Effect of Potassium Bisulphite as a Food Preservative
Published on Feb 21, 2020
The objective of this project is to Study of effect of Potassium bisulphite as a food preservative under various conditions
Growth of microorganisms in a food material can be inhibited by adding certain chemical substances. However the chemical substances should not be harmful to the human beings. Such chemical substances which are added to food materials to prevent their spoilage are known as chemical preservatives. In our country, two chemical preservatives which are permitted for use are:
1. Benzoic acid(or sodium benzoate)
2. Sulphur dioxide(or potassium bisulphite)
Benzoic acid or its sodium salt, sodium benzoate is commonly used for the preservation of food materials. For the preservation of fruits, fruit juices, squashes and jams sodium benzoate is used as preservative because it is soluble in water and hence easily mixes with the food product.
Potassium bisulphite is used for the preservation of colourless food materials such as fruit juices, squashes, apples and raw mango chutney. This is not used for preserving coloured food materials because Sulphur dioxide produced from this chemical is a bleaching powder. Potassium bisulphite on reaction with acid of the juice liberates Sulphur dioxide which is very effective in killing the harmful micro-organisms present in food and thus prevents it from getting spoiled.
HSO3–(aq) + H+(aq) H2O(l) + SO2(g)
The advantage of this method is that no harmful chemical is left in the food.
The aim of this project is to study the effect of potassium bisulphite as food preservative.
i. At different temperatures.
ii. At different concentrations and
iii. For different intervals of time.
1. Beaker, pestle and mortar, glass bottles, balance and peeler.
2. Fresh fruits, potassium bisulphite and sugar.
Food materials undergo natural changes due to temperature, time and enzymatic action and become unfit for consumption. These changes may be checked by adding small amounts of potassium bisulphite. The effectiveness of KHSO3 as preservative depends upon its concentration under different conditions which may be determined experimentally.
1. Take fresh fruits, wash them thoroughly with water and peel off their outer cover.
2. Grind it to a paste in the mortar with a pestle.
3. Mix with sugar and colouring matter.
4. The material so obtained is fruit jam. It may be used to study the effect of concentration of sugar and KHSO3, temperature and time.
(A) Effect of concentration of Sugar: -
1. Take three wide mouthed reagent bottles labeled as I II III.
2. Put 100 gms of fruit jam in each bottle.
3. Add 5.0 gms, 10.0 gms and 15.0 gms of sugar to bottle No. I, II and III respectively.
4. Add 0.5 gm of KHSO3 to each bottle.
5. Mix contents thoroughly with a stirring rod.
6. Close the bottle and allow them to stand for one week or 10 days at room temperature.
7. Observe the changes taking place in Jam every day.
The increase in concentration of sugar causes deterioration of fruit jam due to growth of fungus.
(B) Effect of concentration of KHSO3:–
1. Take bottles labeled as I, II, III.
2. Put 100 gm of Jam in each bottle.
3. Add 5.0 gm of sugar to each bottle.
4. Add 1.0 gm, 2.0 gm and 3.0 gm of KHSO3 to bottle No. I, II and III respectively.
5. Mix the contents thoroughly with a glass rod.
6. Keep all the bottles at room temperature for about 10 days and observe the changes everyday
The increase in concentration of KHSO3 increase more time of preservation
(C) Effect of temperature: –
1. Take 100 gm of Jam in three bottles lebelled as I, II and III.
2. Add 10.0 gm of sugar and 1.0 gm of KHSO3 to each bottle.
3. Mix the contents thoroughly with a stirring rod.
4. Keep bottle No. I in the refrigerator at 0˚C, bottle No. II at room temperature (25˚C) and bottle No. III in a thermostat at 50˚C. Observe the changes taking place in the jam for 10 days.
The increase in Temperature causes fast fermentation of jam
(D) Effect of time: –
1. Take three bottles and label them as I, II and III.
2. To each bottle add 25 g of Jam and 1 g of potassium bisulphite.
3. Keep bottle I for 7 days, bottle II for 14 days and bottle III for 21 days at room temperature.
4. Note the changes taking place in each bottle and record the observations.
With increase of days, the quality of the jam deteriorates
Food containing more amount of sugar is not favorable to keep for a long time Potassium bisulphite is a good preservative.
There are a number of uses for potassium bisulfite as a food preservative. The Manitoba Agriculture, Food and Rural Initiatives reports this product works to prevent the growth of mold, yeast and bacteria in foods. It is also an additive for homemade wine. Potassium bisulfate is found in some cold drinks and fruit juice concentrates. Sulfites are common preservatives in smoked or processed meats and dried fruits. In spray form, it may help prevent foods from discoloring or browning.
Potassium bisulfite is primarily a commercial product. You might find this chemical compound at meat processing plants. Manufacturers of juice drinks and concentrate will use potassium bisulfite to increase the shelf life of their products. The preservative is also available for home use. Sulphites such as potassium bisulfite can trigger an attack for those with asthma. potassium bisulfite may cause lung irritation.