Garlic and its Storage Methods

Garlic is widely used as a flavoring agent in Iranian kitchens. Additionally, it is used in traditional medicine as a remedy with numerous properties. Garlic contains a compound called allicin, which has antibacterial, antifungal, and antioxidant properties, and can help strengthen the immune system. Furthermore, garlic can prevent certain health-related problems, such as heart disease and cancer. Like other agricultural products, garlic has a limited shelf life and, if not stored properly, not only loses its desirable aroma and flavor but also spoils. Therefore, by employing proper storage methods, the shelf life of garlic can be extended.

Physical Changes in Garlic During Home Storage

Healthy garlic has a thin, intact skin that protects the cloves. Its color is usually white, creamy, or slightly purple. The cloves of healthy garlic are firm in texture and do not feel moist or mushy when touched or pressed. Fresh garlic has a strong, natural aroma.

• Sprouting

Long-term storage of garlic in warm, humid conditions, exposed to light and without adequate ventilation, can increase sprouting. Additionally, storing garlic next to products such as potatoes and onions, due to the ethylene released by these products, accelerates the sprouting process. Sprouting causes chemical changes that affect the quality and properties of garlic. One of these changes is a decrease in allicin, the main compound in garlic responsible for its antioxidant and antimicrobial properties. However, a decrease in allicin does not mean a general reduction in garlic's properties. In fact, according to some sources, sprouted garlic may have higher antioxidant activity than fresh garlic due to the production of new antioxidant compounds such as ajoene, diallyl sulfide (DAS), diallyl disulfide (DADS), and diallyl trisulfide (DATS) during the sprouting process. These compounds, in addition to antioxidant properties, also have anti-inflammatory and even anti-cancer properties. Therefore, contrary to some sources that say garlic sprouts are toxic, they are not only non-toxic but may also have higher antioxidant properties. Another change that occurs in sprouted garlic is the creation of sulfur compounds that contribute to its antimicrobial properties but enhance the pungent flavor, which is not necessarily pleasing to everyone. Therefore, sprouting alone is not a sign of spoilage, and the sprout can be easily removed before consumption. However, if, in addition to sprouting, the garlic's texture becomes soft or it emits an unpleasant odor, it is recommended to avoid consuming it.

• Discoloration

Garlic may turn brown during storage for various reasons. One of the main reasons for this discoloration is the reaction of garlic's phenolic compounds with oxygen. These compounds, responsible for garlic's antioxidant and anti-inflammatory properties, oxidize upon contact with air and cause discoloration. This type of browning is a natural and inevitable process, although consuming garlic that has browned for this reason is not harmful. Another factor that can cause garlic to brown is the activity of its internal enzymes, a process that is usually accelerated after peeling and chopping the garlic, but consuming this garlic is still harmless. If, in addition to discoloration, garlic exhibits other signs such as an unpleasant odor and a soft, watery texture, it may be a sign of spoilage. This condition usually occurs due to storing garlic in humid or very warm environments. In such cases, it is recommended to avoid consuming the garlic (causes of spoilage are explained in the odor Change sections).

• Texture Change

Texture changes in garlic during storage depend on various factors. One of these factors is the ambient humidity. Like other foods, garlic tends to adapt to the surrounding humidity when placed in an environment. When placed in a high-humidity environment, it absorbs moisture, which can soften its texture. Also, high humidity can provide suitable conditions for the growth of microorganisms and lead to spoilage. On the other hand, if garlic is stored in a low-humidity environment, it loses moisture and becomes hollow. The combination of high or low humidity with high temperature accelerates texture changes in garlic. If these changes are minor, the garlic is still consumable, but if the changes are more significant or accompanied by signs such as an unpleasant odor, it may indicate spoilage (causes of spoilage are explained in the odor Change sections).

• Odor Change

One of the main indicators of spoilage in garlic is a change in its odor. While fresh garlic has a pungent and distinct smell, spoiled garlic usually develops an unpleasant odor similar to rancidity or decay. This odor change can be the result of the growth and activity of certain bacteria or molds in warm and humid environments.

1. Bacteria

Bacterial spoilage is less common in garlic than mold, but if garlic is placed in a contaminated environment with favorable conditions such as heat and humidity, bacteria can grow and cause various changes, including texture changes and the development of an unpleasant odor. In addition, some bacteria may produce toxins. Although people are usually not inclined to consume spoiled and foul-smelling garlic, if this happens for any reason, there is a risk of food poisoning in both raw and cooked forms. Consuming raw, spoiled garlic can lead to symptoms such as nausea, diarrhea, and abdominal pain. If spoiled garlic is used in food preparation, the bacteria causing spoilage may be killed by heat, but if these bacteria have produced toxins before cooking, heat may not be able to destroy the toxins, and the risk of poisoning remains. Therefore, if you smell an abnormal odor or observe any signs of spoilage, it is recommended to avoid consuming the garlic.

