Preparation of Jam from locally available fruits and vegetables

Preparation of Jam from locally available fruits and vegetables

Jessica Dohtdong
Programme Assistant (Home Science)

Fruits and vegetables are an important nutritional requirement of human beings as these foods not only meet the qualitative needs to some extent but also supply vitamins and minerals which improve the quality of the diet and maintained health. It is therefore necessary to make them available for consumption throughout the year in fresh form or processed / preserved form. (Srivastava & Kumar, 2006). A large amount of food items, especially the perishable ones, are wasted every year due to improper storage condition which cause microbial spoilage and make the food unfit for human consumption. However , application of modern advances in most of the food processing and preservation techniques like preparation of jam, jelly and tuity fruity, etc. have led to elimination of microbial and toxicological hazards to a large extent in the preserved foods while maintaining their nutritional and sensory attributes. (Khetarpaul, 2012). Food processing is the set of methods and techniques used to transform raw ingredients into food or to transform food into other forms for consumption by humans or animals either in the home or by the food industry. (Gaur, 2012).

 

Preservation techniques like Jam, Jelly and tuity fruity are done by sugar. Syrup containing 66 percent or more of sugar do not ferment. Sugar absorbs most of the available water with the result that there is very little water for the growth of micro-organisms hence their multiplication is inhibited, and even those already present die out gradually. Dry sugar does not ferment. Thus sugar acts as a preservative by osmosis and not as a true poison for microorganisms. Fruit syrup, Jam, Jelly, Marmalade, Preserve Candy, crystallised fruits and glazed fruits are preserved by sugar. (Srivastava & Kumar, 2006).

 

Preparation of Jam

Jam is a product made by boiling fruit pulp with sufficient sugar to a reasonably thick consistency, firm enough to hold the fruit tissues in position. Aonla (Gooseberry), Apple, Guava, Mango, Plum, Peach, Pear, Papaya, Sapota (Chiku), Pineapple, etc. can be used for preparation of Jams. Jam can be prepared from one kind of fruit or from two or more kinds. Jam contains 0.5 to 0.6 percent acids and invert sugar should not be more than 40 percent. (Srivastava & Kumar, 2006).

 

Recipes for preparing jam at home:

In the home Jam can be prepared by referring the recipes as given in table1.

 

Method of Jam Preparation:

1. Selection of fruits: Select ripe firm fruits

2. Washing: Wash the fruits with water properly

3. Peeling: Remove the fruit peel

4. Pulping: Extract the fruit pulp by grating or grinding

5. Addition of sugar: Add the required sugar to the pulp

6. Boiling: Add the required water to the pulp and start boiling. Stir the pulp continuously while boiling

7. Addition of citric acid: When the mixture starts boiling add citric acid to the mixture and stir properly and continuously to avoid burning and sticking

8. Judging of end points: When a thick consistency is seen, you can judge the end point by taking a plate test
(* take a small portion of jam on a plate, let it cool down then tilt the plate to one side. If the jam float collectively as one then the jam has reach the end point. If the jam float as a continuously syrup then it has not reach the end point and requires more boiling.)

9. Filling hot into sterilized bottles: When the Jam has reached the end point, fill the jam in clean sterilized bottles

10. Cooling: Cool down the bottles let the steam escape from the jam bottles

11. Capping: When the jam is cool, capped the bottle tightly

12. Storage: Store the Jam in cool dry place or in an ambient temperature. (Srivastava & Kumar, 2006)

 

Problems in jam production:

i) Crystallization: Final product should contain 30 to 50 percent invert sugar. If the percentage is less than 30 percent, cane sugar may crystallize out on storage and if it is more than 50 percent the jam will become a honey like mass due to formation of small crystals of glucose. Corn syrup or glucose may be added along with cane sugar to avoid crystallization.

 

ii) Sticky or gummy Jam: Because of high percentage of total soluble solids, jams tend to become gummy or sticky. This problem can be solved by addition of pectin or citric acid or both.

 

iii) Premature Setting: This is due to low total soluble solids and high pectin content in jam and can be prevented by adding more sugar. If this cannot be done a small quantity of sodium bicarbonate is added to reduce the acidity and thus prevent pre-coagulation.

 

iv) Surface graining and shrinkage: This is caused by evaporation of moisture during storage of jam. Storing in cool place can reduce it.

 

v) Microbial spoilage: Sometimes moulds may spoil the jam during storage but they are destroyed if exposed to less than 90 percent humidity. Hence, jam should be stored at 80 percent humidity. Mould growth can also be prevented by not sealing the filled jar and covering the surface of jam with a disc of wax paper because mould does not grow under open conditions as rapidly as in a closed place. It is also advisable to add 40ppm sulphur dioxide in the form of KMS. In case of cans, sulphur dioxide should not be added to jam as it causes blackening of the internal surface of the can. (Srivastava & Kumar, 2006).

 

Conclusion:

There is a considerable scope for selling preserves jam. Since these products are hygroscopic, water proof packaging like metal, glass containers which are impermeable to water vapour should be used. Plastic pouches are better packaging material for exporting and transportation of such products for income generating. Newer flexible plastic films like standing poly pouches would be cheap and highly effective. There is need for exploring the possibilities of utilizing various types of plastics for packaging of such products (Meininger, 18th December, 2013).