Dehydration Process of Garlic

Garlic (Allium sativum Linn.), commonly called bawang, belongs to the liliaceae or sibuyas family. It is an annual herb consisting mainly of a bulb, also called head, which in turn is divided into several sections called cloves. Each clove has a separate skin or peel that is usually removed before using.

Propagation

Garlic is propagated by bulbs and planted after the rainy season, from September to January. The plant needs sandy loam soil with moderate watering and full sunlight. The plant is usually mulched with dried rice straw to conserve moisture and to control weed. The bulbs moisture in the field before they are harvested, normally, 5 months after planting.

Nutritional Value

Garlic is a rich source of nutrients required for body metabolism. It has a substantial amount of calories and protein. Its mineral content is more than enough to supply the recommended daily intake of an individual. Vitamin content analysis shows the presence of B vitamins specifically thiamine, riboflavin and niacin, all of which are essential for growth. It also contains vitamin C which is needed to strengthen blood veins, gums and teeth.

Utilization

The bulb is mainly used as a condiment. Fresh young cloves and leaves, however, can be eaten as vegetables.

Other properties, mostly medicinal, are attributed to it. At least 2 cloves eaten a day is believed to lower high blood pressure. The whole plant is known to have depressing effect upon the heart by slowing its beat and lessening the contractibility of its muscles. It possesses anti-obesity action and can control against excess cholesterol by removing accumulated cholesterol from the blood vessels. Garlic can be used as lozenges to relieve sore throat. Moreover, it can be used as expectorant (clove tincture), a treatment for insect bites (bulb poultice) and as a temporary cure for toothache (by inserting a macerated piece of clove in the tooth cavity). For external wound, the bulb can be used as a disinfectant due to its bactericidal properties. It can be used to treat athlete’s foot and ringworm.

To exert its medicinal properties, fresh garlic should be used. A word of caution though for those with intestinal ulcers; oral use should be avoided because of its irritating properties.

Processing by Drying or Dehydration

Processing of garlic by drying or dehydration offers the following advantages:

  1. It requires less storage space than the fresh commodity. The average yield is 20% with the final product having an average moisture content of 12-13%.
  2. It is much lighter than the equivalent amount of fresh commodity. Newly harvested farlic has a moisture content of 65.5%, while store bulbs have about 37%.
  3. It does not require prior treatments like blanching or chemical treatment.
  4. Storage losses due to insect infestation are prevented.

Garlic may be dried under the sun or dehydrated by mechanical driers. Drying does not need sophisticated and expensive devices as it is dependent mostly on solar energy. Dehydration on the other hand, uses artificially heated air with carefully controlled temperature, air humidity and air velocity.

Solar drying may be done directly by exposing the garlic material to the sun’s radiation with or without a transparent cover. Using a transparent cover improves the quality of the drying material as dirt is kept out and drying time is shortened. Shorter drying time minimizes production of objectionable flavors in the material. Covering a receiving surface with a sunlight-transparent sheet of glass or plastic produces a higher temperature and minimizes heat losses within the drying chamber. The relative humidity within the drying chamber decreases making the evaporation of water from the material surface faster. Shortening of the drying time also preserves the volatile garlic flavor.

Slicing and chopping garlic increases its surface area resulting to a greater risk of dirt, dust and insect contamination. A solar drier with a transparent cover is therefore recommended for garlic processing by drying. For the small scale processor, a solar dryer with 14 drying trays is recommended. This is similar to the model drier below.

For housewives and cottage level processors, a vertical four-tray drier (Figure 4) would serve the purpose.

The ordinary home oven can take the place of a dehydrator. If properly manipulated, high grade products can be produced. To use it as an evaporator, the door should be partially open so that the warm moist air can escape and cooled air can enter. The cool air in turn becomes heated and again absorbs water from the drying material. This cycle continues until the drying material has reached the final end point. To secure uniform drying, an occasional rearrangement of the trays should be done. Air circulation can be promoted directing an electric fan towards the oven.

There are three general stages in producing dehydrated garlic products: pre-drying, drying, and finishing & packaging.

Pre-Drying Stage

For garlic flakes preparation, slices should be thin to expose more surface and speed up the drying process. The slices should not be too thin, however, as the pieces have the tendency to lose their rigidity and mat together. The quality, appearance and color of the final product are also adversely affected.

Slicing knives should be kept sharp to avoid crushing the garlic tissues. This would minimize undesirable enzyme changes.

In the preparation of garlic granules, the cutting blade of the food chopper should be sharp. Garlic cloves should be fed in small amounts to the chopper. The peels may or may not be removed a these can easily be removed gently blowing on the surface of the material when dried.

Drying Stage

In the preparation of dried garlic products, a two step drying process is undertaken. The first step involves solar drying, while the second step involves the use of the oven. A loading density of 100 grams/sq. ft. enables the garlic slices to be spread in single layers on the tray.

For granules, a one step drying process is possible using the solar drier. However, this takes a longer time. A cream colored product without traces of discoloration has been obtained from newly harvested bulbs, after 24 hours of solar drying.

The moisture content of the products after the drying stage ranges from 12-13%. At this moisture level, the product is no linger susceptible to bruising or flavor formation. The products can the be packed and sold to final consumers or to final processors for further drying operations. The average yield is 20% of the raw material.

Finishing and Packaging

The finished dried product, in the form of flakes, powder or granules has a moisture content of 12%. The moisture level may be further reduced to a level of 6.5% with the use of special driers, especially, if the product is considered for the export market. A moisture level of 6.5% is the maximum requirement prescribed by the American Dehydrated Onion and Garlic Association for dried/dehydrated garlic.

The products should be packed immediately in thick polyethylene bags or in small plastic containers at 5-10 grams weight per pack and sold in this manner to direct consumers. If using plastic bottles, the container should be packed full and covered with aluminum foil.

 

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  1. By Mike Lewis

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