Other Methods of Preserving Food - Science Project Experiment Idea. Science teachers can also use this as a food preservation or bacterial growth prevention lesson plan.
Other Methods of Preserving Food - Science Project Experiment Idea
Use made of heat in food preservation.A visit to a grocery store and observation of the rows of canned vegetables, fruits, and meats are sufficient to indicate the great use made of this method of preserving food.It is one of the chief agencies by which a regular and varied food supply is made possible.Without the modern methods of food preservation, cities such as New York, Philadelphia, and Chicago could not exist.
Experiment.Open a can of meat of some kind, permit some of the contents to be exposed to the air for a day.Put portions of the meat into two test tubes.Place one test tube in boiling water for an hour.Stopper both test tubes with corks, dipping the stoppered ends into melted paraffin to make them air-tight.Put the test tubes aside in a warm place for a few days.Result ?Conclusion ?
Pasteurization of Milk.As diseases may be transmitted by milk, the problem of destroying bacteria contained by it is of great importance.Tuberculosis, typhoid fever, scarlet fever, diphtheria, and very probably dysentery, are diseases spread by milk.The problem is rendered more difficult by the fact that boiling affects milk injuriously to some exterit, causing it to become less digestible.It has been found that by heating milk to a temperature of 142 to 145 degrees F. for at least thirty minutes, the pathogenic (disease-producing) germs will be killed without injuring the digestible qualities of the milk.This process is known as pasteurization.Hospital records show, however, that it is advisable to give orange juice to children whose diet is almost exclusively pasteurized milk.Otherwise, rickets (a disease of the bones) or another disease known as scurvy may develop.
Problem 8.Use made of other methods of food pres- ervation.What methods for preserving food in addition to use of cold and extreme heat can you think of?
The use of sugar to preserve food may be shown by the following experiment.
Experiment.Put some pieces of fruit into a test tube and cover loosely to prevent drying.Cover some similar pieces of fruit with melted sugar.Slightly heat the mixture of sugar and fruit, put into test tube and cover in the same way as the other tube was covered.Put both tubes aside in a warm place.Result ?Conclusion ?
Jellies and marmalades are examples of the use of sugar as a food preservative.From one of our experiments, what was your opinion as to the amount of sugar that should be used?If a smaller percentage is used, yeast will cause fermentation with resulting bubbles of gas and an odor of alcohol.Before canning became common, this method of preservation was much more used than at present.The large percentage of sugar causes some modification in the flavor of the food, and makes the material more of a sweet- meat than a fruit food.Condensed milk, which has come into such general use, remains unspoiled for a considerable time after the can has been opened because there has been added to it 30 to 40 per cent of sugar.
The use of salt as a food preservative is also very common.
Experiment.Put small pieces of fresh fish into two test tubes.Cover the fish in one tube with brine (a saturated mixture of salt and water).Put aside in a warm place.Result?Conclusion?
Although salt preserves food from decay, the flavor of the material is considerably changed and it is usually less easily digested than when fresh.In many cases it is wise to soak the salty food in water before it is prepared for the table.Meats and fish are frequently pre- served in brine.Eggs are also sometimes preserved in the same way.Salted butter can be kept fresh and of good flavor much longer than unsalted butter.Salt is used in connection with other methods of preservation such as drying and smoking.
Use of vinegar and spices.Name foods that you know are preserved in vinegar.Sauerkraut is cabbage which has produced in itself, by the process of fermentation, an acid similar to that of vinegar, which protects it from further decomposition.Most of the spices used in the home have some antiseptic properties.Mince-meat is a good example of the ability of spices to prevent decay.In the same way, the spices in sausages not only give a desirable flavor but also prevent rapid spoiling.Spices, however, are only mildly antiseptic and are consequently of little value in this respect except when used in cold weather.
Science Project Experiment Idea - Drying and smoking are other methods of Preserving foods Experiment.Put some raisins which have been soaked in water for a day into a test tube.Into another test tube put some unsoaked raisins.Put aside in a warm place.Result?Conclusion?
Next to canning, drying is the most important method of preserving food.Compare flour which has been kept dry with some which has been kept slightly moist for a week.In the same way compare bean and pea seeds and grains of corn and wheat which have been kept dry with the same kinds of seeds that have been soaked and permitted to remain moist.What is an advantage of hard-tack and crackers over bread?When fruits are completely dried, their flavor is largely lost.Those which contain a large percentage of sugar, such as grapes, prunes, peaches, figs, dates, currants, etc., may be preserved by the removal of only a limited portion of their water by drying.Why?
Meats are preserved on an immense scale by a combination of salting, drying, and smoking.Give examples.Milk is dried and put upon the market as a powder.When dissolved in water it has a flavor slightly different from that of fresh milk, but none of its nutritive properties has been lost.It possesses the advantages of occupying little space in transportation, and of being able to be kept indefinitely without decaying, souring, or molding.Evaporated milk has had a portion of its water removed, thus greatly reducing its bulk.
Briefly sum up the main points you have learned as to how to keep foods from spoiling, and why these methods are successful.
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