2. Mold

Molds are among the most common causes of garlic spoilage. They are microorganisms that grow in unfavorable conditions, such as heat, high humidity, and lack of adequate ventilation, leading to spoilage. Molds can cause changes in the color, odor, and texture of garlic. Some molds can also produce fungal toxins, which pose health risks to humans. Various types of molds, such as Penicillium, Aspergillus, and Fusarium, may appear on garlic.

3. Penicillium

This mold is usually seen in green or blue. Some Penicillium species can produce a fungal toxin called patulin, which may cause gastrointestinal disorders, liver damage, and weaken the immune system.

4. Aspergillus

This mold appears in black, white, yellow, or brown. Some of its species are capable of producing aflatoxin, a carcinogenic fungal toxin with harmful effects on the liver. However, the probability of aflatoxin production on garlic is low.

5. Fusarium

This mold is identified by colors such as white, pink, purple, or red. Some Fusarium species can produce a fungal toxin called fumonisin, which leads to liver and kidney disorders and even esophageal cancer.

If any mold is observed on garlic, even if it is limited to a small part, there is a possibility that mold hyphae have penetrated other parts of the garlic and produced fungal toxins (mycotoxins). These hyphae may not be visible to the naked eye but may have penetrated apparently healthy parts. Since fungal toxins are highly resistant to heat, even cooking or frying may not completely eliminate these toxins, although it may reduce their amount. Therefore, if mold is observed on garlic, if the garlic is in separated cloves, the moldy clove should be completely discarded. In cases where only one clove of a bulb is moldy, it is recommended to discard the entire bulb to prevent potential risks.

Garlic Storage Methods

Proper and principled garlic storage methods can be very effective in preserving its quality (aroma, flavor, and texture) as well as its safety (free from microorganisms).

• Fresh Garlic Storage

One of the best and most common methods of storing fresh garlic is to keep it in whole bulbs. In this condition, garlic can be stored fresh and healthy for approximately 6 months. This is because the outer layers of the bulb and the garlic skin act as a natural protective barrier and delay changes in garlic caused by the passage of time, such as aging and spoilage. For this reason, it is recommended that garlic cloves not be separated from the bulb until they are ready to be used, as separating the cloves from the bulb reduces their shelf life, and in this case, they can only be stored for about 1 to 2 weeks. To store garlic bulbs, they can be tied together by their stems and hung in a dry, cool, and dark place such as a pantry or a corner of the kitchen (an area away from direct sunlight, the stove, or the sink). Additionally, fresh garlic bulbs can be placed in wire baskets or mesh bags in a cabinet away from the oven and stove. However, it is better to hang the mesh bags in a suitable part (dry, cool, and dark) of the pantry or kitchen so that air can circulate well around them. In both storage methods, garlic should not be placed near potatoes and onions, as they produce ethylene, which accelerates sprouting and the aging process of garlic.

• Garlic Stored in Oil

Storing garlic in oil creates anaerobic (oxygen-free) conditions inside the oil, which increases the likelihood of Clostridium botulinum bacteria growth, raising concerns about the safety of this storage method. Unlike other spoilage agents, Clostridium botulinum bacteria usually do not cause changes in the odor, color, or texture of garlic. If garlic is stored in oil at room temperature, this bacterium can multiply and produce botulinum toxin, which, if consumed, causes botulism poisoning. In the early stages, the person may experience symptoms such as nausea, vomiting, abdominal cramps, diarrhea, or constipation. As the disease progresses, this toxin can gradually affect the nervous system, leading to symptoms such as muscle weakness, respiratory problems, and, in severe cases, death. For this reason, according to the United States Department of Agriculture (USDA), it is recommended that the garlic and oil mixture not be stored at room temperature. This mixture can be stored in the refrigerator for 7 days and in the freezer for a few months (approximately 2 to 3 months).

• Frozen Garlic Storage

Garlic cloves, minced or pureed, can be stored frozen in suitable food storage bags or containers (sealed and insulated) in the freezer. For ease of use when consuming, ice cube trays can be used to freeze garlic, and after freezing, they can be transferred to packaging containers, so each portion of garlic can be used separately for each meal. Frozen garlic can usually be stored for 6 to 12 months. However, it should be noted that the aroma and flavor of garlic decrease over time, so it is best to consume the garlic within a shorter period.

• Dried Garlic Storage

Garlic can be dried using various methods, including drying in a dehydrator, oven, and in the open air (traditional method). After drying, it is best to store dried garlic in glass containers in a dry, dark, and cool environment such as a cabinet. Dried garlic can usually be stored for about 2 years, but the storage time can vary depending on the drying method and storage conditions. It should be noted that dried garlic loses its aroma and flavor over time, so to enjoy the desired aroma and flavor, it is best to consume dried garlic within a shorter period.

In general, the shelf life of garlic in various storage methods is influenced by various factors such as the type of garlic, the degree of freshness and initial quality of the garlic (at the time of purchase), ambient temperature, humidity level, light level, etc. Therefore, the mentioned shelf life times are approximate and may change depending on the conditions. For this reason, before consuming garlic, it is always necessary to carefully examine the garlic for its appearance, texture, and odor to ensure its health and quality.