Objective: To make apple jam

Background: Jams are made using the pulp of fruits while jellies are made using the juice. In this lab, you will be making apple jam. That means you will use the pulp of apples, or apples that are finely shredded or chopped. Three other key ingredients are needed. These include pectin, sugar, water and fruit acid. Pectin is a long chain-like polysaccharide that is naturally found in plants, especially in fruits. They help to provide structure in the plant. During spoilage, pectin breaks down causing fruits to get soft. When making jam, you may either use fruits that are naturally high in pectin or add commercial pectin. Apple is one of those fruits that is naturally high in pectin but the pectin is concentrated in the skin and the core, which we don’t normally include in the jam. We could use commercial pectin to compensate for removing the skin and core, but in this lab I will have you extract the pectin first and then add it back to the formula. In that way nothing is lost and you do not have to spend extra money buying pectin if you don’t have any at home. Because of its long chains, pectin act like a net, grabbing the other components of the jam together to form a firm gel. Sugar is a preservative and sweetener as you know, but in jams it has another function. It helps to trap water and while it does so, it pulls the pectin together. Think of the sugar as a kind of belt pulling the pectin closer to each other, giving you a firmer gel. Water is a universal solvent, it is what dissolves everything out and without it you will not have a proper gel. If there is too much water, the gel is watery and if there is too little, the sugar will crystalize back out of solution, giving you a grainy jam. In some jam formulas, it may not even be necessary to add water since the fruit has enough already. What about the fruit acid? If the fruit is naturally acidic (you usually know from the sour taste) there is no need to add acid but if not, lime juice, lemon juice or citric acid is added. Adding acid not only makes the jam taste better but it is essential in getting the pectin to work. That is because pectin above a pH of 4 has a negative charge. You know what happens when negative and negative charge comes together. They repel, right? Yes. So, what the acid does is to lower the pH below 4.0 which neutralizes this negative charge so that there is no negative repelling charge. In that way, the pectin can do its job as a “bridge” connecting and pulling everything together in a nice gel. 

What is pectin? | Food ingredients | Silvateam

Pectin structure

Materials

  1. Apples
  2. Table sugar
  3. Lime, lemon, or their juices
  4. Pectin (optional – Use a table spoon if you plan to skip the pectin extraction step)
  5. Water 
  6. Cinnamon powder (optional)
  7. Jam jars (or other container you have)
  8. Jam funnel (optional)
  9. Pot
  10. Stove
  11. Mixing spoon

Method

Pectin Extraction

  1. Select five large apples. Note: Greener ones have more pectin so they will be more desirable. Make sure they are mature though
  2. Peel the apples and remove core
  3. Remove seeds from core and discard seeds 
  4. Collect the peel and seedless core in a pot
  5. Add 3 cups of water and bring to boil
  6. Once boiling, lower temperature and let simmer for 40 minutes
  7. Remove from stove and strain through a fine strainer

Jam

  1. Cut up apples in fine pieces or optionally you may shred or pulp them
  2. Collect apple in a pot
  3. Add and combine, 2.5 cups sugar, 1/4 cup lime juice, 1/2 of the pectin juice you extracted (you can freeze the rest to make other jams in the future), and 1/4 t-spoon of cinnamon powder
  4. Cook while stirring intermittently to prevent sticking at the bottom. You know the jam is ready to bottle when it forms a firm lump when you drop it in a glass of cold water. It is not ready if it disintegrates while falling in the water. You can also put the jam on a cold plate and then lean the plate at an angle. The jam should stay in place or flow slowly. If it is runny, it is not ready.
  5. Once the jam is set, pour and seal in jam jars or containers you have available. The yield should be approximately two 8-oz jars
  6. Leave to cool overnight
  7. Open the next day and enjoy!

Courtney Simons
Administrator
Courtney Simons is a food science professor. He holds a BS degree in food science and a Ph.D. in cereal science from North Dakota State University.
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