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Drying and fermentation

methods of preservationMadhushree.A

MK 819


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Introduction

Drying means the removal of water. It isused for drying under the influence ofnon-conventional energy like sun and

wind. Microorganisms need moisture to grow so

when the concentration of water in thefood is brought down below a certainlevel, they are unable to grow. Hencethrough drying we can preserve the food.


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Factors affecting the rate of drying:-

Composition of raw material

Size, shape and arrangement of stackingof produce

Temperature as well as humidity and

velocity of air Pressure

Heat transfer to surface.


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Advantages Drying has some advantages compared to

other methods of preservation: The weight of a produce is reduced to

1/4th to 1/9th its original or fresh weight

and thus the cost of its transport isreduced.

Due to reduction in bulk of the product, itrecords less storage space.

Cost of processing is very low, as lesslabour and no sugar is required.


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Types of drying

There are three basic types of dryingprocess:

sun drying, solar drying Atmospheric drying including batch and

continuous

Sub-atmospheric dehydration.


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Steps for drying of fruits andvegetables

1. Fruits/ vegetables(mature and free frominsects and diseases)

2. Washing3. Peeling

4. Preparation5. Blanching6. Spreading on flat wooden trays7. Sulphuring

8. Drying/dehydration9. Sweating10. Packing(air tight container)11. storage


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Spoilage of dried productsdefects causes prevention

moulding high productmoisture

Reduce watercontent down tooptimum values.Pack in air tightpackages.

infestation Presence in driedproducts of larvaeor insects.

Fumigation ofpacked productsand of package.disinfection by heatof products before

packing.Browning Chemical reactions Reduce as much as

possible watercontent. store atlow temperature.

Reducedreh dration ratio

Too hightem erature in final

Operate inside finaltem erature as


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Some common driers used for drying are:

Air convention driers

Drum or Roller driers

Vacuum driers


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Fermentation

Decomposition of carbohydrates byMicroorganisms or enzymes is calledfermentation.

Fermentation of food results in theproduction of organic acids, alcohol, etc.which not only help in preserving the food

but may also produce distinctive new foodproducts.


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Acetic , lactic and alcoholic are thethree important kinds of fermentation

involved in fruit and vegetable preservation.Some industrial fermentations in fruit andvegetable industries are

a. Acetic acid fermentation(acetic andbacteria)

b. lactic acid fermentation (lactic acidbacteria)

c. alcoholic fermentation(yeasts)


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Reference:

Fruit and vegetable preservation

principles and practices

--R P Srivastava Sanjeevkumar


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