acids & Bases in Foods • Working with foods that contain bases poses no health hazard. • Food acids are not a health problem. • Food acids help prevent spoilage, ex. Pickles keep fresh longer than cucumbers. Vinegar lowers the pH. • Almost no food ingredient has a pH of exactly 7. • The pH balance is important to making baked goods rise.

17. Blood pH • The pH of foods in your diet has no effect on blood chemistry. • The body regulates pH through a system of buffers that holds the pH of blood steady at a slightly basic 7.4. Buffers play a role in blood chemistry to keep blood at a constant pH. • Buffers- substances that help maintain a balance of H+ and OH- ions in a solution. • Alkalosis- a blood pH of 7.6 or higher. • Acidosis- a blood pH of 7.2 or lower • Untreated, both can lead to dull breathing reflex, leading to fatigue, confusion, coma, and possibly death.

18. Acidosis • May be caused by low blood sugar (like with Diabetes), too much alcohol, liver failure, aspirin poisoning, etc.) • There is too much acid in the blood and your kidneys cannot remove it. • Severe acidosis can cause fast breathing, as well as confusion and headaches and ultimately lead to a fatal coma.

19. Alkalosis • Too much base in your blood. • May be caused by liver disease, lung disease, fever, lack of oxygen. • Causes nausea, vomiting, muscle spasms. • Can lead to a coma, electrolyte imbalance, and arrhythmias.

20. Digestive Juices • The digestive system relies on a variety of pH levels to break down foods & nutrients. • Digesting protein in the stomach requires a highly acidic environment. • Gastric acid, which is mostly hydrochloric acid, has a pH around 2. Its release in the stomach is regulated to maintain an overall stomach pH between 1.5 & 1.7. • As food moves from the stomach to the small intestine, basic body fluids are secreted to reduce the acidity of the digested food.

21. Cleaning Pennies using Acids found in foods • Purpose: The purpose of this experiment is to find out which of several household foods can most effectively remove tarnish off of pennies. Furthermore, the products have been chosen based on their acid/base Ph level, which should yield information on which is better for the cleansing of pennies.

22. Hypothesis: The hypothesis of this experiment is that the stronger the acidity of the solution, the better it will remove the tarnish off pennies. The rational is that tarnish is a sign of oxidation, whereas, acids release H+ ions which will combine with the oxidation on the pennies, and therefore remove the tarnish, whereas, bases remove H+ from a solution, and henceforth, will have little effect on the pennies.

23. Procedure:Into each cup place 3 pennies, in one cup add lemon juice, the next add pickle juice, vinegar in the next cup, and continue with each food substance. Shake and stir each of the cups to allow the chemicals to have an effect on the pennies, after 10 or so minutes, remove the pennies from the cups, rinse & dry and compare against the other food items.

24. Observation Sheet • Record your observations and include the pH of each of the food items used. Use your textbook to look up the pH of the food item. • Compare the cleaning power of hot sauce, lemon juice, tomato sauce, vinegar, Coke, orange juice and pickle juice on tarnished pennies. Which is the most effective and why?