More recent food and nutrition questions and answers

Food and nutrition

Liquid loss during fruit processing

What causes my jars of fruit to lose liquid when I process them?

Loss of liquid during processing fruits may be caused by

Filling jars too full.
Failure to work out air bubbles from jars before processing.
Jars less likely to lose liquid if contents are packed hot rather than raw.
Jars not covered with 1-2 inches of water in boiling-water canner throughout processing period.
Too much headspace.

Jars of food that have lost liquid during processing are safe to eat if no signs of spoilage are present. Do not open these jars to add more liquid after processing.

Mary Schroepfer
Nutrition Specialist
Franklin County and East Central Region

Crystals in jelly

I have made apple jelly and mango jam without using pectin. On both occasions the sugar crystalized. Why is this? How do avoid this next time I make jam?

Crystals throughout the jelly may be caused by too much sugar in the jelly mixture or cooking the mixture too little, too slowly, or too long. Crystals that form at the top of jelly that has been opened and allowed to stand are caused by evaporation of the liquid. Undissolved sugar sticking to the sides of the pan may also be a source of crystals in jelly. A few crystals usually remain in freezer jam.

Barbara Willenberg
Nutritional Sciences

Freezing raspberries to make jelly

I have a small raspberry patch and would like to make jelly from my raspberries. I usually don't have enough berries at a picking to yeild enough for a batch. Is it okay to boil down the berries and freeze the juice until I have enough to make several batches at once? If so, how long is the juice good in the freezer?

Fruit can be frozen and made into jam or jelly later. The best fruits for this purpose are blueberries; red and black currants; gooseberries; and rhubarb. Accurate measurements are important in jam making. Some fruits, after being frozen, tend to collapse on thawing. This makes it difficult to measure the fruit accurately. For this reason, it is wise to pack measured quantities and then label them. Do not add any sugar to fruit which is being frozen for jam or jelly making. All the fruits listed above freeze well without sugar. When making jam or jelly from frozen fruit, thaw the fruit in the refrigerator until only a few ice crystals remain. Then follow directions for the type of product you wish to make. Unsweetened juices can be frozen for later use in jelly-making. Use 1/4 underripe and 3/4 ripe fruit.

Barbara Willenberg
Nutritional Sciences

Foil or plastic

Which will keep things colder foil or plastic?

In general, plastic is a better insulator than foil. You could confirm this looking up the heat capacity of the two materials in a standard engineering handbook.

Douglas L. Holt
Food Science Program
State Extension Specialist for Food Safety

Potassium sorbate in baked goods

What is the potassium sorbate percentage in biscuits or cake?

Potassium sorbate is not usually added to biscuits, but you could I suppose. The allowed use level in the United States is 0.1 percent by weight.

Douglas L. Holt
Food Science Program
State Extension Specialist for Food Safety

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Updated 8/4/05